Abnormal posturing

Definition

Abnormal posturing is different from what is commonly called "bad posture" or "slouching." Instead, it is a tendency to hold a particular body position, or to move one or more parts of the body in a particular way.

Certain abnormal posturing behaviors may indicate specific injuries to the nervous system.

Alternative Names

Considerations

Abnormal posturing may be a sign of serious central nervous system damage.

Normally, when a muscle contracts, the muscles on the opposite side of the joint provide some resistance to contraction. Abnormal posturing occurs when damage to the central nervous system (brain or spinal cord) results in complete or partial lack of opposition to muscle contraction in various muscle groups.

See the following types of abnormal postures:

• Decerebrate posture -- rigid extension of the arms and legs, downward pointing of the toes, and backward arching of the head
• Decorticate posture -- rigidity, flexion of the arms, clenched fists, and extended legs
• Opisthotonos -- rigidity and severe arching of the back, with the head thrown backwards

An affected person may alternate between different postures as the condition fluctuates.

Injury or inflammation of a portion of the brain, spinal cord, or nervous system is the most common cause of abnormal posturing. The particular type of posturing can reflect the type and area of nervous system involvement.

Causes

• Cerebral edema
• Increased intracranial pressure
• Injury to nerves
• Reye syndrome
• Severe head injury
• Uncal herniation