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October 2007

Potassium Channel Antibody–Associated Encephalopathy Presenting With a Frontotemporal Dementia–like Syndrome

Author Affiliations

Author Affiliations: Departments of Neurology (Drs McKeon, Marnane, Kelly, and Lynch) and Radiology (Messrs O’Connell and Stack), Mater Misericordiae University Hospital, Dublin, Ireland.

Arch Neurol. 2007;64(10):1528-1530. doi:10.1001/archneur.64.10.1528

Objective  To describe a patient who presented with features suggestive of frontotemporal dementia (FTD) but with some atypical findings and antibodies to neuronal voltage-gated potassium channels (VGKC-Abs).

Design  Case report.

Setting  Mater Misericordiae University Hospital, Dublin, Ireland.

Results  An 82-year-old man presented with progressive changes in personality, social conduct, and executive function with preservation of memory, deteriorating from baseline to requiring acute hospitalization within 6 months. Transient deterioration (episodic speech arrest) with spontaneous recovery, atypical for frontotemporal dementia, was observed. The patient had an elevated VGKC-Ab titer (2624 pM [normal range, < 100 pM]), elevated protein levels in cerebrospinal fluid, and a negative evaluation for malignancy. Magnetic resonance imaging of brain was normal but [18F]-fluorodeoxyglucose positron emission tomographic imaging revealed bifrontal hypometabolism. A marked and sustained improvement with steroid therapy was observed.

Conclusion  Workup for a potentially reversible autoimmune-mediated encephalopathy, including a VGKC-Ab titer, should be considered in patients presenting with rapidly progressive behavioral and cognitive decline.