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.
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. Diseases such as Malaria are also known to cause the brain to swell and cause this posturing effect.
Decerebrate and decorticate posturing can indicate that brain herniation is occurring or is about to occur. Brain herniation is an extremely dangerous condition in which parts of the brain are pushed past hard structures within the skull. In herniation syndrome, which is indicative of brain herniation, decorticate posturing occurs, and, if the condition is left untreated, develops into decerebrate posturing.
For reasons that are poorly understood, but which may be related to high intracranial pressure, children with malaria frequently exhibit decorticate, decerebrate, and opisthotonic 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 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.
There are two parts to decorticate posturing.
The effects on 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. It may also indicate damage to the mesencephalic region, or the corticospinal tract, along which impulses travel from the brain to the spinal cord. While decorticate posturing is still an ominous sign of severe brain damage, decerebrate posturing is usually indicative of more severe damage.
Decerebrate posturing indicates brain stem damage, specifically damage below the level of the red nucleus (e.g. mid-collicular lesion). It is exhibited by people with lesions or compression in the midbrain and lesions in the cerebellum.
A patient with decorticate posturing may begin to show decerebrate posturing, or may go from one form of posturing to the other; progression from decorticate posturing to decerebrate posturing is often indicative of uncal (transtentorial) or tonsilar brain herniation. Posturing may occur on one or the other side of the body, or it may occur on both sides. Activation of gamma motor neurons is thought to be important in decerebrate rigidity due to studies in animals showing that dorsal root transection eliminates decerebrate rigidity symptoms.
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