Alternating hemiplegia

Causes

Note that this description is focused on alternating hemiplegia of childhood. Similar syndromes may develop following a brainstem infarction. The cause of alternating hemiplegia of childhood is the mutation of ATP1A3 gene. In a study of fifteen female and nine male patients with alternating hemiplegia, a mutation in ATP1A3 gene was present. Three patients showed heterozygous de-novo missense mutation. Six patients were found with de-novo missense mutation and one patient was identified with de-novo splice site mutation. De novo mutation is a mutation that occurs in the germ cell of one parent. Neither parent has the mutation, but it is passed to the child through the sperm or egg.

Diagnosis

Criteria for diagnosis

First, the symptoms must be observed before the patient is 18 months of age. Second, there must be frequent episodes of hemiplegia, involving either side of the body. Third, other paroxysmal disorders including tonic attacks, dystonia, nystagmus, strabismus, dyspnoea, and other uncontrollable disorders are noticed to occur. Although common, the paroxysmal disorders involving the eye, nystagmus and strabismus, may not be apparent in older children and may not have been remembered in childhood so a lack of these symptoms does not rule out alternating hemiplegia. Fourth, all symptoms clear up directly after falling asleep and usually come back after waking during an attack. This occurrence is very indicative of alternating hemiplegia and as such those who display this are usually diagnosed with probable alternating hemiplegia. Fifth, indications of developmental delays, learning disability, or neurological irregularities are present. These issues may not be obvious in very young patients; however, it appears in almost all older patients. The final criteria before a diagnosis of alternating hemiplegia can be made is that all of these symptoms must not be due to another disorder. If the symptoms can be attributed to another disease or disorder, then a definitive diagnosis is difficult to make.

Diagnosis of Weber's syndrome

Weber's syndrome is the only form of alternating hemiplegia that is somewhat easy to diagnose beyond the general criteria. Although Weber's syndrome is rare, a child born with the disorder typically has a port-wine stain on the face around the eye. While the port-wine stain does not necessarily mean the child has Weber's syndrome, if the port-wine stain involves the ophthalmic division of the trigeminal nerve than the likelihood of it being weber's syndrome greatly increases. If a port-wine stain around the eye is found, the patient should be screened for intracranial leptomeningeal angiomatosis. Magnetic resonance imaging (MRI) can be used to determine the presence and severity while computed cranial tomography can be used to determine the effect. MRI is the preferred diagnostic test on children presenting with port-wine stain. Other imaging techniques can be used in addition to further determine the severity of the disorder. The initial diagnosis is made based on the presence of neurologic and ophthalmic disease but the disease progresses differently in each patient so after initial diagnosis the patient should be monitored frequently in order to handle further complications resulting from the syndrome.

Treatment

Medical treatment of hemiplegia can be separate into several different categories:

• prophylactic treatment by avoiding triggers and long-term drug treatment
• acute management of the episodes
• management of the epilepsy
• sleep as a management technique.

Seizure trigger include exposure to cold, emotional stress, fatigue, bathing, hyperthermia/hypothermia, and upper respiratory infection. A drug called flunarizine, which is a calcium channel blocker can help to reduce the severity and the length of attacks of the paralysis.

Flunarizine

Many children affected by alternating hemiplegia also have epilepsy. Seizures may occur during an attack but more often occur between attacks. Anti-epilepsy drugs are given to prevent or lessen the seizures, but the drugs often don't work and have severe side effects that require the patient to discontinue use. Flunarizine, which blocks calcium channels, is an antiepilepsy drugs used in 50% of patients, and has been shown to shorten the duration of attacks as well as reducing the severity of the attacks. While Flunarizine does not stop the attacks, it is the most common drug prescribed to treat those with alternating hemiplegia.

Sleep and diet

Sleep is also used as a management technique. An early indication of an episode is tiredness so medication such as melatonin or Buccal midazolam can be administered to induce sleep and avoid the episode. People with alternating hemiplegia are often underweight and with the help of dietitians, a meal plan should be developed for times of attack when consumption of food may be difficult.