Decorticate posturing

Decorticate posturing

Decorticate posturing is characterized by the arm being adducted, elbow flexed, fingers and wrist flexed, legs extended, and plantar flexion of the feet as well as internal rotation of the leg. Decorticate posturing may be bilateral or unilateral. Decorticate posturing is less common than decerebrate posturing. However, it tends to be more serious. Decorticate posturing is associated with a damage to the corticospinal tract which occur in head injury or cerebrovascular accident. Decorticate posturing may occur spontaneously or occur due to exposure to noxious stimuli. The duration of the posture, the intensity of the stimulus and the frequency of the spontaneous episodes varies with the location of the cerebral injury and the severity of the cerebral injury. Decorticate posture may progress to decerebrate posture when the injury extend lower in the brainstem region. Decorticate posture has a better prognosis than decerebrate posture.

The patient who presents with decorticates posture should undergo a series of assessment. History should be taken from the patient confirming the presence of any headache, numbness, dizziness, abnormal vision, nausea and vomiting or tingling. The patient also should be asked regarding the time when he first notices the symptoms. Any family member who noticed any change in behaviour of the patient also should inform the physician. The patient also is asked about any history of trauma, encephalitis, meningitis, cancer or cerebrovascular disease. The assessment involves a series of examination that begin with testing the patient sensory function and motor function. The response of the pupil to light, the equality and the sizes of the pupils are evaluated. The cranial nerves reflexes and deep tendon reflex are also tested.

The causes of the patient to develop decorticate posture may include head injury, cerebrovascular accident, brain tumours and brain abscess.

In head injury, the common associated signs and symptoms may include seizure, nausea, vomiting, and decrease in the level of consciousness, pupillary dilation, unilateral numbness, aphasia, irritability, dizziness and headache. Decorticate posture will be part of the features which depend on the sites, extent and severity of the head injury.

A unilateral decorticate posture which also known as spastic hemiplegia is common in cerebrovascular accident which involves the cerebral cortex. Patient who suffer from cerebrovascular accident may also present with dysphagia, dysarthria, aphasia, agnosia, apraxia, unilateral sensory loss, hemiplegia which is contralateral to the lesion, constipation, urinary incontinence, urine retention, decrease the level of consciousness and loss of memory. The patient may also complain of blurred vision, diplopia and homonymous hemianopia.

Brain tumour will result in raised of the intracranial pressure as the tumour grows in sizes. This condition may result in bilateral decorticate posture. Other signs and symptoms may include aphasia, apraxia, ataxia, loss of sensation, paresis, dizziness, seizures, loss of memory, changes in behaviour, headache, loss of vision, blurred vision, diplopia, papilledema, paraesthesia, hormonal imbalance and vomiting.

Brain abscess is the form of infection in which decorticate posturing may occur. The associated signs and symptoms vary according to the sizes, extent severity and location of the abscess. These may include headache, hemiparesis, aphasia, nausea and vomiting, seizures and dizziness. Besides that the patient may present with loss of consciousness altered vital signs and change in behaviour.

In terms of children, decorticate posture is more common in case of Reye’s syndrome and head injury. It is an unreliable sign in infants’ age less than 2 years old due to immaturity of the central nervous system.

Decerebrate posturing

What is decerebrate posturing? Decerebrate posturing is a form of posture where the arms are extended and adducted while the fingers are flexed and the wrist are pronated. Both of the legs are also stiffly extended. In severe case, patients may present with acutely arched back which is also known as opisthotonus. Decerebrate posture may be bilateral and unilateral.

Decerebrate posturing is associated with severe upper brainstem damage. Decerebrate posturing is caused by primary damage to the brainstem which is related to tumour, abscess, infarction, haemorrhage, head injury, compression due to raised in intracranial pressure and metabolic encephalopathy.

The decerebrate posture may occur spontaneously or associated with noxious stimuli.

In concurrent cases of cerebral damage and brain stem damage, the decerebrate posture may only affect one side of the body or just affecting the arms while both of the patient's legs remains flaccid. Due to the fluctuation of the neurological status of the patient, decerebrate and decorticate posturing may occur alternately. The duration of the decerebrating posture is associated with the severity of the damage of the upper brainstem.

The patient presenting with decerebrating posture should be managed initially by taking the vital signs of the patient. This is followed by evaluating the level of consciousness of the patient using the Glasgow Coma Scale. The pupil of the patient is evaluated for its response to the light, equality and the sizes of the pupils. Cranial nerve reflexes and deep tendon reflex of the patient are tested. The appearance of the doll’s eye sign is also monitored.

History from the patient or family member is obtained. Besides that, look for clues for the causative disorder that include any obvious trauma, needle track, hepatomegaly, diabetic skin changes and cyanosis. This may include a set of questions such as did the decerebrate posturing occur abruptly? Is the patient has any history of aneurysm, blood clot, cancer, diabetes and liver disease? Does the patient have any history of an accident or trauma? What did the patient complain before loss his consciousness if it did happen?

The main causes of decerebrate posturing may include posterior fossa haemorrhage, pontine haemorrhage, hypoxic encephalopathy, hypoglycaemic encephalopathy, cerebral lesion and brainstem infarction.

Posterior fossa haemorrhage is presented with the patient complaining of a stiff neck, headache, vomiting, ataxia, vertigo, papilledema, drowsiness and cranial nerve palsies. Later the patient may slip into decerebrate posture and coma as well as respiratory arrest

Pontine haemorrhage is a life threatening condition. The patient will rapidly slip into coma and decerebrate posturing. Besides that the patient may also suffer from total paralysis with positive Babinski’s reflexes, small reactive pupils and absence of the doll’s eye sign.

Hypoxic encephalopathy is caused by brainstem compression due to raised in the intracranial pressure as a result of anaerobic metabolism. Hypoxic encephalopathy may leads to decerebrate posturing. The patient may slip into coma , present with hypoactive deep tendon reflex, positive Babinski ‘s reflex, fixed pupils, absent of doll’s eye signs and respiratory arrest.

Hypoglycaemic encephalopathy is one of the causes of decerebrate posturing. It is caused by an extremely low blood glucose level. Hypoglycaemic encephalopathy patients may progress into coma and decerebrate posturing. The patient may present with slow respiration, dilated pupil and bradycardia. Eventually the patient may go through the stages of muscle spasm, muscle twitching and seizures which later progress to flaccidity.

Decerebrate posturing may also be caused by cerebral lesions (infarction, abscess, tumour, and trauma) that lead to compression of the lower thalamus. However, decerebrate posturing appears to be a late presentation. Other finding are varies with the state and extent of the lesions which may include the triad of raised intracranial pressure such as widening of the pulse pressure, bradycardia and raised systolic blood pressure. Abnormal size of the pupil and response to the light as well as coma may also present.

Brain stem infarction may present with decerebrate posture and coma. In more extensive and severe brain stem damage, upper extremities may suffer from decerebrate posturing while the lower extremities may present with flaccidity. Other associated signs and symptoms may include loss of sensation, bilateral cerebral ataxia and cranial nerve palsies. It varies with the severity of the infarction. In case of deep coma, the patient’s normal reflex will be lost and the patient may present with flaccidity, positive Babinkski’reflex and absence of the doll’s eye sign.

Decerebrate posturing and coma may also present during diagnostic test. Lumbar puncture that involved in the removal of the spinal fluid to relieve the high intracranial pressure may lead to compression of the brainstem and later leads to decerebrate posture and coma.

Decerebrate posture may not present in children less than 2 years old because of the immaturity of the central nervous system. If decerebrate posturing occurs, than opisthotonus is more common. Opisthotonus is a condition where the back is acutely arched. This opisthotonus signs commonly affects young adult and infant and it is an indication of a terminal sign. Besides that, decerebrate posturing is also common in children who suffer from Reye’s syndrome. Reye’s syndrome is associated with raised intracranial pressure causing brainstem compression. Head injury in children is the most common form of decerebrate posturing.

Besides MRI scan, CT scan and skull X rays other diagnostic test may include brain scans, cerebral angiography, ICP monitoring and digital subtraction angiography.

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