Alternating hemiplegia of childhood
| Alternating hemiplegia of childhood | |
|---|---|
| Classification and external resources | |
| OMIM | 104290 |
| DiseasesDB | 33595 |
| eMedicine | neuro/219 |
Alternating hemiplegia of childhood (AHC) is a rare neurological disorder of uncertain etiology, though growing evidence strongly supports mutation of the ATP1A3 gene as the primary cause of this disease. AHC is named for the episodes, often referred to as attacks or episodes, of hemiplegia from which those with the disorder suffer. These hemiplegic attacks can cause anything from mild weakness to complete paralysis on one or both sides of the body, and they can vary greatly in duration. Attacks may also alternate from one side of the body to the other, or alternate between affecting one or both sides during a single attack. AHC is associated with many symptoms besides hemiplegia, and the majority of these become apparent in early infancy. AHC typically presents before the age of 18 months. Normally, hemiplegia and other associated symptoms cease completely with sleep, but they may recur upon waking. The disorder was only recently discovered, having first been characterized in 1971. AHC is also extremely rare – approximately 1 in 1,000,000 people have this disorder. Besides hemiplegia, symptoms of the disorder include an extremely broad range of neurological and developmental impairments which are not well understood. Much of the literature about AHC is purposefully vague in this respect due to a lack of information on the disorder.
AHC patients exhibit a wide range of symptoms in addition to hemiplegic attacks. These can be further characterized as paroxysmal and non-paroxysmal symptoms. Paroxysmal symptoms are generally associated with hemiplegic attacks and may occur suddenly with hemiplegia or on their own. Paroxysmal symptoms may last for variable amounts of time. Non-paroxysmal symptoms tend to be side effects of AHC which are present at all times, not just during episodes or attacks. Epilepsy, which is also considered a paroxysmal symptom, plays an important role in the progression and diagnosis of AHC.
Chronologically, hemiplegic attacks are not always the first symptom of AHC, but they are the most prominent symptom, as well as the symptom for which the disorder is named. Hemiplegic attacks may affect one or both sides of the body, and attacks which affect both sides of the body may be referred to as either or quadriplegic attacks. One of the unique characteristics of AHC is that hemiplegic attacks, as well as other symptoms which may co-occur with hemiplegia, cease immediately upon sleep. During strong attacks, the symptoms may reoccur upon waking. Hemiplegic attacks can occur suddenly or gradually, and the severity of an attack can vary over its duration. The attacks may alternate from one side of the body to another, though this is rare. The length of attacks may also vary from minutes to weeks, though length of attacks varies more greatly between people than between attacks for one person. Both bilateral and hemiplegic attacks are associated with pseudobulbar features such as dysphagia, dysarthria, and respiratory difficulty. Paralysis is also often accompanied by changes in skin color and temperature, sweating, restlessness, tremor, screaming, and the appearance of pain. Hemiplegic attacks happen irregularly and can occur with speech, eating, and swallowing impairment. Patients with AHC are frequently underweight due to these side effects. The average age of onset for hemiplegic episodes has been found to be 6–7 months of age. This early onset gives the name of this disorder the slightly misleading ending 'of childhood'. AHC is not exclusively limited to childhood – attacks become milder after the first ten years of life, but they never completely disappear.
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