Publications by authors named "Dietmar Stolke"

47 Publications

Outcome After Clipping of Unruptured Intracranial Aneurysms Depends on Caseload.

World Neurosurg 2016 May 28;89:666-671.e1. Epub 2015 Dec 28.

Department of Neurosurgery, University Hospital of Essen, Essen, Germany.

Objective: Although most neurovascular centers currently have a coil first policy, the percentage of coiled versus clipped aneurysms, as well as treatment outcomes, varies strongly between these centers. This study evaluates the impact of an increase in clipping caseload on treatment outcome in a large single-center series.

Methods: All consecutive patients who underwent microsurgical clipping of unruptured intracranial aneurysms between January 2003 and April 2014 in our department were analyzed retrospectively. According to the change of the chairman in the neurosurgical department (1 September 2008) with a subsequent increase in the clipping volume, the entire cohort was divided into 2 groups with equal time intervals (historic and current cohorts).

Results: There were 94 clipped unruptured intracranial aneurysms in the historic cohort and 252 in the current cohort. Unfavorable outcome at 6 months postoperatively (defined as modified Rankin Score >2) was observed in 8 cases (8.5%) in the historic cohort and 7 cases (2.8%) in the current cohort (P < 0.0001). The surgical mortality decreased from 3.2% to 0%. Cerebral infarction on postoperative computed tomography scan was observed in 25 cases (26.6%) in the historic cohort and 19 cases (7.5%) in the current cohort (P < 0.0001). Within the current cohort, there was a progressive improvement of surgical outcome over the time.

Conclusions: The improvement of the surgical outcome after increasing the clipping caseload underlines the importance of sufficient surgical volume for maintenance of competitive treatment results.
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http://dx.doi.org/10.1016/j.wneu.2015.12.043DOI Listing
May 2016

Predictive chromosomal clusters of synchronous and metachronous brain metastases in clear cell renal cell carcinoma.

Cancer Genet 2014 May 17;207(5):206-13. Epub 2014 May 17.

Stereology and Electron Microscopy Laboratory, Department of Clinical Medicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark.

Synchronous (early) and metachronous (late) brain metastasis (BM) events of sporadic clear cell renal cell carcinoma (ccRCC) (n = 148) were retrospectively analyzed using comparative genomic hybridization (CGH). Using oncogenetic tree models and cluster analyses, chromosomal imbalances related to recurrence-free survival until BM (RFS-BM) were analyzed. Losses at 9p and 9q appeared to be hallmarks of metachronous BM events, whereas an absence of detectable chromosomal changes at 3p was often associated with synchronous BM events. Correspondingly, k-means clustering showed that cluster 1 cases generally exhibited low copy number chromosomal changes that did not involve 3p. Cluster 2 cases had a high occurrence of -9p/-9q (94-98%) deletions, whereas cluster 3 cases had a higher frequency of copy number changes, including loss at chromosome 14 (80%). The higher number of synchronous cases in cluster 1 was also associated with a significantly shorter RFS-BM compared with clusters 2 and 3 (P = 0.02). Conversely, a significantly longer RFS-BM was observed for cluster 2 versus clusters 1 and 3 (P = 0.02). Taken together, these data suggest that metachronous BM events of ccRCC are characterized by loss of chromosome 9, whereas synchronous BM events may form independently of detectable genetic changes at chromosomes 9 and 3p.
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http://dx.doi.org/10.1016/j.cancergen.2014.05.004DOI Listing
May 2014

Spontaneous cerebellar hemorrhage--experience with 57 surgically treated patients and review of the literature.

Neurosurg Rev 2011 Jan 10;34(1):77-86. Epub 2010 Aug 10.

Department of Neurosurgery, University Hospital Essen, Hufelandstrasse 55, 45122 Essen, Germany.

The treatment of spontaneous cerebellar hemorrhage is still discussed controversially. We analyzed a series of 57 patients who underwent surgical evacuation of a cerebellar hematoma at our department. Preoperative clinical and radiological parameters were assessed and correlated with the clinical outcome in order to identify factors with impact on outcome. The overall clinical outcome according to the Glasgow Outcome Scale at the last follow-up was good (GOS 4-5) in 27 patients (47%) and poor (GOS 2-3) in 16 patients (28%). Fourteen patients (25%) died. The initial neurological condition and the level of consciousness proved to be significant factors determining clinical outcome (p = 0.0032 and p = 0.0001, respectively). Among radiological parameters, brain stem compression and a tight posterior fossa solely showed to be predictive for clinical outcome (p = 0.0113 and p = 0.0167, respectively). Overall, our results emphasize the predictive impact of the initial neurological condition on clinical outcome confirming the grave outcome of patients in initially poor state as reported in previous studies. The hematoma size solely, in contrast to previous observations, showed not to be predictive for clinical outcome. Especially for the still disputed treatment of patients in good initial neurological condition, a suggestion can be derived from the present study. Based on the excellent outcome of patients with good initial clinical condition undergoing surgery due to secondary deterioration, we do not recommend preventive evacuation of a cerebellar hematoma in these patients.
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http://dx.doi.org/10.1007/s10143-010-0279-0DOI Listing
January 2011

Proliferation activity is significantly elevated in partially embolized cerebral arteriovenous malformations.

Cerebrovasc Dis 2010 5;30(4):396-401. Epub 2010 Aug 5.

Department of Neurosurgery, University Hospital Essen, Hufelandstrasse 55, Essen, Germany.

Background: The natural history of cerebral arteriovenous malformations (AVMs) is yet to be determined. It has been shown that angiogenic factors are involved in the pathogenesis of AVMs, in particular in partially embolized lesions. This study was conducted to investigate the expression of angiogenic and proliferative factors in relation to different clinical conditions and treatment modalities.

Methods: Immunohistochemistry was performed for 145 consecutive cases of cerebral AVMs. The specimens were stained with antibodies against VEGF, bFGF, Ki 67, CD 34 and CD 31. Expression was correlated with clinical presentation (haemorrhage, seizures or other symptoms), AVM localization, size, eloquence and venous drainage, as well as with preoperative AVM embolization.

Results: Whereas no correlation was found between the expression of angiogenic factors and different clinical conditions, we observed a significantly increased proliferation activity as shown by Ki 67 expression in patients with intracerebral haemorrhage (p = 0.02) and in patients with preoperative embolization (p = 0.02).

Conclusions: Increased proliferation activity in partially embolized AVMs supports a 'no-touch' strategy and clinical observation in high-risk AVMs and demands complete AVM elimination in treatable lesions.
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http://dx.doi.org/10.1159/000319568DOI Listing
January 2011

AVM resection after radiation therapy--clinico-morphological features and microsurgical results.

Neurosurg Rev 2010 Jan;33(1):53-61

Department of Neurosurgery, University Hospital Essen, Hufelandstr. 55, 45147 Essen, Germany.

A subgroup of patients initially treated by radiosurgery underwent surgical resection because of recurrent hemorrhage or neurological deterioration. In a retrospective study, we want to analyze the clinical features of these patients and evaluate the effect of microneurosurgery in such rare constellations. Moreover, we hope to find answers about failure of radiation therapy in these cases by correlation of radiobiological and histopathological data. Over a 16-year-period, eight patients with cerebral arteriovenous malformation (AVM) underwent surgical resection, who previously were treated by radiosurgery. The mean duration between radiation therapy and final resection was 7 years. Preoperative evaluation revealed Spetzler-Martin grade III (n=5) and IV (n=3) AVMs. Histological examination was achieved in all resected lesions. Mean neurological follow-up was 14 months. Indications for surgical resection were intracerebral hematoma, progressive neurological deficit, and epilepsy. In comparison to the initial angiographic study before radiation therapy, preoperative angiography revealed newly developed "en passant" feeding vessels and stenosis of the main venous drainage in some patients. The mean Rankin score for all patients was 2.75 before and 3.25 after surgical resection. Postoperatively, three patients (38%) developed neurological deterioration. Histological examination of the resected tissue revealed significant radiation-induced pathology in six patients. We did not see correlation between radiation doses and severity of histolopathological radiation-induced changes. Postoperative angiography confirmed total AVM resection in all patients. AVMs insufficiently treated by radiation bear an increased surgical risk. Often, angiographic studies revealed a more complicated morphology. Microsurgical resection was extremely challenging and led to unfavorable outcomes in many of the patients.
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http://dx.doi.org/10.1007/s10143-009-0216-2DOI Listing
January 2010

Decompressive laminoplasty in multisegmental cervical spondylotic myelopathy: bilateral cutting versus open-door technique.

Acta Neurochir (Wien) 2009 Jul 13;151(7):739-49; discussion 749. Epub 2009 May 13.

Department of Neurosurgery, University Hospital of Essen, Hufelandstr. 55, 45147 Essen, Germany.

Purpose: The aim of the study was to evaluate patients with multisegmental cervical spondylotic myelopathy (MCM) surgically treated via a dorsal approach. Two different laminoplasty techniques were compared by assessment of enlargement of the spinal canal and the neurological outcome.

Methods: Thirteen patients (mean age 49 years, 11 males) underwent decompressive laminoplasty over a 7-year period. The average duration of symptoms was 21 months. The pre- and postoperative degree of myelopathy was assessed by both the Nurick grading and the Japanese Orthopaedic Association myelopathy score (JOA score). Preoperatively, the mean Nurick grade was 3.1 and the mean JOA score was 11. Two different techniques of expansive laminoplasty were used. Six patients underwent a bilateral cutting (BL) technique with retropositioning of the laminae and bilateral mini-plating (BL group). Seven patients were operated on by simple open-door (OD) laminoplasty with unilateral mini-plating (OD group). Postoperatively, CT scans were obtained for all patients to measure the sagittal diameter of the spinal canal. The mean clinical and radiological follow-up was 33 months.

Results: Four to five laminae were involved in all patients.The mean operation time was 180 min. Complications occurred in two patients of BL group, with immediate postoperative neurological deterioration due to ventral displacement of the laminae. Overall, the average sagittal diameter (SD) of the spinal canal increased from 9.2 +/- 1.3 mm to 12.4 +/- 1.3 mm after surgery. The average enlargement of SD was significantly higher for the OD group (p < 0.0075 ). In total, the improvement rate was 38% according to the Nurick grading and 69% according to the JOA score. For the OD group, improvement rates were 57% (Nurick) and 71% (JOA).

Conclusions: Decompressive laminoplasty is comparable with anterior surgery in neurological outcome. The OD technique seems to be superior to our BL technique regarding both the enlargement of SD and complication rate.
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http://dx.doi.org/10.1007/s00701-009-0343-0DOI Listing
July 2009

Anterior clinoidal meningiomas: functional outcome after microsurgical resection in a consecutive series of 106 patients. Clinical article.

J Neurosurg 2009 Nov;111(5):1078-90

Department of Neurosurgery, University Hospital Essen, Germany.

Object: In this study, the authors' goal was to analyze a series of patients treated microsurgically for an anterior clinoid process (ACP) meningioma in regard to long-term functional outcome.

Methods: The authors retrospectively analyzed clinical data in a consecutive series of 106 patients who underwent microsurgical treatment for an ACP meningioma at 2 neurosurgical institutions between 1987 and 2005. The main presenting symptoms of the 84 female and 22 male patients (mean age 56 years) were visual impairment in 54% and headache in 28%. Physical examination revealed decreased visual acuity in 49% and a visual field deficit in 26%. Tumors were primarily resected via a pterional approach. Meningioma extensions invading the cavernous sinus, present in 29% of the patients, were not removed. Complete tumor resection (Simpson Grade I and II) was achieved in 59% of the cases.

Results: Postoperatively, visual acuity improved in 40%, was unchanged in 46%, and deteriorated in 14%. A new oculomotor palsy was observed in 8 patients (8%). Clinical and MR imaging data were available in 95 patients for a mean postsurgical period of 6.9 years (1.5-18 years) and revealed tumor recurrence in 10% and tumor progression after subtotal resection in 38%. Clinical deterioration on long-term follow-up consisting primarily of ophthalmological deficits was observed in 14% of the cases.

Conclusions: Acceptable functional results can be achieved after microsurgical resection of ACP meningiomas; however, long-term treatment remains challenging due to a high tumor recurrence and progression rate.
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http://dx.doi.org/10.3171/2009.3.17685DOI Listing
November 2009

Spinal meningiomas: critical review of 131 surgically treated patients.

Eur Spine J 2008 Aug 15;17(8):1035-41. Epub 2008 May 15.

Neurochirurgische Klinik, Universitätsklinikum Essen, Hufelandstr. 55, 45122, Essen, Germany.

This study was undertaken to analyze the functional outcome of surgically treated spinal meningiomas and to determine factors for surgical morbidity. Between January 1990 and December 2006 a total of 131 patients underwent surgical resection of a spinal menigioma. There were 114 (87%) female and 17 (13%) male patients. Age ranged from 17 to 88 years (mean 69 years). The mean follow-up period was 61 months (range 1-116 months) including a complete neurological examination and postoperative MRI studies. The pre- and postoperative neurological state was graded according to the Frankel Scale. Surgery was performed under standard microsurgical conditions with neurophysiological monitoring. In 73% the lesion was located in the thoracic region, in 16% in the cervical region, in 5% at the cervico-thoracic junction, in 4.5% at the thoraco-lumbar junction and in 1.5% in the lumbar region. Surgical resection was complete in 127 patients (97%) and incomplete in 4 patients (3%). At the last follow-up the neurological state was improved or unchanged in 126 patients (96.2%) and worse in 4 patients (3%). Permanent operative morbidity and mortality rates were 3 and 0.8%, respectively. Extensive tumour calcification proved to be a significant factor for surgical morbidity (P < 0.0001). Radical resection of spinal meningiomas can be performed with good functional results. Extensive tumor calcification, especially in elderly patients proved to harbor an increased risk for surgical morbidity.
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http://dx.doi.org/10.1007/s00586-008-0685-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2518757PMC
August 2008

Meningiomas of the falcotentorial junction: selection of the surgical approach according to the tumor type.

Surg Neurol 2008 Apr 17;69(4):339-49; discussion 349. Epub 2007 Aug 17.

Department of Neurosurgery, University Hospital Essen, 45122 Essen, Germany.

Background: We retrospectively analyzed a series of patients harboring a FT meningioma with regard to clinical presentation, surgical technique, and follow-up results.

Methods: Clinical data in a consecutive series of 13 patients treated for a meningioma of the FT junction were retrospectively reviewed. Tumors were classified into 4 types according to their dural origin and tumor extent as depicted from preoperative MRI.

Results: Main presenting symptom in 9 women and 4 men (mean age, 56 years) was headache (69%) and gait disturbance (54%). Clinical examination revealed gait ataxia in 62% of the patients. The tumor displaced the vein of Galen inferiorly in 6 patients, superiorly in 2, and medially in 5 cases. The main surgical approach to the meningioma was via an occipital interhemispheric route (10 patients). Additional resection of the falx and/or incision of the tentorium was performed in 6 cases each. A complete resection (Simpson grade 1 and 2) was achieved in 85% of patients. Permanent surgical morbidity was 23%. One tumor recurrence in an atypical meningioma was observed after the mean follow-up period of 6.2 years (range, 1-14 years) with clinical and MRI examination and had to be reoperated. Eighty-five percent of the patients regained full daily activity on follow-up.

Conclusions: The surgical approach should be tailored to the dural origin and extent of the tumor as depicted from preoperative MRI. Preservation of the straight sinus and Galenic venous system is recommended.
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http://dx.doi.org/10.1016/j.surneu.2007.02.029DOI Listing
April 2008

The impact of subarachnoid hemorrhage on regional cerebral blood flow and large-vessel diameter in the canine model of chronic vasospasm.

J Stroke Cerebrovasc Dis 2007 Mar-Apr;16(2):45-51

Department of Neurosurgery, University of Essen, Germany.

Objective: The aim of this study was to correlate changes in regional cerebral blood flow (rCBF) to the degree of cerebral vasospasm in the canine two-hemorrhage model of subarachnoid hemorrhage (SAH).

Methods: SAH was induced in 13 adult beagle dogs using the two-hemorrhage model. Eleven beagle dogs served as controls. Angiography of the basilar artery and measurements of rCBF with colored microspheres were performed on days 1 and 8. Diameter of the basilar artery was calculated at equidistant points from the angiogram.

Results: In controls, basilar artery diameter (mm) and rCBF (mL/min/g) were equal on days 1 and 8. In the SAH group, basilar artery diameter decreased significantly (1.27 +/- 0.17 [mean +/- SD]-0.84 +/- 0.15 mm). rCBF decreased significantly (P < .05) in the cerebrum (1.69 +/- 0.54 [mean +/- SD]-1.06 +/- 0.45 mL/min/g), cerebellum (1.18 +/- 0.40-0.80 +/- 0.32 mL/min/g), and brain stem (0.81 +/- 0.33-0.51 +/- 0.21 mL/min/g). However, decrements in CBF were not correlated to the reduction in vessel caliber in the corresponding vascular territory.

Conclusion: Induced SAH in the canine model produces a significant impairment in rCBF irrespective of the degree of vasospasm of large cerebral vessels. The findings support the presumptive role of the microvasculature in regard to delayed cerebral ischemia after SAH.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2006.10.002DOI Listing
September 2007

Analysis of intrathecal interleukin-6 as a potential predictive factor for vasospasm in subarachnoid hemorrhage.

Neurosurgery 2007 May;60(5):828-36; discussion 828-36

Objective: Inflammatory response seems to be one of the relevant pathophysiological aspects for developing vasospasm in subarachnoid hemorrhage. The probable diagnostic value of intrathecal proinflammatory markers is still unclear and is assessed in this study.

Methods: We analyzed daily clinical data and laboratory tests of the cerebrospinal fluid (CSF) of 64 patients with mostly poor-grade subarachnoid hemorrhage during a period of 14 days. Special attention was given to the relationship between the development of vasospasm and the time course of the intrathecal interleukin (IL)-6 concentrations in CSF (IL-6CSF). The potential power of IL-6CSF for predicting vasospasm was studied.

Results: Vasospasm developed in 28.1% of the patients, with a mean onset of 6.4 days after bleeding, and was detected by conventional methods. Patients with vasospasm demonstrated statistically significant higher median values of IL-6CSF on Days 4 and 5 (P < 0.05). Most importantly, the increase of IL-6CSF preceded the conventional signs of vasospasm. A cut-off value of IL-6CSF of at least 2000 pg/ml on Day 4 yielded an 11.72-fold higher relative risk (95% confidence interval, 2.93-46.60) of developing vasospasm, predicting vasospasm with a sensitivity of 88.9% and a specificity of 78.3%. We found a statistically significant correlation between IL-6CSF and delayed cerebral ischemia for Day 7 (P = 0.03). However, there was no correlation with IL-6CSF on any other day and outcome.

Conclusion: IL-6CSF seems to be a reliable early marker for predicting vasospasm after subarachnoid hemorrhage on Days 4 and 5 before clinical onset.
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http://dx.doi.org/10.1227/01.NEU.0000255440.21495.80DOI Listing
May 2007

Foramen magnum meningiomas: clinical outcome after microsurgical resection via a posterolateral suboccipital retrocondylar approach.

Neurosurgery 2006 Dec;59(6):1177-85; discussion 1185-7

Department of Neurosurgery, University Hospital Essen, Essen, Germany.

Objective: We analyzed a consecutive series of patients operated for a foramen magnum (FM) meningioma located on the ventral aspect of the medulla oblongata via a posterolateral suboccipital retrocondylar approach with regard to long-term surgical outcome.

Methods: Clinical data in a consecutive series of 25 patients experiencing a meningioma attached to dura of the anterior or anterolateral FM rim were retrospectively reviewed.

Results: The most common symptoms of the 19 women and six men (mean age, 59.2 yr) was cervico-occipital pain (72%) and gait disturbance (32%). Clinical examination revealed gait ataxia in 48% of the patients. As depicted from preoperative magnetic resonance imaging (MRI), dural attachment of the meningioma at the FM rim was anterior in 36% and anterolateral in 64% of cases. Tumor removal was accomplished via a posterolateral suboccipital retrocondylar approach in all patients. A Simpson Grade 2 resection was achieved in 96% of the patients. Permanent surgical morbidity and mortality rates were 8 and 4%, respectively. No tumor recurrence was observed after a mean follow-up period of 6.1 years (range, 1-14 yr) with clinical and MRI examination, and 80% of the patients have regained full daily activity.

Conclusion: Anterior and anterolateral FM meningiomas that displace the medulla/spinal cord can be safely and completely resected via a posterolateral suboccipital retrocondylar approach. A tumor remnant should be left on critical neurovascular structures in cases with poor arachnoid dissection planes.
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http://dx.doi.org/10.1227/01.NEU.0000245629.77968.37DOI Listing
December 2006

Dural involvement in primary extradural meningiomas of the cranial vault.

J Neurosurg 2006 Jul;105(1):51-9

Department of Neurosurgery, University Hospital Essen, Essen, Germany.

Object: The authors retrospectively analyzed a consecutive series of patients with cranial vault primary extradural meningioma (PEM), with particular regard to the tumor's dural involvement. The pertinent literature was reviewed.

Methods: Clinical data were retrospectively obtained in a consecutive series of 16 patients treated for a PEM at two institutions between 1992 and 2004. The authors created a classification system based on dural involvement of the tumors. Nine women and six men (mean age 55 years) presented with a painless, slowly progressive swelling. Preoperative magnetic resonance (MR) imaging revealed dural enhancement at the site of tumor in 11 patients. On surgical inspection, the tumor infiltrated the dura in all but three patients. Histological examination of tissue samples demonstrated tumor infiltration of the dura in all 14 patients in whom the dura had been resected. Three recurrent tumors were observed on follow-up examination during a mean period of 5.8 years (range 1.5-13 years) and required extirpation. In addition to one patient in whom there was histological evidence of malignancy, the other two cases involved two patients in whom no apparent dural involvement was observed during the first surgery. In a review of the literature, the authors found that histological examination showed dural involvement in 22%; the dura was not histologically evaluated in the remaining patients (78%). Postoperative follow-up data exceeding 2 years were only provided in two of the reported cases.

Conclusions: Tumor infiltration of the dura should be assumed in PEMs of the cranial vault, and resection of the dura at the site of craniotomy is recommended to prevent tumor recurrence.
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http://dx.doi.org/10.3171/jns.2006.105.1.51DOI Listing
July 2006

Tuberculum sellae meningiomas: functional outcome in a consecutive series treated microsurgically.

Surg Neurol 2006 Jul;66(1):37-44; discussion 44-5

Department of Neurosurgery, University Hospital Essen, Essen, Germany.

Objective: The objective of this study was to analyze a series of patients harboring a tuberculum sellae meningioma with regard to clinical presentation and long-term functional outcome.

Methods: Data in a consecutive series of 62 patients harboring a tuberculum sellae meningioma treated microsurgically between 1990 and 2003 were retrospectively reviewed.

Results: The mean age of the 46 women and 16 men enrolled in the study was 53 years (range = 29-81 years). The presenting symptom was visual compromise in 87.1% of the patients, and examination revealed decreased visual acuity in 79% and impaired visual fields in 64.5% of the patients. In addition, 14.5% of the patients had preoperative hormonal abnormalities. Simpson grades I and II resections, usually via a pterional approach, were achieved in 90.3% of the patients. Postoperatively, vision improved in 53.2%, remained unchanged in 29.8%, and deteriorated in 17.0% of the patients. The intraoperative finding predicting an unfavorable visual outcome was a thin atrophic optic nerve, encasement of the nerve, or tumor adhesion to its undersurface. Of the patients, 12.9% required permanent postoperative hormonal replacement. After a mean follow-up period of 6.0 years (range = 18 months-14 years), 88.7% of the patients resumed normal life activity and 2 recurrent tumors were observed (3.2%) and reoperated.

Conclusions: Preoperative magnetic resonance imaging provides reliable information with regard to dislocation of critical vascular structures. However, the relationship between optic nerves and tumors (eg, adhesion and encasement) affected postoperative results and can only be fully appreciated during microsurgery. Visual outcome may be improved by preserving the microvasculature supplying the optic apparatus.
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http://dx.doi.org/10.1016/j.surneu.2005.11.059DOI Listing
July 2006

Vascular endothelial growth factor plasma levels are significantly elevated in patients with cerebral arteriovenous malformations.

Cerebrovasc Dis 2006 23;21(3):154-8. Epub 2005 Dec 23.

Department of Neurosurgery, University Children's Hospital, Essen, Germany.

Background: Since growth and de novo generation of cerebrovascular malformations were demonstrated, a strictly congenital model cannot be further supported as unique factor in the pathogenesis of cerebral arteriovenous malformations (AVMs). Vascular endothelial growth factor (VEGF) has previously been demonstrated to be highly expressed in AVMs by immunohistochemical methods. However, systemic VEGF levels have not been analysed previously. This study aimed to investigate VEGF plasma concentrations as a possible plasma marker for neovascularization in patients with cerebral AVMs compared to healthy controls.

Methods: The study included 17 patients with cerebral AVMs and 40 healthy controls. VEGF plasma concentrations were measured by a specific enzyme immuno-assay.

Results: VEGF plasma concentrations were significantly higher in patients with cerebral AVMs (mean 140.9 pg/ml, SD 148.5 pg/ml and median 63.0 pg/ml) compared to a healthy control group (mean 44.7 pg/ml, SD 36.4 pg/ml and median 35.0 pg/ml), p = 0.0003.

Conclusions: Our findings suggest that VEGF plasma concentrations might play a role in the pathogenesis of cerebral AVMs. Further studies are necessary and would contribute to an improved understanding of the pathogenesis of cerebral AVMs.
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http://dx.doi.org/10.1159/000090526DOI Listing
May 2006

VEGF plasma levels in non-ruptured intracranial aneurysms.

Neurosurg Rev 2006 Jan 25;29(1):26-9. Epub 2005 Aug 25.

Department of Neurosurgery, University Clinic of Essen, Hufelandstrasse 55, 45122 Essen, Germany.

Aneurysm growth appears to be associated with an increased risk of rupture. Therefore, it may be of interest to identify mechanisms contributing to aneurysm growth. Angiogenic factors, particularly vascular endothelial growth factor (VEGF), appear to play an important role in the pathogenesis and growth of cerebrovascular malformations. We aimed to study systemic VEGF levels as a potential systemic marker in patients with non-ruptured intracranial aneurysms compared with healthy controls. Mean VEGF plasma concentrations were found to be increased in patients with non-ruptured intracranial aneurysms compared with healthy controls (85.2 pg/ml versus 44.1 pg/ml). This difference did not reach significance in the analyzed study cohort (p=0.05) but only when the analysis was restricted to male patients (p=0.04). Female patients and controls demonstrated significantly increased VEGF plasma levels only on correlation with age but not with the presence of aneurysms. Neither the presence of multiple aneurysms nor aneurysm location were correlated with VEGF levels. Although overall VEGF plasma difference was not statistically significant, we found significantly increased levels in male patients. Furthermore, we identified a distinct group of female patients with intracranial aneurysms who presented excessively increased VEGF plasma levels to an amount that was not observed in the controls. Further studies may clarify the relationship of aneurysm growth and VEGF.
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http://dx.doi.org/10.1007/s10143-005-0411-8DOI Listing
January 2006

Functional magnetic resonance imaging in anesthetized patients: a relevant step toward real-time intraoperative functional neuroimaging.

Neurosurgery 2005 Jul;57(1 Suppl):94-9; discussion 94-9

Department of Neurosurgery, University of Essen, Essen, Germany.

Objective: The introduction of intraoperative 1.5-T magnetic resonance imaging may provide up-to-date functional information in the surgical environment. However, feasible passive paradigms that allow the examination of anesthetized patients will be a precondition for intraoperative functional magnetic resonance imaging (fMRI). The aim of this study is to evaluate the feasibility of a recently developed passive fMRI paradigm for functional neuroimaging in anesthetized patients.

Methods: We investigated four anesthetized patients with intracranial pathological conditions not related to the sensorimotor cortex. All patients had been anesthetized with standard total intravenous anesthesia for more than 24 hours before the fMRI scan. Anesthesia and monitoring were sustained during the scanning procedure. A simultaneous electrical stimulation of the median and tibial nerves was applied to elicit a cortical activation using a custom-designed magnetoelectrically shielded conductor. Statistical evaluation using Statistical Parametric Mapping software (Wellcome Department of Imaging Neuroscience, University College, London, England) and the Talairach Daemon Client (Version 1.1; Research Imaging Center, University of Texas Health Science Center, San Antonio, TX) followed.

Results: Three of four patients showed a good activation of the sensorimotor cortex under anesthesia. In one patient, no significant activation was observed, presumably as a result of increased body impedance because of severe edema. Standard dosages of the narcotics did not influence the cortical response; however, stimulation intensity had to be increased compared with awake patients. We did not detect relevant interferences with magnetic resonance imaging arising from the technical setup.

Conclusion: The method presented proved to be a feasible paradigm for fMRI evaluation of the sensorimotor cortex in anesthetized patients and thus forms a relevant step toward real intraoperative functional neuroimaging.
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http://dx.doi.org/10.1227/01.neu.0000163488.91335.c5DOI Listing
July 2005

Spheno-orbital meningiomas: interdisciplinary surgical approach, resectability and long-term results.

J Craniomaxillofac Surg 2005 Aug;33(4):260-6

Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Essen, Germany.

Objective: To describe the interdisciplinary surgical approach in spheno-orbital meningiomas and to evaluate the operative results regarding resectability and functional outcome.

Patients And Methods: A series of 16 patients underwent surgical resection of spheno-orbital meningiomas followed by bony reconstruction. Four patients presented with a recurrent meningioma and had undergone surgical resection previously. Radical tumour removal was attempted in all cases, although no aggressive effort was made to remove tumour tissue infiltrating the cavernous sinus or soft tissues deep in the orbit to avoid severe functional disturbances. All patients but one were female (mean age 53 years). Mean follow-up period was 68 months (range 4-155 months).

Results: The leading symptom was proptosis in 14 patients, accompanied in 7 cases by progressive visual impairment. Surgical resection was thought to have been complete in 11 patients (69%) and incomplete in 5 (31%). Residual tumour was deliberately left when there was infiltration of the cavernous sinus (n = 4), the pterygopalatine fossa (n = 2) and/or the deep intraorbital soft tissues (n = 1). Tumour recurrence was observed in 9 patients, among whom were 6 patients with an initially "completely" resected meningioma. Eight patients underwent re-operation. Complete resection was achieved in 3 of these latter patients with an isolated exclusively intraorbital tumour manifestation.

Conclusion: By means of combined skull base approaches, spheno-orbital meningiomas are grossly resected totally with a long-term survival free of recurrence and an acceptable quality of life. In some cases, deliberate subtotal tumour resection is useful to avoid severe neurological damage with sufficient tumour control and a valuable progression-free survival.
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http://dx.doi.org/10.1016/j.jcms.2005.01.013DOI Listing
August 2005

Intraoperative functional MRI: implementation and preliminary experience.

Neuroimage 2005 Jul 29;26(3):685-93. Epub 2005 Mar 29.

Department of Neurosurgery, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany.

For a non-invasive identification of eloquent brain areas in neurosurgical procedures up to now only preoperative functional brain mapping techniques are available. These are based, e.g., on preoperative functional magnetic resonance imaging (fMRI) investigations in awake patients. The aim of this study was to investigate the feasibility to perform fMRI during neurosurgical procedures in anesthetized patients. For that purpose, a passive stimulation paradigm with peripheral nerve stimulation was applied. A 1.5-T MR scanner placed in a radiofrequency-shielded operating room with an adapted operating table was used for intraoperative fMRI. The fMRI data were analyzed during acquisition by an online statistical evaluation package installed on the MR scanner console. In addition, phase reversal of somatosensory evoked potentials was used for verification of intraoperative fMRI. In four anesthetized patients with lesions in the vicinity of the central region a total of 11 fMRI measurements were successfully acquired and analyzed online. Activation was found in the somatosensory cortex, which could be confirmed by intraoperative phase reversal for each measurement. Furthermore, statistical parametric mapping (SPM) was employed for an extensive offline data analysis. We did not observe any neurological deterioration or complications due to the stimulation technique. Intraoperative fMRI is technically feasible allowing a real-time identification of eloquent brain areas despite brain shift.
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http://dx.doi.org/10.1016/j.neuroimage.2005.02.022DOI Listing
July 2005

Fusion of the cerebellar hemispheres ventral to the brainstem: a rare hindbrain-related malformation.

Childs Nerv Syst 2006 Jan 23;22(1):73-7. Epub 2004 Dec 23.

Department of Neurosurgery, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany.

Introduction: New variations of cerebellar malformations are being increasingly recognized using modern neuroimaging techniques. Until now only dorsal cerebellar fusion syndromes, such as the rhombencephalosynapsis and its variations have been recognized.

Case Report: We report on a 17-month-old male infant presenting with an exceptional hindbrain related malformation characterized by midline fusion of the cerebellar hemispheres ventral to the brainstem and causing symptoms due to brainstem compression.

Discussion And Conclusion: A more detailed understanding of the cerebellar embryogenesis is required to unravel the underlying mechanisms leading to this type of cerebellar malformation, which cannot easily be integrated into the common classification systems. Both the morphological features and the clinical presentation are different from those of other cerebellar structural abnormalities. If this type of congenital malformation is detected more frequently in the future, it seems reasonable that it should be added to the list of cerebellar malformations as a distinct type.
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http://dx.doi.org/10.1007/s00381-004-1065-5DOI Listing
January 2006

Clipping versus coiling: neuropsychological follow up after aneurysmal subarachnoid haemorrhage (SAH).

J Clin Exp Neuropsychol 2004 Nov;26(8):1081-92

Department of Neuropsychology, Institute of Cognitive Neuroscience, Ruhr-University Bochum, Germany.

Patients treated with microsurgical clipping of ruptured intracranial aneurysms often suffer from neuropsychological deficits in spite of a good neurological outcome. The purpose of this study was to explore if the deficits are related to the type of therapy. Two groups of 16 patients each suffering from aneurysmal SAH, matched for sex, age, aneurysm-site and Hunt and Hess score, and 16 control subjects were examined with a battery of neuropsychological tests including memory, attention, and executive function. Depression, mood, and quality of life were also assessed. One patient group had been treated with surgical clipping, the other with endovascular coiling. Both patient groups showed deficits in verbal and visual memory. Clipped patients were slightly more impaired than coiled patients, especially on measures of affect and on a self-assessment measure of executive function. The pattern of results suggests that the neuropsychological outcome after aneurysmal SAH is affected by both the severity of the bleeding and the type of therapy.
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http://dx.doi.org/10.1080/13803390490515342DOI Listing
November 2004

Spinal intradural juxtamedullary cysts in the adult: surgical management and outcome.

Neurosurgery 2004 Dec;55(6):1352-9; discussion 1359-60

Department of Neurosurgery, University Hospital Essen, Essen, Germany.

Objective: Intradural nonneoplastic cysts compressing the spinal cord are rare lesions. We retrospectively analyzed a series of patients harboring this entity with regard to clinical and radiological features, surgical management, and follow-up results.

Methods: In a retrospective study, we reviewed the medical charts, radiological investigations, and follow-up data of 11 women and 10 men (mean age, 43.6 yr) with intradural juxtamedullary spinal cysts, which were consecutively treated microsurgically at our institutions between January 1995 and January 2003. All lesions were approached via a laminectomy, hemilaminectomy, or laminoplasty at the corresponding vertebral levels and histopathologically verified. The patients were routinely scheduled for clinical follow-up 2 and 6 months after surgery. Baseline postoperative magnetic resonance imaging (MRI) was ordered 6 months after surgery. Thereafter, follow-up was performed at 1-year intervals, with neurological examination and MRI.

Results: According to presenting symptomatology, two main patient groups could be differentiated: one group with a myelopathic syndrome (10 patients) and another group with a predominant radicular pain syndrome (8 patients). Histopathological examination revealed 16 arachnoid cysts, 4 neuroepithelial cysts, and 1 cervical nerve root cyst. Most arachnoid cysts (12 cases) were located on the dorsal aspect of the thoracic spinal cord. The mean craniocaudal extension of these cysts was 3.7 vertebral levels, and complete resection was performed. In four patients, the arachnoid cyst was situated ventral to the spinal cord and involved up to 17 vertebral levels. These patients had a history of major spinal trauma, and the cyst was generously fenestrated at its greatest circumference as depicted on preoperative MRI scans. The four neuroepithelial cysts and the cervical nerve root cyst were located on the ventral or ventrolateral aspect of the spinal cord, and their maximum sagittal extension was two spinal vertebral levels. Symptoms in all but two patients demonstrated major improvement; in particular, radiating pain disappeared immediately after surgery. There was no cyst recurrence on MRI after a mean follow-up period of 3.2 years.

Conclusion: Intradural cysts should be considered in the differential diagnosis of lesions causing myelopathy and/or a radicular pain syndrome. Microsurgical resection or generous fenestration in cysts with large craniocaudal extensions effectively ameliorated patients' symptomatology. A description of the first documented case of a surgically treated intradural cervical nerve root cyst is provided.
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http://dx.doi.org/10.1227/01.neu.0000143031.98237.6dDOI Listing
December 2004

[Reduced contralateral preponderance of the movement-related potential during execution of self-initiated movements in acute prefrontal traumatic brain injury].

Psychiatr Prax 2004 Nov;31 Suppl 1:S47-9

Neurologische Klinik der Universität Duisburg-Essen.

Objectives: An enhanced ipsilateral motor potential after prefrontal TBI is known. Our aim was to examine, whether this contributes to movement initiation or execution.

Methods: EEGs of 22 patients and 28 healthy controls were recorded. Subjects performed self-initiated movements of their right index finger. From the resulting movement-related potentials difference curves of corresponding left and right hemispheric electrodes were calculated.

Results: We observed significantly reduced difference curves at parietal electrodes P3 - P4 in the patient group during movement execution, but not at movement initiation.

Conclusions: Our results point to compensatorily enhanced monitoring processes during movement execution following TBI. This is provided by enhanced activity of the ipsilateral postrolandic cortex, leading to the reduced preponderance observed in the present study.
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http://dx.doi.org/10.1055/s-2004-828430DOI Listing
November 2004

Recovery of movement-related potentials in the temporal course after prefrontal traumatic brain injury: a follow-up study.

Clin Neurophysiol 2004 Dec;115(12):2677-92

Department of Neurology, University of Duisburg-Essen, Hufelandstr. 55, 45122 Essen, Germany.

Objective: The movement-related potential (MRP) is an EEG measure related to self-initiated movements, consisting of the Bereitschaftspotential (BP), the negative slope, and the motor potential. Since in a former study the BP was reduced in acute prefrontal traumatic brain injury (TBI) patients, the present study examined the MRPs' course in follow-up examinations.

Methods: Right index finger MRPs of 22 patients with contusions of the prefrontal cortex were recorded 12, 26, and 52 weeks after TBI and compared to controls.

Results: Within the patient group, a significant increase of the BP in the temporal course after TBI was observed. MRPs 12 and 26 weeks after TBI did not differ significantly from the control group. One year after TBI, significantly enhanced BPs were found.

Conclusions: In the temporal course after prefrontal TBI, a recovery of the initially reduced BP was observed. The enhanced BP areas 1 year after TBI might represent the need for increased cognitive resources during movement preparation, supporting a recovered, but less effective neuronal network.

Significance: The present study represents the first longitudinal follow-up study of MRPs after prefrontal brain lesion. The observed changes reflect the plastic capacity of the brain, reorganizing the neuronal network function.
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http://dx.doi.org/10.1016/j.clinph.2004.06.015DOI Listing
December 2004

Reconstruction of the laminar roof with miniplates for a posterior approach in intraspinal surgery: technical considerations and critical evaluation of follow-up results.

Spine (Phila Pa 1976) 2004 Aug;29(16):E333-42

Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Essen (UKE), and the Department of Neurosurgery, University of Essen, Essen, Germany.

Study Design: A retrospective clinical follow-up study of patients who underwent intraspinal surgery with reconstruction of the laminar roof using titanium miniplates.

Objective: To evaluate the surgical technique of laminar roof reconstruction and to analyze follow-up results with regard to bony healing of the laminae and the development of spinal deformities.

Summary And Background Data: The reconstruction of the laminar roof was initially proposed to overcome adverse effects associated with extensive cervical laminectomy in children. Because technical evolutions such as the use of an air drill and miniplates have facilitated the procedure, it has gained more widespread use as a posterior approach for intraspinal surgery. Thus, with a sufficient number of patients treated and a longer period of follow up, it seems reasonable to critically evaluate the technique and its suitability as a standard approach for intraspinal surgery.

Methods: The surgical procedures of 79 patient who underwent intraspinal surgery with osteotomy and reconstruction of a total of 323 spinal laminae using an air drill and miniplates were analyzed. In 59 patients, data of a complete clinical and radiologic follow-up examination were evaluated. Plain radiographs and computed tomography scans were analyzed for bony healing of the laminae and spinal alignment.

Results: Minor complications such as cerebrospinal fluid collections and disturbed wound healing occurred within normal ranges. The was no case of dural, nerve root, or spinal cord injury attributable to laminotomy or laminar reconstruction. Eight (14.3%) patients complained of moderate to severe local pain at the time of follow-up examination and 8 patients stated impaired mobility of their spine at the surgical site. Bony healing was confirmed radiologically in 86.1% of the laminae. In 12 patients, a preexisting spinal deformity worsened after surgery and five patients demonstrated a new spinal malalignment. No patient required additional surgery because of progressive spinal deformity. Intramedullary location of the lesion and cervical location of surgery were significantly associated with the development of spinal malalignment, whereas incomplete bony healing of the laminae was not.

Conclusions: The reconstruction of the laminar roof using the technique described is safe, well suitable to serve as a standard posterior approach to intraspinal pathologies, and offers distinct advantages over laminectomy. However, some patients, particularly those with intramedullary cervical lesions, could develop spinal malalignment after surgery despite reconstruction of the laminar roof and sufficient bony healing of the laminae.
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http://dx.doi.org/10.1097/01.brs.0000134592.07941.5eDOI Listing
August 2004

Tentorial meningiomas: clinical results in 81 patients treated microsurgically.

Neurosurgery 2004 Jul;55(1):108-16; discussion 116-8

Department of Neurosurgery, University Hospital Essen, Essen, Germany.

Objective: Even during the microsurgical era, tentorial meningiomas present a formidable surgical challenge when tumor involves critical neurovascular structures. We report our experience with tentorial meningioma with regard to clinical presentation, diagnostic workup, microsurgical technique, complications, and follow-up results.

Methods: In a retrospective study, we reviewed the medical charts, neuroimaging data, and follow-up data of patients treated microsurgically for tentorial meningioma in our department between January 1989 and June 2002. Patients were routinely scheduled for clinical and radiological follow-up 6 months and 1 year after surgery. Thereafter, follow-up was performed every 1 or 2 years on the basis of the results of each follow-up examination.

Results: The main presenting symptoms of the patients (69 women and 12 men) were headache (75%), dizziness (49%), and gait disturbance (46%). The leading neurological signs were gait ataxia (52%) and cranial nerve deficits (28%). Extent of tumor resection was Simpson Grade I in 29 patients, Grade II in 45 patients, Grade III in 1 patient, Grade IV in 4 patients, and unknown in 2 patients. Permanent surgical morbidity and mortality were 19.8 and 2.5%, respectively. Clinical and magnetic resonance imaging follow-up was available in 74 patients for a period ranging from 1 to 13 years (mean, 5.9 yr). Of these, 64 patients (86%) have resumed normal life activity. Seven patients had tumor recurrence and four underwent reoperation.

Conclusion: Careful preoperative planning of the surgical approach tailored to tumor location and extent is a prerequisite to achieve radical microsurgical tumor resection with minimal morbidity and mortality. Resection of an infiltrated but patent venous sinus is not recommended.
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http://dx.doi.org/10.1227/01.neu.0000126886.48372.49DOI Listing
July 2004

Meningiomas of the posterior petrous bone: functional outcome after microsurgery.

J Neurosurg 2004 Jun;100(6):1014-24

Department of Neurosurgery, University Hospital Essen, Germany.

Object: The aim of this study was to analyze a subgroup of patients harboring cerebellopontine angle meningiomas originating from the posterior petrous bone in regard to clinical presentation, surgical anatomy, complications, and long-term functional postoperative results.

Methods: Data in a series of 51 patients with meningiomas of the posterior petrous bone who had undergone microsurgical treatment at the authors' institution between 1989 and 2002 were retrospectively reviewed. The patient population consisted of 46 women and five men with a mean age of 53 years (range 22-70 years). The main symptom on first admission was impaired hearing in 41%, dizziness in 20%, and tinnitus in 18% of the patients. Results of physical examination and audiological testing revealed hypacusis in 65% of patients, cerebellar ataxia in 31%, and impairment of the fifth cranial nerve in 26%. All patients underwent surgical treatment via a lateral suboccipital approach. Intraoperatively, the tumor was found to be attached to the postmeatal dura in 37%, the premeatal dura in 27.5%, the suprameatal dura in 19.6%, the inframeatal dura in 7.8%, and centered on the porus acusticus in 5.9% of cases. Tumor extension into the internal acoustic meatus was present in seven patients. Tumor resection was categorized as Grade I in 14 patients, Grade II in 29, Grade III in six, and Grade IV in two patients, according to the Simpson classification system. The site of displacement of the cranial nerves was predictable in up to 84% of patients, depending on the dural origin of the tumor as depicted on preoperative magnetic resonance (MR) imaging studies. Postoperatively, a new and permanent facial paresis was observed in five patients (9.8%). In 38 patients in whom both pre- and postoperative audiological data were available, hearing function deteriorated after surgery in 18.4% and improved in 7.9%. Clinical and MR imaging postsurgical data from a mean period of 5.8 years (range 13 months-13 years) were available in all patients. Forty-four patients (86%) resumed normal daily activity. Tumor recurrence was observed in two patients (3.9%), and both underwent a second surgery.

Conclusions: Preoperative detailed analysis of MR imaging data gives the surgeon a clue about the dislocation of critical neurovascular structures, particularly the cranial nerves. Nonetheless, the exact relationship of the cranial nerves to the tumor (dislocation, adherence, infiltration, and splaying of nerves) can only be fully appreciated during surgery.
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http://dx.doi.org/10.3171/jns.2004.100.6.1014DOI Listing
June 2004

Impaired movement-related potentials in acute frontal traumatic brain injury.

Clin Neurophysiol 2004 Feb;115(2):289-98

Department of Neurology, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany.

Objective: Focal brain lesions due to traumatic brain injury (TBI) do not only lead to functional deficits in the lesion area, but also disturb the structurally intact neuronal network connected to the lesion site. Therefore we hypothesized dysfunctions of the cortical motor network after frontal TBI. The movement related potential (MRP) is an EEG component related to voluntary movement consisting of the Bereitschaftspotential (BP), the negative slope (NS), and the motor potential (MP). The aim of our study was to demonstrate alterations in the movement related cortical network in the acute stage after TBI by comparing our patients' MRPs to those of a healthy control group.

Methods: EEGs of 22 patients with magnetic resonance imaging defined contusions of the prefrontal cortex were recorded within 8 weeks after TBI. We further recruited a healthy control group. The paradigm consisted of self-paced abductions of the right index finger.

Results: Compared to healthy controls, the BP in the patient group was significantly reduced and its onset delayed. Moreover, an enhanced contribution of the postrolandic hemisphere ipsilateral to the movement and a reduced contribution of the left frontal cortex, ipsilateral to the lesion in the majority of the patients, were observed during motor execution (MP).

Conclusions: Anatomical connections between the prefrontal cortex and the supplementary motor area (SMA) are known to exist. We suggest that prefrontal lesions lead to reduced neuronal input into the SMA. This deficit in the preparatory motor network may cause the reduced BPs in our patients. Moreover, an increased need for attentional resources might explain the enhanced motor potentials during movement execution. In conclusion, we demonstrated altered MRPs in the acute stage after frontal TBI, which are a consequence of disturbed neuronal networks involved in the preparation and execution of voluntary movements.
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http://dx.doi.org/10.1016/s1388-2457(03)00348-1DOI Listing
February 2004

Double-stent method: therapeutic alternative for small wide-necked aneurysms. Technical note.

J Neurosurg 2004 Jan;100(1):150-4

Department of Neuroradiology, Institute of Diagnostic and Interventional Radiology, University of Essen Medical School, Essen, Germany.

The authors present two cases of patients with small, acutely ruptured, wide-necked aneurysms of the distal vertebral artery that were not amenable to conventional coil embolization and were instead treated by means of a double-stent method in which one stent was placed inside another. Angiography performed immediately after the procedure revealed a significant reduction in aneurysm filling; total occlusion of the lesion was observed after 7 days and confirmed 6 months later in both aneurysms. By placing one stent inside the other, stent permeability can be reduced, which may result in significant hemodynamic changes with accelerated aneurysm thrombosis. This double-stent method may represent a therapeutic alternative, especially in cases of small, wide-necked aneurysms in which conventional endovascular techniques or stent-supported coil embolization is not considered feasible or is believed to be too dangerous, and surgical treatment is contra-indicated.
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http://dx.doi.org/10.3171/jns.2004.100.1.0150DOI Listing
January 2004
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