Characteristics of verbal impairment in closed head injured patients.

One hundred twenty-five closed head injured postcoma patients in a rehabilitation medicine center underwent standardized aphasia tests to determine the presence and nature of verbal deficits. Mean time since injury for the group was 45 weeks. All patients evidenced linguistic impairment which was only apparent on testing, not in conversation. The population fell into three relatively equally sized groups: classic aphasia, dysarthria accompanied by linguistic deficits, and "subclinical" aphasic deficits. No patient with a history of coma after closed head injury was spared defective performance on selected language tasks. The patient groups reflected a severity continuum ranging from aphasia, the most severely impaired group, to the least impaired, the subclinical aphasia group. Further, closed head injured patients with a history of coma who manifest motor speech impairment (dysarthria) also manifest linguistic processing deficits. The study results suggest that linguistic functions are particularly vulnerable in severe head injury.