Decerebrate versus decorticate posturing

What it is

Two abnormal postures, told apart by where the lesion sits, below or above the red nucleus.

• Decerebrate rigidity: the lesion is below the red nucleus, in the midbrain, and the posture is abnormal extension.
• Decorticate rigidity: the lesion is above the red nucleus, and the posture is abnormal flexion. Closer to the cortex means above the red nucleus.

How it presents

Decerebrate rigidity is extension posturing. Decorticate rigidity is abnormal flexion, and it is flexion because the rubrospinal tract is preserved.

The tracts behind each:

• In decerebrate rigidity there is no more CST and no more rubrospinal tract, while the vestibulospinal tract, which starts at the medulla, and the pontine reticulospinal tract are intact.
• In decorticate rigidity there is no more CST but the rubrospinal tract is intact. The rubrospinal tract runs only to the cervical level, so the legs are still extended while the arms are flexed.