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

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

Impact of deep learning reconstruction on intracranial 1.5 T magnetic resonance angiography

Purpose The purpose of this study was to evaluate whether deep learning reconstruction (DLR) improves the image quality of intracranial magnetic resonance angiography (MRA) at 1.5 T. Materials and methods In this retrospective study, MRA images of 40 patients (21 males and 19 females; mean age, 65.8 ± 13.2 years) were reconstructed with and without the DLR technique (DLR image and non-DLR image, respectively). Quantitative image analysis was performed by placing regions of interest on the basilar artery and cerebrospinal fluid in the prepontine cistern. We calculated the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for analyses of the basilar artery. Two experienced radiologists evaluated the depiction of structures (the right internal carotid artery, right ophthalmic artery, basilar artery, and right superior cerebellar artery), artifacts, subjective noise and overall image quality in a qualitative image analysis. Scores were compared in the quantitative and qualitative image analyses between the DLR and non-DLR images using Wilcoxon signed-rank tests. Results The SNR and CNR for the basilar artery were significantly higher for the DLR images than for the non-DLR images (p < 0.001). Qualitative image analysis scores (p < 0.003 and p < 0.005 for readers 1 and 2, respectively), excluding those for artifacts (p = 0.072–0.565), were also significantly higher for the DLR images than for the non-DLR images. Conclusion DLR enables the production of higher quality 1.5 T intracranial MRA images with improved visualization of arteries.

Combined endoscopic endonasal transtubercular and transclival approaches for large neurenteric cyst in posterior cranial fossa: A case report and literature review

Background: Intracranial neurenteric cysts (NCs) are extremely rare tumors that more commonly involve the posterior fossa than any other cranial part. While transcranial skull base surgery has been the mainstay of treatment, the utility of endoscopic transnasal surgery (ETS) remains to be established. Case Description: We report a case of a large posterior fossa NC extensively involving the suprasellar region, cerebellopontine angle, and prepontine cistern, which we successfully resected with ETS through a combination of transtubercular and transclival routes. Before surgery, the patient presented with abducens nerve and pseudobulbar palsies, which resolved within 2 weeks postoperatively. The patient remained free from recurrence for 3 years postoperatively. Conclusion: Extended ETS may offer a minimally invasive option for the posterior fossa NC, extensively occupying the ventral space of the brainstem.

Endoscopic Third Ventriculostomy for an Idiopathic Disproportionately Large Communicating Fourth Ventricle: A Case Report

A disproportionately large communicating fourth ventricle (DLCFV) is a rare condition. A 34-year-old man experienced severe headaches, nausea, vomiting, and gait disturbance. Initial brain computed tomography (CT) showed markedly dilated ventricles with prepontine cistern shrinkage. Following extraventricular drain (EVD) insertion, approximately 400 mL/d of cerebrospinal fluid (CSF) was removed over 8 days. During this time, no significant changes in ventricle size were observed on CT images or the facial pain scale (FPS). We then performed an endoscopic third ventriculostomy and changed the drainage catheter. Immediately after surgery, the patient’s symptoms were relieved, and the drainage volume gradually decreased. EVD was successfully removed on the eighth postoperative day. Our experiences suggest that neurosurgeons should consider the importance of a third ventriculostomy for the diagnosis and treatment of DLCFV.

Endoscope-assisted microsurgical repair in trigeminal meningocele: case report

Trigeminal meningocele is a rare disease that results in rhinorrhea. Treatments with endoscopic approaches and open craniotomies have high recurrence rates, and controversy regarding the most effective surgical strategy for trigeminal meningocele is ongoing. The authors report a case of a 13-year-old female patient with a diagnosis of trigeminal meningocele determined after she presented with a history of intermittent headaches, suspected rhinorrhea, and recurrent meningitis. In addition to the conventional method of covering the efflux point of CSF and filling the inside of the meningocele with fascial tissues, the authors selectively closed the influx point of CSF from the prepontine cistern to the meningocele using an anterior transpetrosal approach. On the basis of the preoperative images, the authors hypothesized that the influx point of CSF could not be observed under the microscopic direct view and instead used a flexible endoscope. A check valve–like structure with one-way communication of CSF from the prepontine cistern into the cystic cavity was identified and was closed. At the time of this report, 36 months postoperatively, the patient had no indications of recurrence. Although cases of trigeminal meningoceles are infrequently encountered and require a tailored approach, the results in this case thus far indicate that the use of an endoscope and open craniotomy is an effective strategy for surgical treatment.

Giant Cell Tumour of Clivus: A Rare Case Report

Giant Cell Tumours (GCT) of the skull is rare, being less than 0.05% of all skeletal tumours. They are usually located in the middle cranial fossa affecting the temporal, sphenoid, petrosal and occipital bone. Clival GCT is rarer and 15 cases are described in the literature. Authors report a case of a female patient aged 20 years, who complained of headache with decrease in vision of left eye. Neurological examination revealed left optic nerve palsy. Laboratory test of Vitamin B12, blood urea, Serum Creatinine, Serum Electrolytes were within normal range. Complete blood count showed mild anaemia. The serum calcium and parathyroid hormones were within normal range. Computed Tomography (CT) scan and Magnetic Resonance Imaging (MRI) were done, which demonstrated expansile destructive lytic lesion involving sphenoid bone and clivus, reaching upto sellar, parasellar regions, sphenoid sinus and left posterior ethmoid sinus, effacing left optic foramina and posteriorly effacing prepontine cistern. The left internal carotid artery was partially encased by the mass. The tumour was partially removed by endoscopic trans-nasal trans-sphenoidal approach. Histopathology confirmed it as a benign GCT. Surgical treatment of clival GCTs are fraught with complication because of its close proximity to vital structures. High vascularity, potential malignant behaviour, inaccessibility and very few published cases preclude a definite outcome of this lesion. Histopathology is necessary to differentiate various lytic lesion like chordoma, aneurysmal bone cyst, invasive pituitary adenoma, chondrosarcoma and brown tumour (parathyroidism).

A rare case of adult diffuse midline glioma with H3 K27M mutant in the prepontine cistern

Diffuse midline glioma with the H3.3 histone A ( H3F3A) or H3 clustered histone 2/3 ( HIST1H3B/C) K27M mutation occurs primarily in children and less frequently in adults involving the midline structures of the central nervous system. This case report describes an adult patient with a diffuse midline glioma H3 K27M mutant in the prepontine cistern, which is an unusual site in clinical practice. The clinical, radiographic and histopathological data from the case are presented. Magnetic resonance imaging showed a progressively enlarged and enhanced nodule in the right prepontine cistern, with diffuse involvement of the meninges and communicating hydrocephalus. Analysis of the cerebrospinal fluid occasionally found suspiciously atypical cells with hyperchromatic nuclei and multiple nucleoli, as well as a severely elevated opening pressure and protein level, slightly elevated white cell count and decreased chloride level. Empirical antituberculosis treatment was administered but eventually proved to be ineffective. The definite diagnosis was made by histopathological analysis of the lesion based on the features of positive H3 K27M mutant protein and diffusely infiltrating growth. A diffuse midline glioma with the H3 K27M mutation may rarely present in an unusual site. A biopsy is recommended at an early stage for suspected cases to facilitate a definite diagnosis.

Fatal Case of Cerebral Aspergillum in an Immunocompetent Patient

Introduction: Cerebral aspergillum is rare and usually misdiagnosed because its presentation mimics tuberculous meningitis, brain abscess, or tumor. The diagnosis and treatment of central nervous system (CNS) infections due to Aspergillus are very difficult because accurate diagnosis is often made intra-operatively. Case Presentation: Here, we report a case of cerebral aspergilloma in an immunocompetent host. A 35-year-old man admitted with progressive left hemifacial paresthesia followed by severe pain in trigeminal nerve territory. On physical examination, except for fifth nerve palsy and difficult mastication, there was not any sensory and motor deficit. Magnetic resonance imaging (MRI) of the brain showed T1 iso and T2 low signal lesion in the left parasellar region with enhancement. The lesion is extended to the left side of the prepontine cistern in the course of trigeminal nerve, craniotomy, and total surgical resection of the mass was performed. Isolated brain lesion and the pathology from stereotactic biopsy confirmed cerebral aspergillosis. The result of testing for human immunodeficiency virus (HIV) was negative. Although the patient had two subsequent recurrences, at first, good outcome was achieved by treatment with a combination of surgical intervention, and antifungal amphotericin B deoxycholate was administered, then changed to voriconazole. Unfortunately, after two years, he experienced new progressive symptoms, and the patient died despite several reoperations due to malfunctioning of external ventricle devices as well as the treatment of recurrent post-operation meningitis and voriconazole therapy. Conclusions: Most cases of intracranial aspergillosis show that this infection is pathogenic in immunocompromised hosts; however, in some cases, invasive Aspergillus was reported as an opportunistic infection in immunocompetent patients. In these patients, though primary cranial aspergillosis is very rare, it is possible that isolated brain involvement in a previously healthy case may be explained by unknown defects in immune pathways or massive exposure to spores.