Clinical Reasoning: An 8-Year-Old With Acute Onset Ataxia.

Acute ataxia is a common neurologic presentation in the pediatric population that carries a broad differential diagnosis. The tempo of the presentation, distribution of the ataxia (focal or diffuse), examination findings, and paraclinical testing may be helpful in guiding diagnosis and management. Although Guillain-Barré syndrome (GBS) and its variant, Miller Fisher syndrome (MFS), are well defined, frequently encountered acute autoimmune neuropathies, the GBS/MFS spectrum have at least 12 different phenotypes with distinct neurologic features, 4 of which include ataxia. These lesser-known variants can be diagnosed clinically, in the absence of conclusive laboratory or neuroimaging data, and should always be considered in an acute presentation of ataxia. In this article, we present a previously healthy 8-year-old with acute onset ataxia with associated hyporeflexia that occurred after resolution of a presumed viral infection. We discuss our approach to ataxia, the patient's neurodiagnostic odyssey, and highlight the final diagnosis of acute ataxic neuropathy without ophthalmoplegia-a rare incomplete MFS subtype. Owing to timely recognition of the condition, the patient was treated appropriately and recovered fully.