Reflex epilepsies are characterized by the presence of reflex seizures and the absence of spontaneous seizures. Reflex seizures may occur in epilepsies of varied etiologies (e.g. in structural brain abnormality and in genetic generalized epilepsies), however these are not categorized as reflex epilepsies as spontaneous seizures occur in addition to reflex seizures. There are a number of recognized reflex epilepsies; two examples are described in this section of EpilepsyDiagnosis.org.
NOTE a reflex (also known as stimulus-sensitive or sensory-evoked) seizure is a seizure that is constantly elicited by a specific stimulus, which may be an afferent sensory stimulus or an activity undertaken by the patient. Sensory stimuli may be elementary (e.g. light flashes, patterns, elimination of visual fixation, elimination of light, tactile, hot water, startle or a monotone) or more complex (e.g. eating, tooth-brushing, music or singing). A stimulus activity may be elementary (e.g. a movement) or more complex (e.g. reading, playing chess, calculating, thinking). Such stimuli will constantly elicit a reflex seizure in a patient with reflex epilepsy, in contrast to facilitating stimuli that may facilitate EEG discharges or evoke a seizure (but not constantly) in other epilepsy syndromes.
Reading epilepsy is characterized by seizures that start between 12 and 19 years of age. There is a male predominance (1.8M:F). Seizures are elicited by reading (aloud or silently). Prognosis is good as seizures are usually minor and can be avoided through reducing exposure to the stimulus.
Startle epilepsy is characterized by seizures that may start in childhood or early adolescence (1-16 years). Both sexes are affected. Most patients have underlying structural brain abnormality with neurological (e.g. hemiplegia) and intellectual disability. Seizures are often difficult to control.