Reflex seizures are specific types of epilepsy that are triggered by specific stimuli. Traditionally, there are two types: “generalized” reflex seizures, which are triggered by visual stimuli, thoughts, behavioral and verbal tasks; and “focal” reflex seizures, which are triggered by shock, food, music, hot water, local sensory stimuli and sexual excitement. . Domenico Italiano, Department of Clinical and Experimental Medicine, University of Messina, Italy, reviewed the literature on reflex epilepsy and reviewed the seizure characteristics and treatment of different types of reflex epilepsy.
1. Visual stimulus-evoked reflex epilepsy
Reflex epilepsy induced by visual stimuli, photoparoxysmal epilepsy is the most common, accounting for about 2% of all epilepsies and occurring in 10% of patients aged 7-19 years with epilepsy; it is mostly seen in females and has an autosomal dominant genetic predisposition, but no major gene associated with photoparoxysmal response (PPR) has been identified; its association with congenital generalized epilepsy (IGE idiopathic generalized epilepsy), in which 40%-90% of patients with Juvenile Myoclonic Epilepsy (JME) have photosensitive seizures. Certain epilepsy syndromes also have a high photosensitivity factor, such as Dravet syndrome, Unverricht-Lundborg disease, and Lafora disease. Photosensitive epilepsy is mainly triggered by flashing lights such as light spots in woods, changing lights in dance halls and television, and can be accompanied by mild eyelid myoclonus, preserved or lost consciousness, symmetrical or asymmetrical twitching of the hands and whole body, and sustained light stimulation can cause tonic-clonic seizures. Effective preventive measures are avoiding sudden removal of light, watching TV at a distance of more than 2 meters, wearing Z1 blue glasses, choosing LCD screen and plasma TV, etc. The drug of choice is sodium valproate, and most patients are seizure-free after taking the drug. Lamotrigine, levetiracetam, topiramate and bupropion are useful in reducing PPR seizures, to a certain extent. And 25-30% of patients with photosensitive epilepsy have reduced photosensitivity response over 30 years until termination of seizures.
Different subtypes of photosensitive epilepsy.
(1) graphic-sensitive epilepsy, induced by streak-like objects in the environment. PPR evoked by intermittent light stimulation is almost always present in this group of patients, the most common evoked graphic is a striated object, the origin of the discharge is localized to the occipital lobe, and the treatment is the same as above.
(2) Eyelid closure sensitivity epilepsy, a specific type of photosensitive epilepsy, is mostly associated with eyelid myoclonic seizures. Changes in EEG occur within 2-4 s of eyelid closure and are seen in JME, childhood akathisia, juvenile akathisia epilepsy, eyelid myoclonic akathisia epilepsy, and Jeavons syndrome. The first-line agents are sodium valproate and levetiracetam.
(3) Gaze-disappearing epilepsy is mainly induced by the departure of visual attention from a certain point, mostly related to the hypersensitivity of the occipital lobe, and sodium valproate and clonidine are preferred.
2. Non-verbal cognitive stimulation epilepsy (thinking epilepsy)
Thinking epilepsy is most often seen during calculation or chess activities, with more onset in adolescence. The seizure types are tonic clonic seizures (96%), myoclonic seizures (76%), and atonic seizures (60%). 76% of patients can have all three types of seizures at the same time. eeg shows that about 68% of patients present with generalized seizures and focal discharges are mostly located in the right frontoparietal region. Thoughts associated with limb movements are important in thinking epilepsy, i.e. somatomotor inclined thoughts, which are more likely to cause seizures than simple thoughts without motor inclination. There is evidence that performing complex spatial tasks is more epileptogenic, e.g., complex multiplication and division is more likely to induce seizures than addition and subtraction. Precise computation is associated with the subfrontal and angular gyri of the dominant hemisphere’s speech function areas, whereas ambiguous and complex computation is associated with bilateral parietal visuospatial networks. Unilateral frontotemporal pathway and bilateral parietal activation are most likely necessary to induce seizures. Unlike photosensitive epilepsy, avoidance of triggering stimuli is less effective, and medications preferred are sodium valproate and those effective for JME.
3. Reading epilepsy
The EEG is normal in 80% of patients in the interictal period. EEG and fMRI studies show that the left motor area, premotor area, lateral striatum and medial temporal cortex are activated during reading seizures. Seizure spikes were located mainly in the dorsolateral prefrontal cortex. Modification of reading habits and pharmacological treatment are both effective, with clonazepam or sodium valproate as the main drugs.
Perioral reflex myoclonias (PORM) are mainly asymmetric seizures with a predominantly one-sided focus. Some studies suggest that PORM is a focal epilepsy, which is caused by partial cortical activation of the corresponding sensorimotor area, and is treated with the same medication as JME.
4. Startle epilepsy
Startle epilepsy (SE) mostly develops in childhood and early adolescence in children with large lesions in the sensorimotor and motor areas. Causes include cortical hypoplasia due to hypoxic birth injury, cerebral hemispheric inflammation, metabolic disorders, and trisomy 21. SE without foci has also been reported. It is mainly induced by sensory stimuli such as auditory. The startle response is brief (less than 30 s), with a predominance of axial tonic and semi-anterior postures, etc. accompanied by falls and complicated by autonomic symptoms. There is often adaptation, i.e., repeated stimulation for a few minutes leads to a decrease in sensitivity to the stimulus. The EEG during the seizure phase shows a top abnormal discharge followed by a diffuse low-amplitude fast rhythm of about 10 Hz. Intracranial electrodes suggest that abnormal discharges are transmitted from motor or premotor areas of origin to the ipsilateral medial frontal and parietal lobes. eeg-MEG studies suggest that the cingulate and supplementary motor areas are associated with SE. Although the mechanism of SE is unclear, it is generally believed that SE originates in the motor and premotor cortices, including the supplementary motor areas. SE is drug-refractory epilepsy, and clonazepam, lamotrigine, and levetiracetam may be effective, and some patients may benefit from surgery.
5. Musicogenic epilepsy
Musicogenic seizures are very rare, with an incidence of 1 per 100,000. Only 13% of patients with musicogenic epilepsy have evoked seizures; the rest exhibit both evoked and non-evoked seizure forms. Most of the music-induced seizures occur 1 year after the non-induced seizures. The music for the induced seizures is unique and stereotypical for each patient and takes several seconds to minutes to induce. Patients have also been reported to hear music during sleep or to recall music that triggers the seizure. The EEG may suggest a temporal lobe origin, commonly on the right side. The mechanism of musical seizures is unclear, as the primary auditory cortex is sensitive to a single tone, while its surrounding cortex is sensitive to complex musical stimuli.PET studies confirm that the right hemisphere plays a major role in the transmission of musical information and is not limited to the traditional auditory cortex. EEG and fMRI also found that in addition to the epileptogenic focus, the voxel nucleus, orbitofrontal region, cingulate cortex, and some right insula and occipital regions have increased perfusion during seizures. Patients with musical epilepsy should avoid musical stimulation, and pharmacological control and surgery are effective treatments.
6. Eating epilepsy
Eating epilepsy accounts for about 1/1000-1/2000 of epilepsy patients and has a wide variety of types, but each patient has a very stereotypical seizure trigger. Almost all are symptomatic epilepsy with frequent nonprovoked seizures. Seizures often occur shortly after eating, are not usually repeated during a meal, and single or complex focal seizures are common. Seizures often originate in the temporal-limbic system or the peri-lateral temporal fissure and may be secondary to generalized seizures. Eating can induce periodic convulsions in patients with focal epilepsy, associated with frontal lid activation causing activation of brainstem or cortical motor pathways. In patients with familial feeding epilepsy, the consumption of large amounts of meat and carbohydrates may be the triggering factor. Changing the nature of food may have a preventive effect on feeding epilepsy, such as using a straw instead of a cup to eat liquids and cutting food into smaller pieces. Clobazam before meals can effectively control the seizures of feeding epilepsy, and surgical treatment should be considered when drugs are ineffective.
7. Intrinsic sensory stimulus-induced epilepsy
Intrinsic sensory stimulus-induced epilepsy is very rare, mostly seen in non-ketotic hyperglycemic epilepsy, which is a transient reactive phenomenon. It was thought to be a reflex epilepsy induced by motor posture, but experiments later confirmed that the afferent fibers of intrinsic receptors play a decisive role. It manifests as focal seizures, mostly related to the contralateral sensorimotor area. Clinically, it is necessary to rapidly determine the presence of nonketotic hyperglycemia in such patients, and early antiepileptic and hypoglycemic treatment.
8. Somatosensory epilepsy
Somatosensory epilepsy can be induced by skin rubbing, touching, tapping, brushing, or stimulating the external auditory canal. Stimulus-triggered loci are highly specific, mostly located on the head and back, and manifest as focal seizures, often with sensory aura, or sensory Jackson-like seizures. The presence of motor seizures, such as rigidity of the limbs, suggests involvement of the supplementary motor areas. Consciousness is often present during seizures, which can be followed by generalized seizures. Sudden pain and autonomic disturbances have also been reported. Touch-induced seizures are mostly triggered by involuntary self-directed skin stimulation in children with developmental delays. The treatment principle is the same as that for focal epilepsy.
9. Hot bath epilepsy
Hot water epilepsy (HWE) is epilepsy induced by immersion or exposure to hot water, and is most commonly seen in a religious ritual in southern India where hot water is poured over the head. It presents as complex focal seizures and is thought to be a temperature- and environment-dependent benign epilepsy. Genealogical analysis of this type of epilepsy has been associated with two loci on chromosomes 10 and 4. Animal studies suggest that high temperature has a cortical “ignition” effect similar to electrical stimulation. Genetic mutations, abnormalities in the thermoregulatory system, and sensitivity to elevated temperatures may contribute to the pathogenesis of HWE. The main treatment is to lower the water temperature and to take clobazam before bathing. Continuous medication is not recommended, except for patients with non-induced seizures.
10. Sexual arousal epilepsy
Sexual arousal epilepsy (orgasm epilepsy) is very rare and can occur minutes or hours after orgasm. The vast majority of patients are female, and the epileptogenic focus is mostly located on the right side of the brain. The epileptic discharges originate in the superior postcentral gyrus, parietal sagittal sinus cortex, frontal lobe, and medial basal temporal lobe. Since the vast majority of patients are female, there may be a correlation with sex hormone levels. Most scholars believe that sexual arousal epilepsy is associated with the temporal lobe limbic system, and because some patients present with seizures several hours after orgasm, hyperventilation is not considered an important precipitating factor, and treatment is the same as for focal epilepsy.
Generalized reflex epilepsy is a generalized seizure that is triggered by focal epilepsy through the cortical reticular pathway and the cortico-cortical pathway, such as the presence of hyperexcitable focal areas or multiple hyperexcitable focal areas in patients with IGE that are excited and then rapidly propagate to cause a generalized seizure. Valproate, lamotrigine and levetiracetam are recommended for generalized reflex epilepsy, and carbamazepine and phenytoin are recommended for focal reflex epilepsy. It is important to study reflex epilepsy, using its predictive role, administering stimulus-evoked modulation during the monitoring of patients’ seizures, and performing a combination of neurophysiological and functional imaging studies, which can help explore the connections between different functional areas of the brain.