Electroencephalographic changes during the state of coma

This study is based upon 25 selected comatose subjects investigated from the clinical, EEG, and anatomical standpoint. 1. 1. For practical purpose the different degrees of coma were subdivided using as parameters signs and symptoms commonly found in comatose patients, as follows: 1. (a) impairment of consciousness (C 1): 2 cases; 2. (b) moderate coma (C 2): 14 cases; 3. (c) deep coma (C 3): 9 cases. 1. 2. The type of EEG activity found was grouped under the following three headings: 1. (a) generalized EEG changes: 15 cases; 2. (b) unilateral EEG changes: 7 cases; 3. (c) focal EEG changes: 3 cases. 1. 3. The site of cerebral lesion was reconstructed on the basis of macro and microscopic sections. Electroclinical results show that a generalized slow organized activity is not necessarily the bioelectric expression of the majority of comatose patients. No definite relationships are found between degree of coma and type of electroencephalographic changes. Moreover the possibility of eliciting a bioelectric response to stimuli does not appear to be related to the depth of coma. Some interpretational problems posed by the EEG findings are discussed.