Table 4.

Episodic causes of cerebellar ataxia

Episodic Causes of Ataxia	Features
Genetic  Episodic ataxia type 1  Episodic ataxia type 2  Episodic ataxia types 3–7  Glucose transporter-1 deficiency	Lasts seconds-minutes + myokymia between attacks Lasts hours-days + nystagmus between attacks Rare Recurrent attacks ataxia ± vertigo +/− normal examination between attacks Paroxysmal exertional dyskinesias Ataxia with fasting, exercise, or illness Epilepsy
Inborn errors of metabolism Hartnup disease	Skin photosensitivity, pellagra-like rash
Mitochondrial disorders  MELAS  MERRF  NARP	Short stature Hearing and/or vision loss Polyneuropathy, myopathy +/− Epilepsy
Demyelinating  Multiple sclerosis  Neuromyelitis optica	Holmes tremor, dysarthria, incoordination Cerebellar lesions Can progress to chronic ataxia Bulbar dysfunction, diplopia, vertigo, hiccups Brainstem, periaqueductal, & peri-third and fourth ventricular lesions
Functional movement disorder	Variability in phenomenology Distractable Entrainment

Abbreviations: MELAS, mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes; MERRF, myoclonus epilepsy with ragged red fibers; NARP, neuropathy, ataxia, and retinitis pigmentosa.