Article type: Letter to Editor
Article title: Lacosamide‑induced downbeat nystagmus
Journal: Neurology India
Year: 2025
Authors: Jamir Pitton Rissardo, Ana Letícia Fornari Caprara, Karandeep Singh Bhatti
E-mail: jamirrissardo@gmail.com
ABSTRACT
A 69-year-old woman with a history of depression and gastroesophageal reflux disease presented with fever, headache, and seizures. Continuous video-EEG revealed generalized periodic epileptiform discharges, and she was treated with levetiracetam and lacosamide. Due to agitation, levetiracetam was discontinued and valproic acid initiated. Cerebrospinal fluid analysis confirmed herpes simplex virus type 1, and she received 21 days of intravenous acyclovir. Despite improvement in seizures and headaches, mild cognitive impairment persisted. Lacosamide monotherapy was continued and increased to 250 mg BID IV. Remarkably, 15–20 minutes after administration, the patient developed transient downbeat nystagmus lasting 5–10 minutes, observed consistently over three days. Neuroimaging and metabolic panels were unremarkable. Upon reducing lacosamide to 200 mg BID IV, the nystagmus resolved. Literature review revealed only one prior case of lacosamide-induced downbeat nystagmus, without a clear time-dose relationship. This case is unique for demonstrating a reproducible temporal association with intravenous lacosamide and being the only report involving monotherapy. Downbeat nystagmus is typically linked to vestibulocerebellar dysfunction, and cerebellar Purkinje cells express voltage-gated sodium channels, which may be affected by lacosamide. This report highlights a rare but reversible adverse effect of lacosamide, emphasizing the importance of monitoring for ocular side effects in patients receiving high-dose or intravenous formulations. Clinicians should be aware of this potential reaction, especially when using lacosamide as monotherapy in epilepsy management.
Keywords: lacosamide, downbeat nystagmus, adverse drug reaction, epilepsy, vestibulocerebellum.
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DOI
Citation
Rissardo JP, Fornari Caprara AL, Bhatti KS. Lacosamide‑Induced Downbeat Nystagmus. Neurol India 2025;73:1090-1. doi: 10.4103/neurol-india.Neurol-India-D-24-00895.
Table 1. Summary of previous reported and presented cases with epilepsy and lacosamide‑induced downbeat nystagmus.
Video 1. Downbeat nystagmus.