Choroid plexus hyperplasia: surgical treatment and immunohistochemical results. Case report.

Diffuse villous hyperplasia of the choroid plexus is a rare but potential source of nonobstructive hydrocephalus. In addition to discussing the authors' staged surgical approach and medical management decisions in a patient with this rare and challenging condition, immunohistochemical studies of the choroid plexus epithelium are presented to examine the pathophysiological factors involved in abnormal cerebrospinal fluid (CSF) production in this disease. The patient, a 15-month-old girl born at 36 weeks' gestation, underwent a bilateral craniotomy with resection of the choroid plexus to treat her villous hyperplasia. Immunohistochemical studies of the resected choroid plexus were conducted for the purpose of examining the carbonic anhydrase II (CAII) enzyme and the aquaporin 1 (AQP1) membrane protein. Results were compared with immunohistochemical studies conducted in a small series of autopsy specimens of normal human choroid plexuses. There was no change in the immunoreactivity of CAII in the patient with villous hyperplasia compared with normal controls, whereas AQP1 immunoreactivity was significantly weaker in the patient compared with normal controls. Postoperatively, the patient's CSF overproduction resolved and her neurological symptoms improved over time. Shunting techniques and presently available pharmaceutical treatments alone do not provide adequate treatment of high-output CSF conditions. Surgical removal of the affected choroid plexus is a feasible and effective treatment. Results of the immunohistochemical studies reported here support the suggestion that the CAII enzyme is retained in villous hyperplasia of the choroid plexus. However, there appears to be decreased expression and perhaps downregulation of AQP1 in villous hyperplasia compared with normal choroid plexus. Future studies may elucidate the significance of these observations.