Downbeat nystagmus as a result of lamotrigine toxicity.
BACKGROUND
Downbeat nystagmus (DBN) has been reported with phenytoin and carbamazepine toxicity. DBN has not been described as a result of lamotrigine toxicity.


METHODS
Clinical records, neuroimaging and video recordings were obtained in two patients diagnosed with intractable epilepsy who developed oscillopsia and incoordination while being treated with lamotrigine. One patient had a videonystagmographic (VNG) study.


CONCLUSIONS
Lamotrigine's half-life is extended when used with valproic acid; hence, the increased chance of neurotoxicity associated with DBN. In our cases, DBN and truncal ataxia occurred in conjunction with toxic lamotrigine serum levels.


CONCLUSIONS
Anticonvulsant toxicity should be considered as a cause of DBN. Lamotrigine toxicity may be an unusual cause.
Alkawi
Ammar
A
Department of Neurology, University of Illinois College of Medicine at Peoria, OSF Saint Francis Medical Center, 530N.E. Glen Oak Avenue, Peoria, IL 61637, USA. alkawi@uic.edu
Kattah
Jorge C
JC
Wyman
Katie
K
D000328:Adult; D000927:Anticonvulsants / Q000097:blood / Q000633:toxicity*; D003952:Diagnostic Imaging / Q000379:methods; D005260:Female; D006801:Humans; D000077213:Lamotrigine; D009759:Nystagmus, Pathologic / Q000209:etiology*; D014227:Triazines / Q000097:blood / Q000633:toxicity*; D014741:Video Recording / Q000379:methods
D000927:Anticonvulsants; D014227:Triazines; D000077213:Lamotrigine