In children with epilepsy, comorbidities are frequent. In dyslexia, comorbidities are increasingly acknowledged. Little is known about temporal aspects (dyslexia antedating or postdating epilepsy onset, time interval), epilepsy types, and dyslexia phenotypes.
From over 1000 files of children with epilepsy, 51 cases were retrospectively identified with a formal diagnosis of dyslexia. Ages at diagnoses of dyslexia and epilepsy, epilepsy variables, and dyslexia-related neuro-cognition (phoneme deletion and rapid letter naming) were recorded.
Temporal variables, epilepsy variables, and neuro-cognition were analyzed with chi-squared, t tests, ancova, and generalized linear models.
Duration of epilepsy to diagnosis of dyslexia ranged from − 5.5 years (dyslexia antedating epilepsy) to 10.1 years. In 35% of the children, diagnosis of dyslexia antedated the emergence of epilepsy. Dyslexia was seen across seizure types, with some preference for temporal lobe and rolandic epilepsy; rates for antedating and postdating dyslexia were similar. Notably, encephalopathic development was also seen. No specific dyslexia phenotype was seen. Children with dyslexia diagnoses after or in close temporal relationship to diagnoses of epilepsy (shortly before or after) scored lower on phonology and naming.
Antedating and postdating dyslexia can be seen in all epilepsy types. In a natural setting, dyslexia may antedate or postdate the emergence of epilepsy by several years. Around the time the epilepsy is about to surface, scores on dyslexia-related neuro-cognitive tasks are lowest, suggesting a bidirectional effect of the seizure condition on cognition. Encephalopathic development may be mimicking dyslexia criteria in some cases.