Spinocerebellar ataxia type 36

Spinocerebellar ataxia type 36 (SCA36) is a condition characterized by progressive problems with movement that typically begin in mid-adulthood. People with this condition initially experience problems with coordination and balance (ataxia). Affected individuals often have exaggerated reflexes (hyperreflexia) and problems with speech (dysarthria). They also usually develop muscle twitches (fasciculations) of the tongue and over time, the muscles in the tongue waste away (atrophy). These tongue problems can cause difficulties swallowing liquids. As the condition progresses, individuals with SCA36 develop muscle atrophy in the legs, forearms, and hands. Another common feature of SCA36 is the atrophy of specialized nerve cells that control muscle movement (motor neurons), which can contribute to the tongue and limb muscle atrophy in affected individuals.

Some people with SCA36 have abnormalities of the eye muscles, which can lead to involuntary eye movements (nystagmus), rapid eye movements (saccades), trouble moving the eyes side-to-side (oculomotor apraxia), and droopy eyelids (ptosis). Sensorineural hearing loss, which is hearing loss caused by changes in the inner ear, may also occur in people with SCA36.

Brain imaging of people with SCA36 shows progressive atrophy of various parts of the brain, particularly within the cerebellum, which is the area of the brain involved in coordinating movements. Over time, the loss of cells in the cerebellum causes the movement problems characteristic of SCA36. In older affected individuals, the frontal lobes of the brain may show atrophy resulting in loss of executive function, which is the ability to plan and implement actions and develop problem-solving strategies.

Signs and symptoms of SCA36 typically begin in a person's forties or fifties but can appear anytime during adulthood. People with SCA36 have a normal lifespan and are usually mobile for 15 to 20 years after they are diagnosed.