89. Ataxia episódica tipo 2

89.A 16-year-old girl with a 3-year history of migraines presents with episodes of dizziness and abnormal movements that began 6 months ago while she was playing soccer. The episodes are characterized by nausea, dizziness, and trouble running because her legs “feel clumsy.” Each episode lasts several hours to days, always in the setting of exercise or overheating. The patient usually feels normal by the next morning. Family history is significant for similar symptoms in an older sibling. Which of the following diagnoses is likely the cause for her symptoms.

** = Your answer

Episodic ataxia type 2 is an autosomal dominant paroxyxmal movement disorder of childhood associated mutation in the CACNA1a gene, which encodes the alpha-1A subunit of a voltage-dependent P/Q-type calcium channel. Over 80 mutations in this gene are reported in EA2 which is also allelic to familial hemiplegic migraine and spinocerebellar ataxia 6. Therefore, there is signficant overlap in the clinical presentation of these disorders including the parosxymal patterns, common association wtih triggers, (heat, exertion), motor and epileptic presentations, including espisodic ataxia 1 which is associated mutations KCNA1 (potassium channel, Kv1.1, alpha subunit). However, the long duration of attack makes EA 2 more likely in that patients’ attacks can last several hours to days  versus seconds to hours or few days for the other options. Periodic paralyses are not associated with ataxia or migraines.

References

  • Kurian M, Dale R. Movement disorders presenting in childhood. Continuum Lifelong Learning Neurol. 2016;22(4):1159-1185

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