Objective: The first objective is to evaluate the potential pathophysiological link between vestibular schwannoma (VS) and normal pressure hydrocephalus (NPH) by analyzing clinical features, imaging findings, and treatment outcomes in patients with VS-associated NPH (VS-NPH). The second objective is to compare this cohort with patients who have idiopathic NPH (iNPH).

Background: VS arising from Schwann cells of the eighth cranial nerve is the most common neoplasm of the cerebellopontine angle. An association between VS and hydrocephalus has been noted, mostly of the obstructive type, yet communicating hydrocephalus has also been described, which may present with the clinical triad of NPH. The mechanisms, diagnostic approaches, workup, treatment and long-term outcomes in these patients are not well established.

Method: Population data extraction and exploration were conducted using the MDClone® big data platform, which extracted the patient demographic and clinical data from the Sheba Medical Center (SMC) electronic medical records (EMR) identifying patients diagnosed with both VS and NPH based on ICD-10 codes.  A retrospective chart review was then conducted and further demographic and clinical data, including brain imaging and surgical outcomes, was collected. This cohort was compared to a previously studied cohort of iNPH patients.

Results: The VS-NPH cohort consisted of 18 patients (11 males, mean age 66.8±3.0 years). In 4 cases NPH and VS were diagnosed concomitantly and in the remaining 14, symptoms of NPH developed after, but within 3 years from VS diagnosis, 12 of them after RS. Initial tumor size was <30 mm in 16 patients (mean size 19 ±6.5 mm) inversely correlating with the time to presentation of NPH (r=-0.484, P=0.049). For most patients (11/16, 69%) gait improved following ventriculoperitoneal shunt (VPS), an outcome comparable to the 75% improvement for the iNPH patients. CSF tap test (CTT) was positive in only 55% of VS-NPH shunt responders, compared to 67% in iNPH. A significantly higher CSF protein level was observed in the VS-NPH group (158.8 ± 154.4) compared to the NPH group (56.2 ± 25.9) (P<0.001).

Conclusion: Clinicians should be aware of the association between VS and NPH, possibly related to previous RS, and mediated by elevated CSF protein levels, which contribute to altered CSF dynamics and hydrocephalus development. Most VS-NPH patients improved after VPS, regardless of previous RS or CTT results.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/normal-pressure-hydrocephalus-in-vestibular-schwannoma-patients/