Episodic and Intermittent Ataxias

This chapter describes several episodic ataxia syndromes and highlights the recent genetic discoveries that provide insight into the molecular mechanisms of these dramatic clinical disorders. Episodic ataxia type 1 (EA-1) is characterized by brief episodes of ataxia and interictal myokymia while episodic ataxia type 2 (EA-2) is manifested by longer episodes of ataxia with interictal nystagmus. Magnetic resonance imaging (MRI) often shows atrophy of the cerebellum, particularly the midline, with EA-2. The degree of atrophy with EA-2 is most prominent in patients with longstanding symptoms and signs. Non-specific paroxysmal slowing on electroencephalography (EEC) is reported with both EA-1 and EA-2. Continuous muscle rippling (myokymia) can be detected in patients with EA-1 and EA-2, particularly after provocation by limb ischemia. Repetitive duplets, triplets, or multiplets on EMG underlie the continuous muscle activity. At the present time, genetic testing for EA-1 and EA-2 is not available in clinical laboratories. Automated techniques are available to rapidly screen these genes for the known point mutations. Since emotional stress is often a trigger for attacks in patients with episodic ataxia syndromes, stress management techniques such as biofeedback and meditation can be helpful in controlling symptoms in some patients. Alcohol and caffeine should be avoided and regular modest exercise should be encouraged. Vigorous exercise often triggers attacks of the episodic ataxia. Fluid and food intake should be regularly distributed throughout the day and binges should be avoided.