Transmastoid presigmoid retrolabyrinthine approach for removal of pontine cavernous malformation: how I do it.

BACKGROUND: Bleeding of brainstem cavernous malformations (BSCM) cause high morbidity and should be treated surgically whenever possible. METHOD: We present a 56-year-old man, who was diagnosed with a BSCM at right pons, which caused functional impairments of dorsal column, spinothalamic tract, cochlear nucleus, and middle cerebellar peduncle. A transmastoid presigmoid retorlabyrinthine approach via the lateral pontine zone (LPZ), with an assistance of imaging guidance and intraoperative neurophysiological monitoring, was performed to completely resect the BSCM. The patient recovered despite a transient worsening of cerebellar sign and hemiparesthesia for 1 week, without surgical complications. CONCLUSIONS: A transmastoid presigmoid retrolabyrinthine approach through LPZ is safe and effective for lateral pontine BSCM resection.

Visualization of Culprit Perforators in Anterolateral Pontine Infarction: High-Resolution Magnetic Resonance Imaging Study.

BACKGROUND: The stroke mechanism for anterolateral pontine infarction (ALPI) is poorly understood. We aimed to investigate the perforator arteries relevant to ALPI using high-resolution MRI (HR-MRI). METHODS: Of 62 patients with ALPI who were admitted to the Asan Medical Center, 13 patients agreed to participate in this study. We used HR-MRI with a 3-Tesla scanner and assessed the perforating branches directly connected with the infarcted area. RESULTS: Perforating arteries penetrating ALPI were identified in all 13 patients. Perforators arising from the basilar artery (BA) were involved in the stroke mechanism in 9 patients, the superior cerebellar artery (SCA) perforator in 1 patient, and the anterior inferior cerebellar artery perforator in 1 patient. In 2 patients, both BA and SCA perforators were involved. CONCLUSIONS: Using 3-Tesla HR-MRI may allow visualization of the perforating branches presumably related to ALPI. Identification of the relevant cerebral perforating arteries may help us to understand the stroke mechanism in patients with posterior circulation territory infarction.

Hyperacoustic hypoacusis: A new pontine syndrome-Case report.

We herein report a unique case of a lateral pontine demyelinating lesion presenting with unilateral sensorineural hearing loss and paradoxical ipsilateral hyperacusis. The association of unilateral hearing loss and ipsilateral hyperacusis is a rare manifestation of a central nervous system lesion. The paradoxical combination of these symptoms strongly suggests pontine dysfunction and prompts urgent neurological evaluation.

Arteriovenous malformations in the cerebellopontine angle: assessment of the "backdoor resection" technique and microsurgical results in 38 patients.

OBJECTIVE: Posterior fossa arteriovenous malformations (AVMs) represent 7% to 15% of all intracranial AVMs and are associated with an increased risk of hemorrhage, morbidity, and mortality compared with supratentorial AVMs, thus prompting urgent and definitive treatment. Cerebellopontine angle (CPA) AVMs are a unique group of posterior fossa AVMs incorporating characteristics of brainstem and cerebellar lesions, which are particularly amenable to microsurgical resection. This study reports the clinical, radiological, operative, and outcome features of patients with CPA AVMs in a large cohort. METHODS: The authors conducted a single-surgeon, 2-institution retrospective cohort study of all consecutive patients with CPA AVMs treated with microsurgical resection during a 25-year period. RESULTS: CPA AVMs represented 22% (38 of 176) of all infratentorial AVMs resected by the senior author. Overall, 38 patients (22 [58%] male and 16 [42%] female) met the study inclusion criteria and were analyzed. Most patients presented with hemorrhage (n = 29, 76%). The median age at surgery was 56 (range 6-82) years. Subtypes included 22 (58%) petrosal cerebellar AVMs, 11 (29%) lateral pontine AVMs, and 5 (13%) AVMs involving both the brainstem and cerebellum. Most AVM niduses were small (< 3 cm; n = 35, 92%) and compact (n = 31, 82%). Fourteen (37%) patients harbored flow-related aneurysms. Twenty (53%) patients underwent preoperative embolization. Complete angiographic obliteration was achieved with microsurgery in 35 (92%) patients. Five (13%) patients with poor neurological conditions at presentation died before hospital discharge. Of the 7 (18%) patients with new postoperative neurological deficits, 5 had transient deficits. The median (interquartile range) follow-up was 1.7 (0.5-3.2) years; 32 (84%) patients were alive at last follow-up, and 30 (79%) had achieved a favorable neurological outcome (modified Rankin Scale [mRS] score 0-2). The only independent predictor of unfavorable postoperative outcome (mRS score 3-6) was the preoperative mRS score (p = 0.002). CONCLUSIONS: CPA AVMs are unique posterior fossa lesions, including petrosal cerebellar and lateral pontine AVMs. The "backdoor resection" technique provides a safe and efficient strategy with high obliteration rates and a low risk of treatment-related morbidity. Microsurgical resection should be considered the frontline treatment for most CPA AVMs, except for those with a significant diffuse brainstem component.

Role of cerebellar cortex in associative learning and memory in guinea pigs.

Time-related cognitive function refers to the capacity of the brain to store, extract, and process specific information. Previous studies demonstrated that the cerebellar cortex participates in advanced cognitive functions, but the role of the cerebellar cortex in cognitive functions is unclear. We established a behavioral model using classical eyeblink conditioning to study the role of the cerebellar cortex in associative learning and memory and the underlying mechanisms. We performed an investigation to determine whether eyeblink conditioning could be established by placing the stimulating electrode in the middle cerebellar peduncle. Behavior training was performed using a microcurrent pulse as a conditioned stimulus to stimulate the middle cerebellar peduncle and corneal blow as an unconditioned stimulus. After 10 consecutive days of training, a conditioned response was successfully achieved in the Delay, Trace-200-ms, and Trace-300-ms groups of guinea pigs, with acquisition rates of >60%, but the Trace-400-ms and control groups did not achieve a conditioned stimulus-related blink conditioned response. It could be a good model for studying the function of the cerebellum during the establishment of eyeblink conditioning.

Extended Retrosigmoid Approach for Resection of a Lateral Pontine Arteriovenous Malformation: 2-Dimensional Operative Video.

Pontine arteriovenous malformations (AVMs) are uncommon lesions, with few reports in the literature. The best treatment option is debated, with options including surgical resection, endovascular embolization, and radiosurgery. Patient consent for the procedure was obtained. Herein, we report the successful resection of a ruptured lateral pontine AVM with an associated aneurysm in a woman in her early 70s. Surgical resection can be considered an effective treatment option for brainstem AVMs and should be considered alone or in conjunction with other treatment modalities. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Retrosigmoid Approach for Resecting a Giant Lateral Pontine Ependymoma: Two-Dimensional Operative Video.

Ependymoma is one of the most common pediatric tumors in central nervous system, for which gross total resection has been the most favorable prognostic factor. 1 2 However, surgery of ependymomas located in brain stem is significantly challenging. This video demonstrates the microsurgical removal of an ependymoma originating from ependymal cells of the lateral recess of fourth ventricle via retrosigmoid approach in an 11-year-old female. The patient presented with a 6-month history of continues headache and vomiting. On examination, she had a walking instability and an emaciated body. Neuroimaging revealed a right lateral pontine lesion extending to the cerebellopontine angle region. The patient underwent a suboccipital craniotomy, followed by excellent exposure for the tumor. Petrosal vein encased by the tumor mass and close adhesion of the tumor and the initial segments of facial and acoustic nerves adjoined brain stem could be seen operatively. While preserving trigeminal nerve, facial and acoustic nerves, posterior cranial nerves, anterior inferior cerebellar artery, labyrinth artery, posterior inferior cerebellar artery, and petrosal vein, gross total resection was achieved under the careful operation along arachnoid spaces together with intratumoral decompression. The patient tolerated the procedure well without any neurological deficits. Histological examination confirmed the tumor as an ependymoma (WHO II). The cytology measurement of the cerebrospinal fluid did not find any tumor cells. Postoperative computed tomography and magnetic resonance imaging scan depicted complete resection of the tumor, and adjuvant radiotherapy was recommended. She remained symptom-free without any evidence of recurrence during the follow-up period of 1 year. Informed consent was obtained from the patient. The link to the video can be found at: https://youtu.be/sZ9GhUeltwc .

Usefulness of the middle cerebellar peduncle approach for microsurgical resection of lateral pontine arteriovenous malformation.

Surgical treatment of brainstem arteriovenous malformation (AVM) is challenging and associated with a higher risk of complications and a lower rate of gross-total resection. The authors present their experience with the surgical management of lateral pontine AVM using the middle cerebellar peduncle approach. All cases presented with neurological deficits that were caused by hemorrhage before surgery. In all cases, the AVM was not visualized on postoperative angiography, and there was no deterioration of neurological symptoms. In this video, the authors report the treatment results of one case and describe the technique with a review of the literature. The video can be found here: https://youtu.be/bFvEMtMnrKw.

Whole-Brain Neural Connectivity to Lateral Pontine Tegmentum GABAergic Neurons in Mice.

The GABAergic neurons in the lateral pontine tegmentum (LPT) play key roles in the regulation of sleep and locomotion. The dysfunction of the LPT is related to neurological disorders such as rapid eye movement sleep behavior disorder and ocular flutter. However, the whole-brain neural connectivity to LPT GABAergic neurons remains poorly understood. Using virus-based, cell-type-specific, retrograde and anterograde tracing systems, we mapped the monosynaptic inputs and axonal projections of LPT GABAergic neurons in mice. We found that LPT GABAergic neurons received inputs mainly from the superior colliculus, substantia nigra pars reticulata, dorsal raphe nucleus (DR), lateral hypothalamic area (LHA), parasubthalamic nucleus, and periaqueductal gray (PAG), as well as the limbic system (e.g., central nucleus of the amygdala). Further immunofluorescence assays revealed that the inputs to LPT GABAergic neurons were colocalized with several markers associated with important neural functions, especially the sleep-wake cycle. Moreover, numerous LPT GABAergic neuronal varicosities were observed in the medial and midline part of the thalamus, the LHA, PAG, DR, and parabrachial nuclei. Interestingly, LPT GABAergic neurons formed reciprocal connections with areas related to sleep-wake and motor control, including the LHA, PAG, DR, parabrachial nuclei, and superior colliculus, only the LPT-DR connections were in an equally bidirectional manner. These results provide a structural framework to understand the underlying neural mechanisms of rapid eye movement sleep behavior disorder and disorders of saccades.