Abstract
Thirty-eight patients had their cerebral function measured before and after extra-intracranial carotid bypass surgery using the Halstead-Reitan neuropsychology test battery. Two composite indices of cerebral function for each patient showed them to be impaired before operation. There was no improvement in the composite measures after operation to match that previously demonstrated after carotid endarterectomy. This may reflect the greater pre-operative cerebral impairment of the extra-intracranial group.