Primary Leptomeningeal Medulloblastoma in Adults: A Diagnostic Challenge-Case Report and Systematic Review

Abstract

Primary leptomeningeal medulloblastoma (PL-MB) in adults is a rare disease with a severe prognosis. A 35-year-old woman presented with headaches, diplopia, and gait ataxia, with triventricular hydrocephalus and descent of the cerebellar tonsils beyond the foramen magnum. Endoscopic third ventriculostomy was performed. Six months later, headaches recurred. Dilatation of the supratentorial ventricular system and massive cerebellar swelling without contrast-enhancing nodularities were reported. Occipitocervical decompression with duraplasty was performed. A bioptic diagnosis of PL-MB was made. Craniospinal irradiation and chemotherapy were administered. After 18 months, no recurrence was observed. Few cases of PL-MB have been reported: patients die before treatment or within a few days after surgery. Our long-term survival could be ascribable to a slow clinical presentation and an early diagnosis that allowed surgical treatment and the administration of a combined chemoradiotherapy protocol. Cerebellar swelling, even without associated enhancing lesions, with or without hydrocephalus, should be a neuroradiological alarm sign, and PL-MB should be considered.

Keywords: Chiari-like malformation; endoscopic third ventriculostomy; obstructive hydrocephalus; occipitocervical decompression; primary leptomeningeal medulloblastoma.

Fig. 1

Preendoscopic third ventriculostomy magnetic resonance imaging. The neuroradiological investigations documented triventricular hydrocephalus with signs of transependymal transudations ( A ). On the sagittal scans, a mild dilatation of the aqueduct ( B ) and downward displacement of the cerebellar tonsils beyond the foramen magnum with obstruction of the fourth ventricle ( C ) were evidenced.

Fig. 2

Postendoscopic third ventriculostomy magnetic resonance imaging. The postoperative images documented the patency of the stoma on the floor of the third ventricle ( A, B ), with a regular flow inside it ( C ) and a reduction in the dilatation of the lateral ventricles with resolution of the transependymal transudation ( D ).

Fig. 3

Magnetic resonance imaging at 6 months. Mild triventricular dilatation ( A ) and downward displacement of the cerebellar tonsils ( B ) were associated with areas of hyperintensity in both cerebellar hemispheres and vermis and diffuse cerebellar swelling ( C ). No contrast enhancement was documented ( D ).

Fig. 4

Histological and immunohistochemical specimens. The hematoxylin and eosin-stained section ( A ) showed the neoplastic infiltrate within the subarachnoid space (original magnification 100 × ). A higher magnification ( B ) revealed the neoplastic cells with large, round-oval nuclei, and scant cytoplasm (original magnification 400 × ). The immunohistochemical staining documented the positivity for synaptophysin ( C ) and a high proliferation index ( D ).

Fig. 5

Follow-up magnetic resonance imaging. The patient underwent craniospinal irradiation and subsequent chemotherapy. The sagittal scans ( A ) documented a resolution of the downward displacement of the cerebellar tonsils with enlargement of the fourth ventricle and distension of the cerebellar folia. No evolution of the cerebellar hyperintensities was documented ( B ). No area of contrast enhancement was evidenced ( C ).