Rationale:
Episodic ataxia is often misdiagnosed. Attacks can be mistaken for seizures, therefore, often these patients are admitted to the epilepsy monitoring unit (EMU) for evaluation. Moreover, EEG changes are commonly found during long term monitoring. Here we describe a patient with exacerbation of ataxia symptoms with the use of common anti-seizure medications.
Methods:
Case report/literature review
Results:
The patient is a 49-year-old male with no prior medical history, who presents with episodes of gait instability, incoordination, and dysarthria since he was eight years old. He described these as “dizzy spells." The episodes were happening more frequently and more severely over the past few years. Each episode lasted 30-45 minutes. Initially, he was diagnosed with seizures. His MRI brain showed nonspecific T2 FLAIR changes in R frontal and L parietal lobe. One prior 24hr EEG that showed no abnormalities. He was started on lamotrigine with dose escalations as episodes were occurring more frequently after starting this medication. Zonisamide was added and escalated to 400mg QHS but continued to have frequent episodes.
He was admitted to the epilepsy monitoring unit for further investigation. A typical event was captured, consisting in dysarthria, gait instability, dysmetria, and horizontal nystagmus. No epileptiform changes were seen around the events, but frontally predominant rhythmic delta, at 1-2Hz, for one to three seconds at a time, without definitive embedded spike or sharp, at times of higher amplitude on the R (Fig 1 and 2) were present. After lamotrigine wean his symptoms improved, without changes on EEG interictal abnormalities. He was referred to the movement clinic for further workup and genetic testing, that confirmed episodic ataxia type 2. He was treated with acetazolamide, Diamox, and ampyra, with symptom resolution.
Conclusions:
Episodic ataxia can masquerade as paroxysmal attacks of nausea, vertigo, abnormal movements, and speech changes (Roux, 2021). The paroxysmal and stereotypical nature of the attacks mimic epileptic seizures. Moreover, interictal EEG changes are commonly described in EA2, making the diagnosis more challenging, usually requiring EMU admission for event characterization. We show that treatment with sodium channel blockers have the potential to worsen symptoms in patients with EA2. Lamotrigine on its own has been associated with cerebellar syndromes in a subset of patients and patients with pre-existing movement disorders (Rissardo, 2021). When evaluating patients with recurrent events concerning for seizures and an abnormal interictal EEG, the exacerbation of symptoms after lamotrigine use should be raise the suspicion for EA2.
References:
Rissardo JP, Fornari Caprara AL. Lamotrigine-Associated Movement Disorder: A Literature Review. Neurol India. 2021 Nov-Dec;69(6):1524-1538. doi: 10.4103/0028-3886.333440.
Le Roux et al. CACNA1A-associated epilepsy: Electroclinical findings and treatment response on seizures in 18 patients. Eur J Paediatr Neurol. 2021 Jul;33:75-85. doi: 10.1016/j.ejpn.2021.05.010. Epub 2021 May 26.
Funding: None