Epilepsy syndromes

Cases of epilepsy may be organized into epilepsy syndromes by the specific features that are present. These features include the age at which seizures begin, the seizure types, and EEG findings, among others. Identifying an epilepsy syndrome is useful as it helps determine the underlying causes as well as what anti-seizure medication should be tried.[1][2]

The ability to categorize a case of epilepsy into a specific syndrome occurs more often with children since the onset of seizures is commonly early.[3] Less serious examples are benign rolandic epilepsy (2.8 per 100,000), childhood absence epilepsy (0.8 per 100,000) and juvenile myoclonic epilepsy (0.7 per 100,000).[3] Severe syndromes with diffuse brain dysfunction caused, at least partly, by some aspect of epilepsy, are also referred to as epileptic encephalopathies. These are associated with frequent seizures that are resistant to treatment and severe cognitive dysfunction, for instance Lennox-Gastaut syndrome and West syndrome.[4]

Epilepsies with onset in childhood are a complex group of diseases with a variety of causes and characteristics. Some people have no obvious underlying neurological problems or metabolic disturbances.[5] They may be associated with variable degrees of intellectual disability, elements of autism, other mental disorders, and motor difficulties. Others have underlying inherited metabolic diseases, chromosomal abnormalities, specific eye, skin and nervous system features, or malformations of cortical development.[5] Some of these epilepsies can be categorized into the traditional epilepsy syndromes. Furthermore, a variety of clinical syndromes exist of which the main feature is not epilepsy but which are associated with a higher risk of epilepsy. For instance between 1 and 10% of those with Down syndrome and 90% of those with Angelman syndrome have epilepsy.[6]

In general, genetics is believed to play an important role in epilepsies by a number of mechanisms. Simple and complex modes of inheritance have been identified for some of them. However, extensive screening has failed to identify many single rare gene variants of large effect.[7] In the epileptic encephalopathies, de novo mutagenesis appear to be an important mechanism.[8][9] De novo means that a child is affected, but the parents do not have the mutation. De novo mutations occur in eggs and sperms or at a very early stage of embryonic development. In Dravet syndrome a single affected gene was identified.[9]

Syndromes in which causes are not clearly identified are difficult to match with categories of the current classification of epilepsy. Categorization for these cases is made somewhat arbitrarily.[10] The idiopathic (unknown cause) category of the 2011 classification includes syndromes in which the general clinical features and/or age specificity strongly point to a presumed genetic cause.[10] Some childhood epilepsy syndromes are included in the unknown cause category in which the cause is presumed genetic, for instance benign rolandic epilepsy. Others are included in symptomatic despite a presumed genetic cause (in at least in some cases), for instance Lennox-Gastaut syndrome.[10] Clinical syndromes in which epilepsy is not the main feature (e.g. Angelman syndrome) were categorized symptomatic but it was argued to include these within the category idiopathic.[10] Classification of epilepsies and particularly of epilepsy syndromes will change with advances in research.

Autosomal dominant nocturnal frontal lobe epilepsy

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is an idiopathic localization-related epilepsy that is an inherited epileptic disorder that causes seizures during sleep. Onset is usually in childhood. These seizures arise from the frontal lobes and consist of complex motor movements, such as hand clenching, arm raising/lowering, and knee bending. Vocalizations such as shouting, moaning, or crying are also common. ADNFLE is often misdiagnosed as nightmares. ADNFLE has a genetic basis.[11] These genes encode various nicotinic acetylcholine receptors.

Rolandic epilepsy

Benign centrotemporal lobe epilepsy of childhood or benign Rolandic epilepsy is an idiopathic localization-related epilepsy that occurs in children between the ages of 3 and 13 years, with peak onset in prepubertal late childhood. Apart from their seizure disorder, these patients are otherwise normal. This syndrome features simple focal seizures that involve facial muscles and frequently cause drooling. Although most episodes are brief, seizures sometimes spread and generalize. Seizures are typically nocturnal and confined to sleep. The EEG may demonstrate spike discharges that occur over the centrotemporal scalp over the central sulcus of the brain (the Rolandic sulcus) that are predisposed to occur during drowsiness or light sleep. Seizures cease near puberty.[12] Seizures may require anticonvulsant treatment, but sometimes are infrequent enough to allow physicians to defer treatment.

Benign occipital epilepsy of childhood

Benign occipital epilepsy of childhood (BOEC) is an idiopathic localization-related epilepsy and consists of an evolving group of syndromes. Most authorities include two subtypes, an early subtype with onset between three and five years, and a late onset between seven and 10 years. Seizures in BOEC usually feature visual symptoms such as scotoma or fortifications (brightly colored spots or lines) or amaurosis (blindness or impairment of vision). Convulsions involving one half the body, hemiconvulsions, or forced eye deviation or head turning are common. Younger patients typically experience symptoms similar to migraine with nausea and headache, and older patients typically complain of more visual symptoms. The EEG in BOEC shows spikes recorded from the occipital (back of head) regions. The EEG and genetic pattern suggest an autosomal dominant transmission as described by Ruben Kuzniecky, et al.[13] Lately, a group of epilepsies termed Panayiotopoulos syndrome[14] that share some clinical features of BOEC but have a wider variety of EEG findings are classified by some as BOEC.

Childhood absence epilepsy

Childhood absence epilepsy (CAE) is an idiopathic generalized epilepsy that affects children between the ages of 4 and 12 years of age, although peak onset is around five to six years old. These patients have recurrent absence seizures, brief episodes of unresponsive staring, sometimes with minor motor features such as eye blinking or subtle chewing. The EEG finding in CAE is generalized 3 Hz spike and wave discharges. Some go on to develop generalized tonic-clonic seizures. This condition carries a good prognosis because children do not usually show cognitive decline or neurological deficits, and the seizures in the majority cease spontaneously with ongoing maturation.

Dravet's syndrome

Dravet's syndrome, previously known as severe myoclonic epilepsy of infancy (SMEI), is a neurodevelopmental disorder beginning in infancy and characterized by severe epilepsy that does not respond well to treatment. This syndrome was described by Charlotte Dravet, French psychiatrist and epileptologist (born July 14, 1936). Dravet described this syndrome while working at the Centre Saint Paul at the University of Marseille. At Centre Saint Paul, one of her supervisors was Henri Gastaut, who described the Lennox-Gastaut syndrome. She described this condition in 1978[15] Estimates of the prevalence of this rare disorder have ranged from 1:20,000 to 1:40,000 births, though the incidence may be found to be greater as the syndrome becomes better recognized and new genetic evidence is discovered. It is thought to occur with similar frequency in both genders, and knows no geographic or ethnic boundaries. The course of Dravet syndrome is highly variable from person to person. Seizures begin during the first year of life and development is normal before their onset. In most cases, the first seizures occur with fever and are generalized tonic-clonic (grand mal) or unilateral (one-sided) convulsions. These seizures are often prolonged, and may lead to status epilepticus, a medical emergency. In time, seizures increase in frequency and begin to occur without fever. Additional seizure types appear, most often these are myoclonic, atypical absence, and focal seizures. Additional features that are seen in significant numbers of patients with Dravet syndrome may include sensory processing disorders and other autism spectrumcharacteristics, orthopedic or movement disorders, frequent or chronic upper respiratory and ear infections, sleep disturbance, dysautonomia, and problems with growth and nutrition.[16]

Epilepsy in females with mental retardation

Epilepsy in females with mental retardation, is characterized by seizure onset in infancy or early childhood (6–36 months) and cognitive impairment in some cases. Seizures are predominantly generalized, including tonic-clonic, tonic and atonic seizures. The spectrum of phenotypes has been extended to include female patients with early onset epileptic encephalopathies resembling Dravet syndrome, FIRES, Generalized epilepsy with febrile seizures plus (GEFS+) or focal epilepsy with or without mental retardation. EFMR is caused by mutations in PCDH19 (protocadherin 19).

Febrile infection-related epilepsy syndrome

Febrile infection-related epilepsy syndrome (FIRES)

Frontal lobe epilepsy

Frontal lobe epilepsy, usually a symptomatic or cryptogenic localization-related epilepsy, arises from lesions causing seizures that occur in the frontal lobes of the brain. These epilepsies can be difficult to diagnose because the symptoms of seizures can easily be confused with nonepileptic spells and, because of limitations of the EEG, be difficult to "see" with standard scalp EEG. Juvenile absence epilepsy is an idiopathic generalized epilepsy with later onset than CAE, typically in prepubertal adolescence, with the most frequent seizure type being absence seizures. Generalized tonic-clonic seizures can occur. Often, 3 Hz spike-wave or multiple spike discharges can be seen on EEG. The prognosis is mixed, with some patients going on to a syndrome that is poorly distinguishable from JME.

Interictal dysphoric disorder

Interictal dysphoric disorder (IDD) is a pleomorphic syndrome characterized by intermittent depression between seizures.

Juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy (JME) is an idiopathic generalized epilepsy that occurs in patients aged 8 to 20 years. Patients have normal cognition and are otherwise neurologically intact. The most common seizure is myoclonic jerks, although generalized tonic-clonic seizures and absence seizures may occur as well. Myoclonic jerks usually cluster in the early morning after awakening. The EEG reveals generalized 4–6 Hz spike wave discharges or multiple spike discharges. These patients are often first diagnosed when they have their first generalized tonic-clonic seizure later in life, when they experience sleep deprivation (e.g., freshman year in college after staying up late to study for exams). Alcohol withdrawal can also be a major contributing factor in breakthrough seizures, as well. The risk of the tendency to have seizures is lifelong; however, the majority have well-controlled seizures with anticonvulsant medication and avoidance of seizure precipitants.

Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is a generalized epilepsy that consists of a triad of developmental delay or childhood dementia, mixed generalized seizures, and EEGdemonstrating a pattern of approximately 2 Hz "slow" spike-waves. Onset occurs between two and 18 years.

Epilepsy is consider a chronic (meaning it lasts for a long time) condition that is defined by seizures. Lennox-Gastaut syndrome (LGS) is a rare and severe form of epilepsy.2

As in West syndrome, LGS result from idiopathic, symptomatic, or cryptogenic causes, and many patients first have West syndrome. Authorities emphasize different seizure types as important in LGS, but most have astatic seizures (drop attacks), tonic seizures, tonic-clonic seizures, atypical absence seizures, and sometimes, focal seizures. Anticonvulsants are usually only partially successful in treatment.

Ohtahara syndrome

Ohtahara syndrome is a rare but severe epilepsy syndrome usually starting in the first few days or weeks of life. The seizures are often in the form of stiffening spasms but other seizures including unilateral ones may be seen. The electroencephalogram (EEG) is characteristic. The prognosis is poor with about half of the infants dying in the first year of life; most if not all surviving infants are severely intellectually disabled and many have cerebral palsy. There is no effective treatment. A number of children have underlying structural brain abnormalities.[17]

Reflex epilepsy

About 6% of those with epilepsy have seizures that are often triggered by specific events, known as reflex seizures.[18] A number of epilepsy syndromes, known as reflex epilepsy, have seizures that are only triggered by specific stimuli.[19] Common triggers include: flashing lights and sudden noises.[18]

Those with photosensitive epilepsy can have seizures triggered by flashing lights. Other precipitants can trigger an epileptic seizure in patients who otherwise would be susceptible to spontaneous seizures. For example, children with childhood absence epilepsy may be susceptible to hyperventilation. In fact, flashing lights and hyperventilation are activating procedures used in clinical EEG to help trigger seizures to aid diagnosis. Finally, other precipitants can facilitate, rather than obligately trigger, seizures in susceptible individuals. Emotional stress, sleep deprivation, sleep itself, heat stress, alcohol and febrile illness are examples of precipitants cited by patients with epilepsy. Notably, the influence of various precipitants varies with the epilepsy syndrome.[20] Likewise, the menstrual cycle in women with epilepsy can influence patterns of seizure recurrence. Catamenial epilepsy is the term denoting seizures linked to the menstrual cycle.[21]

Primary reading epilepsy is a reflex epilepsy classified as an idiopathic localization-related epilepsy. Reading in susceptible individuals triggers characteristic seizures.[22] Catamenial epilepsy (CE) is when seizures cluster around certain phases of a woman's menstrual cycle.

Progressive myoclonic epilepsis

Progressive myoclonic epilepsies define a group of symptomatic generalized epilepsies characterized by progressive dementia and myoclonic seizures. Tonic-clonic seizures may occur as well. Diseases usually classified in this group are Unverricht-Lundborg disease, myoclonus epilepsy with ragged red fibers (MERRF syndrome), Lafora disease, neuronal ceroid lipofucinosis, and sialdosis.

Rasmussen's encephalitis

Rasmussen's encephalitis is a symptomatic localization-related epilepsy that is a progressive, inflammatory lesion affecting children with onset before the age of 10. Seizures start as separate focal seizures and may progress to epilepsia partialis continua (simple partial status epilepticus). Neuroimaging shows inflammatory encephalitis on one side of the brain that may spread if not treated. Dementia and hemiparesis are other problems. The cause is hypothesized to involve an immulogical attack against glutamate receptors, a common neurotransmitter in the brain.[23]

Ring chromosome 20 syndrome

The genetic component to epilepsy is receiving interest with conditions such as ring chromosome 20 syndrome (r(20)) gaining acknowledgment, although only 60 cases have been reported in the literature since 1976, "more widespread cytogenetic chromosomal karyotyping in nonetiological cases of epilepsy" is likely.[24] Symptomatic localization-related epilepsies are divided by the location in the brain of the epileptic lesion, since the symptoms of the seizures are more closely tied to the brain location rather than the cause of the lesion. Tumors, atriovenous malformations, cavernous malformations, trauma, and cerebral infarcts can all be causes of epileptic foci in different brain regions.

Temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is not a classic syndrome but mentioned here because it is the most common epilepsy of adults. It is a symptomatic localization-related epilepsy and in most cases the epileptogenic region is found in the midline (mesial) temporal structures (e.g., the hippocampus, amygdala, and parahippocampal gyrus). Seizures begin in late childhood and adolescence. Most of these patients have focal seizures sometimes preceded by an aura, and some TLE patients also have secondary generalized tonic-clonic seizures. Often seizures do not sufficiently respond to medical treatment with anticonvulsants and epilepsy surgery may be considered.[25]

Tuberous sclerosis

Tuberous sclerosis (TSC) is a genetic disorder that causes tumors to form in many organs, primarily in the brain, eyes, heart, kidney, skin and lungs. Several types of brain lesions can occur in individuals with TSC and 60% - 90% of people with TSC develop epilepsy.

West syndrome

West syndrome is a triad of developmental delay, seizures termed infantile spasms, and EEG demonstrating a pattern termed hypsarrhythmia. Onset occurs between three months and two years, with peak onset between eight and 9 months. West syndrome may arise from idiopathic, symptomatic, or cryptogenic causes. The most common cause is tuberous sclerosis. The prognosis varies with the underlying cause. In general, most surviving patients remain with significant cognitive impairment and continuing seizures and may evolve to another eponymic syndrome, Lennox-Gastaut syndrome. It can be classified as idiopathic, syndromic, or cryptogenic depending on cause and can arise from both focal or generalized epileptic lesions.

References

  1. ↑ "Epilepsy syndromes". International league against epilepsy. Retrieved 2014-10-06.
  2. ↑ National Institute for Health and Clinical Excellence (January 2012). "Chapter 9: Classification of seizures and epilepsy syndromes". The Epilepsies: The diagnosis and management of the epilepsies in adults and children in primary and secondary care (PDF). National Clinical Guideline Centre. pp. 119–129.
  3. 1 2 Neligan, A; Hauser, WA; Sander, JW (2012). "The epidemiology of the epilepsies.". Handbook of clinical neurology 107: 113–33. doi:10.1016/B978-0-444-52898-8.00006-9. PMID 22938966.
  4. ↑ Nordli DR jr (2012). "Epileptic encephalopathies in infants and children". J Clin Neurophysiol 29 (5): 420-4. doi:10.1097/WNP.0b013e31826bd961. PMID 23027099.
  5. 1 2 Pandolfo M (2013). "Pediatric epilepsy genetics". Curr Opin Neurol 26 (2): 137-45. doi:10.1097/WCO.0b013e32835f19da. PMID 23449174.
  6. ↑ Bhalla, D.; Godet, B.; Druet-Cabanac, M.; Preux, PM. (Jun 2011). "Etiologies of epilepsy: a comprehensive review.". Expert Rev Neurother 11 (6): 861–76. doi:10.1586/ern.11.51. PMID 21651333.
  7. ↑ Heinzen EL, Depondt C, Cavalleri GL, Ruzzo EK, Walley NM, Need AC, Ge D, He M, Cirulli ET, Zhao Q, Cronin KD, Gumbs CE, Campbell CR, Hong LK, Maia JM, Shianna KV, McCormack M, Radtke RA, O'Conner GD, Mikati MA, Gallentine WB, Husain AM, Sinha SR, Chinthapalli K, Puranam RS, McNamara JO, Ottman R, Sisodiya SM, Delanty N, Goldstein DB (2012). "Exome sequencing followed by large-scale genotyping failed to identify single rare variants of large effect in "idiopathic" generalized epilepsy". Am J Hum Genet 91: 293–302. doi:10.1016/j.ajhg.2012.06.016. PMC 3415540. PMID 22863189.
  8. ↑ Thomas RH, Berkovic SF (2014). "The hidden genetics of epilepsy-a clinically important new paradigm". Nat Rev Neurol 10 (5): 283-92. doi:10.1038/nrneurol.2014.62. PMID 24733163.
  9. 1 2 "De novo mutations in epileptic encephalopathies". Nature 501 (7466): 217-21. 2013. doi:10.1038/nature12439. PMC 3773011. PMID 23934111.
  10. 1 2 3 4 Shorvon SD (2011). "The etiologic classification of epilepsy". Epilepsia 52 (6): 1052–1057. doi:10.1111/j.1528-1167.2011.03041.x.
  11. ↑ Bertrand D (2002). "How mutations in the nAChRs can cause ADNFLE epilepsy". Epilepsia. 43 Supple 5: 112–122. doi:10.1046/j.1528-1157.43.s.5.16.x. PMID 12121305.
  12. ↑ Loiseau P (1988). "Prognosis of benign childhood epilepsy with centro-temporal spikes. A follow-up of 168 patients". Epilepsia 29 (3): 229–235. doi:10.1111/j.1528-1157.1988.tb03711.x. PMID 3371279.
  13. ↑ Kuzniecky R, Rosenblatt B (1987). "Benign occipital epilepsy: a family study". Epilepsia 24 (4): 346–350. doi:10.1111/j.1528-1157.1987.tb03655.x.
  14. ↑ Panayiotopolous CP (2000). "Benign childhood epileptic syndromes with occipital spikes: New classification proposed by the ILAE". J Child Neurol 15 (8): 548–552. doi:10.1177/088307380001500810. PMID 10961795.
  15. ↑ Dravet C (1978) Les epilepsies graves de l'enfant. Vie Médicale 8: 543–548
  16. ↑ "Dravet Syndrome". Retrieved 2010-09-08.
  17. ↑ (Aicardi J and Ohtahara S. Severe neonatal epilepsies with suppression-burst pattern. Epileptic Syndromes in Infancy, Childhood and Adolescence (4th edition) Eds Roger J, Bureau M, Dravet C,Genton P, Tassinari C, and Wolf P. John Libbey Eurotext 2005 ISBN 2-7420-0569-2.
  18. 1 2 Steven C. Schachter, ed. (2008). Behavioral aspects of epilepsy : principles and practice ([Online-Ausg.]. ed.). New York: Demos. p. 125. ISBN 9781933864044.
  19. ↑ Xue, LY; Ritaccio, AL (March 2006). "Reflex seizures and reflex epilepsy.". American journal of electroneurodiagnostic technology 46 (1): 39–48. PMID 16605171.
  20. ↑ Frucht MM, Quigg M, Schwaner C, Fountain NB. (2000). "Distribution of seizure precipitants among epilepsy syndromes". Epilepsia 41 (12): 1534–1539. doi:10.1111/j.1499-1654.2000.001534.x. PMID 11114210.
  21. ↑ Herzog AG; Harden CL; Liporace J; Pennell P; Schomer DL; Sperling M; et al. (2004). "Frequency of catamenial seizure exacerbation in women with localization-related epilepsy". Annals of Neurology 56 (3): 431–34. doi:10.1002/ana.20214. PMID 15349872.
  22. ↑ Koutroumanidis M (1998). "The variants of reading epilepsy. A clinical and video-EEG study of 17 patients with reading-induced seizures". Brain 121 (8): 1409–1427. doi:10.1093/brain/121.8.1409. PMID 9712004.
  23. ↑ Rogers (1994). "Autoantibodies to glutamate receptor GluR3 in Rasmussen's encephalitis". Science 265 (5172): 648–651. doi:10.1126/science.8036512. PMID 8036512.
  24. ↑ http://www.ring20.org/what-is-r20.php
  25. ↑ Bell, Michael; Rao S; So EL; Trenerry M; Kazemi N; Stead SM; Cascino G; Marsh R; Meyer FB; Watson RE; Giannini C; Worrell GA (2009). "Epilepsy surgery outcomes in temporal lobe epilepsy with a normal MRI". Epilepsia 50 (9): 2053–2060. doi:10.1111/j.1528-1167.2009.02079.x. PMC 2841514. PMID 19389144.
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