By Eleanor McDermid, Senior medwireNews Reporter
Symptoms consistent with focal seizures are often reported by patients who have idiopathic generalised epilepsies (IGE) and are associated with a short duration of freedom from seizures, say researchers.
This strong association remained significant after accounting for a number of confounders, including age at onset, duration of epilepsy and the presence of generalised tonic–clonic seizures. The 95% confidence interval did cross zero after adjustment for some confounders, such as the number of antiepileptic drugs used, but the team attributes this to the relatively small sample size, and stresses the clinical relevance of the association.
“Overall, our study raises the possibility that the presence of [focal seizure symptoms] may be an important prognostic factor associated with the duration of seizure freedom”, they write in Neurology.
The study included 135 patients with IGE, of whom 51.9% reported focal seizure symptoms in the Epilepsy Diagnostic Interview Questionnaire and Partial Seizure Symptom Definitions. They tended to be more common in the 32 patients with juvenile absence epilepsy (62.5%) and the 50 with juvenile myoclonic epilepsy (60.0%) than in the 15 with childhood absence epilepsy (33.3%) and the 38 with generalised epilepsy with tonic–clonic seizures only (39.5%), although these differences were not significant.
Over-reliance on focal symptoms when classifying epilepsy “may have far-reaching consequences such as unnecessary investigations, delayed diagnosis, misdiagnosis, and the use of inappropriate antiepileptic drugs”, say Udaya Seneviratne (St Vincent’s Hospital, Melbourne, Australia) and study co-authors.
They add: “Hence, we emphasize the critical role of EEG in the confirmation of diagnosis of IGE.”
The most common focal seizure symptom was aphasia, reported by 24.4% of the patients, followed by visual effects, at 17.8%. Other relatively frequent symptoms were visceral/epigastric symptoms, focal tonic/clonic/myoclonic symptoms, automatisms, and auditory and somatosensory symptoms, reported by between 7% and 12% of the patients.
Of note, these symptoms were as frequent in patients with minor seizures – absence or myoclonic seizures – as they were in those with generalised tonic–clonic seizures.
In a related commentary, J Craig Henry (Winchester Neurological Consultants, Virginia, USA) observes: “The notion that focal seizure symptoms definitively identify focal-onset seizures appears to be dying, if not dead, dogma.”
He says: “Adding to a growing body of literature that is blurring the classic dichotomy of epilepsy syndromes associated with focal- vs generalized-onset seizures, these findings commend circumspection: be careful what you ask for, and particularly careful in what you make of it.”
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