Fourth ventricular roof angle does not predict surgical outcome in paediatric patients with Chiari I malformation.

PURPOSE: Pre-operative fourth ventricle roof angle (FVRA) has recently been highlighted as a novel radiographic predictor of clinical severity in Chiari type-I malformation (CM-I) as reported by Seaman et al. (J Neurosurg Pediatr 25:1-8, 2021). This has led to suggestions that FVRA could be included in algorithms to determine indications for surgery. We aimed to test the accuracy of FVRA as a predictor of clinical severity and its effect on post-operative outcome in a large retrospective cohort of paediatric patients who underwent decompression for CM-I. METHODOLOGY: Patients undergoing craniocervical decompression for CM-I at the Queensland Children's Hospital and Mater Hospital, Brisbane, between 2006 and 2018 were included. Data was collected from 66 patients aged 0-18 years. Post-operative outcome was assessed by calculating Chicago Chiari Outcomes Score (CCOS) at follow-up. The FVRA was taken from a mid-sagittal T1-weighted MRI as previously described (Seaman et al. in J Neurosurg Pediatr 25:1-8, 2021). The angle is subtended between superior and inferior medullary velum. RESULTS: Whilst results from Seaman et al. demonstrated a strong correlation between a FVRA > 65° and symptomatic CM-I, this did not translate to our dataset (p = 0.61). Additionally, pre-operative FVRA is not useful as a predictive tool for post-surgical outcome as assessed by CCOS (p = 0.50), and post-operative reduction in FVRA did not correlate with improved outcomes (p = 0.81). We did note significantly worse outcomes in patients presenting with pre-operative brainstem dysfunction (p = 0.03). CONCLUSION: Paediatric CM-I is a challenging cohort to manage, often due to young age and a lack of language skills. There is a heavy reliance on radiological findings. Whilst FVRA has previously been reported to be of value as a determinant of clinical severity in adult and paediatric patients, we find that this measurement is of dubious value in our retrospective cohort.

Direct Administration of Chemotherapy and Other Agents into the Fourth Ventricle to Treat Recurrent Malignant Brain Tumors in Children.

Direct administration of chemotherapy and other agents into the fourth ventricle of the brain is a novel approach to treating recurrent malignant posterior fossa brain tumors in children. Candidates for this treatment approach include patients with recurrent medulloblastoma, ependymoma, atypical teratoid/rhabdoid tumor, and potentially other neoplasms that originate in the fourth ventricle or elsewhere in the posterior fossa. In this chapter, the authors first explain the rationale for considering fourth ventricular drug infusions in patients with recurrent malignant posterior fossa tumors. We then summarize the results of translational experiments conducted in piglets and non-human primates that demonstrated safety and favorable pharmacokinetics. These translational experiments led to several pilot human clinical trials, and the results of these trials are reviewed. Finally, currently open clinical trials testing infusion of various agents into the fourth ventricle are discussed, and thoughts about potential future directions are shared.

Case report: Gross total resection of a primary fourth ventricular meningioma using the telovelar approach in a dog.

An 11-year-old spayed female Maltese dog presented with a 2-month history of gait alterations, wide-based stance, and chronic vomiting. Neurological examination revealed cerebellovestibular signs, including head tilt, nystagmus, strabismus, intentional tremor, and hypermetric gait. MRI showed a mass with iso- to hypointensity on T1-weighted (T1W) images and heterogeneous hyperintensity on T2-weighted (T2W) images, with marked non-uniform contrast enhancement. The tumor was removed via a telovelar approach without intraoperative complications. Postoperatively, the dog developed non-ambulatory paraparesis with the rigidity of the pelvic limbs but recovered ambulation within 6 days. Preoperative neurological signs progressively improved, and the patient was discharged without complications 10 days after surgery. Histological examination revealed dense spindle cells with an abundant collagen matrix and oval-shaped nucleated cells with small whorls, leading to a diagnosis of transitional meningioma of the fourth ventricle. MRI follow-up at 8 months postoperatively showed no definitive evidence of recurrence. At the final follow-up, 15.4 months postoperatively, mild neurological signs, including a slight head tilt and subtle strabismus, remained, but the rest of the neurological examination was normal. This is the first reported case of a meningioma in the fourth ventricle of a dog successfully removed using the telovelar approach.

Primary Central Nervous System Lymphoma Presenting as a Solitary Fourth Ventricular Mass: A Case Report.

The occurrence of primary fourth ventricular lymphoma is an exceptionally uncommon phenomenon. Here, we present a case of lymphoma in the fourth ventricle in a 30-year-old male who presented with progressive headache and vertigo over the last one month of his presentation. Preoperative MRI revealed a space-occupying lesion of the fourth ventricle. Pathological analysis following complete resection confirmed the lesion as primary central nervous system lymphoma. The patient underwent chemotherapy following the MTR (methotrexate, temozolomide, and rituximab) protocol with four months of uneventful follow-up, indicating no disease recurrence. Therefore, clinicians are advised to consider the potential presence of lymphoma as part of the differential diagnosis for space-occupying lesions, especially when there is a combination of clinical deterioration and rapid imaging progression.

Ultrasonographic evaluation of fetal posterior fossa anomalies: Six years experience of a tertiary center.

PURPOSE: The aim of this study is to reveal ultrasonographic features, associated anomalies and genetic errors in posterior fossa anomalies. As secondary aim postnatal outcomes of the cases were reviewed. METHODS: We conducted a retrospective case series from 2018 to 2024 involving fetuses with posterior fossa anomalies (PFA). Terminated cases confirmed by radiologic and postmortem pathologic findings and cases confirmed by postnatal clinical findings were included in the study. RESULTS: A total of 138 cases were included. In 81 (59%) cases there were multipl anomalies including cranial anomalies other than posterior fossa in 31 (22%) and non-central nerve system anomalies in 69 (50%) cases. Of the 94 cases born, 28 (20%) died within a median of 2 months, within 1.5 years at the latest. Of the 66 (48%) cases still living, 30 (22%) have neurodevelopmental delay in Denver II Turkish standardized test. CONCLUSIONS: It is crucial to have accurate and standardized prenatal classification and a multidisciplinary approach in fetuses with PFA. Specific ultrasonographic findings may be diagnostic especially where fetal MRI is not always available. We offer "arrow sign" to be tested whether it is accurate to diagnose Joubert syndrome by ultrasonography.

The tonsillouvular fissure approach to exophytic cavernous malformation in the lateral recess of the fourth ventricle: 2-dimensional operative video.

Cavernous malformations surrounding the fourth ventricle are challenging lesions to access and treat surgically owing to the complexity and eloquence of adjacent neural tissue [1] Long-standing practice included tissue transgression through the overlying cerebellar cortical surface of the hemisphere or vermis [1-3]. Using natural corridors such as tonsillobiventral fissure, cerebellomedullary fissure, and tonsillouvular fissure (TUF) offers elegant access to the fourth ventricle, avoiding traversing of neural tissue [4-7]. A 32-year-old male presented with headache, nausea, vomiting, double vision, and vertigo. Neuroimaging demonstrated a 17-mm diameter cavernous malformation protruding into the left lateral recess of the fourth ventricle. The patient consented for the procedure and underwent a middline suboccipital craniotomy in a prone position. TUF approach was performed by dissecting the arachnoid to the depth of the fissure, and after identifying the tonsillomedullary segment of the posterior inferior cerebellar artery, minimal white matter transgression was used to reach cavernous malformation. Complete removal of the lesion was achieved and confirmed on postoperative imaging. The postoperative course was uneventful. TUF approach with manipulation by ipsilateral and contralateral retraction of tonsills allows the widening of the surgical corridor and better exposure of lesions of the lateral recess of the fourth ventricle [1]. TUF approach is a valuable alternative to transvermian and transcerebellar approaches that minimize the division of neural tissue [6]. To the best of our knowledge this is the first case describing the TUF approach to exophytic cavernoma presenting in the lateral recess of the fourth ventricle. Under our institutional ethical review board regulations, approval was not necessary.

Atypical epidermoid cyst of the fourth ventricle with minimal diffusion-restriction.

BACKGROUND: Epidermoid cysts are benign, slow growing extra-axial lesions most commonly found in the cerebellopontine angle that have a characteristic imaging pattern of restricted diffusion on diffusion-weighted imaging (DWI). METHODS: A 10-year-old male with a history of asthma and diabetes was found to have a lesion within the fourth ventricle on a magnetic resonance imaging (MRI) brain study. MRI showed a well-circumscribed vermian lesion without contrast enhancement or restricted diffusion with mild hydrocephalus. He was referred to the neurosurgical service once he acutely developed symptoms of dizziness. He underwent a gross-total resection of the lesion on which histopathology confirmed an epidermoid cyst. RESULTS: Here, we report a case of an atypical epidermoid cysts found in the midline of the fourth ventricle without restricted diffusion on MRI. CONCLUSION: Avid restricted-diffusion on DWI is usually pathognomonic for an epidermoid cyst when evaluating an extra-axial lesion, yet we report the second case in the literature of an epidermoid cyst without this classical imaging characteristic.

Rare Complications of CSF Diversion: Paradoxical Neuroimaging Findings in a Double, Chiasmic Case Report.

Two patients with CSF shunting systems exhibited symptoms of altered intracranial pressure. Initial neuroimaging led to misinterpretation, but integrating clinical history and follow-up imaging revealed the true diagnosis. In the first case, reduced ventricular size was mistaken for CSF overdrainage, while the actual problem was increased intracranial pressure, as seen in slit ventricle syndrome. In the second case, symptoms attributed to intracranial hypertension were due to CSF overdrainage causing tonsillar displacement and hydrocephalus. Adjusting the spinoperitoneal shunt pressure resolved symptoms and imaging abnormalities. These cases highlight the necessity of correlating clinical presentation with a deep understanding of CSF dynamics in shunt assessments.

Anatomical considerations and surgical manipulation of the rhomboid lip in microvascular decompression for hemifacial spasm.

BACKGROUND: In microvascular decompression (MVD) procedures for hemifacial spasm (HFS), surgeons often encounter a rhomboid lip which may obscure the root exit zone (REZ) of the facial nerve. This study aims to explore the anatomical variations of rhomboid lips and their surgical implications to improve safety and effectiveness in MVD surgeries. METHODS: A retrospective analysis was conducted on 111 patients treated for HFS between April 2021 and March 2023. The presence of a rhomboid lip was assessed through operative video records, and its characteristics, dissection methods, and impact on nerve decompression outcomes were further examined. Preoperative magnetic resonance imaging (MRI) scans were reviewed for detectability of the rhomboid lip. RESULTS: Rhomboid lips were identified in 33% of the patients undergoing MVD, with a higher prevalence in females and predominantly on the left side. Two distinct types of rhomboid lips were observed: membranous and cystic variations. The membranous type was noted for its smaller size and position ventral to the choroid plexus. In contrast, the cystic variation was distinguished by its larger size and a thin membrane that envelops the choroid plexus. Preoperative MRI successfully identified rhomboid lips in only 21% of the patients who were later confirmed to have them in the surgical procedures. Surgical approaches primarily involved incisions on the dorsal wall and along the glossopharyngeal nerve root, with only limited need for extensive dissection from lower cranial nerves. Immediate spasm relief was observed in 97% of the patients. One case exhibited a lower cranial nerve deficit accompanied by brainstem infarction, which was caused by the dissection from the lower cranial nerves. CONCLUSIONS: Recognizing the two variations of the rhomboid lip and understanding their anatomical structures are essential for reducing lower cranial nerve injuries and ensuring effective nerve decompression.

Bilateral abducens and facial nerve palsies following fourth ventriculoperitoneal shunt with laparoscopic-assisted abdominal catheter placement.

Introduction: Hydrocephalus, altering cerebrospinal fluid (CSF) dynamics, affects 175 per 100,000 adults worldwide. Ventriculoperitoneal shunts (VPS) manage symptomatic hydrocephalus, with 125,000 cases annually. Despite efficacy, VPS face complications, necessitating interventions. Research question: "What are the mechanisms and risk factors for bilateral VIth and VIIth lower motor neuron palsies in hydrocephalus patients with a fourth ventriculoperitoneal shunt?" Material and methods: This study details a 36-year-old female with a neonatal meningitis history, multiple shunt replacements, admitted for abdominal pain secondary to pelvic inflammatory disease. An abdominal shunt catheter removal and external ventricular drain placement occurred after consultation with a general surgeon. A cardiac atrial approach and subsequent laparoscopic abdominal approach were performed without complications. Results: After one month, the patient showed neurological complications, including decreased facial expression, gait instability, and bilateral VIth and VIIth lower motor neuron palsies, specifically upgazed and convergence restriction. Discussion: The complication's pathophysiology is discussed, attributing it to potential brainstem herniation from over-drainage of CSF. Literature suggests flexible endoscopic treatments like aqueductoplasty/transaqueductal approaches into the fourth ventricle. Conclusions: This study underscores the need for increased awareness in monitoring neurological outcomes after the fourth ventriculoperitoneal shunt, particularly in cases with laparoscopic-assisted abdominal catheter placement. The rarity of bilateral abducens and facial nerve palsies emphasizes the importance of ongoing research to understand pathophysiology and develop preventive and therapeutic strategies for this unique complication.