Information on the following diseases can be found in the Related Disorders section of this report:

• Akinetic Mutism
• Quadriplegia
• Reye Syndrome with Total Paralysis
• Spinal Cord Injuries
• Fibromuscular Dysplasia

In the Locked-In Syndrome, all voluntary muscles controlling movement are paralyzed, except for those performing eye and eyelid movements. Individuals with Locked-In Syndrome are conscious, but unable to speak. However, they can learn to communicate through an eye blink code.

Locked-In Syndrome is caused by lesions cutting across corticospinal and corticobulbar nerve tracts, which cut off all motor nerves except for those to the eye muscles. Tissue loss may also occur on both sides of the body caused by lack of oxygen circulated to the internal capsule of the brain (hypoxia). In some cases, the circulation may be blocked by a blood clot within a blood vessel in the brain stem. If circulation can be restored, the affected individual's condition may improve.

Infection in certain portions of the brain (i.e. midbrain), tumors, or damage (lesions) of the brain; bleeding (hemorrhaging) into the brain; or head injuries may cause Locked-In Syndrome. It can also be seen as a result of the loss of protective insulation around nerve cells (myelinolysis); the inflammation of many nerves (polyneuritis); or a rare disorder known as Myasthenia Gravis.

Locked-In Syndrome is a very rare disorder. It affects males and females in equal numbers.

Symptoms of the following disorders may resemble those of Locked-In Syndrome. Comparisons can be useful for a differential diagnosis:

Akinetic Mutism is a disorder characterized by the patient appearing to be in an awake state with open eyes, but without communication. Immobility occurs as a result of lesions causing bilateral frontal lobe damage or destruction of the reticular activating system of the brain. The response of muscles to painful stimuli is poor.

Quadriplegia (quadriparesis; tetraplegia) is a term denoting paralysis of all four limbs. Spinal cord injury is one of the more common causes of Quadriplegia.

Reye Syndrome is a combination of acute brain disease (encephalopathy) and fatty degeneration of the abdominal organs, which tends to follow some acute virus infections such as flu or chicken pox, combined with certain precipitating agents such as aspirin. Seizures may occur. A complete recovery is possible. However, permanent brain damage, ranging from a slight decrease in I.Q. to total paralysis, may occur. (For more information on this disorder, choose "Reye" as your search term in the Rare Diease Database.)

Spinal Cord Injury can be caused by trauma to the spine. Symptoms include retention of urine, possibly incontinence, reflex spasm below the site of the injury, and/or paralysis with sensory loss.

Fibromuscular Dysplasia is a rare disorder characterized by narrowing or blockage (occlusion) of certain blood vessels (i.e., medium or small sized arteries). Fibromuscular Dysplasia usually affects arteries of the kidneys (renal arteries) or the major artery of the neck (carotid arteries). Symptoms may include high bood pressure (hypertension), stroke, an abnormal tear in the wall of the major artery of the body (aortic dissection), and/or heart attack (myocardial intaction). In addition, affected individuals may also experience cramping in the legs when they walk that, in rare cases, may cause affected individuals to limp (claudication). The exact cause of Fibromuscular Dysplasia is not known.

The diagnosis of Locked-In Syndrome may be suspected based upon the results of Computed Tomography (CT Scan), angiography, transcranial doppler, and Magnetic Resonance Imaging (MRI). These test may reveal characteristic brain abnormalities. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of tissue structure. During MRI, a magnetic field and radio waves are used to create cross-sectional images of the brain. During an angiography, the blood vessels within the brain are studied.

Functional neuromuscular stimulation may help activate paralyzed muscles. Several devices to facilitate communication for people who cannot speak are on the market. Other treatment is symptomatic and supportive.

TEXTBOOKS
Thoene JG., ed. Physicians’ Guide to Rare Diseases. Montvale, NJ: Dowden Publishing Company Inc; 1995:326

Fauci AS, et al., eds. Harrison's Principles of Internal Medicine, 14th Ed. New York, NY: McGraw-Hill, Inc; 1998:126

Berkow R., ed. The Merck Manual-Home Edition. Whitehouse Station, NJ: Merck Research Laboratories; 1997:372.

Adams, RD, et al., eds. Principles of Neurology. 6th ed. New York, NY: McGraw-Hill, Companies; 1997:347.

JOURNAL ARTICLES
Hummelsheim H, et al., Repetitive sensorimotor training for arm and hand in a patient with locked-in syndrome. Scand J Rehabil Med. 1999;31:250-56.

Wijdicks EF, et al., Transient locked-in syndrome after uncal herniation. Neurology. 1999;52:1296-97.

Allain P, et al., Cognitive functions in chronic locked-in syndrome: a report of two cases. Cortex. 1998;34;629-34.

Stormark KM, et al., Heart rate responses indicate locked-in attention in alcoholics immediately prior to drinking. Addict Behav. 1998;23:251-55.

Park SA, et al., Locked-in syndrome in an adolescent patient with pneumococcal meningitis, Neuroimaging. 1997;7:126-28.

Gutling E, et al., Electrophysiology in the locked-in syndrome. Neurology. 1996;46:1092-101.

Onofrj M, et al., Reappearance of event-related P3 potential in locked-in syndrome. Brain Res Cogn Brain Res. 1996;4:95-97.

Ueyama T, et al., Traumatic basilar artery dissection presenting with "locked-in" syndrome: Report of a case. No Shinkei Geka. 1996;24:1035-39.

Kennedy PR., 'Locked-in' patients. Neurology. 1994;44:366-67.

Allen CM., Conscious but paralysed: releasing the locked-in. Lancet. 1993;342:130-31.