Decerebrate posture
Decerebrate rigidity, abnormal extensor reflex
Decerebrate posture is characterized by adduction (internal rotation) and extension of the arms, with the wrists pronated and the fingers flexed. The legs are stiffly extended, with forced plantar flexion of the feet. In severe cases, the back is acutely arched (opisthotonos). This sign indicates upper brain stem damage, which may result from primary lesions, such as infarction, hemorrhage, or tumor; metabolic encephalopathy; a head injury; or brain stem compression associated with increased intracranial pressure (ICP).
Decerebrate posture may be elicited by noxious stimuli or may occur spontaneously. It may be unilateral or bilateral. With concurrent brain stem and cerebral damage, decerebrate posture may affect only the arms, with the legs remaining flaccid. Alternatively, decerebrate posture may affect one side of the body and decorticate posture the other. The two postures may also alternate as the patient's neurologic status fluctuates. Generally, the duration of each posturing episode correlates with the severity of brain stem damage. (SeeComparing decerebrate and decorticate postures
Emergency interventions
Your first priority is to ensure a patent airway. Insert an artificial airway and institute measures to prevent aspiration. (Don't disrupt spinal alignment if you suspect spinal cord injury.) Suction the patient as necessary.
Next, examine spontaneous respirations. Give supplemental oxygen, and ventilate the patient with a handheld resuscitation bag, if necessary. Intubation and mechanical ventilation may be indicated. Keep emergency resuscitation equipment handy. Make sure to check the patient's chart for a do-not-resuscitate order.
History and physical examination
After taking the patient's vital signs, determine his level of consciousness (LOC). Use the Glasgow Coma Scale as a reference. Then evaluate the pupils for size, equality, and response to light. Test deep tendon reflexes and cranial nerve reflexes, and check for doll's eye sign.
Next, explore the history of the patient's coma. If you can't obtain this information, look for clues to the causative disorder, such as hepatomegaly, cyanosis, diabetic skin changes, needle tracks, or obvious trauma. If a family member is available, find out when the patient's LOC began deteriorating. Did it occur abruptly? What did the patient complain of before he lost consciousness? Does he have a history of diabetes, liver disease, cancer, blood clots, or aneurysm? Ask about any accident or trauma responsible for the coma.
Medical causes
Brain stem infarction
When brain stem infarction produces a coma, decerebrate posture may be elicited. Associated signs and symptoms vary with the severity of the infarct and may include cranial nerve palsies, bilateral cerebellar ataxia, and sensory loss. With deep coma, all normal reflexes are usually lost, resulting in the absence of doll's eye sign, a positive Babinski's reflex, and flaccidity.
Cerebral lesion
Whether the cause is trauma, a tumor, an abscess, or an infarction, any cerebral lesion that increases ICP may also produce decerebrate posture. Typically, this posture is a late sign. Associated findings vary with the lesion's site and extent, but commonly include coma, abnormal pupil size and response to light, and the classic triad of increased ICP — bradycardia, increasing systolic blood pressure, and a widening pulse pressure.
Hypoglycemic encephalopathy
Characterized by extremely low blood glucose levels, hypoglycemic encephalopathy may produce decerebrate posture and coma. It also causes dilated pupils, slow respirations, and bradycardia. Muscle spasms, twitching, and seizures eventually progress to flaccidity.
Hypoxic encephalopathy
Severe hypoxia may produce decerebrate posture — the result of brain stem compression associated with anaerobic metabolism and increased ICP. Other findings include coma, a positive Babinski's reflex, an absence of doll's eye sign, hypoactive deep tendon reflexes and, possibly, fixed pupils and respiratory arrest.
Pontine hemorrhage
Typically, pontine hemorrhage, a life-threatening disorder, rapidly leads to decerebrate posture with coma. Accompanying signs include total paralysis, the absence of doll's eye sign, a positive Babinski's reflex, and small, reactive pupils.
Posterior fossa hemorrhage
Posterior fossa hemorrhage is a subtentorial lesion that causes decerebrate posture. Its early signs and symptoms include vomiting, a headache, vertigo, ataxia, a stiff neck, drowsiness, papilledema, and cranial nerve palsies. The patient eventually slips into coma and may experience respiratory arrest.
Other causes
Diagnostic tests
Relief from high ICP by removing spinal fluid during a lumbar puncture may precipitate cerebral compression of the brain stem and cause decerebrate posture and coma.
Special considerations
Help prepare the patient and his family for diagnostic tests that will determine the cause of his decerebrate posture. Diagnostic tests include skull X-rays, a computed tomography scan, magnetic resonance imaging, cerebral angiography, digital subtraction angiography, EEG, a brain scan, and ICP monitoring.
Monitor the patient's neurologic status and vital signs every 30 minutes or as indicated. Also, be alert for signs of increased ICP (bradycardia, increasing systolic blood pressure, and a widening pulse pressure) and neurologic deterioration (an altered respiratory pattern and abnormal temperature).
Inform the patient's family that decerebrate posture is a reflex response — not a voluntary response to pain or a sign of recovery. Offer emotional support.
Pediatric pointers
Children younger than age 2 may not display decerebrate posture because the nervous system is still immature. However, if the posture occurs, it's usually the more severe opisthotonos. In fact, opisthotonos is more common in infants and young children than in adults and is usually a terminal sign. In children, the most common cause of decerebrate posture is head injury. It also occurs with Reye's syndrome — the result of increased ICP causing brain stem compression.
Pictures
Book Source Details
- Book Title: Handbook of Signs & Symptoms (Third Edition)
- Author(s): Springhouse
- Year of Publication: 2006
- Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.
Other Book Chapters Related to Posture symptoms
Read excerpts from these other book chapters related to Posture symptoms:
Medical Books Excerpts
- SCOLIOSIS
- "Algorithmic Diagnosis of Symptoms and Signs" (2003)
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- Scoliosis
- "In A Page: Pediatric Signs and Symptoms" (2007)
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- Scoliosis
- "Professional Guide to Diseases (Eighth Edition)" (2005)
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Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2008 Williams & Wilkins.
More About Causes of Posture symptoms
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Orthostatic hypotension [Postural hypotension] (Handbook of Signs & Symptoms (Third Edition))
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