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.

This phenomenon is an important part of evaluating a person in a coma.

Certain abnormal posturing behaviors may be a sign of specific injuries to the central nervous system.

Abnormal posturing present with little or only mild stimulation is a sign of serious central nervous system damage. Subtle abnormalities or damage of the nervous system may be brought out as posturing when performing certain tasks, such as walking on the sides of the feet, on the toes, or heels.

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.

• Cerebral edema
• Increased intracranial pressure due to any cause
• Reye syndrome
• Severe head injury
• Stroke
• Uncal herniation

Abnormal posturing often accompanies reduced consciousness. Anyone who shows such behaviors should be examined promptly by the health care provider.

In some conditions such as prolonged coma, these behaviors can persist for an extended period of time.

All conditions of spontaneously or easily triggered abnormal posturing require hospital treatment. This kind of movement is most normally seen in patients in coma. More subtle posturing that is triggered by a doctor at a medical visit may or may not be important.

At the hospital, emergency measures for abnormal posturing must be started immediately. This includes placement of an artificial airway (breathing tube) and assistance with breathing. The person will likely be hospitalized in intensive care.

The medical history will be obtained from family members and a physical examination will be performed.

Medical history questions documenting abnormal posturing in detail may include:

• When did this behavior start?
• Is there a pattern to the occurrences?
• Is it always the same type of posture?
• What other symptoms preceded or accompanied the abnormal posturing?
• Is there any significant medical history (such as a known head injury)?

The physical examination will include a complete neurological assessment.

Diagnostic testing may include:

• Cerebral angiography
• EEG
• Head CT scan
• Head MRI scan
• Head x-ray
• ICP monitoring (monitoring of the pressure inside the brain)

Bleck T. Levels of consciousness and attention. In: Goetz, CG, ed. Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 1.