Subtemporal Approach and Its Infratentorial Extension: Review and a Comparative Analysis of Different Techniques

Introduction Surgical resection of lesions occupying the incisural space is challenging. In a comparative fashion, we aimed to describe the anatomy and surgical approaches to the tentorial incisura and to the rostral brainstem via the intradural subtemporal approach and its infratentorial extensions. Methods Six fresh human head specimens (12 sides) were prepared for the microscopic dissection of the tentorial incisura using the intradural subtemporal approach and its infratentorial extensions. Endoscope was used to examine the anatomy of the region inadequately exposed with the microscope. Image-guided navigation was used to confirm bony structures visualized around the petrous apex. Results Standard subtemporal approach provides surgical access to the supratentorial brainstem above the pontomesencephalic sulcus and to the lateral surface of the cerebral peduncle. The linear or triangular tentorial divisions can provide access to the infratentorial space below the pontomesencephalic sulcus. The triangular tentorial flap in comparison with the linear incision obstructs the exposure of anterior incisural space and of the prepontine cistern. Visualization of the brainstem below the trigeminal nerve can be achieved by the anterior petrosectomy. Conclusion Infratentorial extension of the intradural subtemporal approach is technically demanding due to critical neurovascular structures and a relatively narrow corridor. In-depth anatomical knowledge is essential for the selection of the appropriate operative approach and safe surgical resections of lesions.

Kernohan-Woltman Notch Phenomenon in Chronic Subdural Hematoma: An under-Diagnosed Phenomenon?

Introduction: Kernohan-Woltman notch phenomenon is a neurological picture of mydriasis and hemiparesis/ hemiplegia ipsilateral to a supratentorial mass lesion causing compression of the contralateral cerebral peduncle against the tentorial edge. The aim of this paper is to report series of cases from a low volume centre of neurosurgical care and highlight the fact that Kernohan’s notch phenomenon, although, reported to be quite rare but it’s not uncommon and to also look out for this phenomenon to avoid wrong site surgeries. Presentation of Cases: We report four cases of chronic subdural hematoma presenting with Kernohan- Woltmann notch phenomenon. The patients include: a young alcoholic who was found in a gutter after binge drinking, a middle aged man who was accidentally hit on the head with a car tire jack, an elderly female with no history of trauma, a fall nor use of anticoagulant and an elderly male, a diabetic. All four patients had emergency burr hole and drainage of subdural hematoma. Discussion: This incidence of this phenomenon among patients with chronic subdural hematoma is rarely reported in the literature, however, a low volume centre for neurosurgical services like ours has seen five cases in a short period of time. Conclusion: This paradoxical neurological sign is probably under-diagnosed judging from the number of cases diagnosed in a low volume center like ours.

Reliability of the freehand region-of-interest method in quantitative cerebral diffusion tensor imaging

Background Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique used for evaluating changes in the white matter in brain parenchyma. The reliability of quantitative DTI analysis is influenced by several factors, such as the imaging protocol, pre-processing and post-processing methods, and selected diffusion parameters. The region-of-interest (ROI) method is most widely used of the post-processing methods because it is found in commercial software. The focus of our research was to study the reliability of the freehand ROI method using various intra- and inter-observer analyses. Methods This study included 40 neurologically healthy participants who underwent diffusion MRI of the brain with a 3 T scanner. The measurements were performed at nine different anatomical locations using a freehand ROI method. The data extracted from the ROIs included the regional mean values, intra- and inter-observer variability and reliability. The used DTI parameters were fractional anisotropy (FA), the apparent diffusion coefficient (ADC), and axial (AD) and radial (RD) diffusivity. Results The average intra-class correlation coefficient (ICC) of the intra-observer was found to be 0.9 (excellent). The single ICC results were excellent (> 0.8) or adequate (> 0.69) in eight out of the nine regions in terms of FA and ADC. The most reliable results were found in the frontobasal regions. Significant differences between age groups were also found in the frontobasal regions. Specifically, the FA and AD values were significantly higher and the RD values lower in the youngest age group (18–30 years) compared to the other age groups. Conclusions The quantitative freehand ROI method can be considered highly reliable for the average ICC and mostly adequate for the single ICC. The freehand method is suitable for research work with a well-experienced observer. Measurements should be performed at least twice in the same region to ensure that the results are sufficiently reliable. In our study, reliability was slightly undermined by artifacts in some regions such as the cerebral peduncle and centrum semiovale. From a clinical point of view, the results are most reliable in adults under the age of 30, when age-related changes in brain white matter have not yet occurred.

Case Report: Paraneoplastic Hashimoto's Encephalopathy Associated With Lymphomatosis Cerebri With Periodic Synchronous Discharges Resembling Creutzfeldt–Jakob Disease

Hashimoto's encephalopathy (HE) is an autoimmune encephalopathy that presents with various clinical symptoms, including cognitive deterioration, convulsive seizures, and personality changes. HE is associated with thyroid autoimmunity; however, few cases have been reported to develop as paraneoplastic syndrome. Herein, we report the case of a 73-year-old woman with onset of rapidly progressive dementia. Brain magnetic resonance imaging showed diffuse T2 hyperintensity areas involving the bilateral cerebral white matter, right midbrain tegmental area, left cerebral peduncle, and right middle cerebellar peduncle without clear diffusion hyperintensities and gadolinium enhancement. Her neurological symptoms worsened rapidly, and she presented with the apallic syndrome. Electroencephalogram showed periodic synchronous discharge, suggestive of Creutzfeldt–Jakob disease. However, a brain biopsy revealed infiltration of atypical lymphoid cells expressing CD20, and the anti-NH2 terminal of the α-enolase antibody was detected, diagnosing the complication with lymphomatosis cerebri and HE. High-dose intravenous methylprednisolone therapy and oral prednisolone with whole cranial irradiation enabled her to have simple conversations and consume food orally; however, severe cognitive impairment persisted. Although HE is a rare complication of malignant lymphoma, clinicians should be aware that it could be strongly suspected if the clinical symptoms worsen in the absence of imaging changes.

RADI-06. Gamma knife surgery for brain stem metastases

Introduction Gamma Knife Surgery (GKS) is widely used for treatment of brainstem metastases (BSMs) with or without whole bran radiation therapy (WBRT). We hypothesized that BSMs treated with GKS using lower doses and omitting WBRT result in acceptable tumor control rates and low complication rates. Methods A retrospective single center study was performed to investigate the outcome following GKS of BSMs. All 33 patients with follow-up information treated with GKS for 39 metastases located in the cerebral peduncle, midbrain, pons or medulla oblongata were included in the study. The median treatment dose, defined as the lowest dose to 95% of the tumor volume, was 18 Gy. The tumor control rate as well as the survival time were related to a number of patients, tumor and treatment parameters. Results The local tumor control rate was 100% at one year and 89% at five years, and the overall median survival was 17 months. A good performance status and a treatable extracranial disease were favorably related to survival time. Two complications were observed, one lethal hemorrhage at the day of the treatment and one transient complication three months following GKS, resulting in a 6% complication rate at five years. Four of the 10 patient with symptomatic BSM improved clinically after GKS, while six remained unchanged. Conclusions High local control and a low complication rates can be achieved using GKS for BSMs using lower doses as compared to brain metastases in other locations.

Pontine hemorrhage presenting as Foville’s syndrome

Foville’s syndrome, also known as inferior medial pontine syndrome is one of the rare brainstem stroke syndromes with only few cases reported worldwide occurring due to involvement of the infero-medial aspect of pons. Condition is characterised by various cluster of neurological features as a result of defect in multiple vital areas like cortico spinal tract, medial lemniscus, middle cerebral peduncle, facial nerve and abducens nerve involvement. We reported one such rare case of a patient with no known systemic co-morbidity, who presented with sudden onset diplopia, lagophthalmos and contralateral weakness of limbs. On evaluation with computed tomography imaging, hemorrhage at the level of inferior pons was found. Patient subsequently treated and commenced on physiotherapy for rehabilitation.

Paraneoplastic AQP4-IgG–Seropositive Neuromyelitis Optica Spectrum Disorder Associated With Teratoma

ObjectivesTo assess a case of paraneoplastic aquaporin-4 (AQP4)-immunoglobulin G (IgG)–seropositive neuromyelitis optica spectrum disorder (NMOSD) associated with teratoma and determine whether it is a paraneoplastic neurologic disorder.MethodsA single case study and literature review of 5 cases.ResultsA 27-year-old woman presented with diplopia, facial nerve palsy, paraplegia, sensory dysfunction of lower limbs, dysuria, nausea, and vomiting. Spinal cord MRI detected an extensive longitudinal lesion in the spinal cord, and brain MRI detected abnormal lesions in the right cerebral peduncle and tegmentum of the pons. CSF analysis revealed positive oligoclonal IgG bands (OCBs). The patient tested positive for AQP4-IgG, confirming a diagnosis of NMOSD. An abdominal CT scan detected an ovarian tumor. After steroid therapy and tumor removal, the patient progressively improved, with only mild sensory dysfunction. Histopathologic analysis of the tumor revealed a teratoma and the presence of glial fibrillary acidic protein (GFAP)+ neural tissue with AQP4 immunoreactivity, accompanied by lymphocyte infiltration. Including the present case, there have been 6 reported cases of AQP4-IgG–seropositive NMOSD associated with ovarian teratoma (mean onset age, 32.7 years). Of these patients, 5 (83%) presented with nausea and/or vomiting, positive OCB, and dorsal brainstem involvement. Pathologic analyses of the teratoma were available in 5 cases, including the present case, revealing neural tissue with AQP4 immunoreactivity and lymphocyte infiltration in all cases.ConclusionsThis study suggests that ovarian teratoma may trigger the development of AQP4-IgG–seropositive NMOSD. Further studies are needed to elucidate the pathogenesis of teratoma-associated NMOSD.

Investigating the Association of Wallerian Degeneration and Diaschisis After Ischemic Stroke With BOLD Cerebrovascular Reactivity

IntroductionWallerian degeneration and diaschisis are considered separate remote entities following ischemic stroke. They may, however, share common neurophysiological denominators, since they are both related to disruption of fiber tracts and brain atrophy over time. Therefore, with advanced multimodal neuroimaging, we investigate Wallerian degeneration and its association with diaschisis.MethodsIn order to determine different characteristics of Wallerian degeneration, we conducted examinations on seventeen patients with chronic unilateral ischemic stroke and persisting large vessel occlusion, conducting high-resolution anatomical magnetic resonance imaging (MRI) and blood oxygenation-level dependent cerebrovascular reactivity (BOLD-CVR) tests, as well as Diamox 15(O)–H2O–PET hemodynamic examinations. Wallerian degeneration was determined using a cerebral peduncle asymmetry index (% difference of volume of ipsilateral and contralateral cerebral peduncle) of more than two standard deviations away from the average of age-matched, healthy subjects (Here a cerebral peduncle asymmetry index > 11%). Diaschisis was derived from BOLD-CVR to assess the presence of ipsilateral thalamus diaschisis and/or crossed cerebellar diaschisis.ResultsWallerian degeneration, found in 8 (47%) subjects, had a strong association with ipsilateral thalamic volume reduction (r2 = 0.60) and corticospinal-tract involvement of stroke (p < 0.001). It was also associated with ipsilateral thalamic diaschisis (p = 0.021), No cerebral peduncular hemodynamic differences were found in patients with Wallerian degeneration. In particular, no CBF decrease or BOLD-CVR impairment was found.ConclusionWe show a strong association between Wallerian degeneration and ipsilateral thalamic diaschisis, indicating a structural pathophysiological relationship.

A Case of Anterior Choroidal Artery Occlusion and Stroke Secondary to External Compression

The anterior choroidal artery (AChA) is a small artery commonly arising from the supraclinoid segment of the internal carotid artery (ICA). The significance of the AChA is related to its strategic supply to various important structures of the brain, such as the optic tract, the posterior limb of the internal capsule, the cerebral peduncle, the lateral geniculate body, medial temporal lobe, medial area of pallidum, and the choroid plexus [<i>J Neurol</i>. 1988;235:387–91]. The AChA syndrome in its complete form consists of the triad of hemiplegia, hemisensory loss, and hemianopia. However, incomplete forms are more frequent in clinical practice [<i>Stroke</i>. 1994;25:837–42]. Isolated infarction in the AChA territory is relatively rare. The presumed pathogenic mechanisms of AChA infarction are cardiac emboli, large-vessel atherosclerosis, dissection of the ICA, small-vessel occlusion, or other determined or undetermined causes [<i>Stroke</i>. 1994;25:837–42 and <i>J Neurol Sci</i>. 2009;281:80–4].