The variants of reading epilepsy. A clinical and video-EEG study of 17 patients with reading-induced seizures.

We present the clinical and electrographic data of 17 patients with reading-induced seizures documented with ictal video-EEG studies during provocation with language related tasks. The median age at onset was 15 years (range 11-22 years) and the male:female ratio was 2.4. Fourteen patients had no spontaneous seizures of any type while the remaining three had infrequent generalized tonic-clonic seizures during nocturnal sleep. Two distinct electroclinical ictal patterns were confirmed on video-EEG analysis. (i) Fifteen patients had reading-induced jerks which invariably involved the region of the jaw but also included the upper limbs in five of them. Ictal EEG discharges were noted in 12 patients; these were brief but varied in terms of morphology and spatial distribution, with a clear tendency for left-sided predominance. All but one of these patients had similar myoclonic seizures induced by linguistic activities other than reading, the phenomenon probably justifying the term 'language-induced epilepsy'. Some patients had evidence of transient cognitive impairment associated with the reading-induced jaw or limb jerks. Three patients had a sibling with reading epilepsy but there was no other family history of epileptic seizures. (ii) Two patients had reading-provoked paroxysmal alexia without motor symptoms, associated with prolonged focal ictal EEG abnormalities. Reading provoked a subclinical, continuous and reproducible EEG activation over the left posterior temporal area. We propose that ictogenesis in reading or language-induced epilepsy is based on the reflex activation of a hyperexcitable network that subserves the function of speech and extends over multiple cerebral areas on both hemispheres. The parts of this network responding to the stimulus may, secondarily, drive the relative motor areas producing the typical regional myoclonus. This network hyperexcitability can be genetically determined and its clinical expression is age-related.