Abnormal posturing
Encyclopedia
Abnormal posturing is an involuntary flexion
or extension
of the arms and legs, indicating severe brain injury
. It occurs when one set of muscle
s becomes incapacitated while the opposing set is not, and an external stimulus
such as pain
causes the working set of muscles to contract. The posturing may also occur without a stimulus. Since posturing is an important indicator of the amount of damage that has occurred to the brain, it is used by medical professionals to measure the severity of a coma
with the Glasgow Coma Scale
(for adults) and the Pediatric Glasgow Coma Scale
(for infants).
The presence of posturing indicates a severe medical emergency
requiring immediate medical attention. Decerebrate and decorticate posturing are strongly associated with poor outcome in a variety of conditions. For example, near-drowning
victims that display decerebrate or decorticate posturing have worse outcomes than those that do not. Changes in the condition of the patient may cause him or her to alternate between different types of posturing.
. Such conditions include traumatic brain injury
, stroke
, intracranial hemorrhage
, brain tumor
s, and encephalopathy
. Posturing due to stroke usually only occurs on one side of the body and may also be referred to as spastic hemiplegia. Diseases such as malaria
are also known to cause the brain to swell and cause this posturing effect.
Decerebrate and decorticate posturing can indicate that brain herniation
is occurring or is about to occur. Brain herniation is an extremely dangerous condition in which parts of the brain are pushed past hard structures within the skull. In herniation syndrome, which is indicative of brain herniation, decorticate posturing occurs, and, if the condition is left untreated, develops into decerebrate posturing.
Posturing has also been displayed by patients with Creutzfeldt-Jakob disease
, diffuse cerebral hypoxia
, and brain abscess
es.
and traumatic brain injury can both cause decorticate posturing in children.
For reasons that are poorly understood, but which may be related to high intracranial pressure, children with malaria
frequently exhibit decorticate, decerebrate, and opisthotonic posturing.
Decorticate posturing is also called decorticate response, decorticate rigidity, flexor posturing, or, colloquially, mummy baby. Patients with decorticate posturing present with the arms flexed, or bent inward on the chest, the hands are clenched into fists, and the legs extended and feet turned inward. A person displaying decorticate posturing in response to pain gets a score of three in the motor section of the Glasgow Coma Scale
.
There are two parts to decorticate posturing.
The effects on these two tracts (corticospinal and rubrospinal) by lesions above the red nucleus is what leads to the characteristic flexion posturing of the upper extremities and extensor posturing of the lower extremities.
Decorticate posturing indicates that there may be damage to areas including the cerebral hemisphere
s, the internal capsule
, and the thalamus
. It may also indicate damage to the midbrain
. While decorticate posturing is still an ominous sign of severe brain damage
, decerebrate posturing is usually indicative of more severe damage as the rubrospinal tract and hence, the red nucleus, is also involved indicating lesion lower in the brainstem.
. In decerebrate posturing, the head is arched back, the arms are extended by the sides, and the legs are extended. A hallmark of decerebrate posturing is extended elbows. The arms and legs are extended and rotated internally. The patient is rigid, with the teeth clenched. The signs can be on just one or the other side of the body or on both sides, and it may be just in the arms and may be intermittent.
A person displaying decerebrate posturing in response to pain gets a score of two in the motor section of the Glasgow Coma Scale
(for adults) and the Pediatric Glasgow Coma Scale
(for infants).
Decerebrate posturing indicates brain stem
damage, specifically damage below the level of the red nucleus
(e.g. mid-collicular lesion). It is exhibited by people with lesions or compression in the midbrain and lesions in the cerebellum
. Decerebrate posturing is commonly seen in Pontine strokes which are also known as Locked-In Syndrome. A patient with decorticate posturing may begin to show decerebrate posturing, or may go from one form of posturing to the other. Progression from decorticate posturing to decerebrate posturing is often indicative of uncal (transtentorial) or tonsilar brain herniation
. Activation of gamma motor neurons is thought to be important in decerebrate rigidity due to studies in animals showing that dorsal root transection eliminates decerebrate rigidity symptoms.
In competitive contact sports, posturing (typically of the forearms) can occur with an impact to the head and is termed the fencing response
. In this case, the temporary posturing display indicates transient disruption of brain neurochemicals, which wanes within seconds.
and have poor prognoses
, with risks for cardiac arrythmia or arrest
and respiratory failure
.
s of cats and monkeys, causing them to exhibit the posturing.
Flexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
or extension
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
of the arms and legs, indicating severe brain injury
Acquired brain injury
An acquired brain injury is brain damage caused by events after birth, rather than as part of a genetic or congenital disorder such as fetal alcohol syndrome, perinatal illness or perinatal hypoxia. ABI can result in cognitive, physical, emotional, or behavioural impairments that lead to permanent...
. It occurs when one set of muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s becomes incapacitated while the opposing set is not, and an external stimulus
Stimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
such as pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
causes the working set of muscles to contract. The posturing may also occur without a stimulus. Since posturing is an important indicator of the amount of damage that has occurred to the brain, it is used by medical professionals to measure the severity of a coma
Coma
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
with the Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...
(for adults) and the Pediatric Glasgow Coma Scale
Pediatric Glasgow Coma Scale
The Paediatric Glasgow Coma Scale is the equivalent of the Glasgow Coma Scale used to assess the mental state of adult patients. As many of the assessments for an adult patient would not be appropriate for infants, the scale was modified slightly...
(for infants).
The presence of posturing indicates a severe medical emergency
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
requiring immediate medical attention. Decerebrate and decorticate posturing are strongly associated with poor outcome in a variety of conditions. For example, near-drowning
Drowning
Drowning is death from asphyxia due to suffocation caused by water entering the lungs and preventing the absorption of oxygen leading to cerebral hypoxia....
victims that display decerebrate or decorticate posturing have worse outcomes than those that do not. Changes in the condition of the patient may cause him or her to alternate between different types of posturing.
Causes
Posturing can be caused by conditions that lead to large increases in intracranial pressureIntracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
. Such conditions include traumatic brain injury
Traumatic brain injury
Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
, stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, intracranial hemorrhage
Intracranial hemorrhage
An intracranial hemorrhage is a hemorrhage, or bleeding, within the skull.-Causes:Intracranial bleeding occurs when a blood vessel within the skull is ruptured or leaks. It can result from physical trauma or nontraumatic causes such as a ruptured aneurysm...
, brain tumor
Brain tumor
A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...
s, and encephalopathy
Encephalopathy
Encephalopathy means disorder or disease of the brain. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of global brain dysfunction; this syndrome can be caused by many different illnesses.-Terminology:...
. Posturing due to stroke usually only occurs on one side of the body and may also be referred to as spastic hemiplegia. Diseases such as malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
are also known to cause the brain to swell and cause this posturing effect.
Decerebrate and decorticate posturing can indicate that brain herniation
Brain herniation
Brain herniation, also known as cistern obliteration, is a deadly side effect of very high intracranial pressure that occurs when the brain shifts across structures within the skull...
is occurring or is about to occur. Brain herniation is an extremely dangerous condition in which parts of the brain are pushed past hard structures within the skull. In herniation syndrome, which is indicative of brain herniation, decorticate posturing occurs, and, if the condition is left untreated, develops into decerebrate posturing.
Posturing has also been displayed by patients with Creutzfeldt-Jakob disease
Creutzfeldt-Jakob disease
Creutzfeldt–Jakob disease or CJD is a degenerative neurological disorder that is incurable and invariably fatal. CJD is at times called a human form of mad cow disease, given that bovine spongiform encephalopathy is believed to be the cause of variant Creutzfeldt–Jakob disease in humans.CJD...
, diffuse cerebral hypoxia
Cerebral hypoxia
Cerebral hypoxia refers to a reduced supply of oxygen to the brain. Cerebral anoxia refers to a complete lack of oxygen to the brain. There are four separate categories of cerebral hypoxia; in order of severity they are; diffuse cerebral hypoxia , focal cerebral ischemia, cerebral infarction, and...
, and brain abscess
Brain abscess
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local or remote infectious sources, within the brain tissue...
es.
Children
In children younger than age two, posturing is not a reliable finding because their nervous systems are not yet developed. However, Reye's syndromeReye's syndrome
Reye's syndrome is a potentially fatal disease that causes numerous detrimental effects to many organs, especially the brain and liver, as well as causing a lower than usual level of blood sugar . The classic features are liver damage, aspirin use and a viral infection...
and traumatic brain injury can both cause decorticate posturing in children.
For reasons that are poorly understood, but which may be related to high intracranial pressure, children with malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
frequently exhibit decorticate, decerebrate, and opisthotonic posturing.
Types
Three types of abnormal posturing are decorticate posturing, with the arms flexed over the chest; decerebrate posturing, with the arms extended at the sides; and opisthotonos, in which the head and back are arched backward.Decorticate
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...
.
There are two parts to decorticate posturing.
- The first is the disinhibition of the red nucleusRed nucleusThe red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...
with facilitation of the rubrospinal tractRubrospinal tractThe rubrospinal tract is a part of the nervous system. It is a part of the lateral indirect extra-pyramidal tract.-Function:In humans, the rubrospinal tract is one of several major motor control pathways. It is smaller and has fewer axons than the corticospinal tract, suggesting that it is less...
. The rubrospinal tract facilitates motor neuronMotor neuronIn vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
s in the cervical spinal cord supplying the flexor muscles of the upper extremities. The rubrospinal tract and medullary reticulospinal tractReticulospinal tractThe reticulospinal tract is an extrapyramidal motor tract which travels from the reticular formation.-Functions:...
biased flexion outweighs the medial and lateral vestibulospinalVestibulospinal tractThe vestibulospinal tract is a component of the extrapyramidal system and also can be classified as a component of the medial pathway. The vestibulospinal fibers relay information from nuclei to motor neurons, like other descending motor pathways. Specifically, the vestibular nuclei receive...
and pontine reticulospinal tractReticulospinal tractThe reticulospinal tract is an extrapyramidal motor tract which travels from the reticular formation.-Functions:...
biased extension in the upper extremities. - The second component of decorticate posturing is the disruption of the lateral corticospinal tractCorticospinal tractThe corticospinal or pyramidal tract is a collection of axons that travel between the cerebral cortex of the brain and the spinal cord....
which facilitates motor neurons in the lower spinal cord supplying flexor muscles of the lower extremities. Since the corticospinal tract is interrupted, the pontine reticulospinal and the medial and lateral vestibulospinal biased extension tracts greatly overwhelm the medullary reticulospinal biased flexion tract.
The effects on these two tracts (corticospinal and rubrospinal) by lesions above the red nucleus is what leads to the characteristic flexion posturing of the upper extremities and extensor posturing of the lower extremities.
Decorticate posturing indicates that there may be damage to areas including the cerebral hemisphere
Cerebral hemisphere
A cerebral hemisphere is one of the two regions of the eutherian brain that are delineated by the median plane, . The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres has an outer layer of grey matter called the cerebral cortex that is...
s, the internal capsule
Internal capsule
The internal capsule is an area of white matter in the brain that separates the caudate nucleus and the thalamus from the lenticular nucleus. The internal capsule contains both ascending and descending axons....
, and the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
. It may also indicate damage to the midbrain
Mesencephalon
The midbrain or mesencephalon is a portion of the central nervous system associated with vision, hearing, motor control, sleep/wake, arousal , and temperature regulation....
. While decorticate posturing is still an ominous sign of severe brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
, decerebrate posturing is usually indicative of more severe damage as the rubrospinal tract and hence, the red nucleus, is also involved indicating lesion lower in the brainstem.
Decerebrate
Decerebrate posturing is also called decerebrate response, decerebrate rigidity, or extensor posturing. It describes the involuntary extension of the upper extremities in response to external stimuliStimulus (physiology)
In physiology, a stimulus is a detectable change in the internal or external environment. The ability of an organism or organ to respond to external stimuli is called sensitivity....
. In decerebrate posturing, the head is arched back, the arms are extended by the sides, and the legs are extended. A hallmark of decerebrate posturing is extended elbows. The arms and legs are extended and rotated internally. The patient is rigid, with the teeth clenched. The signs can be on just one or the other side of the body or on both sides, and it may be just in the arms and may be intermittent.
A person displaying decerebrate posturing in response to pain gets a score of two in the motor section of the Glasgow Coma Scale
Glasgow Coma Scale
Glasgow Coma Scale or GCS is a neurological scale that aims to give a reliable, objective way of recording the conscious state of a person for initial as well as subsequent assessment...
(for adults) and the Pediatric Glasgow Coma Scale
Pediatric Glasgow Coma Scale
The Paediatric Glasgow Coma Scale is the equivalent of the Glasgow Coma Scale used to assess the mental state of adult patients. As many of the assessments for an adult patient would not be appropriate for infants, the scale was modified slightly...
(for infants).
Decerebrate posturing indicates brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
damage, specifically damage below the level of the red nucleus
Red nucleus
The red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...
(e.g. mid-collicular lesion). It is exhibited by people with lesions or compression in the midbrain and lesions in the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
. Decerebrate posturing is commonly seen in Pontine strokes which are also known as Locked-In Syndrome. A patient with decorticate posturing may begin to show decerebrate posturing, or may go from one form of posturing to the other. Progression from decorticate posturing to decerebrate posturing is often indicative of uncal (transtentorial) or tonsilar brain herniation
Brain herniation
Brain herniation, also known as cistern obliteration, is a deadly side effect of very high intracranial pressure that occurs when the brain shifts across structures within the skull...
. Activation of gamma motor neurons is thought to be important in decerebrate rigidity due to studies in animals showing that dorsal root transection eliminates decerebrate rigidity symptoms.
In competitive contact sports, posturing (typically of the forearms) can occur with an impact to the head and is termed the fencing response
Fencing response
The fencing response is a peculiar position of the arms following a concussion. Immediately after moderate forces have been applied to the brainstem, the forearms are held flexed or extended for a period lasting up to several seconds after the impact...
. In this case, the temporary posturing display indicates transient disruption of brain neurochemicals, which wanes within seconds.
Prognosis
Normally people displaying decerebrate or decorticate posturing are in a comaComa
In medicine, a coma is a state of unconsciousness, lasting more than 6 hours in which a person cannot be awakened, fails to respond normally to painful stimuli, light or sound, lacks a normal sleep-wake cycle and does not initiate voluntary actions. A person in a state of coma is described as...
and have poor prognoses
Prognosis
Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...
, with risks for cardiac arrythmia or arrest
Cardiac arrest
Cardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
and respiratory failure
Respiratory failure
The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...
.
History
Sir Charles Sherrington was first to describe decerebrate posturing after transecting the brain stemBrain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
s of cats and monkeys, causing them to exhibit the posturing.