SNP Shot: Genomic Insights

Familial hemiplegic migraine (FHM) is a type of migraine that is passed down through families. Migraines are typically characterized by severe, pulsating pain, usually on one side of the head, and are often accompanied by nausea, vomiting, and heightened sensitivity to light and sound. These recurring headaches often start during childhood or the teenage years and can be triggered by factors such as specific foods, emotional stress, or minor head injuries. A headache episode can last from a few hours to several days.

Certain types of migraine, including FHM, involve neurological symptoms called an aura that occur before the headache. The most common aura symptoms are temporary visual disturbances, such as blind spots (scotomas), seeing flashing lights or zig-zag lines, and double vision. In FHM, auras also include temporary numbness or weakness, frequently affecting one side of the body (hemiparesis). Other aura symptoms may involve speech difficulties, confusion, and sleepiness. Auras usually develop gradually over several minutes and last approximately one hour.

Some individuals with FHM experience exceptionally severe migraine episodes. These episodes may involve fever, seizures, prolonged weakness, coma, and, in rare cases, death. While most individuals with FHM fully recover between episodes, neurological symptoms like memory problems and attention deficits can persist for weeks or months. Roughly 20% of individuals with FHM develop a mild, permanent lack of coordination (ataxia), which can worsen over time, along with rapid, involuntary eye movements (nystagmus).

Inheritance:

FHM follows an autosomal dominant inheritance pattern. This means that having only one copy of a mutated gene in each cell is enough to cause the condition. Typically, affected individuals have one parent who also has the condition. However, some people who inherit the mutated gene may never develop symptoms of FHM. (This is known as reduced penetrance.) Sporadic hemiplegic migraine is a related condition with the same signs and symptoms as FHM but occurs in people with no family history of the disorder.