Decerebrate rigidity in acute head injury.

A comprehensive study of the motor patterns, usually grouped under the heading "decerebrate rigidity," was carried out in a series of 800 patients with severe head injuries. The incidence of these manifestations was 39.6%, and when they were present chances of survival were reduced from 79.4% to 28.1%. Clinical and electromyographic investigations revealed heterogeneous and unstable motor manifestations that did not fit into the classical groups of experimental models of decerebrate rigidity. Combinations of extensor and flexor attitudes and/or responses were frequently found in same patient, but could be separated into homogeneous groups. Each recognized postural pattern had its own distinct neurological signs and prognosis. Age did not significantly affect the outcome, however, intracranial exapnding lesions (73.5%), impairment of the brain-stem oculomotor system (49.8%), and deep coma (88.9%) all contributed to an unfavorable course. Surgical treatment was effective when performed for intracranial hematomas and in patients with incomplete extensor rigidity. Good recovery was achieved in 16% of decerebrate patients, while 12.1% survived in prolonged coma or with severe disabilities. All clinical and neuropathological data suggest that extensor motor abnormalities in the acute phase of cerebral traumatic disease do not always conclusively indicate structural brain-stem damage. A critical analysis of so-called "decerebrate rigidity" (rejecting in some instances its Sherringtonian implications) may allow for a more accurate clinical assessment of the severity of head injury.