A clinical primer for the glymphatic system.

The complex and dynamic system of fluid flow through the perivascular and interstitial spaces of the CNS has new-found implications for neurological diseases. CSF movement throughout the CNS parenchyma is more dynamic than could be explained via passive diffusion mechanisms alone. Indeed, a semistructured glial-lymphatic (glymphatic) system of astrocyte-supported extracellular perivascular channels serves to directionally channel extracellular fluid, clearing metabolites and peptides to optimize neurological function. Clinical studies of the glymphatic network have to date proven challenging, with most data gleaned from rodent models and post-mortem investigations. However, increasing evidence suggests that disordered glymphatic function contributes to the pathophysiology of CNS ageing, neurodegenerative disease and CNS injuries, as well as normal pressure hydrocephalus. Unlocking such pathophysiology could provide important avenues towards novel therapeutics. We here provide a multidisciplinary overview of glymphatics and critically review accumulating evidence regarding its structure, function and hypothesized relevance to neurological disease. We highlight emerging technologies of relevance to the longitudinal evaluation of glymphatic function in health and disease. Finally, we discuss the translational opportunities and challenges of studying glymphatic science.

That which is unseen: 3D printing for pediatric cerebrovascular education.

INTRODUCTION: Pediatric cerebrovascular lesions are very rare and include aneurysms, arteriovenous malformations (AVM), and vein of Galen malformations (VOGM). OBJECTIVE: To describe and disseminate a validated, reproducible set of 3D models for optimization of neurosurgical training with respect to pediatric cerebrovascular diseases METHODS: All pediatric cerebrovascular lesions treated at our institution with adequate imaging studies during the study period 2015-2020 were reviewed by the study team. Three major diagnostic groups were identified: aneurysm, AVM, and VOGM. For each group, a case deemed highly illustrative of the core diagnostic and therapeutic principles was selected by the lead and senior investigators for printing (CSG/JM). Files for model reproduction and free distribution were prepared for inclusion as Supplemental Materials. RESULTS: Representative cases included a 7-month-old female with a giant left MCA aneurysm; a 3-day-old male with a large, complex, high-flow, choroidal-type VOGM, supplied from bilateral thalamic, choroidal, and pericallosal perforators, with drainage into a large prosencephalic vein; and a 7-year-old male with a left frontal AVM with one feeding arterial vessel from the anterior cerebral artery and one single draining vein into the superior sagittal sinus CONCLUSION: Pediatric cerebrovascular lesions are representative of rare but important neurosurgical diseases that require creative approaches for training optimization. As these lesions are quite rare, 3D-printed models and open source educational materials may provide a meaningful avenue for impactful clinical teaching with respect to a wide swath of uncommon or unusual neurosurgical diseases.

C1 lateral mass screw insertion using cannulated, navigated screws: preliminary results of a novel technique.

PURPOSE: The upper cervical spine region is densely populated by neural and vascular structures impeding the approach for fusion surgery. Technological advancement simplify the approach to C1-C2 fusion, thus reduce risks. The current paper purpose is to describe initial experience with a novel technique modification for C1 lateral screw insertion that incorporates cannulated-navigated screw system with intra-operative 3D imaging. METHODS: A single-center single surgeon database was reviewed to identify all patients who underwent placement of C1 lateral mass screw insertion using the novel technique modification described below, on 2020. This cohort was retrospectively analyzed and compared with a cohort of patients who were operated on by the same surgeon with non-cannulated, navigated screws with intra-operative 3D imaging (O-arm, Medtronic, USA) between 2011 and 2019. Following navigated starting hole and drilling of the C1 lateral mass, a blunt guide-wire is used to palpate the hole and cannulated screw is advanced to the correct position over the wire. After initial purchase, a navigated screw driver is used for final screw depth position. RESULTS: Twelve C1 lateral mass screws were inserted in six patients using this novel cannulated-navigated screw placement technique and compared to 24 patients operated using navigated non-cannulated screws. Minimal Estimated Blood Loss (EBL) was recorded in five of six cases undergoing the novel cannulated navigated placement of C1 lateral mass screws. Comparison to non-cannulated cohort demonstrated an EBL of 83CC vs. 354CC (Not significant). Mean surgery time was 97min and 118min for the cannulated-navigated and navigated only procedures (p = 0.03, statistically significant) respectively. In the current cohort, all screws were rated in optimal position and no repositioning procedures were performed. CONCLUSION: The new method presented allows for faster and possibly safer and more accurate C1 lateral mass screw insertion.

Presentation, imaging, patterns of care, growth, and outcome in sporadic and von Hippel-Lindau-associated central nervous system hemangioblastomas.

OBJECT: Hemangioblastoma is a relatively rare neoplasm occurring mostly in the cerebellum that may arise sporadically or in the context of von Hippel-Lindau (VHL) syndrome. Presentation, imaging, natural history, surgical patterns of care, and outcomes are incompletely defined for this uncommon lesion. We reviewed our large institutional series to help clarify these issues. METHODS: Retrospective analysis of consecutive, neurosurgically managed CNS hemangioblastomas at Mayo Clinic, 1988-2018. RESULTS: Two hundred and eighty five hemangioblastomas were treated in 184 unique patients (115 sporadic, 69 VHL). Compared to sporadic patients, VHL patients were younger (36.7 vs 51.7 years; p < 0.0001), were treated while asymptomatic more commonly (47.3 vs 4.2%; p < 0.0001), had smaller lesions (6.6 vs 13.9 mL; p < 0.0001), and harbored lesions with associated cysts less frequently (51.0 vs 75.0%; p = 0.0002). Macrocystic tumor architecture was associated with larger lesion size and greater symptom severity. Solid lesions later formed cysts at a median 130 months. Growth in both total volume and solid component accelerated after cyst formation (10.6 and 6.0 times median rate prior to cyst emergence). VHL patients died at a younger age (47.9 vs 74.5, p = 0.0017) and were more likely to die of direct disease sequelae. Though treatment-free survival time was significantly longer in sporadic cases, a substantial fraction (> 40%) developed tumor recurrence/progression requiring additional treatment. CONCLUSIONS: Hemangioblastoma presentation varies with etiology and clinical course is more complicated in VHL cases. Nodular lesions often develop cysts over time which is associated with accelerated tumor growth. Sporadic cases have a previously unappreciated but substantial risk of late recurrence/progression requiring treatment.

Histopathology and prognosis of germ cell tumors metastatic to brain: cohort study.

INTRODUCTION: Germ cell tumors (GCTs) are uncommon neoplasms predominantly arising in midline tissues. The prognostic significance of histopathology in predicting metastatic GCT behavior is poorly understood. METHODS: Multicenter international cohort study including 29 patients with GCTs metastatic to brain were retrospectively investigated (18 patients from Mayo Clinic and 11 patients from the intracranial germ cell tumor genome analysis consortium in Japan). Clinical characteristics were analyzed using the Chi-square test (two-tailed) for categorical variables and using the log-rank test for survival data. RESULTS: Median age at treatment was 31 years (range 14-58). Primary disease sites were testis (71%), mediastinum (18%), and female reproductive organs (11%). Median metastatic interval was 223 days (range, 6-6124). Median follow-up was 346 days (range, 1-5356), with 16 deaths (57%) occurring after the median overall survival of 455 days. Actuarial one-year survival was 51%; 12-of-16 deaths (75%) were attributed to intracranial disease. Appearance of the same GCT subtype at the metastatic site as the primary was high for non-seminomatous GCT (NSGCT, 64-100%), but low for seminoma/dysgerminoma and mature teratoma (MT, 14, 17%, respectively). Gain of a new component was seen in 4 (20%)-3 of which included embryonal carcinoma (EC) at the primary site (75%). Incidence of cases without seminoma/dysgerminoma increased significantly after metastasis (p = 0.02). Metastatic interval was shorter in cases with histological change (199 vs 454 days, p = 0.009). Overall survival was associated with MT primary histopathology (p = 0.02). CONCLUSION: Histological differentiation at the primary GCT site influences metastatic prognosis. Aggressive behavior is associated with NSGCT, while EC frequently demonstrates multi-directional histological differentiation after brain metastasis, and such histological dynamism is associated with shorter metastatic interval. Most metastases occurred within one year of diagnosis, emphasizing the need for close surveillance in newly diagnosed extra-cranial GCT.

Long-term outcomes of grade I/II skull base chondrosarcoma: an insight into the role of surgery and upfront radiotherapy.

PURPOSE: To clarify the need for post-operative radiation treatment in skull base chondrosarcomas (SBCs). METHODS: A retrospective analysis of patients with grade I or II SBC. Patients were divided according to post-surgical treatment strategies: (A) planned upfront radiotherapy and (B) watchful waiting. Tumor control and survival were compared between the treatment groups. The median follow-up after resection was 105 months (range, 9-376). RESULTS: Thirty-two patients (Grade 1, n = 16; Grade 2, n = 16) were included. The most frequent location was petroclival (21, 64%). A gross total resection (GTR) was achieved in 11 patients (34%). Fourteen (44%) underwent upfront radiotherapy (group A) whereas 18 (56%) were followed with serial MRI alone (group B). The tumor control rate for the entire group was 77% and 69% at 10- and 15-year, respectively. Upfront radiotherapy (P = 0.25), extent of resection (P = 0.11) or tumor grade (P = 0.83) did not affect tumor control. The majority of Group B patients with recurrent tumors (5/7) obtained tumor control with repeat resection (n = 2), salvage radiotherapy (n = 2), or a combination of both (n = 1). The 10-year disease-specific survival was 95% with no difference between the group A and B (P = 0.50). CONCLUSION: For patients with grade I/II SBC, a reasonable strategy is deferral of radiotherapy after maximum safe resection until tumor progression or recurrence. At that time, most patients can be successfully managed with salvage radiotherapy or surgery. Late recurrences may occur, and life-long follow-up is advisable.

An arrow that missed the mark: a pediatric case report of remarkable neurologic improvement following penetrating spinal cord injury.

Penetrating spinal cord injuries are rare in children but result in devastating impacts on long-term morbidity and mortality-with little known about the recovery capacity in this age group. We present the case of an eight-year-old child who sustained a penetrating injury through the right anterior thorax. Thoracic CT showed the arrow tip extending through the spinal canal at T6. Neurologic examination revealed no motor or sensory function below T6. The arrow was surgically removed without complications through an anterior-only approach. MRI on post-operative day (POD) 4 showed focal T2 hyperintensity at the T6 spinal cord. Patient was discharged on POD33 with an American Spinal Injury Association (ASIA)-D score and trace voluntary control over bowel and bladder function. Remarkably, four months later, he had near normal bowel and bladder function, with near-intact lower extremity strength and self-sustained ambulation. Follow-up imaging revealed hemicord formation at the level of injury. We review our case of penetrating spinal cord injury in a child and similar reports in the literature. Penetrating thoracic spinal cord trauma portends poor clinical outcomes, particularly when employing available adult prognostic spinal cord injury scoring metrics. Incomplete spinal cord injury, and often-associated spinal shock, can mimic a complete injury-as in our patient, which improved to near-complete motor and sensory restoration of function and resulted in the formation of a split hemicord. This case represents a unique penetrating spinal cord injury with remarkable neurologic recovery, which would advocate against definitive early prognostication in the pediatric population.

Prognostic significance of subdural hygroma for post-traumatic hydrocephalus after decompressive craniectomy in the traumatic brain injury setting: a systematic review and meta-analysis.

Post-traumatic hydrocephalus (PTH) is a potentially morbid sequela of decompressive craniectomy for traumatic brain injury (TBI). Subdural hygromas are commonly identified following decompressive craniectomy, but the clinical relevance and predictive relationship with PTH in this patient cohort is not completely understood. Survey of seven electronic databases from inception to June 2019 was conducted following PRISMA guidelines. Articles were screened against pre-specified criteria. Multivariate hazard ratios (HRs) for PTH by the presence of subdural hygroma were extracted and pooled by meta-analysis of proportions with random effects modeling. We systematically identified nine pertinent studies describing outcomes of 1010 TBI patients managed by decompressive craniectomy. Of the overall cohort, there were 211 (21%) females and median age was 37.5 years (range 33-53). On presentation, median Glasgow Coma Scale was 7 (range, 5-8). In sum, PTH was reported in 228/840 (27%) cases, and subdural hygroma was reported in 449/1010 (44%) cases across all studies. Pooling multivariate-derived HRs indicated that subdural hygroma was a significant, independent predictor of PTH (HR, 7.1; 95% CI, 3.3-15.1). The certainty of this association was deemed low due to heterogeneity concerns. The presence of subdural hygroma is associated with increased risk of PTH after decompressive craniectomy among TBI patients based on the current literature and may mandate closer clinical surveillance when detected. Prospective studies, including those of intracranial hydrodynamics following decompressive craniectomy in the setting of TBI, will better validate the certainty of these findings.

Anterior interhemispheric approach for clipping of subcallosal distal anterior cerebral artery aneurysms: case series and technical notes.

Distal anterior cerebral artery (DACA) aneurysms are rare, accounting for 1-9% of all intracranial aneurysms. Previous systematic reviews have highlighted that given the markedly increased incidence of major complications after endovascular treatment, microsurgical clipping is the more attractive treatment option with generally excellent clinical outcomes. Subcallosal DACA aneurysms constitute a rare subset of these aneurysms, requiring special anatomic considerations-particularly with regard to the approach. The aim of this study is to review the technical nuances of microsurgical treatment of subcallosal DACA aneurysms, including review of contemporary techniques through presentation of a microneurosurgical operative video. This is a retrospective case series and intraoperative microsurgical videos review. Three subcallosal DACA aneurysms were identified via retrospective query of our institutional neurosurgical database from December 2017 to May 2018. Two were female; median age was 74 years (range 70-83); all 3 underwent bifrontal craniotomy via bicoronal skin incision for aneurysm clipping. Aneurysms were located in left pericallosal-callosomarginal artery junction, bifurcation of azygos A2, and pericallosal artery related with azygos A2, and the anterior interhemispheric approach was used in all 3 operations. No acute stroke, hemorrhage, or major complications occurred, and all patients remained neurologically intact at the time of last follow-up (median 3 months, range 1-6). Although DACA aneurysms are rare, they represent an important variant for cerebrovascular neurosurgeons where microsurgical clipping can have better angiographic outcomes than endovascular treatment. Detail-oriented anterior interhemispheric arachnoid dissection through bifrontal craniotomy with its lower margin sitting at the superior orbital rim maximizes safe and effective clipping of subcallosal DACA aneurysms.

Recurrence of Rathke's cleft cysts based on gross total resection of cyst wall: a meta-analysis.

Rathke's cleft cysts (RCCs) are benign growths of the embryological Rathke's pouch. Surgical decompression provides effective symptomatic relief in most cases; however, the effect of gross total resection (GTR) of the cyst wall on recurrence, as well as pituitary function, is unclear. The aim of this meta-analysis was to pool the current literature and ascertain the recurrence control afforded by GTR of the cyst wall compared with subtotal resection (STR). Searches of seven electronic databases from inception to January 2019 were conducted following PRISMA guidelines, resulting in 476 articles to be screened. Outcomes were analyzed using meta-analysis of proportions. A total of 10 retrospective cohort studies satisfied selection criteria, describing 655 surgically managed RCC cases, with 254 (39%) and 401 (61%) achieving GTR and STR of the cyst wall, respectively. GTR was associated with significantly reduced overall RCC recurrence by fixed-effects (FE) modeling (RR, 0.66; 95% CI, 0.45-0.96), but not by random effects (RE) modeling (RR, 0.75; 95% CI, 0.51-1.12). Based on both models, GTR was associated with significantly reduced symptomatic recurrence (RE model, RR, 0.37, 95% CI, 0.14-0.95) and significantly increased postoperative diabetes insipidus (RE model, RR, 2.60; 95% CI, 1.34-5.03). There was insufficient data to evaluate other pituitary axes in this context. The current evidence indicates that GTR of the RCC cyst wall has the potential to affect the incidence of overall and symptomatic RCC recurrences, as well as drive postoperative DI incidence. However, expectations of clinical and pragmatic benefit following cyst wall resection should be titrated carefully against the potential for postoperative and pituitary morbidities which currently remain poorly defined. Greater granularity is required to understand all factors that can influence recurrence and quality of life when evaluating resection of RCC.

Single-fraction stereotactic radiosurgery for spindle cell oncocytoma: preliminary experience and systematic review of the literature.

PURPOSE: Spindle cell oncocytoma (SCO) is a rare benign pituitary tumor. No patient series regarding stereotactic radiosurgery (SRS) for SCO has been published. We report the clinical outcomes of SCO treated with single-fraction SRS, as well as a systematic review of the literature. METHODS: Retrospective cohort series and systematic literature review. RESULTS: Five patients (four male, one female) having single-fraction SRS for persistent or recurrent SCO between 2002 and 2018. Median age was 56 (range 54-79) years. Pre-SRS treatments included transsphenoidal resection (TSR) (n = 3), multiple TSR (n = 1), and TSR, radiotherapy, and craniotomy (n = 1). Median target volume was 4.7 (range 1.8-8.4) cm3, with a median tumor margin dose of 17 (range 14-20) Gy. Median follow-up was 24 (range 10-69) months. All radiation-naïve patients achieved tumor control after SRS; tumor progression was noted 24 months after SRS in one patient who failed prior radiotherapy. No radiation-induced complications were observed after SRS. Systematic literature review of 43 cases in addition to the five cases presented here showed that tumor progression/recurrence was more frequent after STR compared to GTR (P < 0.001). Ten previous cases of radiotherapy for SCO have been reported, but most did not detail radiation volumes, doses, or outcomes. CONCLUSIONS: SCO are uncommon sellar lesions with a propensity for progression or recurrence. Based on the clinically aggressive course of these tumors, adjuvant SRS after STR or at the time of tumor recurrence should be considered. Further case accumulation and follow-up is required to better understand the long-term treatment outcomes after single-fraction SRS for these rare tumors.

Efficacy and safety of bevacizumab for vestibular schwannoma in neurofibromatosis type 2: a systematic review and meta-analysis of treatment outcomes.

BACKGROUND: Individual evidence suggests that the anti-angiogenic agent bevacizumab may control vestibular schwannoma (VS) growth and promote hearing preservation in patients with neurofibromatosis type 2 (NF2). However, such metadata has yet to be consolidated, as well as its side-effect profile yet to be fully understood. Our aim was to pool systematically-identified metadata in the literature and substantiate the clinical efficacy and safety of bevacizumab with respect to radiographic tumor response, hearing, and treatment outcomes. METHODS: Searches of seven electronic databases from inception to March 2019 were conducted following PRISMA guidelines. Articles were screened against pre-specified criteria. The incidence of outcomes was then extracted and pooled by random-effects meta-analysis of proportions. RESULTS: Eight articles reporting 161 NF2 patients with 196 assessable VS met satisfied all criteria. Radiographic response to bevacizumab was partial regression in 41% (95% CI 31-51%), no change in 47% (95% CI 39-55%), and tumor progression in 7% (95% CI 1-15%). In patients with assessable audiometric data, bevacizumab treatment resulted in hearing improvement in 20% (95% CI 9-33%), stability in 69% (95% CI 51-85%) and additional loss in 6% (95% CI 1-15%) Serious bevacizumab toxicity was observed in 17% (95% CI 10-26%). Subsequent surgical intervention was required in 11% (95% CI 2-20%). CONCLUSIONS: Bevacizumab may arrest both tumor progression and hearing loss in select NF2 patients presenting with VS lesions. However, a considerable proportion of patients are anticipated to experience serious adverse events; correspondingly, judicious use of bevacizumab for symptomatic management of VS in NF2 is recommended.

Novel rodent model for simulation of sylvian fissure dissection and cerebrovascular bypass under subarachnoid hemorrhage conditions: technical note and timing study.

OBJECTIVESylvian fissure dissection following subarachnoid hemorrhage (SAH) is a challenging but fundamental skill in microneurosurgery, and one that has become increasingly difficult to develop during residency, given the overarching management trends. The authors describe a novel rodent model for simulation of sylvian fissure dissection and cerebrovascular bypass under SAH conditions.METHODSA standardized microvascular anastomosis model comprising rat femoral arteries and veins was used for the experimental framework. In the experimental protocol, following exposure and skeletonization of the vessels, extensive, superficial (1- to 2-mm) soft-tissue debridement was conducted and followed by wound closure and delayed reexploration at intervals of 7, 14, and 28 days. Two residents dissected 1 rat each per time point (n = 6 rats), completing vessel skeletonization followed by end-to-end artery/vein anastomoses. Videos were reviewed postprocedure to assess scar score and relative difficulty of dissection by blinded raters using 4-point Likert scales.RESULTSAt all time points, vessels were markedly invested in friable scar, and exposure was subjectively assessed as a reasonable surrogate for sylvian fissure dissection under SAH conditions. Scar score and relative difficulty of dissection both indicated 14 days as the most challenging time point.CONCLUSIONSThe authors' experimental model of femoral vessel skeletonization, circumferential superficial soft-tissue injury, and delayed reexploration provides a novel approximation of sylvian fissure dissection and cerebrovascular bypass under SAH conditions. The optimal reexploration interval appears to be 7-14 days. To the authors' knowledge, this is the first model of SAH simulation for microsurgical training, particularly in a live animal system.

The dangers of the "Head Down" position in patients with untreated pituitary macroadenomas: case series and review of literature.

PURPOSE: Cavernous sinus syndrome is a rare phenomenon, characterized by simultaneous neuropathies of cranial nerves III-VI. Various pathological processes have been reported as precipitating etiologies, including infection, inflammation, vascular lesions, and neoplasms. PURPOSE: We report a unique case series of cavernous sinus syndrome attributable to prolonged Trendelenburg or prone positioning during non-cranial procedures and review the pertinent literature to enlighten on this rare but catastrophic phenomenon. METHODS: Retrospective case series. RESULTS: In the past year we encountered two patients who presented with acute cavernous sinus syndrome upon awakening from non-cranial operations. One patient underwent an extensive urologic resection of a bladder malignancy positioned in Trendelenburg for approximately 4 h. The second patient underwent a lumbar laminectomy and discectomy in prone position. Both patients were discovered to have infarcted large pituitary macroadenomas as the etiology of their acute ophthalmoplegias, and transnasal, transsphenoidal resection was performed acutely to decompress the cavernous sinus contents. Pathologic analysis of the resected specimens in each case confirmed necrotic, infarcted pituitary adenoma. Both patients made a complete recovery with no evidence of residual or recurrent tumor in short term follow-up. CONCLUSION: We report a brief case series of acute cavernous sinus syndrome resulting from dependent positioning during non-cranial operations in patients with pituitary macroadenoma. Although rare, this highlights a potential danger of "head down" positioning in patients with intracranial pathology-particularly in or around the sella and cavernous sinus. Despite multiple cranial neuropathies upon presentation, both patients made complete recovery following surgical decompression of the cavernous sinuses.

MR Elastography Demonstrates Unique Regional Brain Stiffness Patterns in Dementias.

OBJECTIVE: The purpose of this study was to investigate age-corrected brain MR elastography (MRE) findings in four dementia cohorts (Alzheimer disease, dementia with Lewy bodies, frontotemporal dementia, and normal pressure hydrocephalus) and determine the potential use as a differentiating biomarker in dementia subtypes. SUBJECTS AND METHODS: Institutional review board approval and written informed consent were obtained to perform MRE on 84 subjects: 20 patients with normal pressure hydrocephalus, eight with Alzheimer disease, five with dementia with Lewy bodies, five with frontotemporal dementia, and 46 cognitively normal control subjects. Shear waves of 60-Hz vibration frequency were transmitted into the brain using a pillowlike passive driver, and brain stiffness was determined in eight different regions (cerebrum, frontal, occipital, parietal, temporal, deep gray matter-white matter, sensorimotor cortex, and cerebellum). All stiffness values were age-corrected and compared with control subjects. The Wilcoxon rank sum test and linear regression were used for statistical analysis. RESULTS: Regional stiffness patterns unique to each dementing disorder were observed. Patients with Alzheimer disease and frontotemporal dementia showed decreased cerebral stiffness (p = 0.001 and p = 0.002, respectively) with regional softening of the frontal and temporal lobes. Patients with Alzheimer disease additionally showed parietal lobe and sensorimotor region softening (p = 0.039 and p = 0.018, respectively). Patients with normal pressure hydrocephalus showed stiffening of the parietal, occipital, and sensorimotor regions (p = 0.007, p < 0.001, and p < 0.0001, respectively). Patients with dementia with Lewy bodies did not show significant stiffness changes in any of the regions. CONCLUSION: Quantitative MRE of changes in brain viscoelastic structure shows unique regional brain stiffness patterns between common dementia subtypes.

Subarachnoid Hemorrhage and Spinal Subdural Hematoma Due to Acute CSF Hypotension.

BACKGROUND: Intracranial subarachnoid hemorrhage (SAH) and spinal subdural hematoma (SDH) are rare complications of spine surgery, thought to be precipitated by cerebrospinal fluid (CSF) hypotension in the setting of an intraoperative durotomy or postoperative CSF leak. Considerable clinical variability has been reported, requiring a high level of clinical suspicion in patients with a new, unexplained neurologic deficit after spine surgery. METHODS: Case report. RESULTS: An 84-year-old man developed symptomatic spinal stenosis with bilateral lower extremity pseudoclaudication. He underwent L3-5 laminectomy at an outside institution, complicated by a small, incidental, unrepairable intraoperative durotomy. On postoperative day 2, he became confused; and head CT demonstrated intracranial SAH with blood products along the superior cerebellum and bilateral posterior Sylvian fissures. He was transferred to our neurosciences ICU for routine SAH care, with improvement in encephalopathy over several days of supportive care. On postoperative day 10, the patient developed new bilateral lower extremity weakness; MRI of the lumbar spine demonstrated worsening acute spinal SDH above the laminectomy defect, from L4-T12. He was taken to the OR for decompression, at which time a complex 1.5-cm lumbar durotomy was identified and repaired primarily. CONCLUSIONS: We report the first case of simultaneous intracranial SAH and spinal SDH attributable to postoperative CSF hypotension in the setting of a known intraoperative durotomy. Although rare, each of these entities has the potential to precipitate a poor neurologic outcome, which may be mitigated by early recognition and treatment.

Dual-Energy CT to Diagnose Pseudoedema in Contrast-Induced Encephalopathy Following Cerebral Angiography.

BACKGROUND: Contrast-induced encephalopathy (CIE) is a syndrome that may be clinically unrecognized and misdiagnosed as cerebral edema. METHODS: Case report and review. RESULTS: A 72-year-old woman was admitted for elective endovascular embolization of a 10-mm left anterior communicating artery aneurysm. One hour post-procedure, she acutely developed global aphasia. Emergent head computed tomography (CT) and computed tomography-angiography (CTA) showed high attenuation of the left hemispheric subarachnoid spaces interpreted as hemispheric edema; emergent magnetic resonance imaging revealed left hemispheric punctate infarcts. At 12 h, she developed right hemiparesis and encephalopathy. Repeat CTA and CT perfusion revealed decreased left hemisphere cerebral blood flow and diminutive caliber of distal left middle cerebral artery territory vasculature. Repeated angiography with intra-arterial verapamil and systemic blood pressure augmentation were performed for presumed vasospasm. At 20 h, head CT was concerning for worsening left hemispheric edema, but dual-energy, iodine-subtracting sequences revealed significant contrast extravasation contributing to the appearance of sulcal effacement but without actual edema. Out of concern for blood-brain barrier breakdown from CIE, pressor augmentation was discontinued and the patient gradually improved to full neurological recovery within 72 h of symptom onset. CONCLUSIONS: Our case is the first known to report the use of dual-energy, iodine-subtracting CT as a diagnostic tool in differentiating between cerebral edema and pseudoedema in CIE.

Histology of the distal dural ring.

The distal dural ring (DDR) is a conserved intracranial anatomic structure marking the boundary point at which the internal carotid artery (ICA) exits the cavernous sinus (CS) and enters the subarachnoid space. Although the CS has been well described in a range of anatomic studies, to our knowledge no prior study has analyzed the histologic relationship between the ICA and DDR. Correspondingly, our objective was to assess the relationship of the DDR to the ICA and determine whether the DDR can be dissected from the ICA and thus divided, or can only be circumferentially trimmed around the artery. The authors examined ten fresh-frozen, adult cadaveric specimens. A standard frontotemporal craniotomy, orbito-optic osteotomy, and extradural anterior clinoidectomy was performed bilaterally. The cavernous ICA, DDR, and supraclinoid ICA were harvested as an en bloc specimen. Specimens formalin-fixed and paraffin-embedded prior to routine histochemical staining with hematoxylin and eosin and Masson trichrome. In all specimens, marked microscopic investment of the DDR throughout the ICA adventitia was noted. Dural collagen fibers extensively permeated the arterial layers superficial to the muscularis propria, with no evidence of a clear separation between the DDR and arterial adventitia. Histologic analysis suggests that the ICA and DDR are highly interrelated, continuous structures, and therefore attempted intraoperative dissection between these structures may carry an elevated risk of injury to the ICA. We correspondingly recommend careful circumferential trimming of the DDR in lieu of direct dissection in cases requiring mobilization of the clinoidal ICA. Clin. Anat. 30:742-746, 2017. © 2017Wiley Periodicals, Inc.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Frontotemporal and Orbitozygomatic Craniotomies.

Introduction Although many neuroanatomic atlases have been published, few have detailed complex cranial approaches and pertinent anatomic considerations in a stepwise fashion intended for rapid comprehension by neurosurgery students, residents, and fellows. Methods Five sides of formalin-fixed latex-injected specimens were dissected under microscopic magnification. The frontotemporal and orbitozygomatic approaches were performed by neurosurgical residents and fellows at different training levels with limited previous experience in anatomical dissection mentored by the senior authors (M.P.C. and M.J.L.). Meticulous surgical anatomic dissections were performed until sufficient visual and technical completion was attained, with parameters of effectively demonstrating key surgical steps for educational training purposes. Following the completion of dissection and three-dimensional photography, illustrative case examples were reviewed to demonstrate the relative benefits and optimal applications of each approach. Results The frontotemporal and orbitozygomatic approaches afford excellent access to anterior and middle skull base pathologies, as well as the exposure of the infratemporal fossa. Key considerations include head positioning, skin incision, scalp retraction, fat pad dissection and facial nerve protection, true or false MacCarty keyhole fashioning, sphenoid wing drilling and anterior clinoidectomy, completion of the craniotomy and accessory orbital osteotomy cuts, dural opening, and intradural neurovascular access. Conclusion The frontotemporal and orbitozygomatic approaches are core craniotomies that offer distinct advantages for complex cranial operations. Learning and internalizing their key steps and nuanced applications in a clinical context is critical for trainees of many levels. The orbitozygomatic craniotomy in particular is a versatile but challenging approach; operative-style laboratory dissection is an essential component of its mastery and one that will be powerfully enhanced by the current work.

Lower Cranial Nerve Schwannomas: Cohort Study and Systematic Review.

BACKGROUND AND OBJECTIVES: Schwannomas originating from the lower cranial nerves (LCNS) are rare and pose a significant surgical challenge. Resection is the mainstay treatment; however, risk of treatment morbidity is considerable, and the available literature regarding differential treatment outcomes in this vulnerable population is sparse. METHODS: A single-institution cohort study and systematic literature review of LCNS were performed. RESULTS: Fifty-eight patients were included: 34 underwent surgical resection and 24 underwent stereotactic radiosurgery (SRS). The median age at diagnosis was 48 years (range 17-74). Presenting symptoms were dysphagia (63%), dysarthria/hypophonia (47%), imbalance (33%), and hearing loss/tinnitus (30%). Tumor size was associated with surgical resection, as compared with initial SRS (4.1 cm vs 1.5 cm, P = .0001). Gross total resection was obtained in 52%, with tumor remnants predominantly localized to the jugular foramen (62%). Post-treatment worsening of symptoms occurred in 68% of surgical and 29% of SRS patients ( P = .003). Postoperative symptoms were mostly commonly hypophonia/hoarseness (63%) and dysphagia (59%). Seven patients (29%) had new neurological issues after SRS treatment, but symptoms were overall milder. The median follow-up was 60 months (range 12-252); 98% demonstrated meaningful clinical improvement. Eighteen surgical patients (53%) underwent adjuvant radiation at a median of 5 months after resection (range 2-32). At follow-up, tumor control was 97% in the surgical cohort and 96% among SRS patients. CONCLUSION: Although LCNS resection is potentially morbid, most postoperative deficits are transient, and patients achieve excellent tumor control-particularly when paired with adjuvant SRS. For minimally symptomatic patients undergoing surgical intervention, we advise maximally safe resection with intracapsular dissection to preserve nerve integrity where possible. For residual or as a primary treatment modality, SRS is associated with low morbidity and high rates of long-term tumor control.