Communicating Hydrocephalus after Gamma Knife Radiosurgery for Vestibular Schwannoma: An MR Imaging Study

Abstract

SUMMARY: Vestibular schwannomas are common, and gamma knife radiosurgery is a treatment option of symptomatic tumors. Hydrocephalus may be a complication of gamma knife treatment of vestibular schwannoma, though the cause-and-effect relationship can be debated because tumors can cause hydrocephalus without treatment. We present an MR imaging study of an unusual case of communicating hydrocephalus after gamma knife radiosurgery of a vestibular schwannoma in which the timeline of events strongly suggests that gamma knife played a contributory role in the development of hydrocephalus. We discuss risk factors for the development of hydrocephalus after radiation therapy and the role of MR CSF cine-flow study in the evaluation of treatment options for hydrocephalus in this setting. Hydrocephalus is an uncommon and controversial complication of gamma knife radiosurgery for vestibular schwannomas. We report a complete MR imaging study including pretreatment and posttreatment imaging and MR CSF cine-flow study of such a case. The findings are consistent with a communicating hydrocephalus secondary to tumor necrosis, likely accelerated or worsened by gamma knife treatment. Case ReportThe patient was a 22-year-old previously healthy woman with a long history of left-sided tinnitus and decreased hearing. An MR imaging study was performed and demonstrated a 3-cm enhancing mass that was closely associated with the left vestibular nerve, with extension into the left porous acousticus. The appearance was consistent with vestibular schwannoma. After reviewing her options, the patient and her parents elected gamma knife radiosurgery instead of surgical removal. Nine months after the gamma knife procedure, the patient presented with headache, 2ϩ papilledema bilaterally, and a partial third nerve palsy. Another MR imaging scan was obtained, which demonstrated severe ventriculomegaly, with enlargement of the lateral, third, and fourth ventricles. No intraventricular point of obstruction of CSF flow was identified. The 3-cm vestibular schwannoma was again demonstrated, now with decreased central enhancement consistent with central necrosis (Figs 1-3). A lumbar puncture procedure was performed, and CSF demonstrated a protein level of 127 mg/dL (nmL 15-60 mg/dL) and trace red blood cells (128/mm 3 and 66/mm 3 , tubes 1 and 2). White blood cells were slightly elevated at 19/mm 3 (nmL range 1-5) and glucose levels were 56 mg/dL. Gram smear and culture results were negative, and there was no clinical evidence of infection. MR imaging cine-flow study was performed and confirmed free flow of CSF, without evidence of intraventricular obstruction (Fig 4). Endoscopic third ventriculostomy was performed without effect. A ventriculoperitoneal shunt was placed with relief of symptoms.

Hydrocephalus after gamma knife radiosurgery for schwannoma

“…It has been suggested that communicating hydrocephalus accompanying VS is caused by tumor necrosis with subsequent CSF protein elevation. [16] Elevated CSF protein levels may lead to CSF malabsorption at the level of the arachnoid granulations. [17] The lumbar CSF protein concentration in all the 92 patients was analyzed, and hydrocephalus was reported to be related to high protein levels in the CSF.…”

Communicating hydrocephalus associated with surgery or radiosurgery for vestibular schwannoma

“…It has been suggested that communicating HCP accompanying VS is caused by tumor necrosis with subsequent CSF protein elevation. 5,7 Elevated CSF protein levels may lead to CSF malabsorption at the level of the arachnoid granulations. 3,6,12,13 Some investigators have suggested that obstructive or communicating HCP is significantly correlated with increasing tumor size, however, we found no such correlation in our population.…”

“…2,4,5,11 With an increasing number of patients presenting with VS, and those who are treated using GKS in particular, understanding the pathogenesis of the development of HCP is crucial for the management of these patients. It has been suggested that communicating HCP accompanying VS is caused by tumor necrosis with subsequent CSF protein elevation.…”

“…1,2 By contrast, since its introduction in 1969, stereotactic radiosurgery has become widely advocated as a minimally invasive treatment of VS. 3 However, despite the associated low morbidity and acceptable efficacy of GKS, some factors during follow-up need to be considered. Some investigators have suggested that communicating hydrocephalus (HCP) may develop after GKS for of VS. [4][5][6] To date, the mechanism by which communicating HCP occurs is unknown. Radiosurgery may aggravate cerebrospinal fluid (CSF) malabsorption by causing radiation necrosis, with elevated CSF protein levels.…”

Hydrocephalies and Vestibular Schwannoma of Great Size: Therapeutic Strategies: About a Series of 32 Cases

“…The association between vestibular schwannoma (VS) and hydrocephalus represents 3.7% to 18% of all cases of VS. More frequently, it is a communicating type hydrocephalus [5] [6]. In our study, the prevalence of this pathological as- …”