Decerebrate posture
Decerebrate posture, also known as decerebrate rigidity or abnormal extensor reflex, is characterized by adduction (internal rotation) and extension of the arms while the wrists are pronated and the fingers are flexed. In addition, 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; 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 coancurrent 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. (See Comparing decerebrate and decorticate postures.)
Emergency Actions
Ensuring a patent airway is the priority when caring for a patient who exhibits decerebrate posture. If necessary, 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. (Be sure to check the patient’s chart for a do-not-resuscitate order.)
History
Explore the history of the patient’s symptoms. 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 level of consciousness (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.
Physical assessment
After taking vital signs, determine the patient’s 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. After completing the neurologic examination, perform a full physical assessment.
Medical causes
Brain stem infarction
When brain stem infarction produces a coma, it may be accompanied by decerebrate posture. 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 absence of doll’s eye sign, a positive Babinski’s reflex, and flaccidity.
Brain stem tumor
Decerebrate posture is a late sign of a brain stem tumor that accompanies coma. Commonly, the posture is preceded by hemiparesis or quadriparesis, cranial nerve palsies, vertigo, dizziness, ataxia, and vomiting.
Cerebral lesion
Whether the cause is trauma, tumor, abscess, or 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 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, absence of doll’s eye sign, hypoactive deep tendon reflexes and, possibly, fixed pupils and respiratory arrest.
Pontine hemorrhage
Typically, pontine hemorrhage rapidly leads to decerebrate posture with coma. Accompanying signs of this life-threatening disorder include total paralysis, 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, headache, vertigo, ataxia, stiff neck, drowsiness, papilledema, and cranial nerve palsies. The patient eventually slips into a coma and may experience respiratory arrest.
Other causes
Diagnostic tests
Relief of high ICP by removal of spinal fluid during a lumbar puncture may precipitate cerebral compression of the brain stem and cause decerebrate posture and coma.
Special considerations
Prepare the patient for diagnostic tests that will help determine the cause of his decerebrate posture. Testing may include skull X-rays, computed tomography scanning, magnetic resonance imaging, cerebral angiography, digital subtraction angiography, EEG, brain scanning, 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 widening pulse pressure) and neurologic deterioration (altered respiratory pattern and abnormal temperature).
Pediatric pointers
Children younger than age 2 may not display decerebrate posture because of nervous system immaturity. 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.
Patient counseling
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.
Pictures
Book Source Details
- Book Title: Signs & Symptoms: A 2-in-1 Reference for Nurses
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2007 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)
- [ read ]
- Scoliosis
- "Professional Guide to Diseases (Eighth Edition)" (2005)
- [ read ]
Copyright Details: Signs & Symptoms: A 2-in-1 Reference for Nurses, Copyright © 2008 Williams & Wilkins.
More About Causes of Posture symptoms
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Decerebrate posture [Decerebrate rigidity, abnormal extensor reflex] (Nursing: Interpreting Signs and Symptoms)
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