Abnormal posturing
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| Decorticate posturing, with elbows, wrists and fingers flexed, and legs extended and rotated inward. |
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Abnormal posturing Microchapters |
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Abnormal posturing On the Web |
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American Roentgen Ray Society Images of Abnormal posturing |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Causes
Posturing can be caused by conditions that lead to large increases in intracranial pressure.[1] Such conditions include traumatic brain injury, stroke, intracranial hemorrhage, brain tumors, and encephalopathy.[2] Posturing due to stroke usually only occurs on one side of the body and may also be referred to as spastic hemiplegia.[3] 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[4] or is about to occur.[1] 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.[4]
Posturing has also been displayed by patients with Creutzfeldt-Jakob disease.[5]
Decerebrate posturing can occur with diffuse cerebral hypoxia.[6]
Brain abscesses may also cause decorticate posturing.[3]
In Children
In children younger than age 2, posturing is not a reliable finding because their nervous systems are not yet developed.[3] However, Reye's syndrome and traumatic brain injury can both cause decorticate posturing in children.[3]
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.[7]
Decorticate posturing
Decorticate posturing is also called decorticate response, decorticate rigidity, flexor posturing, or "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. Decorticate posturing indicates damage to the mesencephalic region, or the corticospinal tract, along which impulses travel from the brain to the spinal cord.[8]
There are two parts to decorticate posturing. The first is the disinhibition of the red nucleus with facilitation of the rubrospinal tract. The rubrospinal tract facilitates motor neurons in the cervical spinal cord subserving flexor muscles of the upper extremities. The second component of decorticate posturing is the disinhibition of the lateral vestibulospinal tract which facilitates motor neurons in the lower cord subserving extensor muscles of the lower extremities. The disinhibition of these two tracts 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. While an ominous sign of severe brain damage, the damage of which decorticate posturing is indicative is not as serious as that indicated by decerebrate posturing.
Decerebrate posturing
Decerebrate posturing is also called decerebrate response, decerebrate rigidity, or extensor posturing. In decerebrate posturing, the head is arched back, the arms are extended by the sides, and the legs are extended. [2] Decerebrate posturing indicates brain stem damage or rather damage below the level of the red nucleus (eg. mid-collicular lesion). A patient with decorticate posturing may begin to show decerebrate posturing, or may go from one form of posturing to the other;[8] progression from decorticate posturing to decerebrate posturing is often indicative of uncal (transtentorial) or tonsilar brain herniation. Posturing may occur on one or the other side of the body, or it may occur on both sides.[8] 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.[9]
References
- ↑ 1.0 1.1 Yamamoto, Loren G. 1996. “Intracranial Hypertension and Brain Herniation Syndromes: Radiology Cases in Pediatric Emergency Medicine". 5(6). Kapiolani Medical Center for Women and Children; University of Hawaii; John A. Burns School of Medicine. Retrieved January 24, 2007.
- ↑ 2.0 2.1 ADAM. 2005. "Decorticate Posture". Retrieved January 15, 2007.
- ↑ 3.0 3.1 3.2 3.3
- ↑ 4.0 4.1 Ayling, J (2002). "Managing head injuries". Emergency Medical Services. 31 (8): 42. PMID 12224233.
|access-date=requires|url=(help) - ↑ Obi, T (1996). "A case of Creutzfeldt-Jakob disease (CJD) started with monoparesis of the left arm". Rinsho Shinkeigaku (Clinical Neurology). 36 (11): 1245–1248. PMID 9046857. Unknown parameter
|coauthors=ignored (help);|access-date=requires|url=(help) - ↑ De Rosa G, Delogu AB, Piastra M, Chiaretti A, Bloise R, Priori SG (2004). "Catecholaminergic polymorphic ventricular tachycardia: successful emergency treatment with intravenous propranolol". Pediatric emergency care. 20 (3): 175–7. PMID 15094576.
- ↑ Idro, R. "Decorticate, decerebrate and opisthotonic posturing and seizures in Kenyan children with cerebral malaria". Malaria Journal. 4 (57). PMID 16336645. Retrieved 2007-01-21. Unknown parameter
|coauthors=ignored (help) - ↑ 8.0 8.1 8.2
- ↑ Berne and Levy principles of physiology/[editors] Metthew N. Levy, Bruce M. Koeppen, Bruce A. Stanton.-4th ed.Philadelphia, PA: Elsevier Mosby, 2006.
- Victor M, Ropper A. Adams and Victor's principles of neurology. 7th ed. New York: McGraw-Hill, 2001.
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