Publications by authors named "Michael Link"

451 Publications

Long-term surgical outcomes of intracranial epidermoid tumors: impact of extent of resection on recurrence and functional outcomes in 63 patients.

J Neurosurg 2021 Oct 15:1-9. Epub 2021 Oct 15.

Departments of1Neurologic Surgery and.

Objective: The authors' objective was to reevaluate the role of microsurgery for epidermoid tumors by examining the associations between extent of resection (EOR), tumor control, and clinical outcomes.

Methods: This was a retrospective study of patients with microsurgically treated intracranial epidermoid tumors. The recurrence-free and intervention-free rates were calculated using the Kaplan-Meier method. EOR was graded as gross-total resection (GTR) (total resection without residual on MRI), near-total resection (NTR) (a cyst lining was left in place), subtotal resection (STR) (> 90% resection), and partial resection (PR) (any other suboptimal resection) and used to stratify outcomes.

Results: Sixty-three patients with mean clinical and radiological follow-up periods of 87.3 and 81.8 months, respectively, were included. Sixteen patients underwent second resections, and 5 underwent third resections. The rates of GTR/NTR, STR, and PR were 43%, 35%, and 22%, respectively, for the initial resections; 44%, 13%, and 44% for the second resections; and 40%, 0%, and 60% for the third resections (p < 0.001). The 5- and 10-year cumulative recurrence-free rates after initial resection were 64% and 32%, respectively. When stratified according to EOR, the 10-year recurrence-free rate after GTR/NTR was marginally better than that after STR (61% vs 35%, p = 0.130) and significantly better than that after PR (61% vs 0%, p < 0.001). The recurrence-free rates after initial microsurgery were marginally better than those after second surgery (p = 0.102) and third surgery (p = 0.065). The 5- and 10-year cumulative intervention-free rates after initial resection were 91% and 58%, respectively. When stratified according to EOR, the 10-year intervention-free rate after GTR/NTR was significantly better than that after STR (100% vs 51%, p = 0.022) and PR (100% vs 27%, p < 0.001). The 5-year intervention-free rate after initial surgery was marginally better than that after second surgery (52%, p = 0.088) and significantly better than that after third surgery (0%, p = 0.004). After initial, second, and third resections, permanent neurological complications were observed in 6 (10%), 1 (6%), and 1 (20%) patients, respectively. At the last follow-up visit, 82%, 23%, and 7% of patients were free from radiological recurrence after GTR/NTR, STR, and PR as the initial surgical procedure, respectively.

Conclusions: GTR/NTR seems to contribute to better disease control without significantly impairing functional status. Initial resection offers the best chance to achieve better EOR, leading to better disease control.
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http://dx.doi.org/10.3171/2021.5.JNS21650DOI Listing
October 2021

Defining clinically significant tumor size in vestibular schwannoma to inform timing of microsurgery during wait-and-scan management: moving beyond minimum detectable growth.

J Neurosurg 2021 Oct 15:1-9. Epub 2021 Oct 15.

1Department of Otolaryngology-Head and Neck Surgery.

Objective: Detection of vestibular schwannoma (VS) growth during observation leads to definitive treatment at most centers globally. Although ≥ 2 mm represents an established benchmark of tumor growth on serial MRI studies, 2 mm of linear tumor growth is unlikely to significantly alter microsurgical outcomes. The objective of the current work was to ascertain where the magnitude of change in clinical outcome is the greatest based on size.

Methods: A single-institution retrospective review of a consecutive series of patients with sporadic VS who underwent microsurgical resection between January 2000 and May 2020 was performed. Preoperative tumor size cutpoints were defined in 1-mm increments and used to identify optimal size thresholds for three primary outcomes: 1) the ability to achieve gross-total resection (GTR); 2) maintenance of normal House-Brackmann (HB) grade I facial nerve function; and 3) preservation of serviceable hearing (American Academy of Otolaryngology-Head and Neck Surgery class A/B). Optimal size thresholds were obtained by maximizing c-indices from logistic regression models.

Results: Of 603 patients meeting inclusion criteria, 502 (83%) had tumors with cerebellopontine angle (CPA) extension. CPA tumor size was significantly associated with achieving GTR, postoperative HB grade I facial nerve function, and maintenance of serviceable hearing (all p < 0.001). The optimal tumor size threshold to distinguish between GTR and less than GTR was 17 mm of CPA extension (c-index 0.73). In the immediate postoperative period, the size threshold between HB grade I and HB grade > I was 17 mm of CPA extension (c-index 0.65). At the most recent evaluation, the size threshold between HB grade I and HB grade > I was 23 mm (c-index 0.68) and between class A/B and C/D hearing was 18 mm (c-index 0.68). Tumors within 3 mm of the 17-mm CPA threshold displayed similarly strong c-indices. Among purely intracanalicular tumors, linear size was not found to portend worse outcomes for all measures.

Conclusions: The probability of incurring less optimal microsurgical outcomes begins to significantly increase at 14-20 mm of CPA extension. Although many factors ultimately influence decision-making, when considering timing of microsurgical resection, using a size threshold range as depicted in this study offers an evidence-based approach that moves beyond reflexively recommending treatment for all tumors after detecting ≥ 2 mm of tumor growth on serial MRI studies.
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http://dx.doi.org/10.3171/2021.4.JNS21465DOI Listing
October 2021

Detection of Asymptomatic Radiation Induced Optic Neuropathy with Optical Coherence Tomography.

Neuroophthalmology 2021 3;45(5):339-342. Epub 2021 May 3.

Mayo Clinic Alix School of Medicine, Rochester, Minnesota, USA.

Radiation-induced optic neuropathy is a rare complication of radiation therapy that often results in profound, irreversible vision loss. We present a unique case of a patient in whom optical coherence tomography detected an early underlying optic neuropathy despite being visually asymptomatic in the affected eye.
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http://dx.doi.org/10.1080/01658107.2020.1871031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8409771PMC
May 2021

Microsurgical Resection of a Petroclival Epidermoid Cyst Using an Anterior Petrosectomy Approach: 2-Dimensional Operative Video.

Oper Neurosurg (Hagerstown) 2021 Sep 24. Epub 2021 Sep 24.

Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota, USA.

Epidermoid cysts are rare, benign lesions that result from inclusion of ectodermal elements during neural tube closure.1 Cysts are composed of desquamated epithelial cells and restrict diffusion on magnetic resonance imaging (MRI).2,3 Symptoms are attributable to anatomic location.4,5 In this video, we illustrate the surgical treatment of an epidermoid cyst located in the right cerebellopontine angle, petrous apex, and Meckel's cave. The patient, a 33-yr-old female with right-sided V1 trigeminal hypoesthesia, underwent surveillance imaging for 2 yr. However, she developed progressive V1 and V2 trigeminal hypoesthesia and imaging revealed enlargement of the lesion. Therefore, surgical resection was pursued. The patient consented to the procedure. The patient underwent a right middle fossa craniotomy and anterior petrosectomy. After identifying the greater superficial petrosal nerve and cutting the middle meningeal artery as it exited foramen spinosum, Kawase's triangle was drilled, and the dura over Meckel's cave and the subtemporal dura were opened. The lesion was resected, taking care to preserve the trigeminal nerve and the basilar artery. A retrosigmoid craniotomy was then fashioned. The cyst and its capsule were dissected off the brainstem and cranial nerves utilizing natural corridors between the trigeminal and vestibulocochlear nerves as well as between the facial and lower cranial nerves. Gross total resection was confirmed on postoperative MRI, and she was discharged home on postoperative day 5. Three months after surgery, she underwent formal pinprick testing, which revealed 95% loss of sensation in V1, 20% loss in V2, and normal sensation in V3. Three-month postoperative MRI showed no residual tumor.
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http://dx.doi.org/10.1093/ons/opab364DOI Listing
September 2021

Intraoperative lateral rectus electromyographic recordings optimized by deep intraorbital needle electrodes.

Clin Neurophysiol 2021 Oct 12;132(10):2510-2518. Epub 2021 Aug 12.

Department of Neurology, Mayo Clinic, 200 First St SW, Rochester, MN 55902, USA. Electronic address:

Objective: We demonstrate the advantages and safety of long, intraorbitally-placed needle electrodes, compared to standard-length subdermal electrodes, when recording lateral rectus electromyography (EMG) during intracranial surgeries.

Methods: Insulated 25 mm and uninsulated 13 mm needle electrodes, aimed at the lateral rectus muscle, were placed in parallel during 10 intracranial surgeries, examining spontaneous and stimulation-induced EMG activities. Postoperative complications in these patients were reviewed, alongside additional patients who underwent long electrode placement in the lateral rectus.

Results: In 40 stimulation-induced recordings from 10 patients, the 25 mm electrodes recorded 6- to 26-fold greater amplitude EMG waveforms than the 13 mm electrodes. The 13 mm electrodes detected greater unwanted volume conduction upon facial nerve stimulation, typically exceeding the amplitude of abducens nerve stimulation. Except for one case with lateral canthus ecchymosis, no clinical or radiographic complications occurred in 36 patients (41 lateral rectus muscles) following needle placement.

Conclusions: Intramuscular recordings from long electrode in the lateral rectus offers more reliable EMG monitoring than 13 mm needles, with excellent discrimination between abducens and facial nerve stimulations, and without significant complications from needle placement.

Significance: Long intramuscular electrode within the orbit for lateral rectus EMG recording is practical and reliable for abducens nerve monitoring.
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http://dx.doi.org/10.1016/j.clinph.2021.08.002DOI Listing
October 2021

Salvage Radiosurgery for Optic Nerve Sheath Meningioma.

Cureus 2021 Jul 18;13(7):e16450. Epub 2021 Jul 18.

Neurological Surgery, Mayo Clinic, Rochester, USA.

Optic nerve sheath meningiomas (ONSMs) are rare and benign tumors that affect the optic nerve. Although surgical decompression may be used for large tumors that cause mass effect on the surrounding structures, the mainstay of treatment is radiotherapy. We report the case of a 54-year-old female patient who presented with progressive vision loss due to a recurrent right ONSM despite fractionated radiotherapy eight years prior and the subsequent interval regression of the tumor. The optical coherence tomography at the time of recurrence revealed thinning of the right retinal nerve fiber layer. She underwent salvage stereotactic radiosurgery using a marginal dose of 15 Gy. At six months post-radiosurgery, the patient had a dramatic improvement in visual acuity and visual fields despite persistent thinning of the retinal nerve fiber layer. This case illustrates how salvage radiosurgery can be a useful treatment modality in these challenging situations. This tumor's exophytic growth and the steep dose fall-off of Gamma Knife radiosurgery might favorably affect visual recovery. However, the outcomes of single-session radiosurgery for ONSMs should be further evaluated.
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http://dx.doi.org/10.7759/cureus.16450DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8369972PMC
July 2021

Measuring Photodissociation Product Quantum Yields Using Chemical Ionization Mass Spectrometry: A Case Study with Ketones.

J Phys Chem A 2021 Aug 29;125(31):6836-6844. Epub 2021 Jul 29.

Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States.

Measurements of photolysis quantum yields are challenging because of the difficulties in measuring the first-generation photodissociation products, interference from other products or contaminants, sufficient photon fluxes and/or low absorption cross sections of the photolyte to make detectable amounts of products, and quantification of the photon flux. In the case of acetone (and other atmospherically relevant ketones) the uncertainty in the photolysis quantum yield creates uncertainty in the calculated OH radical and acyl peroxy nitrate production in the atmosphere. We present a new method for determining photodissociation product quantum yields by measuring acyl peroxy radicals (RC(O)O) produced in the photolysis of ketones in air using chemical ionization mass spectrometry (CIMS). We show good agreement of our CIMS method with previously published quantum yields of the acyl radical from photolysis of biacetyl and methyl ethyl ketone (MEK) at 254 nm. Additionally, we highlight the capabilities of this CIMS method through the measurement of photolysis branching ratios for MEK. We suggest future applications of CIMS (in the laboratory and field) to measure RC(O)O and associated photolysis processes.
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http://dx.doi.org/10.1021/acs.jpca.1c03140DOI Listing
August 2021

Foundations of Advanced Neuroanatomy: Technical Guidelines for Specimen Preparation, Dissection, and 3D-Photodocumentation in a Surgical Anatomy Laboratory.

J Neurol Surg B Skull Base 2021 Jul 28;82(Suppl 3):e248-e258. Epub 2019 Nov 28.

Department of Neurosurgery, Albany Medical Center, Albany, New York, United States.

 This study was aimed to provide a key update to the seminal works of Prof. Albert L. Rhoton Jr., MD, with particular attention to previously unpublished insights from the oral tradition of his fellows, recent technological advances including endoscopy, and high-dynamic range (HDR) photodocumentation, and, local improvements in technique, we have developed to optimize efficient neuroanatomic study.  Two formaldehyde-fixed cadaveric heads were injected with colored latex to demonstrate step-by-step specimen preparation for microscopic or endoscopic dissection. One formaldehyde-fixed brain was utilized to demonstrate optimal three-dimensional (3D) photodocumentation techniques.  Key steps of specimen preparation include vessel cannulation and securing, serial tap water flushing, specimen drainage, vessel injection with optimized and color-augmented latex material, and storage in 70% ethanol. Optimizations for photodocumentation included the incorporation of dry black drop cloth and covering materials, an imaging-oriented approach to specimen positioning and illumination, and single-camera stereoscopic capture techniques, emphasizing the three-exposure-times-per-eye approach to generating images for HDR postprocessing. Recommended tools, materials, and technical nuances were emphasized throughout. Relative advantages and limitations of major 3D projection systems were comparatively assessed, with sensitivity to audience size and purpose specific recommendations.  We describe the first consolidated step-by-step approach to advanced neuroanatomy, including specimen preparation, dissection, and 3D photodocumentation, supplemented by previously unpublished insights from the Rhoton fellowship experience and lessons learned in our laboratories in the past years such that Prof. Rhoton's model can be realized, reproduced, and expanded upon in surgical neuroanatomy laboratories worldwide.
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http://dx.doi.org/10.1055/s-0039-3399590DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8289531PMC
July 2021

Delaying Postoperative Radiotherapy in Low-Grade Esthesioneuroblastoma: Is It Worth the Wait?

J Neurol Surg B Skull Base 2021 Jul 25;82(Suppl 3):e166-e171. Epub 2020 Mar 25.

Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, United States.

 Consensus in timing of radiotherapy is yet to be established in esthesioneuroblastoma (ENB).  This study was aimed to investigate if planned adjuvant radiotherapy improves tumor control after complete margin negative resection of low Hyams' grade (1 or 2) ENB.  A retrospective review of patients with pathologically confirmed negative margin resection of Kadish's stage B or C and Hyams' grade 1 and 2 ENBs was conducted. Seventeen patients meeting the criteria were divided into the following two groups for cohort study: (1) those who underwent planned immediate postoperative adjuvant radiotherapy (IR group) and (2) those who did not (delayed radiotherapy [DR] group).  The IR group included nine patients (Kadish's stage B in one and stage C in eight; Hyams' grade 1 in two and grade 2 in seven). Mean follow-up was 140.8 months. Seven patients (78%) had disease progression (DP) at a median of 88 months (four with cervical lymph node metastasis [CLNM], one with distant metastasis, and two with both local recurrence and CLNM). One patient experienced frontal lobe abscess. The DR group included eight patients (Kadish's stage B in six and stage C in two; all Hyams' grade 2). Mean follow-up was 123.3 months. Four (50%) patients who developed DP (all local recurrence) were salvaged with surgery and adjuvant radiotherapy at a median of 37.5 months. There was no statistically significant difference in DP rate (  = 0.23), time to DP (  = 0.26), or the local tumor control rate (  = 0.23).  In our limited cohort, immediate postoperative radiotherapy did not demonstrate superiority in tumor control, although risk of radiotherapy toxicity appears low.
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http://dx.doi.org/10.1055/s-0040-1708854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8289555PMC
July 2021

Sinonasal Osteosarcoma: Report of 14 New Cases and Systematic Review of the Literature.

J Neurol Surg B Skull Base 2021 Jul 24;82(Suppl 3):e138-e147. Epub 2020 Jan 24.

Department of Otolaryngology-Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota, United States.

 The objective of this study is to describe the clinical presentation, tumor characteristics, natural history, and treatment patterns of sinonasal osteosarcoma.  Fourteen patients who had been treated for osteosarcoma of the nasal cavity and paranasal sinuses at a tertiary care center were reviewed. In addition, a systematic review of the literature for osteosarcoma of the sinonasal cavity was performed.  In a systematic review, including 14 patients from the authors' institution, 53 total studies including 88 patients were assessed. Median follow-up was 18 months (interquartile range: 8-39 months). The most common presenting symptoms were facial mass or swelling (34%), and nasal obstruction (30%). The most common paranasal sinus involved by tumor was the maxillary sinus (64%), followed by the ethmoid sinuses (52%). The orbit (33%), dura (13%) and infratemporal fossa (10%) were the most common sites of local invasion. The majority of patients underwent surgery followed by adjuvant therapy (52.4%). Increasing age was associated with decreased overall survival rate (unit risk ratio [95% confidence interval (CI)] = 1.02 [1.003-1.043];  = 0.0216) and T4 disease was associated with decreased disease-specific survival rate (hazard ratio [HR] = 2.87;  = 0.0495). The 2- and 5-year overall survival rates were 68 and 40%, respectively, while 2- and 5-year disease-specific survival rates were 71% and 44%, respectively.  Sinonasal osteosarcomas are uncommon tumors and can pose a significant therapeutic challenge. Increasing age and T4 disease are associated with worse prognosis. This disease usually warrants consultation by a multidisciplinary team and consideration of multimodality therapy.
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http://dx.doi.org/10.1055/s-0040-1701221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8289535PMC
July 2021

Induction Therapy Prior to Surgical Resection for Patients Presenting with Locally Advanced Esthesioneuroblastoma.

J Neurol Surg B Skull Base 2021 Jul 14;82(Suppl 3):e131-e137. Epub 2020 Jan 14.

Department of Otolaryngology Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota, United States.

Esthesioneuroblastoma (ENB) is a rare olfactory malignancy that can present with locally advanced disease. At our institution, patients with ENB in whom the treating surgeon believes that a margin-negative resection is initially not achievable are selected to undergo induction with chemotherapy with or without radiotherapy prior to surgery. In a retrospective review of 61 patient records, we identified six patients (10%) treated with this approach. Five of six patients (83%) went on to definitive surgery. Prior to surgery, three of five patients (60%) had a partial response after induction therapy, whereas two of five (40%) had stable disease. Microscopically margin-negative resection was achieved in four of five (80%) of the patients who went on to surgery, while one patient had negative margins on frozen section but microscopically positive margins on permanent section. Three of five patients (60%) recurred after surgery; two of these patients died with recurrent/metastatic ENB. In summary, induction therapy may facilitate margin-negative resection in locally advanced ENB. Given the apparent sensitivity of ENB to chemotherapy and radiotherapy, future prospective studies should investigate the optimal multidisciplinary approach to improve long-term survival in this rare disease.
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http://dx.doi.org/10.1055/s-0039-3402026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8289526PMC
July 2021

Vestibular Schwannomas. Reply.

N Engl J Med 2021 07;385(4):381-382

Mayo Clinic, Rochester, MN

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http://dx.doi.org/10.1056/NEJMc2108279DOI Listing
July 2021

Cochlear implantation after radiosurgery for vestibular schwannoma.

J Neurosurg 2021 07 24;135(1):126-135. Epub 2021 Jun 24.

1Department of Otolaryngology-Head and Neck Surgery, and.

Objective: The object of this study was to ascertain outcomes of cochlear implantation (CI) following stereotactic radiosurgery (SRS) for vestibular schwannoma (VS).

Methods: The authors conducted a retrospective chart review of adult patients with VS treated with SRS who underwent CI between 1990 and 2019 at a single tertiary care referral center. Patient demographics, tumor features, treatment parameters, and pre- and postimplantation audiometric and clinical outcomes are presented.

Results: Seventeen patients (18 ears) underwent SRS and ipsilateral CI during the study period. Thirteen patients (76%) had neurofibromatosis type 2 (NF2). Median age at SRS and CI were 44 and 48 years, respectively. Median time from SRS to CI was 60 days, but notably, 4 patients underwent SRS and CI within 1 day and 5 patients underwent CI more than 7 years after SRS. Median marginal dose was 13 Gy. Median treatment volume at the time of SRS was 1400 mm3 (range 84-6080 mm3, n = 15 patients). Median post-CI PTA was 28 dB HL, improved from 101 dB HL preoperatively (p < 0.001). Overall, 11 patients (12 ears) exhibited open-set speech understanding. Sentence testing was performed at a median of 10 months (range 1-143 months) post-CI. The median AzBio sentence score for patients with open-set speech understanding was 76% (range 19%-95%, n = 10 ears). Two ears exhibited Hearing in Noise Test (HINT) sentence scores of 49% and 95%, respectively. Four patients achieved environmental sound awareness without open-set speech recognition. Two had no detectable auditory percepts.

Conclusions: Most patients who underwent CI following SRS for VS enjoyed access to sound at near-normal levels, with the majority achieving good open-set speech understanding. Implantation can be performed immediately following SRS or in a delayed fashion, depending on hearing status as well as other factors. This strategy may be applied to cases of sporadic or NF2-associated VS.

Abbreviations: AAO-HNS = American Academy of Otolaryngology-Head and Neck Surgery; ABI = auditory brainstem implant; CI = cochlear implantation; CN = cranial nerve; CNC = consonant-nucleus-consonant; CPA = cerebellopontine angle; EPS = electrical promontory stimulation; ESA = environmental sound awareness; HINT = Hearing in Noise Test; IAC = internal auditory canal; NF2 = neurofibromatosis type 2; OSP = open-set speech perception; PTA = pure tone average; SRS = stereotactic radiosurgery; VS = vestibular schwannoma; WRS = word recognition score.
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http://dx.doi.org/10.3171/2020.4.JNS201069DOI Listing
July 2021

Clinical utility of brain biopsy for presumed CNS relapse of systemic lymphoma.

J Neurosurg 2021 Jul 2:1-10. Epub 2021 Jul 2.

1Department of Neurosurgery and.

Objective: The objective of this study was to determine the frequency with which brain biopsy for presumed CNS relapse of systemic hematological malignancies yields new, actionable diagnostic information. Hematological malignancies represent a disparate group of genetic and histopathological disorders. Proclivity for brain involvement is dependent on the unique entity and may occur synchronously or metasynchronously with the systemic lesion. Diffuse large B-cell lymphomas (DLBCLs) have a high propensity for brain involvement. Patients in remission from systemic DLBCL may present with a lesion suspicious for brain relapse. These patients often undergo brain biopsy. The authors' a priori hypothesis was that brain biopsy in patients with a history of systemic DLBCL and a new brain MRI lesion would have lower diagnostic utility compared with patients with non-DLBCL systemic malignancies.

Methods: The authors performed a retrospective review of patients who underwent brain biopsy between 2000 and 2019. Inclusion criteria were patients ≥ 18 years of age with a prior systemic hematological malignancy in remission presenting with a new brain MRI lesion concerning for CNS relapse. Patients with a history of any CNS neoplasms, demyelinating disorders, or active systemic disease were excluded. The main outcome was the proportion of patients with a distinct histopathological brain diagnosis compared with the systemic malignancy. The authors secondarily assessed overall survival, procedure-related morbidity, and 30-day mortality.

Results: Sixty patients met inclusion criteria (40 males and 20 females); the median age at brain biopsy was 67 years (range 23-88 years). The median follow-up was 8.5 months (range 0.1-231 months). Thirty-nine (65.0%) patients had DLBCL and 21 (35%) had non-DLBCL malignancies. Thirty-five of 36 (97.2%) patients with prior systemic DLBCL and a diagnostic biopsy had histopathological confirmation of the original systemic disease versus 0 of 21 patients with non-DLBCL systemic malignancies (p < 0.001). Morbidity and 30-day mortality were 8.3% and 10.0%, respectively; 2 of 6 30-day mortalities were directly attributable to the biopsy. The median overall survival following brain biopsy was 10.8 months.

Conclusions: Patients with a history of systemic DLBCL and presumed CNS relapse gained minimal clinical benefit from brain biopsy but were at high risk of morbidity and mortality. In patients with a history of non-DLBCL systemic malignancies, brain biopsy remained critical given the high likelihood for discovery of distinct diagnostic entities. It was determined that patients with a prior systemic DLBCL and presumed brain relapse should likely receive empirical therapy obviating treatment delay and the risks of brain biopsy.
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http://dx.doi.org/10.3171/2020.12.JNS202517DOI Listing
July 2021

Natural History of Growing Sporadic Vestibular Schwannomas During Observation: An International Multi-Institutional Study.

Otol Neurotol 2021 09;42(8):e1118-e1124

Department of Oto-rhinolaryngology-Head and Neck Surgery, and Audiology Copenhagen University Hospital Rigshospitalet.

Objective: Active treatment of small- or medium-sized vestibular schwannoma during wait-and-scan management is currently recommended at most centers globally once growth is detected. The primary aim of the current study was to characterize the natural history of growing sporadic vestibular schwannoma during observation.

Study Design: Cohort study.

Setting: Four tertiary referral centers across the United States and Denmark.

Patients: Patients with two prior MRI scans demonstrating ≥2 mm of linear growth who continued observational management.

Intervention: Observation with serial imaging.

Main Outcome Measure: Subsequent linear growth-free survival (i.e., an additional ≥2 mm of growth) following initial growth of ≥2 mm from tumor size at diagnosis.

Results: Among 3,402 patients undergoing observation, 592 met inclusion criteria. Median age at initial growth was 66 years (IQR 59-73) for intracanalicular tumors (N = 65) and 62 years (IQR 54-70) for tumors with cerebellopontine angle extension (N = 527). The median duration of MRI surveillance following initial detection of tumor growth was 5.2 years (IQR 2.4-6.9) for intracanalicular tumors and 1.0 year (IQR 1.0-3.3) for cerebellopontine angle tumors. For intracanalicular tumors, subsequent growth-free survival rates (95% CI; number still at risk) at 1, 2, 3, 4, and 5 years following the initial MRI that demonstrated growth were 77% (67-88; 49), 53% (42-67; 31), 46% (35-60; 23), 34% (24-49; 17), and 32% (22-47; 13), respectively. For cerebellopontine angle tumors, subsequent growth-free survival rates were 72% (68-76; 450), 47% (42-52; 258), 32% (28-38; 139), 26% (21-31; 82), and 22% (18-28; 57), respectively. For every 1 mm increase in magnitude of growth from diagnosis to tumor size at detection of initial growth, the HRs associated with subsequent growth were 1.64 (95% CI 1.25-2.15; p < 0.001) for intracanalicular tumors and 1.08 (95% CI 1.01-1.15; p = 0.02) for cerebellopontine angle tumors.

Conclusions: Growth detected during observation does not necessarily portend future growth, especially for slowly growing tumors. Because early treatment does not confer improved long-term quality of life outcomes, toleration of some growth during observation is justifiable in appropriately selected cases.
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http://dx.doi.org/10.1097/MAO.0000000000003224DOI Listing
September 2021

Growth arrest of a refractory vestibular schwannoma after anti-PD-1 antibody treatment.

BMJ Case Rep 2021 May 27;14(5). Epub 2021 May 27.

Neurosurgery, Mayo Clinic, Rochester, Minnesota, USA.

A 25-year-old man presented with left-sided hearing loss, blurred vision and papilloedema. Imaging revealed a large, left-sided, contrast-enhancing cerebellopontine mass causing obstructive hydrocephalus, consistent with vestibular schwannoma (VS). Following an incomplete resection via retrosigmoid craniotomy at an outside facility, he was referred to our department, and cerebrospinal fluid diversion followed by repeat resection was recommended. A subtotal resection was achieved, and the patient was subsequently treated with adjuvant stereotactic radiosurgery (SRS). Progressive interval growth was observed on serial post-SRS MRI studies; correspondingly, at 31 months after treatment, the patient was initiated on antiprogrammed-death receptor 1 (PD-1) antibody treatment with pembrolizumab. Growth arrest was noted on subsequent serial imaging studies, which have been maintained for a total of 30 months since initiation of a 18-month anti-PD-1 course of therapy. Additional case accumulation and translational study is required to better characterise this therapeutic strategy; however, PD-1/programmed death-ligand 1 inhibition may offer a promising salvage therapy for refractory VS.
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http://dx.doi.org/10.1136/bcr-2021-241834DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8162073PMC
May 2021

Differential Impact of Advanced Age on Clinical Outcomes After Vestibular Schwannoma Resection in the Very Elderly: Cohort Study.

Oper Neurosurg (Hagerstown) 2021 08;21(3):104-110

Department of Neurosurgery, Mayo Clinic, Rochester, Minnesota.

Background: Vestibular schwannomas (VS) have a peak incidence in the sixth and seventh decades of life. Stereotactic radiosurgery is often the preferred treatment for VS among patients of advanced age. The fraction of elderly patients potentially requiring consideration for surgical treatment is anticipated to expand, mandating an update to management paradigms in this population.

Objective: To describe our experience with surgical management of VS in patients aged 75 yr and older.

Methods: Cohort study of all patients aged ≥75 yr with sporadic VS requiring surgical treatment at our institution between 1999 and 2020. Data included preoperative baseline characteristics and outcome data including extent of resection, facial nerve and hearing status, functional outcome, length of stay, and complications.

Results: A total of 24 patients were included, spanning an age range of 75 to 90 yr. Average tumor size was 2.76 ± 1.04 cm, and average baseline Modified 5-item Frailty Index (mFI-5) score was 1.08 ± 0.93. Extent of resection was gross total in 5 (20.8%), near total in 3 (12.5%), and sub-total resection in the remaining 16 (66.7%). One patient died in the postoperative period because of an acute sub-dural hematoma. Favorable facial nerve function (HB1-2) was preserved in 12 patients (75%) between 75 and 79 yr and 2 patients (28.6%) aged ≥ 80 yr. No cerebrospinal fluid leak or surgical site infection was observed; 3 patients developed hydrocephalus requiring ventriculo-peritoneal shunt placement. Nine patients required out-of-home disposition; all patients eventually returned to independent living.

Conclusion: Microsurgical resection of VS can be safely undertaken in patients greater than 75 y/o but may carry an increased risk of poor facial function.
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http://dx.doi.org/10.1093/ons/opab170DOI Listing
August 2021

Preoperative embolization of jugular paraganglioma tumors using particles is safe and effective.

Interv Neuroradiol 2021 May 26:15910199211019175. Epub 2021 May 26.

Department of Otolaryngology-Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota, United States.

Background: Jugular paragangliomas represent a surgical challenge due to their vascularity and proximity to vital neurovascular structures. Preoperative embolization aids in reducing intraoperative blood loss, transfusion requirements, and improves surgical visualization. Several embolization agents have been used.

Objective: The aim of this study is to evaluate the safety and efficacy of PVA in pre-operative embolization of jugular paragangliomas.

Methods: A retrospective review of all patients who underwent jugular paraganglioma resection with pre-operative embolization between 2000 and 2020 was performed. Pre-operative data including baseline patient and tumor characteristics were documented. Outcomes of preoperative embolization including extent of devascularization and post-embolization complications were recorded. Early and long-term postoperative outcomes were reported.

Results: Twenty-nine patients met study criteria with a median age of 38 years. Average tumor size was 3.4±1.8 cm. The most commonly encountered arterial feeder was the ascending pharyngeal artery followed by the posterior auricular artery. More than 50% reduction in tumor blush was achieved in 25 patients (86.2%). None of the patients experienced new or worsening cranial neuropathy following embolization. Gross total or Near total resection was achieved in 13 patients (44.8%). A STR or NTR was chosen in these patients to preserve cranial nerve function or large vessel integrity. Average intraoperative estimated blood loss was 888 ml, 9 patients (31%) required intra-operative transfusion of blood products. Extent of resection and post-operative complications did not correlate with extent of devascularization.

Conclusion: Pre-operative embolization of jugular paraganglioma tumors with PVA particles is an effective strategy with a high safety profile.
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http://dx.doi.org/10.1177/15910199211019175DOI Listing
May 2021

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Retrosigmoid Approach.

J Neurol Surg B Skull Base 2021 Jun 28;82(3):321-332. Epub 2019 Oct 28.

Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, United States.

 Neurosurgical anatomy is traditionally taught via anatomic and operative atlases; however, these resources present the skull base using views that emphasize three-dimensional (3D) relationships rather than operative perspectives, and are frequently written above a typical resident's understanding. Our objective is to describe, step-by-step, a retrosigmoid approach dissection, in a way that is educationally valuable for trainees at numerous levels.  Six sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A retrosigmoid was performed by each of three neurosurgery residents, under supervision by the senior authors (C.L.W.D. and M.J.L.) and a graduated skull base fellow, neurosurgeon, and neuroanatomist (M.P.C.). Dissections were supplemented with representative case applications.  The retrosigmoid craniotomy (aka lateral suboccipital approach) affords excellent access to cranial nerve (CN) IV to XII, with corresponding applicability to numerous posterior fossa operations. Key steps include positioning and skin incision, scalp and muscle flaps, burr hole and parasigmoid trough, craniotomy flap elevation, initial durotomy and deep cistern access, completion durotomy, and final exposure.  The retrosigmoid craniotomy is a workhorse skull base exposure, particularly for lesions located predominantly in the cerebellopontine angle. Operatively oriented neuroanatomy dissections provide trainees with a critical foundation for learning this fundamental skull base technique. We outline a comprehensive approach for neurosurgery residents to develop their familiarity with the retrosigmoid craniotomy in the cadaver laboratory in a way that simultaneously informs rapid learning in the operating room, and an understanding of its potential for wide clinical application to skull base diseases.
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http://dx.doi.org/10.1055/s-0039-1700513DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8133810PMC
June 2021
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