Abstracts

Rationale: Calcium- and glutamate-mediated exitotoxicity is thought to be important in the pathogenesis of both ALS and epilepsy caused by structural or metabolic lesions. Increased cortical hyperexcitability in ALS may be caused by degeneration of intracortical inhibitory neurons. Cognitive impairment is found in ALS patients, implicating damage of cortical networks wider than primary motor areas alone, predisposing for epilepsy. Yet there are hardly any reports of ALS and seizures affecting the same patient. Methods: We retrospectively identified all patients visiting Helsinki University Central Hospital neurological outpatient clinics during 2004-2011 due to ALS. Medical records were reviewed to find patients with prior diagnosis of epilepsy or in whom investigations had been carried out due to suspected seizures. Results: Among 122 male and 121 female patients with ALS, we identified four patients (1.6%) with an established diagnosis of epilepsy before ALS symptom onset. No change in seizure control was recorded during ALS progression in these patients. In three other patients, a single epileptiform seizure with etiology separate from ALS had been registered. In four additional patients, paroxysmal events occurring in temporal association with ALS symptom onset had been diagnosed as epilepsy. In three out of four patients, EEG had showed interictal focal disturbance, which had been classified epileptiform in two patients. In retrospective medical chart review, many features atypical for seizures were found. In one case, symptoms leading to diagnosis of epilepsy were later thought to have heralded evolving frontotemporal dementia. Conclusions: Symptoms raising suspicion of seizures in ALS patients are fairly frequent and should be evaluated with caution. There may be a phase in ALS development during which symptomatology clinically resembling seizures occurs. The pathophysiology of these symptoms requires to be addressed in prospective follow-up studies and with ictal EEG recordings.