A distributed auditory network mediated by pontine central gray underlies ultra-fast awakening in response to alerting sounds.

Sleeping animals can be woken up rapidly by external threat signals, which is an essential defense mechanism for survival. However, neuronal circuits underlying the fast transmission of sensory signals for this process remain unclear. Here, we report in mice that alerting sound can induce rapid awakening within hundreds of milliseconds and that glutamatergic neurons in the pontine central gray (PCG) play an important role in this process. These neurons exhibit higher sensitivity to auditory stimuli in sleep than wakefulness. Suppressing these neurons results in reduced sound-induced awakening and increased sleep in intrinsic sleep/wake cycles, whereas their activation induces ultra-fast awakening from sleep and accelerates awakening from anesthesia. Additionally, the sound-induced awakening can be attributed to the propagation of auditory signals from the PCG to multiple arousal-related regions, including the mediodorsal thalamus, lateral hypothalamus, and ventral tegmental area. Thus, the PCG serves as an essential distribution center to orchestrate a global auditory network to promote rapid awakening.

The pontine Kölliker-Fuse nucleus is important for reduced postinspiratory airflow elicited by stimulation of the ventral respiratory parafacial region.

Considering that the retrotrapezoid nucleus/respiratory parafacial region (RTN/pFRG) would be an important center in the central nervous system involved in the maintenance and modulation of respiratory activity, we hypothesized that neurons in this nucleus would also be involved in the postinspiratory (post-I) phase of the respiratory cycle through a connection with the pontine Kölliker-Fuse (KF) region. Here, we performed pharmacogenetic manipulation (AAV-hM3D(Gq)-mCherry or AAV-hM4D(Gi)-mCherry) in VGlut2-cre, Ai6 conscious mice to evaluate breathing parameters through whole body plethysmography under baseline conditions (normoxia: [Formula: see text] = 0.21) or under hypercapnia or hypoxia challenges ([Formula: see text] = 0.07 or [Formula: see text] = 0.08). Under normoxia, selective stimulation of RTN/pFRG resulted in a smaller increase in V̇e (1,272 ± 102.5, vs. RTN/pFRG stimulation: 1,878 ± 122.1 mL/kg/min), due to a smaller increase in VT (5.4 ± 0.35, vs. RTN/pFRG stimulation: 7.77 ± 0.21 mL/kg) without changing fR in a condition of KF inhibition. However, inhibition of the VGlut2 neurons in the KF did affect the TE1 produced by selective activation of RTN/pFRG (119.9 ± 2.53, vs. RTN/pFRG stimulation: 104 ± 2.46 ms). Both the hypercapnia and hypoxia ventilatory response were reduced after inhibition of VGlut2-expressing KF neurons. Therefore, consistent with anatomical projections RTN/pFRG neurons regulate lung ventilation by controlling all aspects of breathing, i.e., breathing frequency, inspiration, postinspiration, and active expiration. All the modulation seems to be dependent on the integrity of the glutamatergic neurons in the KF region.NEW & NOTEWORTHY Our research reveals specific roles and interactions between the retrotrapezoid nucleus/respiratory parafacial region (RTN/pFRG) and the pontine Kölliker-Fuse (KF) region in controlling respiratory phases. RTN/pFRG neurons are key in regulating all aspects of breathing, including frequency, inspiration, postinspiration, and active expiration. This regulation depends on the functional integrity of glutamatergic neurons in the KF region, aligning with anatomical projections.

Transcranial motor-evoked potentials disappear with pons transection.

Motor-evoked potential (MEP) monitoring by transcranial electrical stimulation (TES) is important for intraoperative motor function assessment in neurosurgery; however, false-negative results sometimes occur, and these findings should be interpreted with caution. Herein, we report an interesting MEP change resulting from a pons transection. The patient was a boy aged 5 years and 2 months. He underwent multiple craniotomies for cerebellar anaplastic ependymoma and was already paralyzed in the right upper and lower limbs. Therefore, we decided to remove the recurrent lesion from the left anterior pons. MEPs were recorded on both the right and left sides after the start of surgery but disappeared 1 h 30 min after the start of surgery in the TES on the operative side, even when the stimulation intensity was increased. The contralateral TES consistently recorded stable MEPs throughout the surgery. The tumor was completely resected on imaging. Immediately postoperatively, the patient experienced flaccid paralysis on the right side of the body, which recovered to preoperative levels over time. A transcranial MEP cannot be derived if the corticospinal tract is transected at the pons. Transcranial MEP findings may accurately reflect the corticospinal tract function if the injury is caudal to the pons.

High throughput mRNA sequencing reveals potential therapeutic targets of Si-Ni-San in the pons for a stress-induced depression model.

Background: An accumulating body of research indicates that the pons is related to the occurrence of depression. Si-Ni-San (SNS) is a well-known Chinese herbal formula that is used to treat depression. Chinese herbal formulae have multiple therapeutic characteristics. Although it has been proven that SNS can exert antidepressant effects by improving changes in the limbic system, it is currently unclear whether SNS has therapeutic targets in the pons. This study aimed to explore the therapeutic targets of SNS in the pons for depression treatment. Materials and methods: Two experiments were conducted. In Experiment 1, 32 rats were divided into four groups: (1) a Control (C) group that received distilled water as a vehicle; (2) a Model (M) group that received the chronic unpredictable mild stress (CUMS) procedure and was administered distilled water; (3) a Stress + SNS (MS) group that received the CUMS procedure and was administered SNS dissolved in distilled water; and (4) a Stress + Fluoxetine (MF) group that received the CUMS procedure and was administered fluoxetine dissolved in distilled water. The open field test (OFT), the sucrose preference test (SPT), and the novel object recognition test (NOR) were performed to test the antidepressant effects of SNS. High-throughput mRNA sequencing (RNA-seq) was used to explore possible gene targets of SNS in the pons, and quantitative real-time PCR was performed to verify the results. High-performance liquid chromatography was used to detect neurotransmitters. Finally, correlation analyses were conducted between behaviors, genes expression, and neurotransmitters. In Experiment 2, 18 rats were divided into the same three groups as in Experiment 1: (1) C, (2) M, and (3) MS. fMRI was used to confirm whether SNS altered the pons in a rat model of depression. Results: SNS significantly improved sucrose preference in the SPT and TN-TO in the NOR compared to the M group (P < 0.05). RNA-seq filtered 49 differentially expressed genes(DEGs) that SNS could reverse in the pons of the CUMS depression model. Real-time PCR detected six genes, including Complexin2 (Cplx2), Serpinf1, Neuregulin1 (Nrg1), Annexin A1 (Anxa1), ß-arrestin 1 (Arrb1) and presenilin 1 (Psen1). SNS significantly reversed changes in the expression of Anxa1, Nrg1, and Psen1 caused by CUMS (P < 0.05), which is consistent with the DEGs results. Additionally, SNS significantly reversed norepinephrine (NE) changes in the pons. There were 18 noteworthy correlations between behavior, genes, and neurotransmitters (P < 0.05). fMRI showed that SNS can decrease the amplitude of low-frequency fluctuations (ALFF) in the pons of living depressed rats. Conclusion: The pons is an important target brain region for SNS to exert its antidepressant effects. SNS may improve pontine NE levels by regulating the Anxa1, Nrg1, and Psen1 genes, thereby exerting antidepressant effects and improving cognitive function.

Morphological characteristics of cerebellum, pons and thalamus in Reccurent isolated sleep paralysis - A pilot study.

Introduction: Recurrent isolated sleep paralysis (RISP) is a rapid eye movement sleep (REM) parasomnia, characterized by the loss of voluntary movements upon sleep onset and/or awakening with preserved consciousness. Evidence suggests microstructural changes of sleep in RISP, although the mechanism of this difference has not been clarified yet. Our research aims to identify potential morphological changes in the brain that can reflect these regulations. Materials and methods: We recruited 10 participants with RISP (8 women; mean age 24.7 years; SD 2.4) and 10 healthy control subjects (w/o RISP; 3 women; mean age 26.3 years; SD 3.7). They underwent video-polysomnography (vPSG) and sleep macrostructure was analyzed. After that participants underwent magnetic resonance imaging (MRI) of the brain. We focused on 2-dimensional measurements of cerebellum, pons and thalamus. Statistical analysis was done in SPSS program. After analysis for normality we performed Mann-Whitney U test to compare our data. Results: We did not find any statistically significant difference in sleep macrostructure between patients with and w/o RISP. No evidence of other sleep disturbances was found. 2-dimensional MRI measurements revealed statistically significant increase in cerebellar vermis height (p = 0.044) and antero-posterior diameter of midbrain-pons junction (p = 0.018) in RISP compared to w/o RISP. Discussion: Our results suggest increase in size of cerebellum and midbrain-pons junction in RISP. This enlargement could be a sign of an over-compensatory mechanism to otherwise dysfunctional regulatory pathways. Further research should be done to measure these differences in time and with closer respect to the frequency of RISP episodes.

Unique presentation of acute neuro-Behçet's disease involving a cytotoxic edema core surrounded by vasogenic edema.

A 53-year-old woman with recurrent stomatitis, genital ulcers, and folliculitis was admitted to our hospital after experiencing visual disturbances for the past two weeks, and a non-throbbing headache for the past three days. She had also developed numbness in her left extremities. An ophthalmological examination revealed inflammatory changes in the eye. Cerebrospinal fluid analysis showed increased cell counts, protein, and interleukin-6 levels. Brain magnetic resonance imaging revealed multiple high signal intensities on T2-weighted (T2W)/fluid-attenuated inversion recovery (FLAIR) images of the pons and occipital and parietal lobes. The T2W/FLAIR high-signal-intensity lesion in the pons was hyperintense on diffusion-weighted imaging (DWI) and hypointense on apparent diffusion coefficient mapping (ADC), suggesting cytotoxic edema. Another high-signal-intensity lesion on T2W/FLAIR was isointense to hyperintense on DWI and hyperintense on ADC, indicating vasogenic edema. The vasogenic edema in the left occipital lobe contained a small core that was hyperintense on DWI and hypointense on ADC, suggesting cytotoxic edema. The patient was diagnosed with acute neuro-Behçet's disease (neuro-BD) and responded well to high-dose glucocorticoid and colchicine treatment. The present report emphasizes that patients with acute neuro-BD may present with cytotoxic edema in the pons and cerebral spheres. Further reports of similar cases would contribute to a better understanding of the role of cytotoxic edema in the pathophysiology of neuro-BD and help elucidate the mechanisms underlying a unique presentation characterized by a central cytotoxic edema core within vasogenic edema. (233 words).

An Analysis of the Anomalous Fissure of the Ligamentum Teres Hepatis: A Morphological Perspective in the North Indian Population.

Background The liver, being the largest internal organ of the body shows a variety of gross morphological variations about lobes, fissures and processes which may be clinically significant. Among various anatomical variations, the most found is the variant fissure for ligamentum teres hepatis. The present study was done to classify, review, compare and discuss the literature for anomalies in fissures for ligamentum teres hepatis. Methods A total of 100 formalin-preserved human livers were obtained from the Department of Anatomy of King George's Medical University, Lucknow, and studied for one year. Result In our study, 15% of the liver showed morphological variations in fissures for ligamentum teres hepatis. These were classified into four types. In type I (2%), the fissure was converted into a tunnel by pons hepatis. In type II (3%), there was an incomplete fissure for ligamentum teres hepatis extending into the diaphragmatic surface. In type III (4%), there was an incomplete fissure for ligamentum teres hepatis present only on the visceral surface. In type IV (6%), the fissure was covered by a thin membrane. Conclusion In this study of the North Indian population, 15% of liver have gross morphological variations. So thorough anatomical knowledge of the existence of variant or abnormal surface features on the liver is imperative to understanding the underlying pathology for radiologists and surgeons so that a favorable outcome can be achieved.

Chronic intermittent hypoxia elicits distinct transcriptomic responses among neurons and oligodendrocytes within the brainstem of mice.

Chronic intermittent hypoxia (CIH) is a prevalent condition characterized by recurrent episodes of oxygen deprivation, linked to respiratory and neurological disorders. Prolonged CIH is known to have adverse effects, including endothelial dysfunction, chronic inflammation, oxidative stress, and impaired neuronal function. These factors can contribute to serious comorbidities, including metabolic disorders and cardiovascular diseases. To investigate the molecular impact of CIH, we examined male C57BL/6J mice exposed to CIH for 21 days, comparing with normoxic controls. We used single-nucleus RNA sequencing to comprehensively examine the transcriptomic impact of CIH on key cell classes within the brainstem, specifically excitatory neurons, inhibitory neurons, and oligodendrocytes. These cell classes regulate essential physiological functions, including autonomic tone, cardiovascular control, and respiration. Through analysis of 10,995 nuclei isolated from pontine-medullary tissue, we identified seven major cell classes, further subdivided into 24 clusters. Our findings among these cell classes, revealed significant differential gene expression, underscoring their distinct responses to CIH. Notably, neurons exhibited transcriptional dysregulation of genes associated with synaptic transmission, and structural remodeling. In addition, we found dysregulated genes encoding ion channels and inflammatory response. Concurrently, oligodendrocytes exhibited dysregulated genes associated with oxidative phosphorylation and oxidative stress. Utilizing CellChat network analysis, we uncovered CIH-dependent altered patterns of diffusible intercellular signaling. These insights offer a comprehensive transcriptomic cellular atlas of the pons-medulla and provide a fundamental resource for the analysis of molecular adaptations triggered by CIH.NEW & NOTEWORTHY This study on chronic intermittent hypoxia (CIH) from pons-medulla provides initial insights into the molecular effects on excitatory neurons, inhibitory neurons, and oligodendrocytes, highlighting our unbiased approach, in comparison with earlier studies focusing on single target genes. Our findings reveal that CIH affects cell classes distinctly, and the dysregulated genes in distinct cell classes are associated with synaptic transmission, ion channels, inflammation, oxidative stress, and intercellular signaling, advancing our understanding of CIH-induced molecular responses.

ALSUntangled #75: Portable neuromodulation stimulator therapy.

Spurred by patient interest, ALSUntangled herein examines the potential of the Portable Neuromodulation Stimulator (PoNS™) in treating amyotrophic lateral sclerosis (ALS). The PoNS™ device, FDA-approved for the treatment of gait deficits in adult patients with multiple sclerosis, utilizes translingual neurostimulation to stimulate trigeminal and facial nerves via the tongue, aiming to induce neuroplastic changes. While there are early, promising data for PoNS treatment to improve gait and balance in multiple sclerosis, stroke, and traumatic brain injury, no pre-clinical or clinical studies have been performed in ALS. Although reasonably safe, high costs and prescription requirements will limit PoNS accessibility. At this time, due to the lack of ALS-relevant data, we cannot endorse the use of PoNS as an ALS treatment.

Quantitative brain stem assessment in discriminating neurodegenerative disorders from normal pressure hydrocephalus.

BACKGROUND AND PURPOSE: Differentiating idiopathic normal pressure hydrocephalus (iNPH) from neurodegenerative disorders such as progressive supranuclear palsy (PSP), Multiple System Atrophy-parkinsonian type (MSA-P), and vascular dementia (VaD) is challenging due to overlapping clinical and neuroimaging findings. This study assesses if quantitative brain stem and cerebellum metrics can aid in this differentiation. METHODS: We retrospectively compared the sagittal midbrain area, midbrain to pons ratio, MR parkinsonism index (MRPI), and cerebellar atrophy in 30 PSP patients, 31 iNPH patients, 27 MSA-P patients, 32 VaD patients, and 25 healthy controls. Statistical analyses determined group differences, sensitivity, specificity, and the area under the receiver operating characteristic curves. RESULTS: There was an overlap in midbrain morphology between PSP and iNPH, as assessed with MRPI, midbrain to pons ratio, and midbrain area. A cutoff value of MRPI > 13 exhibited 84% specificity in distinguishing PSP from iNPH and 100% in discriminating PSP from all other conditions. A cutoff value of midbrain to pons ratio at <0.15 yielded 95% specificity for differentiating PSP from iNPH and 100% from all other conditions. A cutoff value of midbrain area at <87 mm2 exhibited 97% specificity for differentiating PSP from iNPH and 100% from all other conditions. All measures showed low sensitivity. Cerebellar atrophy did not differ significantly among groups. CONCLUSION: Our study questions MRPI's diagnostic performance in distinguishing PSP from iNPH. Simpler indices such as midbrain to pons ratio and midbrain area showed similar or better accuracy. However, all these indices displayed low sensitivity despite significant differences among PSP, MSA-P, and VaD.

Complex Dysautonomia in a Patient With Cerebral Cavernous Malformations Due to a KRIT1 Pleiotropic Gene Mutation.

Dysautonomia is a disruption of the body's autonomic processes. Symptoms vary among patients, depending on the underlying disease pathways. Given that symptoms can affect all organ functions, dysautonomia often significantly impacts quality of life. However, due to its complex and varied presentation, early recognition of dysautonomia remains a challenge, yet it is crucial for improving patient outcomes. We report a case of a patient with a KRIT1 mutation presenting with dysautonomia causing urological, sexual, and bowel dysfunction. We hypothesize that the patient's symptoms are due to a pontine cavernous malformation (CM) caused by the KRIT1 mutation. A literature review was conducted to establish a link between pontine CM and dysautonomia.

Unusual presentation of glioblastoma in the brainstem: a case report of a diffuse pontine glioblastoma multiforme and surgical management.

Diffuse pontine glioblastoma multiforme is a rare subtype of glioblastoma associated with a poor prognosis. In this case report, we present a unique case of diffuse primary pontine glioblastoma multiforme in a patient without any supratentorial lesions. We review the symptoms, treatment options, and case management of patients with infratentorial glioblastoma multiforme and compare these with our patient. Our patient presented with symptoms including progressive diplopia, gait disturbance, and lower extremity weakness. Magnetic resonance imaging revealed a diffuse lesion involving the pons and biopsy revealed only mildly-atypical glial infiltrates. Consequentially, diagnosis was driven by genetic analysis. Due to the location of the tumor, surgery was not considered a viable option. Instead, the patient received radiation therapy along with concomitant and adjuvant temozolomide chemotherapy which has resulted in improvement of symptoms. This case highlights the challenges of managing diffuse primary pontine glioblastoma multiforme and the need for more effective treatment options for this rare subtype of glioblastoma. Despite aggressive treatment, the prognosis for patients with infratentorial glioblastoma multiforme remains poor, with a median survival time of less than a year. Further research is needed to improve our understanding of the biology and optimal management of this disease.

Morphological Study of Human Cadaveric Livers and Its Clinical Significance.

Introduction The liver is the largest gland in the body and shows wide variation in surface features. Knowledge of external features is essential for radiological investigations and during abdominal surgeries. Morphological variation of the liver should be considered for better patient outcomes. Segmental anatomy has received more attention for segmental resection and transplant surgery. The present study aimed to determine variations in external features of the liver and indicate its clinical importance. Materials and method A cross-sectional observational study was conducted on 52 specimens of human cadaveric livers, obtained during routine dissection in the anatomy departments of various medical colleges of Gujarat, India. Livers were examined for their morphology (lobes, notches, fissures, grooves), including their variations; pictures were taken; and results were tabulated. Result In the present study, 28 (53.84%) livers were normal in appearance in reference to surfaces, borders, lobes, and fissures. Specifically, 3.84% of livers were found with a very small left lobe, and 1.92% of livers with a large saddle-shaped left lobe. Five (9.61%) livers show the presence of Riedel's lobe, three (5.76%) livers show deep renal impression, and 13 (25%) livers show grooves on its antero-superior surface. One or two extra fissures were present in 28 livers, either present on the visceral surface of the right lobe, between the caudate process and papillary process of the caudate lobe or quadrate lobe. Pons hepatis was found in 10 (19.22%) livers. Tongue-like projection of the right lobe of the liver was observed in five (9.61%) livers, while an elongated left lobe was observed in three (5.76%) livers. Conclusion Livers show wide variations in their surface features. The variations observed in the present study will be of great help to anatomists, radiologists, and surgeons during diagnosis or surgical procedures.

Enigmatic echoes: Exploring brainstem neurenteric cysts - A case series and literature review.

INTRODUCTION AND IMPORTANCE: Neurenteric cysts (NCs) are rare congenital anomalies within the central nervous system, originating from the endodermal layer due to inappropriate embryonic notochordal plate and endoderm separation. Despite constituting a minute fraction of CNS tumors, their diverse clinical presentations and brainstem occurrence pose diagnostic challenges. CASE PRESENTATION: This study presents a series of three brainstem NCs, detailing demographics, clinical presentations, radiological features, and operative findings. Patients aged 2-40 years exhibited varied symptoms including headaches, vomiting, cranial nerve deficits, and motor/sensory deficits. Literature review of 27 cases showed a mean age of 26.8 years, predominantly in females, with diverse cystic characteristics on MRI. Surgical intervention achieved mostly complete resection, with varying outcomes including recurrence and malignant transformation. CLINICAL DISCUSSION: This study sheds light on the rare entity of brainstem NCs, emphasizing their diagnostic complexity. NCs, though constituting a minute fraction of CNS tumors, present a diagnostic challenge due to their diverse clinical presentations and rarity in the brainstem. CONCLUSION: This study provides insights into brainstem NCs, emphasizing diagnostic complexity and the importance of MRI in accurate diagnosis and surgical intervention. Enhanced collaboration is needed to refine management strategies for these intriguing lesions.

Lesiones inflamatorias del troncoencéfalo: claves diagnósticas en RM / Inflammatory lesions of the brainstem: Keys for the diagnosis by MRI

Objetivo: Describir los hallazgos en resonancia magnética (RM) de las principales enfermedades inflamatorias e inmunomediadas que afectan al troncoencéfalo. Conclusión: El diagnóstico diferencial de las lesiones inflamatorias localizadas en el troncoencéfalo es complicado debido al amplio espectro de enfermedades autoinmunes, infecciosas y síndromes paraneoplásicos que pueden causarlas. Conocer estas entidades, sus características clínicas y sus manifestaciones en RM, sobre todo en cuanto a número, morfología, extensión y apariencia en las diferentes secuencias, es útil a la hora de orientar el diagnóstico radiológico.(AU)

Objective: To describe the magnetic resonance imaging (MRI) findings for the most common inflammatory and immune-mediated diseases that involve the brainstem. Conclusion: Inflammatory lesions involving the brainstem are associated with a wide range of autoimmune, infectious, and paraneoplastic syndromes, making the differential diagnosis complex. Being familiar with these entities, their clinical characteristics, and their manifestations on MRI, particularly the number of lesions, their shape and extension, and their appearance in different sequences, is useful for orienting the radiological diagnosis.(AU)

Diverse roles of pontine NPS-expressing neurons in sleep regulation.

Neuropeptide S (NPS) was postulated to be a wake-promoting neuropeptide with unknown mechanism, and a mutation in its receptor (NPSR1) causes the short sleep duration trait in humans. We investigated the role of different NPS+ nuclei in sleep/wake regulation. Loss-of-function and chemogenetic studies revealed that NPS+ neurons in the parabrachial nucleus (PB) are wake-promoting, whereas peri-locus coeruleus (peri-LC) NPS+ neurons are not important for sleep/wake modulation. Further, we found that a NPS+ nucleus in the central gray of the pons (CGPn) strongly promotes sleep. Fiber photometry recordings showed that NPS+ neurons are wake-active in the CGPn and wake/REM-sleep active in the PB and peri-LC. Blocking NPS-NPSR1 signaling or knockdown of Nps supported the function of the NPS-NPSR1 pathway in sleep/wake regulation. Together, these results reveal that NPS and NPS+ neurons play dichotomous roles in sleep/wake regulation at both the molecular and circuit levels.

Inflammatory lesions of the brainstem: Keys for the diagnosis by MRI.

OBJECTIVE: To describe the magnetic resonance imaging (MRI) findings for the most common inflammatory and immune-mediated diseases that involve the brainstem. CONCLUSION: Inflammatory lesions involving the brainstem are associated with a wide range of autoimmune, infectious, and paraneoplastic syndromes, making the differential diagnosis complex. Being familiar with these entities, their clinical characteristics, and their manifestations on MRI, especially the number of lesions, their shape and extension, and their appearance in different sequences, is useful for orienting the radiological diagnosis.

Keyhole Retrosigmoid Craniotomy for Lateral Pontine Cavernous Malformation.

With improvements in anesthesia, monitoring, and peroperative care, the surgical removal of intrinsic brainstem pathology has become a possibility.1 Although surgical removal of deep-seated lesions continues to have significant morbidity, at least temporarily, associated with it, removal of exophytic lesions can be accomplished with little disability for the patient. The key to a good outcome, when removing cerebral cavernous malformation, is preservation of adjacent neurovascular bundles, use of sharp dissection over blunt pulling, judicious use of cautery in and around the brainstem, and preservation of the developmental venous anomaly, when present. The authors present a case of a lateral pontine cerebral cavernous malformation that was exophytic at the lateral and peritrigeminal safe entry zones.2 Neuromonitoring was used an adjunct to ensure safety of the procedure. The lesion is accessed using a keyhole retrosigmoid craniotomy (Video 1). We do not routinely use lumbar drains for these procedures as careful arachnoid dissection can result in adequate cerebrospinal fluid release. The window of access to this area is between CN 5 and the CN 7/8 complex. The arachnoid over the nerves is preserved, but the layer between the nerves is exposed to gain access to the lateral pons. The lesion is sharply dissected from the lateral pons, taking care to save the developmental venous anomaly, from which this lesion arises.