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Ring Chromosome 20 Syndrome


  • We present a girl diagnosed at the age of 13 years who suffered from an atypical clinical presentation, with minimal cognitive problems, absence of dysmorphic symptoms, and hypermotor/gelastic seizures. [Published with video sequences].[ncbi.nlm.nih.gov]
  • METHODS: Karyotyping for r20 was done in patients presenting with cryptogenic refractory epilepsy suggestive of r20 from August 2008 to September 2010. We identified three patients with r20 associated with refractory epilepsy.[ncbi.nlm.nih.gov]
  • RESULTS: All patients presented with pharmacoresistant frontal lobe complex partial seizures. The earliest onset of epilepsy was seen in patients without mosaicism.[ncbi.nlm.nih.gov]
  • However, our patient presents the typical epilepsy disorder but no detectable deletion in the ring chromosome 20.[ncbi.nlm.nih.gov]
  • Because of the variability of the clinical presentation, some patients with r(20) undergo invasive investigations before being diagnosed.[ncbi.nlm.nih.gov]
Panic Attacks
  • Aggressiveness, compulsiveness with self-injury, and panic attacks developed at the age of 13 years, and were more pronounced after callosotomy.[ncbi.nlm.nih.gov]
Focal Seizure
  • In the long-term, progressive stabilization of drug resistant epilepsy associated with non-convulsive status epilepticus, focal seizures with motor and autonomic features, and eyelid myoclonia were noticed.[ncbi.nlm.nih.gov]
  • Epileptic spasms, atypical absences and focal seizures may also occur.[epilepsydiagnosis.org]
  • A prolonged partial status at 10 years was associated with fronto-temporal focal seizure activity and bilateral spikes on the EEG, compatible with partial, secondarily generalized epilepsy. MRI was normal.[pediatricneurologybriefs.com]
  • Epilepsy has been described in detail in only 2 such cases, with focal seizures from sleep and prolonged nonconvulsive status epilepticus in wakefulness [Ricard-Mousnier et al., 2007; de Palma et al., 2015].[karger.com]
  • Howell KB, Mcmahon JM, Carvill GL et al (2015) SCN2A encephalopathy: a major cause of epilepsy of infancy with migrating focal seizures. Neurology 85:958–966. CrossRef PubMed PubMedCentral Google Scholar 15.[link.springer.com]
Nocturnal Seizure
  • Non-convulsive status epilepticus and nocturnal seizures are frequently noted as are frontal lobe epileptiform electroencephalography abnormalities. Structural brain imaging is normal in most cases and is non-contributory.[content.iospress.com]
  • However, electroencephalography (EEG) studies during these events show abnormal electrical seizure activity, indicating that nocturnal behavioral events are actually subtle nocturnal seizures or non-convulsive status epilepticus.[en.wikipedia.org]
  • Subtle nocturnal behavioral changes such as stretching, rubbing, turning that resemble arousal, subtle nocturnal seizures (SNS), and subtle nocturnal frontal lobe seizures (SNFL) have also been reported in studies of RC20 patients.[epilepsy.com]
  • In addition, subtle nocturnal seizures (SNS) and subtle nocturnal frontal lobe seizures (SNFLS) are also reported Seizures are often difficult to control with antiepileptic medications. 4, 5, 6, 7, 8 Nocturnal seizures are a frequent occurrence in this[ring20researchsupport.co.uk]
Automatic Behavior
  • They are often complex partial, usually with altered consciousness, staring, oral automatisms, unspecified automatic behavior, focal motor symptoms and/or head turning.[epilepsy.com]
  • Other features you may see in these complex partial seizures include staring, oral automatisms, unspecified automatic behavior, involuntary motor movements and/or head turning.[en.wikipedia.org]
  • Seizures are complex partial in type and reported as episodes of sudden fear altered awareness with staring, oral automatisms, unspecified automatic behavior, focal motor symptoms and/or head turning.[ring20researchsupport.co.uk]
Mental Deterioration
  • The authors' findings in four children, all without dysmorphic features, indicate that mental deterioration and frequent subtle nocturnal frontal lobe seizures, associated with a characteristic EEG pattern, represent prominent additional clinical features[ncbi.nlm.nih.gov]
  • The authors’ findings in four children, all without dysmorphic features, indicate that mental deterioration and frequent subtle nocturnal frontal lobe seizures, associated with a characteristic EEG pattern, represent prominent additional clinical features[neurology.org]
Mild Cognitive Impairment
  • This syndrome is also characterized by behavioral problems, mild cognitive impairment and learning disabilities. Tell me more Seizures usually are the first and major clinical symptom of this syndrome& and usually do not respond to medications.[epilepsy.com]
Onset in Adolescence
  • Epilepsy onset in adolescence (3 patients) was accompanied by a milder developmental course, dyscognitive seizures and non-convulsive status epilepticus, and no cognitive decline.[ncbi.nlm.nih.gov]
  • Our personal patient with a neonatal onset had severe psychomotor delay. In both infancy and early childhood, the EEG showed no interictal frontal localization of the anomalies, and no long-lasting seizure was recorded.[ncbi.nlm.nih.gov]


  • Leen WG, Wevers RA, Kamsteeg EJ et al (2013) Cerebrospinal fluid analysis in the workup of GLUT1 deficiency syndrome: a systematic review. JAMA Neurol 70(11):1440–1444. CrossRef PubMed Google Scholar 17.[link.springer.com]
Rhythmic Slowing
  • Ictal electroencephalograms performed during nonconvulsive status epilepticus episodes typically record spike wave discharges, superimposed with 2- to 3-Hz rhythmic slow waves predominantly in the frontal lesion.[thieme-connect.com]


  • As not all cases of ring chromosome 20 syndrome are the same, different individuals may respond to treatment in different ways.Alternates to antiepileptic drug treatment include the ketogenic diet and vagus nerve stimulation but not epilepsy surgery.[en.wikipedia.org]
  • […] was unrelated to clinical phenotype, our reassessment of all 57 reported cases has revealed that the ratio is significantly associated with age at seizure onset, intelligence quotient, and malformation, but not with the response of epilepsy to drug treatment[ncbi.nlm.nih.gov]
  • We herein presented a case of a 17-year-old female with [r(20)] syndrome who developed recurrent status epilepticus (SE) at 14years of age that evolved into unremitting SE in spite of vigorous antiepileptic treatments.[ncbi.nlm.nih.gov]
  • […] and r(20) mosaicism was detected (r 0.903, P CONCLUSION: Striatal neurons are involved in r(20) epilepsy; the relationship found between r(20) mosaicism and DAT expression suggests that drugs acting on the dopaminergic system could have a place in the treatment[ncbi.nlm.nih.gov]
  • Finally, surgical treatment (corpus callosotomy) was performed at the age of 13 years; severity of tonic seizures was diminished, but frequency was unchanged.[ncbi.nlm.nih.gov]


  • Limited data is available for the long-term prognosis of ring chromosome 20 syndrome since only over 60 patients with this syndrome have been reported in published literature.[en.wikipedia.org]
  • Genotype-phenotype correlations to aid in the prognosis of individuals with uncommon 20q13.33 subtelomere deletions: a collaborative study on behalf of the ‘association des Cytogénéticiens de langue Française’.[thieme-connect.com]
  • Treatment is often difficult with continued medically refractory seizure with overall better prognosis in the mosaic type. References Borgaonkar DS, Lacassie YE, Stoll C. Usefulness of chromosome catalog in delineating new syndromes.[ring20researchsupport.co.uk]
  • As far as prognosis is concerned, follow-up time was too short for conclusions to be drawn.[nature.com]


  • With more widespread cytogenetic chromosomal karyotyping in non-etiological cases of epilepsy, more cases of r(20) will undoubtedly be recognized.[content.iospress.com]
  • While the underlying etiology of the phenotype is still not understood, evidence is accumulating which suggests the deletion of candidate genes on chromosome 20 is not responsible.[ncbi.nlm.nih.gov]
  • This review discusses the current knowledge about the genetic etiology of r(20) syndrome. Keywords ringed chromosome 20 - epilepsy - NCSE - haploinsufficiency - KCNQ2 - CHRNA4 - mosaic References 1 Atkins L, Miller WL, Salam M. A ring-20 chromosome.[thieme-connect.com]
  • Our goal is to determine the molecular etiology of the seizures associated with the ring chromosome 14 syndrome.[ring14.org]
  • 結節性硬化症 Tuberous sclerosis complex (TSC), unknown genetic etiology 結節性硬化症、遺伝子型不明 1 不要 有 HPS2395 HPS2396 HPS2397 HPS2398 HPS2399 HPS2400 159.[cell.brc.riken.jp]


  • From our latest events and fundraising, to Raised: 0,00 Goal: 0,00 RING20 KNOWLEDGE BASE At Ring20 Research Support UK we aim to establish an ever-growing knowledge-base on epidemiology, Raised: 3.210,00 Goal: 6.500,00 SIGNS & SYMPTOMS Find out how to[ring20researchsupport.co.uk]
Sex distribution
Age distribution

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