Epileptic seizures can arise in a ‘spontaneous’ fashion with no detectable precipitating factors, or they can be provoked by certain recognizable stimuli. Stimuli that contribute towards the initiation of a seizure are provided by the individual’s internal and external environment.
Internal factors as hormones, electrolytes, state of consciousness and body temperature. External factors may be sensory, electrical or biochemical.
Reflex seizures have a 4–7% prevalence among patients with epilepsies. Their aetiology may be idiopathic or symptomatic.
With reference to the classifications of the epileptic syndromes of the International League Against Epilepsy (ILAE) (1989), reflex epilepsies can be recognized with among generalized and focal epileptic syndromes, and with among idiopathic and symptomatic.
Reflex seizures can be either generalized or focal, with or without impairment of consciousness. It may be genetically inherited or acquired supported by a brain lesion.
Photosensitivity is the susceptibility to produce epileptic seizures in response to light stimuli. It has higher prevalence in females and in the adolescence.
Photosensitivity can be found in a wide range of epilepsies. It is very frequent in idiopathic generalized epilepsies, in particular in juvenile myoclonic epilepsy.
Photosensitivity is also found in some idiopathic focal epileptic syndromes, in particular, (idiopathic photosensitive occipital lobe epilepsy). In some symptomatic generalized epilepsies, in particular, (progressive myoclonic epilepsies).
The most frequently found EEG pattern is the photoparoxysmal response, usually easily provoked in laboratory with intermittent light stimulation.
Seizures can be triggered by natural flickering light such as rays of sunlight filtering through the trees, or reflected by the waves of the sea or snow.
The development of artificial light stimulation (television, video-games, and so on) has much increased the occurrence of seizures. These seizures are usually clinically and EEG generalized in type (absence, myoclonus, tonic—clonic seizures).
Epilepsia Arithmetices is idiopathic in nature and generalized in type. Triggered by mental calculation or by other complex mental processes (thinking epilepsy), with the pressure to decide (decision-making epilepsy).
Reading epilepsy is a rare form of reflex epilepsy in which almost all seizures are precipitated by reading. Generalized seizures were always preceded by a clicking sensation or actual jerks in the jaws (i.e., jaw or tongue clicking) with generalized or focal (temporo-parieto-occipital areas) paroxysmal activity.
Startle epilepsy is seizures triggered by a sudden and unexpected auditory stimulus. Patients have usually large brain lesions, mostly perinatal hypoxic injury (Little syndrome, congenital hemiparesis), and frequently they show also enhanced startle reaction.
Startle seizures have been reported also in large or focal dysplasias, in Lennox Gastaut syndrome and in Down syndrome.
Eating-induced seizures are rare seizures, exclusively triggered by eating (eating epilepsy). Seizures are generally partial, more often complex partial, generalized seizures may coexist, in particular atypical absences.
Amygdala play an important role as an integrative centre, particularly in temporo- mesial focal seizures. Bulky meals rich in carbohydrates have been postulated as possible triggering factors.
Musicogenic epilepsy is a form of temporal lobe epiIepsy and belongs to the group of reflex epilepsies. Musicogenic epilepsy is a seizure induction by listening to the music.
The musicogenic epilepsy has a strong correlation to the temporal lobe mainly mesial side. The majority of cases appear to depend on a certain emotional reaction mediated through limbic mesial temporal lobe structures.
Seizures are typically complex partial, with possible secondary generalization, and more rarely simple partial. Autonomic symptoms and signs may occur before onset of the ictal behavior.
Hot-water epilepsy is triggered by contact or immersion in hot water. This type of epilepsy is frequent in southern of India. This form of geographically specific reflex epilepsy is age related, more frequent in males, usually self- limited and frequently familial.
Seizures may be elicited by particular stimulations such as skin friction (rubbing epilepsy), touching or tapping, tooth brushing (tooth-brushing epilepsy), stimulation of external ear conduct (auricular epilepsy).
Usually these reflex seizures are linked to brain lesions of various type (dysplastic, inflammatory as in Rasmussen syndrome). Involving the parietal and sensorimotor cortex or supplementary motor area, but other regions may be involved, namely temporal lobe.