Reflex seizure

Reflex seizure
Other names: Reflex epilepsy; stimulus-sensitive seizures; triggered seizures; sensory-evoked seizures[1]
SpecialtyNeurology
SymptomsSeizures due to a specific trigger[2]
CausesOften genetic[2]
Differential diagnosisMigraine, psychogenic non-epileptic seizures[1]
TreatmentAvoiding triggers, anti-epileptic medications[2]
Frequency1 in 4,000 (5% of epilepsy)[2][1]

Reflex seizures are seizures that are consistently triggered by a specific stimulus, unlike most seizures which are unprovoked.[2][3] The seizures may be of any type including focal, generalized, myoclonic, or absence.[2][4] Epilepsy syndromes characterized by repeated reflex seizures, without unprovoked seizures, are known as reflex epilepsies.[2][5]

The trigger in 75% of cases are visual patterns, such as from television, resulting in photosensitive seizures.[2] Other triggers may include music, specific thought patterns, or reading.[2] It does not include seizures related to alcohol or a fever.[2] Many cases have a genetic component and may be inherited in an autosomal dominant pattern.[2] The underlying mechanism involves the stimulation of networks of neurons by the trigger.[2] Seizures trigger by light often begin in the occipital lobe, while music related seizures often begin in the temporal lobe.[2]

Treatment generally involves decreasing exposure to a person's triggers, and if this is not effective anti-epileptic medications.[2] About 25% of people with vision related seizures have them resolve by the age of 30.[2] Outcomes in other types may be more variable.[2] Reflex epilepsy affects about 1 in 4,000 people, making up approximately 5% of epilepsy cases.[1][2] The condition has been described since ancient times.[6]

Signs and symptoms

Reflex seizures can be either generalized or focal seizures or both.[1] However, for any given stimulus there may be a large variation in the kind of elicited seizure. For example, reading epilepsy may cause myoclonic jerks in the jaw or may cause focal seizures in the regions of the brain responsible for reading.[1] In reflex epilepsy generalized seizures are more common than focal seizures.[7]

Generalized

Generalized seizures are seizures that arise in large areas of the brain including both hemispheres.[8] Generalized seizures can take the form of myoclonic jerks, absences, or generalized tonic-clonic seizures.[1] Myoclonic jerks are the most common generalized seizures seen among reflex seizures and can be the located in the limbs, trunk, or in specific regions of the body (Ex. in the muscles of the jaw or the eyelids). Reflex absence seizures are also common especially in response to certain kinds of triggering stimuli such as light, proprioseptive, cognitive, emotional, or linguistic.[1] Generalized tonic-clonic seizures are less common and can occur independently or more commonly after a cluster of myoclonic jerks or absence seizures.[1]

Focal

Focal seizures are seizures that arise from a small area of the brain in one hemisphere.[8] Focal seizures are divided into simple or complex focal seizures.[8] Simple focal seizures do not involve the impairment of consciousness but instead may have motor, sensory, or autonomic manifestations.[8] Complex focal seizures do involve impairment or loss of consciousness.[8] Focal seizures are usually only seen in certain types of reflex epilepsies such as occipital lobe seizures in photosensitive occipital lobe epilepsies or temporal lobe seizures in musicogenic epilepsies.[1] Focal seizures can be located only in the area of the brain responsible for the stimulus, spread to other areas of the brain, or even develop into a generalized seizure.[1]

Cause

Triggers

Stimuli that cause reflex seizures can be categorized as either intrinsic or extrinsic. For a given person, the stimulus that triggers may be intrinsic, extrinsic, or a combination of both.[1]

Extrinsic stimuli

Extrinsic stimuli are sensory stimuli that originate from the person's environment. Similar to intrinsic stimuli, extrinsic stimuli can be divided into two categories, either simple or complex.[1][9] Examples of simple extrinsic stimuli include flashing lights or touch while complex extrinsic stimuli can include music, language, reading, or stimulation from eating.[1][9][2][6] Some of the more common types of reflex epilepsy include light and music.[2]

Photosensitive epilepsy is an abnormal sensitivity of the brain to visual stimuli and is the most common trigger in reflex seizures.[2] Reflex seizures can be induced by both flickering or non-flicking light, television, video games, or other visual patterns.[2] Most people who have photosensitive epilepsy are sensitive to specific patterns for visual stimuli. Visual stimuli of a particular frequency (15-25 flashes/second), wavelength (red light at 660-720 nm), and high contrast have been shown to have a higher risk of inducing seizures in people who are photosensitive.[2] In addition, emotional excitement, fatigue, or length of exposure can all effect the risk of seizures.[2]

Musicogenic epilepsy is a rare reflex epilepsy that is thought to be an abnormal sensitivity of the brain to musical stimuli, however, the exact mechanism of these seizures is unknown.[2] People with musicogenic epilepsy may have seizures triggered not just by musical stimuli but also by the emotional content or memory associated with that melody or rhythm.[2] Seizures can also be triggered when people with the condition think about certain kinds of music without actually hearing the music.[2] In addition, musicogenic epilepsy may occur with sounds that one would not usually associate with music, the sounds of machinery for example.[2] While certain types of music may induce a seizure in a certain person, listening to other kinds of music may prevent or terminate the epileptic activity.[2]

Intrinsic stimuli

Intrinsic stimuli are specific actions or activities performed by the person that result in a reflex seizure. Intrinsic stimuli can be divided into two categories, either elementary or elaborate.[1][9] Elementary intrinsic stimuli are usually simple motor movements while elaborate intrinsic stimuli can include emotions, thoughts, calculations or decision making.[1][9]

Thinking epilepsy is a rare form of reflex epilepsy that is triggered by a specific cognitive task. This can include thinking, calculations, solving problems, abstract reasoning, or making decisions.[2] Thinking epilepsy does not occur in response to reading, writing, or verbal communication.[2] Reading epilepsy is recognized as another distinct kind of reflex epilepsy.[2] Thinking epilepsy usually results in generalized seizures which manifest as bilateral monoclonus, absence seizures, or generalized tonic-clonic seizure that are preceded by myoclonic jerks.[2]

Genetics

Although reflex seizures are thought to have a genetic component, the exact genes involved are unclear.[10] As of 2016, some genes of interest include:

Inheritance patterns and genes of interests[11][10]
Types Inheritance pattern Genes of interest
Photosensitive Autosomal dominant 6p21

7q32 13q31 16p13

Musicogenic None or overlaps with rare genetic epilepsies LGI1SCN1A
Thinking Overlaps with Idiopathic Generalized Epilepsies none
Eating Unknown MECP2
Hot water Autosomal dominant 10q21.3–q22.3

4q24–q28 Synapsin 1 GPR56

Reading Autosomal dominant with incomplete penetrance None
Orgasm None None
Movement induced None None
Somatosensory induced Unknown None

Pathophysiology

Epileptic seizures occur due to changes in the brain that result in the lowering of the seizure threshold in a particular individual making that person vulnerable to recurring seizures.[9] These changes can be a result of a structural abnormality, brain lesions, or simply a genetic disposition to seizures.[9] In reflex epilepsy, these changes in the brain result in a small area that is capable of interrupting normal firing patterns and is more likely to produce the synchronous firing patterns that characterize a seizure. These hyper-excitable areas may then be activated by certain stimuli resulting in a reflex seizure. Reflex seizures are thus notable because the presentation of a particular stimulus, that activates the hyper-excitable areas of the brain, directly overcomes the seizure threshold, and results in a reflex seizure.[9]

The activation of the hyper-excitable areas of the brain is additionally regulated by facilitating factors that may increase the likelihood of eliciting a seizure.[9] Most commonly these include fatigue, sleep deprivation, or stress.[12] Facilitating factors are different for each individual.[12] Due to the large variance between the different kinds of reflex epilepsies, the specific mechanism causing reflex seizures may vary.[2]

Diagnosis

The diagnosis of reflex epilepsy usually includes a comprehensive medical and family history as well as a variety of tests.[13] These tests may include a electroencephalography (EEG), magnetic resonance imaging (MRI), as well as genetic testing.[13]

The procedure for diagnosing epilepsy generally follows three steps:[13]

  1. Determining if the seizure or seizure like event is truly an epileptic seizure.
  2. Determining what kind of seizure that someone has had.
  3. Determining if this seizure or seizures are a part of a specific epilepsy syndrome or disease.

Treatment

The treatment of reflex epilepsy generally involves decreasing exposure to a person's triggers as well as anti-epileptic medications.[1][2] Specific treatment depends both on the person as well on the kind of reflex triggers.[1] For example, in photosensitive epilepsy, some people may rely only on managing exposure to their triggers, while others, may benefit greatly from anti-epileptic drugs.[1] In addition, different anti-epileptic medications may be used in order to treat a given person's reflex epilepsy depending on the kind of seizures that they experience.[1]

Photosensitive epilepsy

Photosensitive reflex epilepsy is usually treated with both lifestyle changes and anti-epileptic medications. Some lifestyle modifications that may be recommended are limiting the amount of time one is exposed to television or screens, watching television in a bright well-lit room at a distance of at least 2 meters, and avoiding television or video games when tired. LCD TV screens or Televisions with higher refresh rates (100 Hz) cause less flickering and thus lower the likelihood of a seizure.[11][1] In addition, special blue lens Z1 glasses have been shown to reduce seizures in many people with photosensitive reflex epilepsy.[11]

If the above lifestyle modifications do not manage the condition, anti-epileptic medications may also be used. Valproate is usually the first line medication of choice in people with photosensitive reflex epilepsy with many people becoming seizure free.[11][1][2] Second line anti-epileptic medications include levetiracetam, benzodiazepines (such as clonazepam), lamotrigine, carbamazepine, brivaracetam, ethosuximide, and topiramate.[2][1][11]

Photosensitive reflex epilepsy tends to decrease with age, especially in one's thirties.[11] In 25-50% of people, seizures may spontaneously subside or disappear.[11]

Epidemiology

In 2015 epilepsy was present in about 1.3% of the population of the United States, approximately 3 million adults and 470,000 children.[14] Reflex epilepsy is found in approximately 5% of people who have epilepsy.[2] Photosensitive epilepsy is the most common type of reflex epilepsy, accounting for 75-80% of cases.[2] In addition, reflex epilepsies may show preferential distribution between the two sexes or certain age groups. Photosensitive epilepsy, for example, is more common in females (60% of cases) and is also more common in younger people (7–19 years old).[2][1][11]

References[2][1][11]
Type of epilepsy Frequency Groups typically affected
Photosensitive 1 in 4000 people More common in females (60%)

More common in younger people

Musicogenic 1 in 10,000,000 people No sex predominance
Thinking Overlaps with juvenile myoclonic epilepsy Unknown
Eating 1 in 1000-2000 of people with epilepsy More common in males (3:1)
Hot water Rare More common in males (70%)
Reading Rare More common in males (1.8:1)
Orgasm Rare More common in females
Movement induced Rare Unknown
Somatosensory induced Rare Unknown

History

Triggering seizures in epilepsy has been a phenomenon that has been observed since ancient times.[6] The Apologia records instances of a spinning potter's wheel causing seizures in epileptic slaves.[6] In 1850 Marshal Hall described the role of specific stimuli on causing seizures.[2] Since then, many types of stimuli that can trigger seizures have been identified.[2] The International League Against Epilepsy (ILAE) identified epilepsy caused by a specific stimuli in 1989 in their official definition of epilepsy and more recently, has updated this definition to recognize new types of focal and generalized seizures.[2] Currently reflex epilepsies are classified as miscellaneous types of epilepsy and are identified by the type of triggering stimulus.[6]

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Panayiotopoulos, C. P. (2005). Reflex Seizures and Reflex Epilepsies. Bladon Medical Publishing. Archived from the original on 2020-11-17. Retrieved 2023-09-04.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 Okudan ZV, Özkara Ç (2018-01-18). "Reflex epilepsy: triggers and management strategies". Neuropsychiatric Disease and Treatment. 14: 327–337. doi:10.2147/NDT.S107669. PMC 5779309. PMID 29403278.
  3. ↑ Fisher RS, Acevedo C, Arzimanoglou A, Bogacz A, Cross JH, Elger CE, Engel J, Forsgren L, French JA, Glynn M, Hesdorffer DC, Lee BI, Mathern GW, Moshé SL, Perucca E, Scheffer IE, Tomson T, Watanabe M, Wiebe S (April 2014). "ILAE official report: a practical clinical definition of epilepsy" (PDF). Epilepsia. 55 (4): 475–82. doi:10.1111/epi.12550. PMID 24730690. S2CID 35958237. Archived (PDF) from the original on 2018-07-19. Retrieved 2023-09-04.
  4. ↑ Kasteleijn-Nolst Trenité DG (September 2012). "Provoked and reflex seizures: surprising or common?". Epilepsia. 53 (Suppl 4): 105–13. doi:10.1111/j.1528-1167.2012.03620.x. PMID 22946728.
  5. ↑ "Reflex epilepsies". www.epilepsydiagnosis.org. Archived from the original on 3 August 2023. Retrieved 10 September 2023.
  6. 1 2 3 4 5 Striano, Salvatore; Coppola, Antonietta; del Gaudio, Luigi; Striano, Pasquale (June 2012). "Reflex seizures and reflex epilepsies: old models for understanding mechanisms of epileptogenesis". Epilepsy Research. 100 (1–2): 1–11. doi:10.1016/j.eplepsyres.2012.01.013. ISSN 1872-6844. PMID 22361339. S2CID 31436270.
  7. ↑ Xue LY, Ritaccio AL (March 2006). "Reflex seizures and reflex epilepsy". American Journal of Electroneurodiagnostic Technology. 46 (1): 39–48. doi:10.1080/1086508X.2006.11079556. PMID 16605171. S2CID 10098600.
  8. 1 2 3 4 5 Tamber, Mandeep S.; Mountz, James M. (November 2012). "Advances in the diagnosis and treatment of epilepsy". Seminars in Nuclear Medicine. 42 (6): 371–386. doi:10.1053/j.semnuclmed.2012.06.005. ISSN 1558-4623. PMID 23026360.
  9. 1 2 3 4 5 6 7 8 Irmen, Friederike; Wehner, Tim; Lemieux, Louis (February 2015). "Do reflex seizures and spontaneous seizures form a continuum? - triggering factors and possible common mechanisms". Seizure. 25: 72–79. doi:10.1016/j.seizure.2014.12.006. ISSN 1532-2688. PMID 25645641.
  10. 1 2 Italiano, Domenico; Striano, Pasquale; Russo, Emilio; Leo, Antonio; Spina, Edoardo; Zara, Federico; Striano, Salvatore; Gambardella, Antonio; Labate, Angelo (March 2016). "Genetics of reflex seizures and epilepsies in humans and animals". Epilepsy Research. 121: 47–54. doi:10.1016/j.eplepsyres.2016.01.010. ISSN 1872-6844. PMID 26875109. S2CID 22040184.
  11. 1 2 3 4 5 6 7 8 9 Italiano, Domenico; Ferlazzo, Edoardo; Gasparini, Sara; Spina, Edoardo; Mondello, Stefania; Labate, Angelo; Gambardella, Antonio; Aguglia, Umberto (August 2014). "Generalized versus partial reflex seizures: a review". Seizure. 23 (7): 512–520. doi:10.1016/j.seizure.2014.03.014. ISSN 1532-2688. PMID 24766826.
  12. 1 2 Ferlisi, Monica; Shorvon, Simon (April 2014). "Seizure precipitants (triggering factors) in patients with epilepsy". Epilepsy & Behavior. 33: 101–105. doi:10.1016/j.yebeh.2014.02.019. ISSN 1525-5069. PMID 24632482. S2CID 21228396.
  13. 1 2 3 Panayiotopoulos, CP (2010). A Clinical Guide to Epileptic Syndromes and their Treatment. Springer. ISBN 978-1-84996-160-8.
  14. ↑ Zack, Mathew (August 11, 2017). "National and State Estimates of the Numbers of Adults and Children with Active Epilepsy — United States, 2015". MMWR. Morbidity and Mortality Weekly Report. 66 (31): 821–825. doi:10.15585/mmwr.mm6631a1. PMC 5687788. PMID 28796763.
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