A common tumour in a rare location: a single centre case series of cerebellar glioblastoma.

Although glioblastoma is the commonest primary brain tumour in adults, its location in the cerebellum is extremely rare. We present thirteen cases (3 female, 10 male; median age at presentation 56 [age range 21-77]) of surgically managed, histologically confirmed, primary cerebellar glioblastoma (cGB) over a 17 year period (2005-2022). Pre-operative radiological diagnosis was challenging given cGB rarity, although MRI demonstrated ring enhancement in all cases. Surgical management included posterior fossa craniectomy and debulking in 11 cases and burr hole biopsy in two. CSF diversion was necessary in four cases. No evidence of IDH or ATRX gene mutations was found when tested. Survival ranged from 1 to 22 months after diagnosis (mean 10.9 months). We also seek to understand why glioblastoma is rare in this location and discuss potential reasons for this. We hypothesise that increasing anatomical distance from germinal regions and decreased local endogenous neural stem cell activity (which has been associated with glioblastoma) may explain why glioblastoma is rare in the cerebellum. We hereby seek to add to the limited literature on cGB as this is the largest UK cGB series to date.

A Reappraisal of the Pathophysiology of Cushing Ulcer: A Narrative Review.

In 1932, Harvey Cushing described peptic ulceration secondary to raised intracranial pressure and attributed this to vagal overactivity, causing excess gastric acid secretion. Cushing ulcer remains a cause of morbidity in patients, albeit one that is preventable. This narrative review evaluates the evidence pertaining to the pathophysiology of neurogenic peptic ulceration. Review of the literature suggests that the pathophysiology of Cushing ulcer may extend beyond vagal mechanisms for several reasons: (1) clinical and experimental studies have shown only a modest increase in gastric acid secretion in head-injured patients; (2) increased vagal tone is found in only a minority of cases of intracranial hypertension, most of which are related to catastrophic, nonsurvivable brain injury; (3) direct stimulation of the vagus nerve does not cause peptic ulceration, and; (4) Cushing ulcer can occur after acute ischemic stroke, but only a minority of strokes are associated with raised intracranial pressure and/or increased vagal tone. The 2005 Nobel Prize in Medicine honored the discovery that bacteria play key roles in the pathogenesis of peptic ulcer disease. Brain injury results in widespread changes in the gut microbiome in addition to gastrointestinal inflammation, including systemic upregulation of proinflammatory cytokines. Alternations in the gut microbiome in patients with severe traumatic brain injury include colonization with commensal flora associated with peptic ulceration. The brain-gut-microbiome axis integrates the central nervous system, the enteric nervous system, and the immune system. Following the review of the literature, we propose a novel hypothesis that neurogenic peptic ulcer may be associated with alterations in the gut microbiome, resulting in gastrointestinal inflammation leading to ulceration.

Olfactory neuroblastoma limited to sphenoid sinus.

Olfactory neuroblastoma (ONB) is a rare tumour of the skull base, typically originating from the nasal cavity and around the cribriform plate. We present the rare case of ONB originating from and limited to the sphenoid sinus in a 42-year old lady. Pre-operatively the lesion was thought to be a sinonasal polyp and underwent functional endoscopic sinus surgery (FESS) and total excision of the polypoid lesion. Review of histology unexpectedly revealed ONB. She underwent further surgery to ensure wide local excision was achieved with negative margins on histology, followed by radiotherapy. This is only the third reported case of ONB limited to the sphenoid sinus and the ninth reported case of primary sphenoid ONB in the literature. We review the literature pertaining with primary sphenoidal ONB here and suggest complete resection is indicated in ectopic ONB, not unlike classical ONB. There may be a role for adjuvant oncological treatments and lifelong follow up in a multidisciplinary approach is recommended.

Terson syndrome in reverse: intraventricular haemorrhage following primary intraocular haemorrhage.

Terson syndrome (TS) describes the presence of intraocular haemorrhage in patients with intracranial haemorrhage or traumatic brain injury. The aetiology of TS is controversial as an anatomical conduit between the vitreous humour and subarachnoid space remains contested. We herewith present a case of primary vitreous haemorrhage with secondary intracranial extension into the ventricles. Cranial CT demonstrates blood within the left optic nerve and chiasm but not within the subarachnoid space. This unusual phenomenon, which has not been reported before, may be described as 'Terson syndrome in reverse'. We explore mechanisms by which blood within the globe may track into the ventricular system, contextualising recent advances in the understanding of ocular-intracranial fluid transport.

Trigeminal schwannoma presenting as a gelastic seizure: no laughing matter.

We present the case of a 66 year old gentleman with trigeminal schwannoma whose only presenting feature was a single gelastic seizure. This is the first case report of pathological laughter in trigeminal schwannoma in the absence of other trigeminal, brainstem, cerebellar or other cranial nerve dysfunction.

Glioblastoma multiforme metastatic to lung in the absence of intracranial recurrence: case report.

We present the case of a 65 year old gentleman who underwent craniotomy and debulking of a left temporal glioblastoma multiforme (GBM). Post-operatively he received chemotherapy and radiotherapy with good response demonstrated on interval MRI scans. At 17 months post-diagnosis and in the absence of clinical or radiological recurrence, he presented with respiratory distress. He was found to have an exudative right-sided pleural effusion, nodular pleural thickening, a hilar mass and associated lymphadenopathy. Percutaneous pleural biopsy revealed metastatic GBM. Systemic GBM metastasis despite good response to oncological treatments and in the absence of intracranial recurrence is exceedingly rare. We review the literature concerning extra-neuraxial GBM metastasis and speculate why this phenomenon is extremely rare.

An explanation for Terson syndrome at last: the glymphatic reflux theory.

Terson Syndrome (TS) describes the presence of intraocular hemorrhage in patients with intracranial hemorrhage, typically subarachnoid hemorrhage. Despite TS being a well-defined and frequently occurring phenomenon, its pathophysiology remains controversial. This review will present the current understanding of TS, with view to describing a contemporary and more plausible pathomechanism of TS, given recent advances in ophthalmic science and neurobiology. Previously proposed theories include a sudden rise in intracranial pressure (ICP) transmitted to the optic nerve sheath leading to rupture of retinal vessels; or intracranial blood extending to the orbit via the optic nerve sheath. The origin of blood in TS is uncertain, but retinal vessels appear to be an unlikely source. In addition, an anatomical pathway for blood to enter the eye from the intracranial space remains poorly defined. An ocular glymphatic system has recently been described, drainage of which from the globe into intracranial glymphatics is reliant on the pressure gradient between intraocular pressure and intracranial pressure. The glymphatic pathway is the only extravascular anatomical conduit between the subarachnoid space and the retina. We propose that subarachnoid blood in skull base cisterns near the optic nerve is the substrate of blood in TS. Raised ICP causes it to be refluxed through glymphatic channels into the globe, resulting in intraocular hemorrhage. We herewith present glymphatic reflux as an alternative theory to explain the phenomenon of Terson Syndrome.

Spontaneous regression of a large skull base meningioma: case report.

We present the case of a 58 year old lady with a large middle cranial fossa meningioma (5 cm × 4 cm in maximal dimensions) which has considerably regressed without any treatment during seven years of follow up. While the tumour had remained radiologically static for the first three years, scans from year five post-diagnosis onwards have shown shrinkage of the meningioma from a calculated volume of 36 cm3 to 11.2 cm3. There has been no intratumoral haemorrhage or infarction and no medication or exogenous hormonal effect that could account for this effect. We reviewed the literature and report that this is only the second ever case of spontaneous regression of meningioma.