Ventriculostomy and Risk of Upward Herniation in Patients with Obstructive Hydrocephalus from Posterior Fossa Mass Lesions

Background: Patients with posterior fossa lesions causing obstructive hydrocephalus present a unique clinical challenge, as relief of hydrocephalus can improve symptoms, but the perceived risk of upward herniation must also be weighed against the risk of worsening or continued hydrocephalus and its consequences. The aim of our study was to evaluate for clinically relevant upward herniation following external ventricular drainage (EVD) in patients with obstructive hydrocephalus due to posterior fossa lesions.

Methods: We performed a retrospective review of patients undergoing urgent/emergent EVD placement at our institution between 2007 and 2014, evaluating the radiographic and clinical changes following treatment of obstructive hydrocephalus.

Results: Even prior to EVD placement, radiographic upward herniation was present in 22 of 25 (88%) patients. The average Glasgow Coma Scale of patients before and after EVD placement was 10 and 11, respectively. Radiographic worsening of upward herniation occurred in two patients, and upward herniation in general persisted in 21 patients. Clinical worsening occurred in two patients (8%), though in all others the clinical examination remained stable (44%) or improved (48%) following EVD placement. Of the patients who had a worsening clinical exam, other variables likely also contributed to their decline, and cerebrospinal fluid diversion was likely not the main factor that prompted the clinical change.

Conclusions: Radiographic presence of upward herniation was often present prior to EVD placement. Clinically relevant upward herniation was rare, with only two patients worsening after the procedure, in the presence of other clinical confounders that likely contributed as well.