EEG analysis for evaluating chronic cerebral ischemia treated by hyperbaric oxygenation and microneurosurgery.

Abstract

Thirty-five chronic stroke patients, who had internal carotid occlusion that resulted in considerable neurological deficit persisting for an average of 10 weeks, were studied. First, hyperbaric oxygen (HO) therapy was administered to each patient. Subsequently an extra-intracranial anastomosis operation was performed on 21 of these patients. Serial neurological examinations and EEG analyses were performed to assess the clinical course of the cerebral lesion. According to the effect of HO treatment and of the subsequent extra-intracranial anastomosis operation these patients were divided into three groups. Group I—15 of the 35 patients—showed a significant improvement of cerebral function and electrical brain activity at the conclusion of HO therapy. Subsequently an extra-intracranial anastomosis operation was performed on each patient of group I. This resulted in further recovery of cerebral function and electrical brain activity. Postoperative angiography revealed patency of the anastomosis in 14 of the group I patients. Group IIa (14 patients) had only little change in the neurological deficit and electrical brain activity at the conclusion of HO therapy as well as at later examinations. Extra-intracranial anastomosis operation was not performed on the six patients in group IIb who also revealed only little change in their condition at the conclusion to HO treatment. Subsequent extra-intracranial anastomosis operation was, however, performed on these six patients. Although postoperative angiography demonstrated a patent anastomosis in each of these six cases only little change in their status was observed subsequently. The 35 patients were clinically very similar and were in a chronic poststroke stage where spontaneous recovery rarely occurs. None of them manifested any clinical evidence of reversibility of the cerebral alteration before beginning HO therapy. These findings indicate that (a) EEG interval-amplitude analysis is of value for an objective assessment of the course of the cerebral lesion, (b) EEG analyses performed during HO treatment can help to differentiate between reversible and irreversible ischemic hypoxic alterations of the brain, (c) unilateral internal carotid occlusion can lead to neurological deficits and, in particular to bilateral EEG alterations with an accentuated reduction of electrical brain activity over the ipsilateral hemisphere, (d) chronic ischemic alterations of the brain can be improved by HO therapy and additional recovery can take place after subsequent extra-intracranial anastomosis, and (e) brain tissue can tolerate chronic ischemia leading to considerable neurological deficit for an average period of 3 months.