Pediatric Primary Leptomeningeal PNET presenting with Psychiatric Symptoms and Deceiving MR Imaging
Purpose: To review a complicated case of primary leptomeningeal PNET (primitive neuroectodermal tumor) in a pediatric patient presenting with misleading clinical symptoms and to illustrate deceiving imaging findings including “pseudo-T2” appearance on post contrast T1 imaging. Case Report: We present the case of a 10 year-old male who had a history including 6 weeks of mood changes and behavior problems which had been referred to psychiatric care. Somatic complaints developed and included diffuse pain, headache, photophobia, and phonophobia. A generalized seizure prompted presentation to our tertiary care center. Physical examination revealed papilledema and bilateral lower extremity paralysis. Cerebrospinal fluid analysis demonstrated elevated protein. Following imaging, biopsy of the arachnoid matter was performed after L5 laminectomy which showed PNET with glial differentiation, WHO grade IV. The patient was started on chemotherapy along with radiation therapy. Although more recent imaging shows partial remission, the patient has severe residual treatment related changes including arachnoiditis. Imaging Findings: Computed tomography scan of the head showed symmetric ventriculomegaly suggestive of communicating hydrocephalus. Head magnetic resonance imaging (MRI) showed smooth diffuse leptomeningeal enhancement throughout bilateral sylvian fissures in T1 sequences with contrast. Spine MRI revealed diffuse and homogeneous leptomeningeal enhancement of the subarachnoid space on T1 sequences with contrast with a very deceiving “pseudo-T2” appearance. Significant interval decrease in burden of leptomeningeal enhancement was seen post-chemotherapy. However, the presence of severe arachnoiditis remains evident. Summary: Primary leptomeningeal PNET is a rare tumor with little reliable peer-reviewed literature available. Here we present a challenging case of pediatric diffuse primary leptomeningeal PNET.