Neuromagnetic cortical signals in a patient with hydrocephalus.

We studied a patient with a communicating hydrocephalus using a whole-head neuromagnetometer. Auditory evoked fields (AEFs) were elicited with 600 ms tones, 0.25, 0.5, 1, 2 and 4 kHz in frequency. The source locations were more superficial and posterior in the patient than in controls, but still agreed with activation of the supratemporal cortex. Tonotopic organization of the AEF sources was similar in the patient and healthy control subjects. The amplitude spectra, source strengths and sites, and reactivity of the patient's spontaneous activity were normal. Despite apparent decrease of white matter, the patient's thalamocortical connections thus seem to be able to maintain normal evoked and spontaneous cortical activity.