Lateral Pons Research Articles

Expanding the reach of the trans-middle cerebellar peduncle approach: pontine cavernous malformations, tissue transgression beyond the safe entry zone, and the invisible triangle.

In the authors' microsurgical experience, the trans-middle cerebellar peduncle (MCP) approach to the lateral and central pons has been the most common approach to brainstem cavernous malformations (BSCMs). This approach through a well-tolerated safe entry zone (SEZ) allows a wide vertical or posterior trajectory, reaching pontine lesions extending into the midbrain, medulla, and pontine tegmentum. Better understanding of the relationships among lesion location, surgical trajectory, and long-term clinical outcomes could determine areas of safe passage. A single-surgeon cohort study of all primary trans-MCP BSCM resections was conducted from July 1, 2017, to June 30, 2021. Preoperative and postoperative MR images were independently reviewed by 3 investigators blinded to the intervention, using a standardized rubric to define BSCM regions of interest (ROIs) involved with a lesion or microsurgical tract. Statistical testing, including the chi-square test with the Bonferroni correction, logistic regression, and structural equation modeling, was performed to analyze relationships between ROIs and clinical outcomes. Thirty-one patients underwent primary trans-MCP BSCM resection during the study period. The median age was 50 years (IQR 24-49 years); 19 (61%) patients were female, and 12 (39%) were male. Seven (23%) patients had familial cavernous malformation syndromes. The median follow-up was 9 months (range 6-37 months). At the last follow-up, composite neurological outcomes were favorable: 22 (71%) patients had 0 (n = 12, 39%) or 1 (n = 10, 32%) major persistent deficit, 5 patients (16%) had 2 deficits, 2 (7%) had 3 deficits, and 1 patient each (3%) had 4 or 6 deficits. Unfavorable composite outcomes were significantly associated with lesions (OR 7.14, p = 0.04) or surgical tracts (OR 12.18, p < 0.001) extending from the superior cerebellar peduncle (SCP) into the contralateral medial midbrain. The ipsilateral dorsal pons was the most frequently implicated ROI involving a surgical tract and the development of new postoperative deficits. This region involved the rhomboid pontine territory and transgression of the pontine tegmentum (OR 7.53, p < 0.001). Structural equation modeling supported medial midbrain and pontine tegmentum transgression as the primary drivers of morbidity. Trans-MCP resection is a safe and effective treatment for BSCMs, including lesions with marked superior or inferior ipsilateral extension. Two trajectories are associated with increased neurological risk: first, a superomedial trajectory to lesions extending into the midbrain that transgresses the SCP, its decussation, or both; and second, a posteromedial trajectory to lesions extending into the pontine tegmentum. The corticospinal tract, SCP, and pontine tegmentum form an invisible triangle within the pontine white matter tolerant of transgression. When the surgeon works within this triangle, most deep pontine BSCMs, including large lesions, those with contralateral or posterior extension, and others extending into the midbrain and medulla, can be resected safely with the trans-MCP approach.

Abstract 123: First Off‐Label Use of the XIENCE Skypoint Stent for Mechanical Thrombectomy Rescue

Introduction Despite technical advances in mechanical thrombectomy (MT), failure to achieve recanalization in the posterior circulation remains a significant challenge. Rescue strategies to increase MT success in the posterior circulation have been explored. We demonstrate the first successful off‐label use of XIENCE Skypoint™ (Abbott), a balloon‐mounted drug‐eluting stent (DES), for intracranial MT rescue in the posterior circulation. Methods Case report and endovascular technique. Results A 52‐year‐old man with hypertension, hyperlipidemia, and deep venous thrombosis who presented with acute ischemic stroke in bilateral occipital, lateral pons, and cerebellar regions. Computed tomography angiography (CTA) showed bilateral vertebral artery occlusion consistent with a history of dissection in the setting of cervical manipulation. Admission National Institutes of Health Stroke Scale (NIHSS) 20. Last known well less than 12 hours from presentation. Intravenous thrombolysis was deferred as the patient was on pre‐admission anticoagulants. Mechanical thrombectomy failed after several unsuccessful passes (Fig 1). XIENCE Skypoint™ stent was deployed within the left vertebral artery (V4 segment) with restoration of flow preceded by eptifibatide drip (Fig 2). Repeat CTA at six months showed patent left vertebral and basilar arteries. Conclusion Rescue stenting using DES may be a successful and safe therapeutic intervention for challenging failed MT. The off‐label use of DES for intracranial pathologies continues to expand. This is the first case report in the literature describing successful rescue stenting using XIENCE Skypoint™ in the posterior circulation. Further investigation is warranted to fully elucidate the risks and benefits of this treatment approach.

Widening the clinical, radiological and genetic spectrum of autosomal recessive ataxia of Charlevoix-Saguenay in Indian patients.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS), classically presenting as a triad of early-onset cerebellar ataxia, lower extremity spasticity and peripheral neuropathy, is caused by mutations in SACS gene which encodes the protein sacsin. To provide new insight into the occurrence of SACS mutations in South India. Patients with three cardinal features of ARSACS-peripheral neuropathy, cerebellar ataxia, and pyramidal tract signs were included. Nine patients were clinically identified and genetically evaluated. Mutation screening of SACS by targeted sequencing of 40 recessive ataxia genes panel by next-generation sequencing was conducted. Additional investigations included magnetic resonance imaging (MRI), fundoscopy, optical coherence tomography (OCT) and nerve conduction studies (NCS). Functional disability was assessed by the Spinocerebellar Degeneration Functional Score. Two hundred and fifteen cerebellar ataxia patients were screened, and 9 patients with cerebellar ataxia with spasticity, peripheral neuropathy and MRI brain characteristics, consistent with a clinical diagnosis of ARSACS were identified, of which 7 patients were identified to have mutation in the SACS gene and are detailed hereafter. Age of presentation ranged from 20 to 55years (29.8 ± 11.9) with a mean disease duration of 12.7years (SD-7.65, range 5-22years). All except one had onset of symptoms in the form of an ataxic gait noticed before 20years of age. Additional features were subnormal intelligence (4/7), slow and hypometric saccades (1/7), seizures (1/7), kyphoscoliosis (1/7) and dysmorphic facies (1/7). SDFS was 3 in 5/7 patients signifying moderate disability with independent ambulation. MRI showed cerebellar atrophy with predominant atrophy of the superior vermis (7/7), horizontal linear T2 hypointensities in the pons(7/7), hyperintensities where lateral pons merges with the middle cerebellar peduncle (MCP) (7/7) well seen in fluid-attenuated inversion recovery (FLAIR) images, thickening of MCP (3/7), symmetric lateral thalamic hyperintensities (6/7), posterior fossa arachnoid cyst (4/7),thinning of posterior mid-body of corpus callosum (7/7), marginal mineralisation of the basal ganglia (7/7), bilateral parietal atrophy (7/7) and thinning of corticospinal tract on diffusion tensor imaging (DTI) (7/7). We identified pathogenic homozygous frameshift mutations in the SACS gene in six patients (including two siblings), while one patient had a heterozygous pathogenic deletion. This is the largest series of genetically confirmed ARSACS patients from India highlighting the clinical, ophthalmological, imaging and genetic features of this cohort.

Genetic and prenatal diagnosis of a Chinese pedigree with pathogenic TOE1 variants causing pontocerebellar hypoplasia type 7

Objective: Biallelic pathogenic variants in TOE1 cause pontocerebellar hypoplasia type 7 (PCH7), a rare neurological condition characterized by psychomotor retardation, spastic paraplegia, seizures, gonadal abnormalities and brain anomalies. Currently, only 14 postnatally diagnosed PCH7 patients have been described. However, the prenatal clinical profile of PCH7 has not yet been reported. Method: Whole-exome sequencing (WES) was performed to screen for causal variants. Results: We report the pedigree of a Chinese woman with two eventful pregnancies with fetuses that showed brain anomalies, including microcephaly, cerebral anomalies, enlarged ventricles, corpus callosum thinning, abnormal lateral fissure, underdeveloped insula and pons and brainstem hypoplasia. Interestingly, corpus callosum thinning was observed in fetus 1 but not in fetus 2. An abnormal lateral fissure and an underdeveloped insula were shown in fetus 2 but not fetus 1. Biallelic variants c.716T > C (p.Phe239Ser) and c.955C > T (p.His319Tyr) in TOE1 were identified in both fetuses. Conclusion: We first describe the prenatal features of a Chinese pedigree with PCH7 caused by biallelic pathogenic variants in TOE1, with phenotypic variability observed even within the same family. Novel phenotypes, an abnormal lateral fissure and an underdeveloped insula were observed in the fetus in our study. These findings will enrich our knowledge of the clinical characteristics, management and genetic counseling of PCH7.

71-year Old Male Patient with 20 Hour Onset of Infarct Stroke that was Performed with Intra-Arterial Thrombolysis, Mechanical Thrombectomy, Balloon Angioplasty, and Carotid Stenting: A Case Report

Introduction: For above 2 decades, the definitive management for acute ischemic stroke is intravenous or intra-arterial thrombolysis (IAT), using recombinant tissue-type plasminogen activator. Recently mechanical thrombectomy (MT) was developed to overcome the problem that intravenous thrombolysis is only effective in removing large artery occlusions in the range of 10-30%. Early treatment with intra-arterial thrombolysis, permanent stent insertion and clot extraction devices evolved into the stent-retriever device used in most of the important trials and, recently, emerged aspiration tool. This case report presented 71-year-old male patient with infarct stroke who performed with MT. Case presentation: This case report presented 71-year-old male patient with the main complaint of right limbs weakness. A non-contrast head CT scan found infarction in the cortical-subcortical left parietal lobe, posterior pericornu of the right lateral ventricle and right temporal cornu periventricular; lacunar infarction in the right and left paramedian pons; old lacunar infarction in the left and right centrum semiovale, left corona radiata, right internal capsule, right parietal lobe white matter, left lentiform nucleus, left posterior crus of the internal capsule-thalamus, right thalamus, right lateral ventricular pericornu and left paramedian pons. The patient underwent cerebral digital substraction angiography (DSA), as well as IAT, MT, balloon angioplasty, and carotid stenting with good clinical outcome. Conclusion: With the overwhelming positive results of studies evaluating the safety, efficiency, and efficacy of mechanical thrombectomy; the standard of care for the treatment of patients with anterior circulation vessel occlusion is becoming clear.

Restless legs syndrome due to brainstem stroke: A systematic review.

Restless Legs Syndrome (RLS) is a sleep-related movement disorder, which can also result from brainstem pathology. A systematic review of articles published in the electronic databases PubMed and Web of Science was conducted to summarize the existent literature on RLS associated with a brainstem stroke. We identified eight articles including 19 subjects with RLS due to brainstem ischemic lesion. The symptoms occurred simultaneously with the infarction (66.7%) or few days after (33.3%). The most common location of infarction was pons and less commonly medulla. In most cases (68.4%), symptoms were unilateral. In the majority of those cases (92.3%), the contralateral limb was affected due to a lateral pons infarction. RLS symptoms after infarction improved or resolved in almost 90% of cases within a few days up to 3 months. In almost all patients who received dopaminergic treatment (11 out of 13, 91.7%), the symptoms improved significantly or resolved completely. Screening for RLS has to be considered in patients suffering a brainstem stroke, particularly anteromedial pontine infarction. The appearance of acute unilateral RLS symptoms, usually in association with other sensorimotor deficits, should prompt the clinician to consider a vascular event in the brainstem. RLS in these cases seem to have a favorable outcome and respond well to dopaminergic treatment.

Mechanisms of opioid-induced respiratory depression.

Opioid-induced respiratory depression (OIRD), the primary cause of opioid-induced death, is the neural depression of respiratory drive which, together with a decreased level of consciousness and obstructive sleep apnea, cause ventilatory insufficiency. Variability of responses to opioids and individual differences in physiological and neurological states (e.g., anesthesia, sleep-disordered breathing, concurrent drug administration) add to the risk. Multiple sites can independently exert a depressive effect on breathing, making it unclear which sites are necessary for the induction of OIRD. The generatorof inspiratoryrhythm is the preBötzinger complex (preBötC) in the ventrolateral medulla. Other important brainstem respiratory centres includethe pontine Kölliker-Fuse and adjacent parabrachial nuclei (KF/PBN) in the dorsal lateral pons, and the dorsal respiratory group in the medulla. Deletion of μ opioid receptors from neurons showed that the preBötC and KF/PBN contribute to OIRD with the KF as a respiratory modulator and the preBötC as inspiratory rhythm generator. Glutamatergic neurons expressing NK-1R and somatostatin involved in the autonomic function of breathing, and modulatory signal pathways involvingGIRK and KCNQ potassium channels, remain poorly understood. Reversal of OIRD has relied heavily on naloxone which also reverses analgesia but mismatches between the half-lives of naloxone and opioids can make it difficult to clinically safely avoid OIRD. Maternal opioid use, which is rising, increases apneas and destabilizes neonatal breathing but opioid effects on maternal and neonatal respiratory circuits in neonatal abstinence syndrome (NAS) are not well understood. Methadone, administered to alleviate symptoms of NAS in humans, desensitizes rats to RD.

A rare case of lateral pontine syndrome-Marie Foix syndrome

Lateral pontine syndrome or Marie Foix Alajouanine syndrome refers to the brainstem stroke syndrome involving lateral pons due to the infarction in the distribution of the anterior inferior cerebellar artery. It involves the lateral inferior part of the pons, middle cerebellar peduncle, and floccular region. Computed Tomography (CT) is less sensitive in brainstem infarction than Magnetic Resonance Imaging (MRI). With the introduction of MRI, it is possible to precisely locate the brainstem infarcts. We present a case with a typical clinical picture of brainstem stroke with radiological findings consistent with the lateral pontine syndrome. Proper correlation with the clinical picture and radiological findings is important for the diagnosis of brainstem infarctions.

Truncal pulsion in acute ischemic stroke – Clinico-anatomical correlation

Context: Truncal pulsion is a compelling sensation of being pulled to one side, in the context of normal motor and sensory functions and normal co-ordination. It is seen in a variety of ischemic strokes.&#x0D; Aims: This article aims at identifying ischemic stroke syndromes associated with truncal pulsion, with review of the neural substrate responsible, to help in recognition and reporting.&#x0D; Settings and Design: This was a prospective study conducted at Department of Neurology, at Pushpagiri institute of medical sciences and research centre, Thiruvalla, Kerala, India, over a period of 5 years, among patients with acute ischemic stroke.&#x0D; Methods and Material: We studied all patients with acute ischemic stroke, who were admitted to our department, over a five-year period. Patients presenting with truncal pulsion were shortlisted and were assessed by investigators independently. All patients underwent MRI brain, which was assessed by investigators 1 and 2, independently. The demographic profile, risk factors, clinical features, neuroimaging findings and outcomes were analysed using SPSSv21.&#x0D; Results: A total of 1456 patients with acute ischemic strokes were identified, of which 27 with truncal pulsion were included in the study. The common sites of infarction resulting in truncal pulsion were lateral medulla, cerebellum, thalamus, pons and midbrain. One patient had infarct involving anterior cingulate. Truncal pulsion was ipsilateral in infarcts involving medulla and cerebellum and contralateral in infarcts involving the pons, midbrain, mesencephalo-diencephalic junction, thalamus and cingulate.&#x0D; Conclusions: Truncal pulsion, a compelling sensation of falling, is a disabling symptom occurring in a variety of strokes and it poses significant challenge in neuro-rehabilitation.&#x0D;

IMMUNOHISTOCHEMICAL IDENTIFICATION AND DISTRIBUTION OF GLUTAMATERGIC NMDA AND mGlu1 RECEPTORS IN THE PONTINE INTERTRIGEMINAL REGION IN RATS

Local glutamate simulation of intertrigeminal region (ITR) in the lateral pons evoked immediate cardiovascular and respiratory effects proposing its role in central cardiorespiratory control. Since pharmacological studies provided only functional evidence for the existence of glutamate receptors in the ITR and thereby specifying putative neurochemical substrate involved in this control, here we employed immunohistochemistry to examine expression and distribution of NMDA and mGlu1 receptors in this structure. Thirty adult male Sprague-Dawley rats were perfuse-fixed, their brains frozen and cut into sequential series of 20 µm thick sections through the ITR. Immunohistochemistry was performed using polyclonal antibodies against NMDA-NR1, NMDA-NR2A and mGlu1 receptors. Labeled neurons in the ITR were analyzed using light microscope and computerized image analysis system for quantification of relative immunoreactivity as the mean of integrated optical density (IOD), and counting the immunopositive cells. Light microscopic analyses demonstrated NMDA-NR1-immunoreactivity mainly localized in the neuronal cell bodies with sparse distribution on primary dendrites, while NMDA-NR2A-immunoreactivity was basically somatically distributed. The mGlu1-immunoreactivity was moderate and observed both in neuronal bodies and primary dendrites or extracellular matrix suggesting somatodendritic localization. Quantitative analyses of IOD showed very strong expression of NMDA-NR1, weak of NMDA-NR2A and strong-to-moderate expression of mGluR1, with differences in immunostaining signal distribution over rostro-caudal span of the ITR. Counting of immunopositive cells followed similar expression profile. Our data directly confirm the presence of glutamatergic NMDA and mGlu1 receptors in the ITR apparently involved in signaling pathways by which this region modulates cardiorespiratory functions such as blood pressure, heart rate and breathing.

Surgical treatment of pontine cavernous malformations via subtemporal transtentorial and intradural anterior transpetrosal approaches.

The aim of this study was to report our surgical experience on resection of the pontine cavernous malformations (CMs) via subtemporal transtentorial approach (STTA) and intradural anterior transpetrosal approach (ATPA). Clinical data were retrospectively reviewed in 61 patients with pontine CMs that were surgically treated by the STTA and the intradural ATPA. The surgical procedures, complications, and outcomes were analyzed. The study consists of 61 patients with a total of 61 pontine CMs. Other than 4 lesions located medially in the pons, all CMs were in the lateral pons with a left or right lateral epicenter (the left/right ratio was 22/35). Totally, 11 patients (18.0%) with lesions located in the upper pons were treated by the STTA, and 50 patients (82.0%) with lesions involving the lower pons were treated by the intradural ATPA. Postoperatively, the complete resection was achieved in 58 patients (95.1%) and incomplete resection in 3 patients (4.9%). Twenty-seven patients (44.3%) suffered from a new or worsened neurological deficit in the immediate postoperative period, and 8 patients (13.1%) encountered a non-neural complication, including rebleeding, cerebrospinal fluid leak, intracranial infection, and pulmonary infection, and 3 patients had contusion of temporal lobe. With a mean follow-up of 54.2months, the patients' neurological condition had improved in 43 cases (71.6%), not changed in 10 cases (16.7%), and worsened in 7 cases (11.7%), respectively. The Karnofsky Performance Scale (KPS) score evaluated at the last time for per patient was significantly better than their baseline status (t = 6.677, p < 0.001). However, 21 patients (35.0%) suffered from a new or worsened persistent postoperative deficit. The lateral and anterolateral pons can be exposed well by the subtemporal transtentorial and intradural anterior transpetrosal approaches. Lesions of CMs located in the lateral pons, including ventrolateral and dorsolateral pons, could be totally removed by these two lateral approaches with an acceptable surgical morbidity.

Unilateral loss of trigeminal nerve fibers at the ventral pons

The trigeminal nerve has the largest territory of sensory innervation across the head and neck. It leaves the lateral pons through a large lateral sensory and small medial motor root. Root Entry Zone is an anatomical landmark of great functional hierarchy where variants in nervous tract trajectories and arterial loops, may result in neurovascular conflicts leading to neuralgias. The sensory root holds clinical significance because it innervates sensory receptors of the head and neck. This case reports a cadaveric brain stem with significant loss/ hypotrophy of left trigerminal nerve fibers. Such forfeit (weather due to congenital hypotrophy or postnatal lesion) can lead to variable degree of sensory loss along the nerve course and the innervation of mastication apparatus, change in of cerebellopontine angel and cistern volumes. The clinical outcomes of missing fibers might be not only hold symptomatic indicators for neurosurgeons but also morphologic benchmarks for biological anthropologists. These incidental findings are noteworthy to understand the causes, intricacies and clinical consequences of such neuroscience dilemmas. The case reported here might have presented with perplexing neurosensory ambiguities while alive and leaves ground of speculation for anatomists and neurologists. It is fundamental to identify spatial relations between different portions of the nervous tract, (especially while establishing possible vascular contact conflicts) that could explain lesser known Trigerminus syndromes. In future, high spatial resolution imaging would allow the study of each portion of the trigeminal nerve, recognizing with more clarity the anatomical variants or pathological elements.

Anatomical and Objective Evaluation of the Main Surgical Approaches to Pontine Intra-Axial Lesions

Apparently similar intra-axial pontine lesions may demand distinct surgical approaches. Selecting the optimal approach reduces unnecessary manipulation of tracts and nuclei. This study aims to reveal a quantitative analysis of main surgical corridors dealing with intrinsic pontine pathology. Six approaches were performed repeatedly in 10 cadaveric heads: 1) retrosigmoid, 2) retrolabyrinthine, 3) subtemporal transtentorial, 4) anterior petrosectomy, 5) combined petrosal approach, and 6) suboccipital telovelar. Six safe entry zones were studied: peritrigeminal, supratrigeminal, lateral pontine, supracollicular, infracollicular, and median sulcus of fourth ventricle. A neuronavigation device was used to collect 3-dimensional coordinates from fixed points over the edge of craniotomies and brainstem surface; 4 variables were studied: 1) angles of attack; 2) areas of exposure; 3) lengths of exposure; and 4) trajectories. The mean area of exposure generated by theretrosigmoid approach over the brainstem was 538.6 ± 161.0 mm2, whereas that yielded by the retrolabyrinthine was 475.0 ± 173.4 mm2. There were no significant differences between both when considering areas of exposure and angles. Adding a tentorial cut to the subtemporal approach exposed the superior part of the lateral surface ofpons; the area of exposure increased a mean of 33% (P<0.001). In addition to producing similar areas and angles of attack, the retrolabyrinthine yields a more orthogonal trajectory to lateral pons than the retrosigmoid approach. Adding a tentorial cut and anterior petrosectomy significantly increased areas and lengths of exposure of a regular subtemporal approach. The combined approach significantly increased angles of attack to both the supratrigeminal and lateral pontine safe zones.

Preliminary Phenotypic Cluster Analysis of Cardiorespiratory Modulated Neuronal Discharge Patterns with Dynamic Visualizations

Multi‐dimensional cluster analysis has been applied successfully to many taxonomy problems. Building on previous work (see Carroll et al., 2013 &amp; Zuperku et al., 2015), we have developed a quantitative, reproducible clustering classification of respiratory neuron phenotypes based upon activity. We displayed the results with a multi‐factorial visualization tool.We curated 100‐bin, normalized, cycle triggered histograms of spike trains with significant respiratory modulation (n=573 from a library of 1,373), recorded in lateral respiratory column (ventral respiratory group, pre‐Bötzinger, Bötzinger), pons, raphé, and dorsal lateral medulla. Initial analysis by Ward clustering with Cartesian distance in 100‐space differentiated three groups: predominantly inspiratory, predominantly expiratory and low respiratory modulation.Subsequent application of the same clustering paradigm to each of these 3 groups yielded a preliminary set of 24 archetypes, the averaged histograms of the elements of each cluster. We used those archetypes as clustering centroids on naïve recordings of 229 spike trains; all were clustered, with 20 of the archetypes. A 3‐D brainstem atlas displayed neuronal firing rates during periods of control and/or stimulated activity such as chemoreception, cough, swallow and vagotomy; cell activity was colored by type (cluster), illuminated in proportion to firing rate, and could be displayed in stereo or as a side‐by‐side or differential comparisons of stimulated vs. control activity.The data do not support a continuum of phenotypes based on discharge identity but instead are consistent with definable phenotypes.Support or Funding InformationOT2OD023854, HL109025This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Extended Middle Fossa Approach to Lateralized Pontine Cavernomas in Children

Objective Treatment of hemorrhagic cavernous malformations within the lateral pontine region demands meticulous surgical planning and execution to maximize resection while minimizing morbidity. We report a single-institution's experience using the extended middle fossa rhomboid approach for the safe resection of hemorrhagic cavernomas involving the lateral pons.

Brainstem Reflexes in Systemic Lupus Erythematosus Patients Without Clinical Neurological Manifestations.

We aimed to assess central and peripheral nervous system involvement in systemic lupus erythematosus (SLE) patients without any neurological signs and symptoms by performing electrophysiological investigations. Thirty-eight SLE patients and 35 healthy volunteers participated in this study. Peripheral nerve conduction and brainstem reflexes were evaluated by performing nerve conduction studies (NCSs) and blink reflex (BR) and masseter inhibitory reflex (MIR) recordings. Eleven patients (29%) had an abnormality in at least 1 NCS parameter, and 1 (2.6%) patient was diagnosed with polyneuropathy. The number of patients with abnormal BR and MIR was 23 (60.5%) and 14 (37%), respectively. The contralateral R2 latency of BR and the silent period 1 (SP1) latency of MIR were significantly prolonged in the patients compared with the controls (p=0.015 and p<0.001, respectively). This study showed that irrespective of peripheral nervous system involvement, brainstem reflexes could be affected in SLE patients even without clinical neurological findings. Brainstem reflex abnormalities suggested that the functional integrity of the inhibitory or excitatory interneurons in the lateral caudal pons and lateral medulla is disturbed in SLE patients.

Embolization of ruptured arteriovenous malformations in the cerebellopontine angle cistern.

Among brainstem arteriovenous malformations (AVMs), there exist small AVMs predominantly located in the cerebellopontine angle cistern (CPAC) with minimal extension into the pial surface of the brainstem. However, previous studies of CPAC AVMs did not particularly discuss the role of embolization in the treatment of these lesions. This study was conducted to clarify the effectiveness and validity of embolization in the treatment of CPAC AVMs. We retrospectively reviewed five patients with CPAC AVMs who underwent endovascular treatment. These patients were treated with embolization followed by open surgery or gamma knife (GK) radiosurgery. Radiological findings and clinical course for these patients were then assessed. All five patients presented with a hemorrhage. Angiography revealed that the main feeder contained a dilated pontine perforating artery in all cases. Embolization through the dilated pontine perforating artery effectively reduced shunt flow within the nidus or obliterated associated aneurysms. Magnetic resonance imaging showed infarction on the lateral pons in four patients, one of which developed transient mild dizziness and mild ataxia of the right side. Subsequent open surgery was performed in three patients, and GK radiosurgery was performed in two patients without complications. At the end of the follow-up period, all patients demonstrated favorable outcomes. Postoperative rebleeding did not occur in any of the patients. Disappearance of the AVM was confirmed in four patients, except in the one patient treated with GK. Although ischemic complications should be noted, embolization of CPAC AVMs may be an appropriate treatment option to reduce the risk of subsequent surgery or radiosurgery.

Clinical Study of Seven Patients with Infarction in Territories of the Anterior Inferior Cerebellar Artery

The prominent features of anterior inferior cerebellar artery (AICA) infarction are vertigo, cerebellar ataxia, and impaired hearing. The present study investigated neurological characteristics associated with AICA infarction. The locations of infarcts in 7 patients (age, 32-72 years) with AICA infarction were divided into the lower lateral pons, the middle cerebellar peduncle (MCP), and the cerebellum. Ischemic lesions were located in the MCP in 6 patients, spread to the lower lateral pons in 3, and involved the cerebellum in 4 patients. Standing posture and gait were impaired in all patients. Five and 4 patients had impaired hearing and vertigo, respectively. Two patients had only symptoms of labyrinthine disease, and 1 had these symptoms accompanied by impaired hearing. The symptoms in 2 patients with the lesion in the lateral pons were consistent with those in Gasperini syndrome. Two of 3 patients without vertigo had ataxia of the extremities. Stenosis of the vertebral artery or basilar artery in 5 patients indicated that the etiology was branch atheromatous disease. The most prominent symptom of truncal and gait ataxia and the frequent association between vertigo and impaired hearing were consistent with the characteristics of AICA infarction. Two patients without vertigo had ataxia of the trunk and extremities that might have been due to involvement of the dorsal spinocerebellar tract in the inferior cerebellar peduncle.

Perpetuation of errors in illustrations of cranial nerve anatomy.

For more than 230 years, anatomical illustrations have faithfully reproduced the German medical student Thomas Soemmerring's cranial nerve (CN) arrangement. Virtually all contemporary atlases show the abducens, facial, and vestibulocochlear nerves (CNs VI-VIII) all emerging from the pontomedullary groove, as originally depicted by Soemmerring in 1778. Direct observation at microsurgery of the cerebellopontine angle reveals that CN VII emerges caudal to the CN VIII root from the lower lateral pons rather than the pontomedullary groove. Additionally, the CN VI root lies in the pontomedullary groove caudal to both CN VII and VIII in the vast majority of cases. In this high-resolution 3D MRI study, the exit location of CN VI was caudal to the CN VII/VIII complex in 93% of the cases. Clearly, Soemmerring's rostrocaudal numbering system of CN VI-VII-VIII (abducens-facial-vestibulocochlear CNs) should instead be VIII-VII-VI (vestibulocochlear-facial-abducens CNs). While the inaccuracy of the CN numbering system is of note, what is remarkable is that generations of authors have almost universally chosen to perpetuate this ancient error. No doubt some did this through faithful copying of their predecessors. Others, it could be speculated, chose to depict the CN relationships incorrectly rather than run contrary to long-established dogma. This study is not advocating that a universally recognized numbering scheme be revised, as this would certainly create confusion. The authors do advocate that future depictions of the anatomical arrangements of the brainstem roots of CNs VI, VII, and VIII ought to reflect actual anatomy, rather than be contorted to conform with the classical CN numbering system.

Anatomy and approaches along the cerebellar-brainstem fissures.

OBJECT Fissure dissection is routinely used in the supratentorial region to access deeply situated pathology while minimizing division of neural tissue. Use of fissure dissection is also practical in the posterior fossa. In this study, the microsurgical anatomy of the 3 cerebellar-brainstem fissures (cerebellomesencephalic, cerebellopontine, and cerebellomedullary) and the various procedures exposing these fissures in brainstem surgery were examined. METHODS Seven cadaveric heads were examined with a microsurgical technique and 3 with fiber dissection to clarify the anatomy of the cerebellar-brainstem and adjacent cerebellar fissures, in which the major vessels and neural structures are located. Several approaches directed along the cerebellar surfaces and fissures, including the supracerebellar infratentorial, occipital transtentorial, retrosigmoid, and midline suboccipital approaches, were examined. The 3 heads examined using fiber dissection defined the anatomy of the cerebellar peduncles coursing in the depths of these fissures. RESULTS Dissections directed along the cerebellar-brainstem and cerebellar fissures provided access to the posterior and posterolateral midbrain and upper pons, lateral pons, floor and lateral wall of the fourth ventricle, and dorsal and lateral medulla. CONCLUSIONS Opening the cerebellar-brainstem and adjacent cerebellar fissures provided access to the brainstem surface hidden by the cerebellum, while minimizing division of neural tissue. Most of the major cerebellar arteries, veins, and vital neural structures are located in or near these fissures and can be accessed through them.