Brainstem tumors in patients with neurofibromatosis type 1: a distinct clinical entity

Abstract

The natural history and the clinical and neuroimaging features of brainstem tumors in neurofibromatosis type 1 (NF1) are poorly understood. Magnetic resonance imaging (MRI) has been useful in NF1 in detecting intracranial abnormalities, especially of the brainstem. Brainstem tumors in NF1 have been confused clinically with non-NF1 brainstem tumors and radiographically with the increased T2 signal abnormalities, also known as "unidentified bright objects" (UBOs), which are common in NF1 and often located in the brainstem. This study, which evaluated 17 NF1 patients with brainstem tumors, is the largest series to date. Fifteen of 17 patients (88%) had neurologic signs and symptoms referable to brainstem dysfunction, including dysarthria, cranial neuropathies, and gross motor incoordination. Tumors were located primarily in the medulla in 14 of 17 NF1 patients (82%), in contrast to the pontine tumor location in the non-NF1 population. Seven NF1 patients (41%) required shunt placement for hydrocephalus at initial diagnosis, more frequent than in non-NF1 brainstem tumor patients. Six of 17 patients (35%) had evidence of radiographic tumor progression, but only three of them (18%) had correlative clinical progression. Two patients with progressive symptoms had partial surgical resection, and pathology revealed either fibrillary or anaplastic astrocytomas. Three patients were treated with radiation therapy, chemotherapy, or both, with two deaths. With a median follow-up of 52 months, 15 of 17 patients remain alive; 14 of them did not require adjuvant therapy. In our series, we describe NF1 brainstem tumors as a distinct clinical entity, much less aggressive than non-NF1 pontine tumors but more symptomatic than brainstem UBOs in NF1.