Everything about Abnormal Posturing totally explained
Abnormal posturing is an involuntary
flexion or
extension of the arms and legs, indicating severe
brain injury. It occurs when one set of
muscles becomes incapacitated while the opposing set is not, and an external
stimulus such as
pain causes the working set of muscles to contract. The posturing may also occur without a stimulus. Since posturing is an important indicator of the amount of damage that has occurred to the brain, it's used by medical professionals to measure the severity of a
coma with the
Glasgow Coma Scale (for adults) and the
Pediatric Glasgow Coma Scale (for infants).
The presence of posturing indicates a severe
medical emergency requiring immediate medical attention. Decerebrate and decorticate posturing are strongly associated with poor outcome in a variety of conditions. For example, near-
drowning victims that display decerebrate or decorticate posturing have worse outcomes than those that do not. Changes in the condition of the patient may cause him or her to alternate between different types of posturing.
Causes
Posturing can be caused by conditions that lead to large increases in
intracranial pressure. Such conditions include
traumatic brain injury,
stroke,
intracranial hemorrhage,
brain tumors, and
encephalopathy. Posturing due to stroke usually only occurs on one side of the body and may also be referred to as
spastic hemiplegia. or is about to occur. diffuse
cerebral hypoxia, and
brain abscesses.
Types
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
opisthotonos, in which the head and back are arched backward.
Decorticate posturing
Decorticate posturing is also called
decorticate response,
decorticate rigidity, or
flexor posturing. 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. A person displaying decorticate posturing in response to pain gets a score of three in the motor section of the
Glasgow Coma Score.
There are two parts to decorticate posturing.
- The first is the disinhibition of the red nucleus with facilitation of the rubrospinal tract. The rubrospinal tract facilitates motor neurons in the cervical spinal cord subserving flexor muscles of the upper extremities.
- The second component of decorticate posturing is the disinhibition of the lateral corticospinal tract which facilitates motor neurons in the lower cord serving extensor muscles of the lower extremities.
The disinhibition of these two tracts 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.
History
Sir Charles Sherrington was first to describe decerebrate posturing after transecting the
brain stems of cats and monkeys, causing them to exhibit the posturing.
Further Information
Get more info on 'Abnormal Posturing'.
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