Symptomatic congenital hydrocephalus in the elderly simulating normal pressure hydrocephalus.

In a series of 30 older patients shunted for symptomatic hydrocephalus, we found 3 with a head circumference at or greater than the 98th percentile. In 2, we demonstrated deterioration over 6 and 12 months by serial videotaping of gait and neuropsychological testing. In the 3rd, serial lumbar punctures over a 6-month period gave temporary improvement. In each, CTs showed ventriculomegaly without transependymal flow. One patient had an Arnold-Chiari type I abnormality identified by MRI. All had systemic hypertension. CSF pressure monitoring showed CSF pressure greater than 15 mm Hg 39% of the time in 1 patient, and 100% in another. All improved with ventriculoperitoneal shunting. Patients with probable compensated congenital hydrocephalus who functioned well throughout most of their lives may become symptomatic as they age but improve with shunt surgery. The head circumference should be measured in all older hydrocephalic patients.