THE LONG-TERM OUTCOME IN CHILDREN WITH LATE-ONSET AQUEDUCTAL STENOSISRESULTING FROM BENIGN INTRINSIC TECTAL TUMORS

Benign intrinsic tumors arising in the dorsal midbrain have long been recognized as a potential cause of late-onset aqueductal stenosis. Whe re histopathological studies of such lesions have been performed, the majority have been reported to be low-grade gliomas. Because these tum ors often present with a paucity of neurological findings and a charac teristic radiographic appearance and because there has been substantia l uncertainty regarding their potential for long-term progression, the authors have routinely deferred biopsy and/or radiotherapy for these lesions until there has been clear-cut evidence of disease progression . Herein, the authors report their experience with 16 children manifes ting this syndrome who were treated between 1979 and 1992. The patient s ranged in age from 6 months to 14 years at presentation (median 9.75 years). In general, symptoms of increased intracranial pressure devel oped insidiously; three of the older children had exhibited profound m acrocephaly since infancy, which predated the onset of other symptoms of hydrocephalus by several years. Only one of the 16 children showed evidence of brain-stem dysfunction at presentation, a partial Parinaud 's syndrome that resolved following placement of a ventriculoperitonea l shunt. In 12 patients, the tumor was detected by magnetic resonance (MR) imaging at initial evaluation as a bulbous enlargement of the tec tal plate. In four patients who presented before the advent of MR imag ing, initial computerized tomography (CT) scans failed to delineate th e tectal lesion convincingly:, however, subsequent MR studies clearly demonstrated the presence of an intrinsic tectal mass. All 16 patients underwent cerebrospinal fluid diversion initially, with conservative management of the tectal lesion and close long-term follow-up monitori ng. Four children ultimately demonstrated clinical signs of progressiv e tumor growth with the insidious onset of partial or complete Parinau d's syndrome, despite the presence of a functioning shunt. The median interval to symptom progression was 7.8 years from the time of shunt i nsertion and 11.5 years from the onset of initial symptoms and signs o f hydrocephalus. Follow-up CT and MR studies demonstrated obvious tumo r enlargement in three of the four patients who then underwent stereot actic or open biopsy. The histological diagnosis in these three was be nign mixed glioma, anaplastic astrocytoma, and low-grade astrocytoma. All four patients with clinical evidence of disease progression were t reated with conventional radiotherapy; the patient with an anaplastic astrocytoma also received focal stereotactic radiosurgery. These patie nts subsequently remained clinically stable, with three showing tumor regression and one showing stable disease on serial MR studies (median follow-up period from tumor progression, 4.25 years). One other child was noted to have progressive tumor enlargement during the 2 years af ter shunt insertion; she remains asymptomatic and has not yet undergon e biopsy or radiotherapy. It is concluded that benign intrinsic tectal tumors, although generally indolent, merit conscientious long-term fo llow-up monitoring since these lesions may ultimately show evidence of progressive growth and require therapeutic intervention to maintain d isease control. These tumors are best visualized on MR imaging, which should be included in the workup of all patients with late-onset aqued uctal stenosis.