Causes of AHC
The cause of AHC is still unknown. Most cases of AHC are sporadic, meaning that there is no family history of the disease. The chance of having additional children with AHC after having an affected child appears to be quite low (<5%). However, we suspect that AHC may have a genetic cause, as there are rare families who have more than one affected family member. These families are critical in helping researchers to identify a possible genetic cause for the disease. Males and females are equally affected.
Although the cause of AHC is unknown, a number of different triggers have been identified in association with episodes. Stress, infection and certain environmental triggers commonly trigger episodes in susceptible children. Common environmental triggers include exposure to bright lights, loud sounds, changes in temperature, excitement or other strong emotions, or bath or pool water. However, often attacks seem to occur without any trigger at all.
Other disorders can have similar symptoms as those seen in AHC. A careful clinical history, review of available video of episodes if possible, and specific testing (refer to section on how is AHC diagnosed) can help determine whether or not the disorder meets criteria for the diagnosis of AHC.
Table I. Diseases with symptoms similar to those seen in Alternating Hemiplegia of Childhood
- Migraine variants
- Familial Hemiplegic Migraine
- Basilar Migraine
- Vascular disorders
- Arteriovenous malformations
- Stroke, emboli
- Moya Moya Syndrome
- Epilepsy syndromes
- Metabolic disorders
- Pyruvate Dehydrogenase Deficiency
- Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS)
- Cataplexy
- Neurotransmitter Deficiency Disorders
