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. (See Comparing decerebrate and decorticate postures, page 178.)
Action stat!
Next, examine spontaneous respirations. Give supplemental oxygen, and ventilate the patient with a handheld resuscitation bag if needed. Endotracheal intubation and mechanical ventilation may be indicated. Keep emergency resuscitation equipment handy. Monitor the patient's neurologic status, vital signs, and oxygen saturation.
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. 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.
Nursing considerations
▪ Prepare the patient and his family for diagnostic tests that will determine the cause of his decerebrate posture, such as skull X-rays, a computed tomography scan, magnetic resonance imaging, cerebral angiography, digital subtraction angiography, electroencephalography, a brain scan, and ICP monitoring.
▪ Monitor the patient's neurologic status and vital signs every 30 minutes or as indicated.
▪ Be alert for signs of increased ICP (such s bradycardia, increasing systolic blood pressure, and a widening pulse pressure) and neurologic deterioration (for example, an altered respiratory pattern and abnormal temperature).
Patient teaching
▪ 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 to the patient and his family.
▪ Explain the diagnosis and treatment plan.
Pictures
![Decerebrate posture [Decerebrate rigidity, abnormal extensor reflex] - 5652.1.png](/bookimages/16/5652.1.png)
Book Source Details
- Book Title: Nursing: Interpreting Signs and Symptoms
- Author(s): Springhouse
- Year of Publication: 2007
- Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright Details: Nursing: Interpreting Signs and Symptoms, Copyright © 2008 Williams & Wilkins.
More About Causes of Posture symptoms
» Next page:
Decorticate posture [Decorticate rigidity, abnormal flexor response] (Nursing: Interpreting Signs and Symptoms)
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