Three types of abnormal posturing are decorticate posturing, with the arms flexed over the chest; decerebrate posturing, with the arms extended at the sides; and
opisthotonus, in which the head and back are arched backward.
Decorticate Decorticate posturing is also called decorticate response, decorticate rigidity, flexor posturing, or, colloquially, "mummy baby". Patients with decorticate posturing present with the arms flexed, or bent inward on the chest, the hands are clenched into fists, and the legs extended and feet turned inward. A person displaying decorticate posturing in response to pain gets a score of three in the motor section of the
Glasgow Coma Scale, caused by the flexion of muscles due to the neuro-muscular response to the trauma. There are two parts to decorticate posturing. • The first is the disinhibition of the
red nucleus with facilitation of the
rubrospinal tract due to severment of the
corticospinal tract. The rubrospinal tract facilitates
motor neurons in the cervical spinal cord supplying the flexor muscles of the upper extremities. The rubrospinal tract and
medullary reticulospinal tract biased flexion outweighs the
medial and lateral vestibulospinal and
pontine reticulospinal tract biased extension in the upper extremities. • The second component of decorticate posturing is the disruption of the lateral
corticospinal tract which facilitates motor neurons in the lower spinal cord supplying flexor muscles of the lower extremities. Since the corticospinal tract is interrupted, the pontine reticulospinal and the medial and lateral vestibulospinal biased extension tracts greatly overwhelm the medullary reticulospinal biased flexion tract. The effects on these two tracts (corticospinal and rubrospinal) by lesions above the red nucleus is what leads to the characteristic flexion posturing of the upper extremities and extensor posturing of the lower extremities. Decorticate posturing indicates that there may be damage to areas including the
cerebral hemispheres, the
internal capsule, and the
thalamus. The patient is rigid, with the teeth clenched. Transection releases the centres below the site from higher inhibitory controls. In competitive contact sports, posturing (typically of the forearms) can occur with an impact to the head and is termed the
fencing response. ==Causes==