Sign Up for a Free Account
  • Updated 12.04.2023
  • Released 06.21.2004
  • Expires For CME 12.04.2026

Reflex seizures



Reflex epileptic seizures are seizures elicited by specific extrinsic (light, tactile, acoustic), intrinsic (thinking, reading, emotional), or combined stimuli. They affect patients of all ages and have a 4% to 7% prevalence among patients with epilepsies and up to 21% in those with idiopathic generalized epilepsies (119).

The specific precipitating stimulus and the clinical or EEG response determine reflex epileptic seizures. Seizures may be generalized (absences, myoclonic jerks, or generalized tonic-clonic seizures) or focal (visual, sensorimotor, or limbic). The electroclinical events may only be limited to the stimulus-related receptive brain region, spread to other cortical areas, or become generalized. Flickering lights are the commoner triggering stimuli, and this is particularly relevant to modern life, with ever-increasing numbers of television- and video game-induced seizures. The flickering lights in nightclubs and discotheques are particularly potent. The etiology is diverse, from just a mild genetically determined propensity for reflex seizures in otherwise normal people to severe forms of focal or generalized epilepsies. The role of EEG is fundamental in establishing the precipitating stimulus in reflex epilepsies because it allows subclinical EEG reflex abnormalities, or minor clinical ictal events, to be reproduced on demand by application of the appropriate stimulus. Identifying the offending stimuli has significant clinical implications in managing patients because some may not need anything other than avoiding or modifying the precipitating factors.

Key points

• Heterogeneous extrinsic and intrinsic stimuli provoke reflex seizures and affect 4% to 7% of all epilepsies.

• Visually induced seizures are the most common types of reflex seizures.

• Reflex seizures elicited by reading, thinking, music, eating, hot water, emotions, or movement are less common.

• Clinically, reflex seizures are focal or generalized (absences, myoclonic jerks, generalized tonic-clonic seizures).

• Patients may have reflex seizures alone or together with spontaneous ones.

• Certain epileptic syndromes (juvenile myoclonic epilepsy, Dravet syndrome, progressive myoclonic epilepsies) commonly manifest with reflex epileptic seizures.

• EEG's role is fundamental in identifying the offending stimuli, with significant clinical and pathophysiological implications.

• Avoidance or modification of the provocative stimulus is the key point of management, and this may be sufficient for patients with reflex seizures only.

• Appropriate antiepileptic medication is needed for those with continuing reflex and spontaneous seizures.

Historical note and terminology

Reflex seizures of different types have been known for centuries (09). Recognition of seizures induced by flashing light predates the invention of EEG and the stroboscope and reaches to classical antiquity (122; 83; 62).

The first reference to reflex epilepsy is attributed to Apuleius Lucius (150 AD), a Roman philosopher, in his Apologia and Florida. However, Apuleius does not refer to flickering lights.

Nay, even supposing I had thought it a great achievement to cast an epileptic into a fit, why should I use charms when, as I am told by writers on natural history, the burning of the stone named gagates is an equally sure and easy proof of the disease? For its scent is commonly used as a test of the soundness or infirmity of slaves even in the slave-market. Again, the spinning of a potter's wheel will easily infect a man suffering from this disease with its own giddiness. For the sight of its rotations weakens his already feeble mind, and the potter is far more effective than the magician for casting epileptics into convulsions.

“Gagates” is an old name for the stone “jet” or “black amber,” a carbon fossil that is compact and very light. Jet was known in ancient Egypt, where it was used for making mirrors; in Greece and Rome, it was used for cutting amulets, bracelets, and rings. In Medieval times, jet was popular as a talisman and a medicine for migraines, toothache, stomach pains, and epilepsy, and it reached the height of its popularity during the Victorian period. Also, the potter’s wheel in that time was solid, not spoked, which would be needed to produce intermittent light.

The oldest clear reference to photosensitive epilepsy is by Soranus of Ephesus (2nd century AD), a Greek gynecologist, obstetrician, and pediatrician who wrote On Acute and Chronic Diseases, which contains an excellent chapter on nervous disorders.

The use of flame, or very bright light obtained from flame has an agitating effect. In fact when a case of epilepsy is in its quiescent stage, the ultimate use of light with its sharp penetrating action may cause the recurrence of an attack.

Reflex epilepsy was first documented in animals by the Italian school of neurophysiologists in the 1920s and 1930s (173). In his pioneering studies of “epilepsy from afferent stimuli,” Amantea found that clonus induced by the application of a small disc of blotting paper soaked with strychnine to the sensorimotor cortex of dogs was enhanced by the stimulation of the peripheral area somatotopically related to excited cortex (03; 04). Moreover, when stimulation of the skin persisted, clonus progressed to a generalized tonic-clonic seizure in approximately 25% of animals. Later, strychninization of the visual cortex was used by Clementi, the first to describe experimental light-induced epilepsy in studies of photic stimulation in dogs after strychnine application to the visual cortex (21).

The first medical evidence of photosensitive epilepsy by Gowers (60), and later by Holmes (71), refers to occipital seizures induced by light.

In very rare instances the influence of light seems to excite a fit. I have met with two examples of this. One was a girl of seventeen whose first attack occurred on going into bright sunshine for the first time, after an attack of typhoid fever. The immediate warning of an attack was giddiness and rotation to the left. At any time an attack could be produced by going out suddenly into bright sunshine. If there was no sunshine an attack did not occur.

The other case was that of a man, the warning of whose fits was the appearance before the eyes of “bright blue lights, like stars — always the same”. The warning, and a fit, could be brought on at any time by looking at a bright light, even a bright fire. The relation is, in this case, intelligible, since the discharge apparently commenced in the visual centre (60).

Some men subject to epileptiform attacks commencing with visual phenomena owing to gunshot wounds of the occipital region, have told me that bright lights, cinema exhibitions and other strong retinal stimuli tend to bring on attacks (71).

Holmes attributed this reflex epilepsy to an enhanced excitability of the visual cortex (71).

In 1932, Radovici and associates reported the first case of eyelid myoclonia (often erroneously cited as self-induced epilepsy) with experimental provocation of seizures documented with cine film (135).

AA...age de 20 ans, presente des troubles moteurs sous forme de mouvements involontaires de la tete et des yeux sous l' influence des rayons solaires.

In 1936, Goodkind also detailed various methods used to experimentally induce “myoclonic and epileptic attacks precipitated by bright light” in a photosensitive woman (58).

The patient was placed on a bed in a darkened room in such a position that when the black window shade was raised her face only, was directed towards the early afternoon sunlight, which came through an ordinary wire Window screen. On such exposure of the eyes to the sun, she responded within a few seconds with marked, diffuse, and apparently uncontrollable clonic jactitatory movements. The movements ceased the moment a blindfold was applied, or the black window shade was lowered. She reacted definitely also when either eye was uncovered separately… The patient was also exposed to ultra violet radiation from a quartz mercury vapour lamp, and to bright pocket flash light had little or no effect. A small beam from a carbon arc lamp produced several rapid myoclonic jerks.

With the advent of EEG by Berger in 1929, a new era started for the study of reflex and photosensitive epilepsies (see article on visual-sensitive epilepsies).

ILAE definitions and classification

In recent decades, the ILAE has significantly improved communication among clinicians and in clinical and basic research on epilepsy by establishing standardized classification and terminology for epileptic seizures, epilepsies, and syndromes. This work in progress provided a universal vocabulary and greatly impacted patient care. Much has changed during that time, especially regarding the concept of reflex seizures, reflex epilepsies, and reflex epilepsy syndromes, although these changes have not been straightforward. The Task Force on Classification and Terminology is constantly revising and updating the classifications according to the new knowledge. These classifications particularly affect the position on reflex epilepsies and reflex syndromes.

Reflex seizures were already included in the 1981 ILAE classification of seizures as follows (22):

Repeated epileptic seizures occur under a variety of circumstances:

(1) as fortuitous attacks, coming unexpectedly and without any apparent provocation;

(2) as cyclic attacks, at more or less regular intervals (eg, in relation to the menstrual cycle, or the sleep-waking cycle);

(3) as attacks provoked by: (a) nonsensory factors (fatigue, alcohol, emotion, etc.), or (b) sensory factors, sometimes referred to as “reflex seizures.”

The 1985 ILAE classification of syndromes classified “epilepsies characterized by specific modes of seizure precipitation (reflex epilepsies)” under special syndromes and commended as follows (23):

In simple forms, seizures are precipitated by simple sensory stimuli (eg, light flashes). The intensity of the stimuli is decisive, the latency of the response short (seconds or less), and mental anticipation of stimulus without effect. In complex forms, the triggering mechanisms are elaborate (eg, sight of one’s own hand, listening to a certain piece of music). The specific pattern of the stimulus, not the intensity, is the decisive factor. Latency of response is longer (in the range of minutes), and mental anticipation of stimulus, even in dreams, may be effective.

These properties were first systematically described in the pioneering work of Forster (45).

Epilepsies with specific stimuli were defined for the first time in the 1989 ILAE classification. Precipitating seizures and precipitating factors of “syndromes characterized by seizures with specific modes of precipitation” are detailed in Appendix II as follows (24).

Precipitated seizures are those in which environmental or internal factors consistently precede the attacks and are differentiated from spontaneous epileptic attacks in which precipitating factors cannot be identified. Certain nonspecific factors (eg, sleeplessness, alcohol or drug withdrawal, or hyperventilation) are common precipitators and are not specific modes of seizure precipitation. In certain epileptic syndromes, the seizures clearly may be somewhat more susceptible to nonspecific factors, but this is only occasionally useful in classifying epileptic syndromes. An epilepsy characterized by specific modes of seizure precipitation, however, is one in which a consistent relationship can be recognized between the occurrence of one or more definable nonictal events and subsequent occurrence of a specific stereotyped seizure. Some epilepsies have seizures precipitated by specific sensation or perception (the reflex epilepsies) in which seizures occur in response to discrete or specific stimuli. These stimuli are usually limited in individual patients to a single specific stimulus or a limited number of closely related stimuli. Although the epilepsies which result are usually generalized and of idiopathic nature, certain partial seizures may also occur following acquired lesions, usually involving tactile or proprioceptive stimuli.

According to the ILAE Glossary (15), reflex seizures are

objectively and consistently demonstrated to be evoked by a specific afferent stimulus or by activity of the patient. Afferent stimuli can be: elementary, ie, unstructured (light flashes, startle, a monotone) or elaborate, ie, structured. Activity may be elementary, eg, motor (a movement); or elaborate, eg, cognitive function (reading, chess playing), or both (reading aloud).

In 2001, “A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology” was released (35). For the first time, the diagnostic scheme was divided into parts or “axes” organized to facilitate a logical clinical approach in individual patients: axis 1 = ictal phenomenology, axis 2 = seizure type, axis 3 = syndrome, axis 4 = etiology, and axis 5 = impairment. Furthermore, the terminology was again revised.

Precipitating stimuli for reflex seizures were part of the axis 2 seizure type and were listed as shown in Table 1.

Table 1. Precipitating Stimuli and Reflex Seizures and Syndromes Listed in the ILAE Classification Scheme

• Visual stimuli

- Flickering light--color to be specified when possible
- Patterns
- Other visual stimuli

• Thinking
• Music
• Eating
• Praxis
• Somatosensory
• Proprioceptive
• Reading
• Hot water
• Startle

The terms “reflex seizures in generalized epilepsy syndromes” and “reflex seizures in focal epilepsy syndromes” were specifically listed as axis 2 seizure types.

Additionally, the task force defined reflex epilepsy syndrome as a syndrome in which sensory stimuli precipitate all epileptic seizures. Reflex seizures that occur in focal and generalized epilepsy syndromes that are also associated with spontaneous seizures are listed as seizure types. Isolated reflex seizures can occur in situations that do not necessarily require a diagnosis of epilepsy. Seizures precipitated by other special circumstances, such as fever or alcohol withdrawal, are not reflex seizures.

Under axis 3 epilepsy syndromes, only four distinct reflex epilepsies were delineated:

• Idiopathic photosensitive occipital lobe epilepsy
• Other visual sensitive epilepsies
• Primary reading epilepsy
• Startle epilepsy

Besides those, under the umbrella of “conditions with epileptic seizures that do not require a diagnosis of epilepsy,” reflex seizures are determined as a special entity.

The ILAE Classification Core Group report published in 2006 again evaluated the list of epileptic seizure types and epilepsy syndromes approved by the General Assembly in 2001 and considered some possible alternatives (35; 36). Regarding reflex epilepsies, the following is stated:

Reflex epilepsies: Although idiopathic photosensitive occipital lobe epilepsy, primary reading epilepsy, and hot water epilepsy in infants are syndromes, it is unclear whether other reflex epilepsies constitute unique syndromes” (36), leaving again uncertainty how to classify those entities, at that point still listed under Special epilepsy conditions.

In 2014, the ILAE official report titled “A Practical Clinical Definition of Epilepsy” was released (43).

The task force proposed that epilepsy should be considered a disease of the brain defined by any of the following conditions: (1) at least two unprovoked (or reflex) seizures occurring more than 24 hours apart; (2) one unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years; (3) diagnosis of an epilepsy syndrome.

The task force elucidated the terms as follows.

Epilepsy exists in a patient who has had a seizure and whose brain, for whatever reason, demonstrates a pathologic and enduring tendency to have recurrent seizures. This tendency can be imagined as a pathologic lowering of the seizure threshold compared to persons without the condition.

A seizure that is provoked by a transient factor acting on an otherwise normal brain to temporarily lower the seizure threshold does not count toward a diagnosis of epilepsy. The term “provoked seizure” can be considered as being synonymous with a “reactive seizure” or an “acute symptomatic seizure.”

The condition of recurrent reflex seizures, for instance, in response to photic stimuli, represents provoked seizures that are defined as epilepsy. Even though the seizures are provoked, the tendency to respond repeatedly to such stimuli with seizures meets the conceptual definition of epilepsy in that reflex epilepsies are associated with an enduring abnormal predisposition to have such seizures.

A seizure after a concussion, with fever, or in association with alcohol withdrawal would exemplify a provoked seizure that would not lead to a diagnosis of epilepsy. The term “unprovoked” implies absence of a temporary or reversible factor lowering the threshold and producing a seizure at that point in time. Unprovoked is, however, an imprecise term because we can never be sure that there was no provocative factor. Conversely, the identification of a provocative factor does not necessarily contradict the presence of an enduring epileptogenic abnormality. In an individual with an enduring predisposition to have seizures, a borderline provocation might trigger a seizure, whereas in a nonpredisposed individual, it might not. The Definitions Task Force recognizes the imprecise borders of provoked and unprovoked seizures but defers discussion to another venue (42; 42).

The latest official changes in the terminology were presented in 2017. The ILAE Commission for Classification and Terminology published updated position papers on both the seizure types (eg, “An Operational Classification of Seizure Types”) and the classification of epilepsies that year. In those papers, reflex seizures or reflex epilepsy were not considered.

The revised framework for the classification of epilepsies used a multilevel approach, with the third level being epilepsy syndrome. Although many well-recognized syndromes were included in both the 1985 and 1989 proposals, definitions of these epilepsy syndromes have never been formally accepted by the ILAE. Following the above-mentioned publications by the ILAE Commission of Classification and Terminology, the new Nosology and Definitions Task Force was created with the main purpose of providing a means to classify and define epilepsy syndromes. In the last decade, several ILAE reports were published concerning the terminology of epileptic seizures (42; 42), epilepsies (145), and epileptic syndromes (70; 140; 156; 192).

Are epilepsies with reflex seizures distinct epilepsy syndromes? Current ILAE position on the matter.

Epilepsy syndromes have been recognized for more than 100 years (a prototype can be West syndrome) as distinct electroclinical phenotypes with therapeutic and prognostic implications; thus, they were recognized as distinctive conditions long before the first International League Against Epilepsy (ILAE) Classification of Epilepsies and Epilepsy Syndromes was proposed in 1985. Nonetheless, no formally accepted ILAE classification of epilepsy syndromes has existed.

Epilepsy syndromes have traditionally been grouped according to the age at onset; therefore, special working groups were established with the following divisions: (1) neonatal and infantile-onset, (2) childhood onset, (3) variable age at onset, and (4) idiopathic generalized epilepsies. A syndrome has a "variable age" of onset if it can begin both in those aged 18 years or younger and those aged 19 years and older (ie, in both pediatric and adult patients). In keeping with the 2017 Epilepsy Classification, the ILAE Task Force on Classification and Terminology further subdivided syndromes in each age group into generalized, focal, or generalized and focal epilepsy syndromes based on seizure types and established a separate category for syndromes with developmental or epileptic encephalopathy and syndromes with progressive neurologic deterioration.

Four distinct position papers arose from working groups, including:

• Idiopathic generalized epilepsies.

• Epilepsy syndromes with onset in neonates and infants (for the purpose of the proposed classification, infancy was defined as the period up to age 24 months).

• Epilepsy syndromes with onset in childhood.

• Epilepsy syndromes with onset at a variable age.

The only publication that particularly addressed reflex epileptic syndromes with the latest definition of reflex seizures comes from the paper describing epilepsy syndromes with onset at variable ages, where reflex seizure is defined as a seizure that is consistently or nearly consistently elicited by a specific stimulus that may be sensory, sensory-motor, or cognitive (140). The stimulus may be "elementary" (eg, light, elimination of visual fixation, touch), "complex" (eg, tooth-brushing, eating), or cognitive (eg, reading, calculating, thinking, listening to music). Such a stimulus will likely elicit a seizure, unlike a stimulus that may facilitate epileptiform abnormality (such as photoparoxysmal responses on EEG) or evoke a seizure but not consistently.

In that paper, only epilepsy with reading-induced seizures classified as combined generalized and focal epilepsy syndrome with polygenic etiology was considered to be a genuine reflex epilepsy syndrome (140). The task force explains not including other well-known entities in the following paragraph:

The task force considered whether disorders that result in seizures with characteristic clinical and EEG features implicating specific focal brain networks should be considered epilepsy syndromes. Although such epilepsies involving specific networks and reflex epilepsies may have a consistent constellation of symptoms and EEG findings, they lack other features that are often seen in syndromes, including specific etiologies, prognoses, and a range of comorbidities. Thus, we have not included these epilepsies as syndromes (140).

The ILAE Task Force on Classification and Terminology considered whether conditions other than epilepsy with reading-induced seizures, in which reflex seizures occur, might be epilepsy syndromes. Although patients with these conditions have in common a specific stimulus triggering their seizures, their electroclinical features, etiologies, and prognosis are diverse. Therefore, the task force decided not to include these as epilepsy syndromes. Photosensitivity is a common feature of many epilepsy syndromes, and the task force concluded that disorders associated with photosensitivity were too diverse, when grouped, to satisfy the criteria for an epilepsy syndrome.

ILAE classification and definition of epilepsy syndromes with onset in neonates and infants included myoclonic epilepsy in infancy as an entity wherein myoclonic seizures may be activated by sudden noise, startle, or touch, and less commonly by photic stimulation. Some authors proposed that the term “reflex myoclonic epilepsy in infancy” should be used if myoclonic seizures are activated by triggering factors (sudden noise or startle), stating that such patients have a slightly earlier age at onset and higher remission rate with the more favorable cognitive outcome; still, the task force did not recognize this entity as a distinct reflex epilepsy syndrome and considered it a subgroup of myoclonic epilepsy in infancy.

The ILAE classification and definition of epilepsy syndromes with onset in childhood recognized photosensitive occipital lobe epilepsy as a distinct reflex syndrome. Children, commonly between 4 and 17 years of age (although age at onset can be between 1 and 50 years), have photic-induced focal seizures involving the occipital lobe. Seizures can be induced by video games or other photic stimuli and watching analog television with slower frequency outputs.

Sartle epilepsy is no longer considered a particular reflex epilepsy syndrome, eg, not specified in any age group as such in the recent publications, and it wasn’t mentioned in the ILAE Commission for Classification and Terminology published in 2017. However, in 2023 it is still listed in the ILAE Online Diagnostic Manual under epilepsy syndromes regardless of age (“any age”).

Startle epilepsy is characterized by seizures that may start in childhood or early adolescence (1 to 16 years). Both sexes are affected. Most patients have an underlying structural brain abnormality with neurologic (eg, hemiplegia) and intellectual disability. Seizures are often difficult to control.

A systematic review of definitions used in the research literature for reflex and nonreflex precipitated seizures has been published (76). Koepp and colleagues provide a comprehensive review of reflex seizure, traits, and epilepsies, focusing on physiology to pathology (90). Hanif and Musick authored a comprehensive review focusing on each subtype and providing updates regarding the current scientific landscape (65).

Three excellent books are exclusively devoted to nearly all aspects of reflex seizures and related epileptic syndromes (Beaumanoir et al 1985; 189; 184).

This is an article preview.
Start a Free Account
to access the full version.

  • Nearly 3,000 illustrations, including video clips of neurologic disorders.

  • Every article is reviewed by our esteemed Editorial Board for accuracy and currency.

  • Full spectrum of neurology in 1,200 comprehensive articles.

  • Listen to MedLink on the go with Audio versions of each article.

Questions or Comment?

MedLink®, LLC

3525 Del Mar Heights Rd, Ste 304
San Diego, CA 92130-2122

Toll Free (U.S. + Canada): 800-452-2400

US Number: +1-619-640-4660



ISSN: 2831-9125