Alternating hemiplegia is a very rare condition characterized by recurrent episodes of temporary paralysis.
Alternating hemiplegia usually begins affecting a child before the age of four. Bouts of recurrent, temporary paralysis may involve the arms, legs, facial muscles, and/or eye muscles. The manifestations may range from numbness or tingling in the affected body part to complete paralysis. The episodes last between minutes and days, and are usually resolved by sleep. A variety of other neurological problems may also be present in children with alternating hemiplegia.
A less-severe variant of alternating hemiplegia is called "benign nocturnal alternating hemiplegia of childhood." In this variant, a child awakens from sleep to a state of paralysis that resolves completely over 2–15 minutes. Children with this variant do not suffer from other associated neurological problems. This particular condition is thought to be a variant of a migraine headache .
Alternating hemiplegia is quite rare, with fewer than 100 diagnosed cases in the United States, and fewer than 240 diagnosed patients worldwide.
Causes and symptoms
The underlying cause of alternating hemiplegia is unknown. Benign nocturnal alternating hemiplegia of childhood is thought to be a variant of migraine headache, and therefore may be caused by a similar mechanism (abnormal dilatation of blood vessels in the brain, followed by chemical release and then painful spasms of the blood vessels).
Individual episodes seem to occur spontaneously, although in some individuals they may be precipitated by stress, sleep deprivation, or viral illness.
Symptoms of alternating hemiplegia
Episodes of alternating hemiplegia come on suddenly during wakefulness, and can last between hours and days. Either or both sides of the body may become numb, tingly, or completely paralyzed. Limbs may be limp or stiff (dystonic). Facial and eye muscles are often affected, as well as the limbs. Children with alternating hemiplegia also usually experience progressive difficulty with balance and walking, excess sweating, mental impairment, developmental delay, problems with body temperature, shortness of breath, and seizures . Although sleep can ameliorate the symptoms, the symptoms may recur upon awakening.
Symptoms of benign nocturnal alternating hemiplegia of childhood
Symptoms of benign nocturnal alternating hemiplegia of childhood may begin when the child is about two years of age. Boys appear to be more frequently affected than girls. Episodes may be preceded by several days by headache, abnormal irritability, and oppositional behavior. The actual episodes commence when a child is asleep, causing the child to awaken suddenly, screaming or crying and drooling. Although the child may appear to be awake, he or she usually does not respond normally to questions or commands. Usually only one side of the body appears limp and paralyzed. The episodes usually last about fifteen minutes, end with the child falling back into sleep, and are completely resolved when the child awakens again. Some children experience headache and vomiting with each episode, further underscoring the proposed link with migraine headache. Although children with this condition do not seem to exhibit any permanent effects of their hemiplegic episodes, and generally have normal intelligence, there does appear to be an increased risk of hyperactivity, irritability, and oppositional defiant disorder in children who experience episodes of benign nocturnal alternating hemiplegia of childhood.
There are no available tests to definitively diagnose either form of alternating hemiplegia. These disorders are diagnosed by ruling out other possible reasons for a child's episodes and symptoms.
Children with the more benign form of alternating hemiplegia may not require an extensive treatment team, other than a neurologist to help in diagnosis. Children with the more severe form of alternating hemiplegia may require a neurologist, as well as other specialists to help with their progressive problems with walking, such as a physical and occupational therapist. Children with this disorder usually require a specialized educational setting.
There is no cure for either form of alternating hemiplegia. A drug called flunarizine has been used to treat the more severe type of alternating hemiplegia, in an effort to decrease the frequency of hemiplegic episodes, as well as their duration and severity. Some researchers believe that decreasing the number and severity of attacks may improve the child's overall cognitive prognosis, by preventing damage to the brain.
The classic form of alternating hemiplegia has a poor prognosis, with progressively severe impairment of mobility and cognitive functioning, requiring long-term care. About half of all children with benign nocturnal alternating hemiplegia of childhood outgrow their episodes over time.
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National Institute of Neurological Disorders and Stroke (NINDS). NINDS Alternating Hemiplegia Information Page. January 17, 2002. (June 3, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/alternatinghemiplegia.htm>.
Rosalyn Carson-Dewitt, MD