MedGen

Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. [from HPO]

A rare group of disorders characterized by the development of myoclonic and tonic-clonic epileptic seizures associated with progressive degeneration of the nervous system. [from NCI]

A rare disorder characterized clinically by the onset of fragmentary myoclonus appearing in the first month of life, often associated with erratic focal seizures and a suppression-burst EEG pattern. [from ORDO]

A myoclonic seizure is a type of motor seizure characterized by sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus. [from HPO]

Gliosis is the focal proliferation of glial cells in the central nervous system. [from HPO]

Proliferation of astrocytes in the area of a lesion of the central nervous system. [from HPO]

Individuals with biallelic PRICKLE1-related disorders typically present with progressive myoclonus epilepsy (PME) with ataxia characterized by myoclonic seizures (lightning-like jerks), generalized convulsive seizures, varying degrees of neurologic regression mainly presenting with ataxia, and mild cognitive impairment or normal cognition. Onset of symptoms is between ages five and ten years. Action myoclonus may affect the limbs or bulbar muscles, while spontaneous myoclonus may occasionally involve facial muscles. Dysarthria may also be an early feature of this condition. The main seizure types are myoclonic or tonic-clonic with frequent nocturnal occurrence. Individuals with heterozygous PRICKLE1 pathogenic variants have presented with non-PME seizures (isolated myoclonic seizures, juvenile myoclonic epilepsy), myoclonic epilepsy, developmental delay, intellectual disability, autism spectrum disorder, and/or central nervous system malformations. [from GeneReviews]

Progressive myoclonic epilepsy type 1(EPM1) is a neurodegenerative disorder characterized by onset from age six to 15 years, stimulus-sensitive myoclonus, and tonic-clonic epileptic seizures. Some years after the onset, ataxia, incoordination, intentional tremor, and dysarthria develop. Individuals with EPM1 are cognitively mostly within the normal range, but show emotional lability and depression. The epileptic seizures are usually well controlled by anti-seizure medication, but the myoclonic jerks are progressive, action activated, and treatment resistant, and can be severely disabling. [from GeneReviews]

EPILEPTIC SEIZURES that are of similar type and age of onset and have other similar features (e.g., clinical course, EEG findings, genetic association and neuropathology). [from MeSH]

TBC1D24-related disorders comprise a continuum of features that were originally described as distinct, recognized phenotypes: DOORS syndrome (deafness, onychodystrophy, osteodystrophy, mental retardation, and seizures). Profound sensorineural hearing loss, onychodystrophy, osteodystrophy, intellectual disability / developmental delay, and seizures. Familial infantile myoclonic epilepsy (FIME). Early-onset myoclonic seizures, focal epilepsy, dysarthria, and mild-to-moderate intellectual disability. Progressive myoclonus epilepsy (PME). Action myoclonus, tonic-clonic seizures, progressive neurologic decline, and ataxia. Early-infantile epileptic encephalopathy 16 (EIEE16). Epileptiform EEG abnormalities which themselves are believed to contribute to progressive disturbance in cerebral function. Autosomal recessive nonsyndromic hearing loss, DFNB86. Profound prelingual deafness. Autosomal dominant nonsyndromic hearing loss, DFNA65. Slowly progressive deafness with onset in the third decade, initially affecting the high frequencies. [from GeneReviews]

SCN1A seizure disorders encompass a spectrum that ranges from simple febrile seizures and generalized epilepsy with febrile seizures plus (GEFS+) at the mild end to Dravet syndrome and intractable childhood epilepsy with generalized tonic-clonic seizures (ICE-GTC) at the severe end. Phenotypes with intractable seizures including Dravet syndrome are often associated with cognitive decline. Less commonly observed phenotypes include myoclonic astatic epilepsy (MAE), Lennox-Gastaut syndrome, infantile spasms, epilepsy with focal seizures, and vaccine-related encephalopathy and seizures. The phenotype of SCN1A seizure disorders can vary even within the same family. [from GeneReviews]

A clinically diverse group of epilepsy syndromes characterized either by myoclonic seizures or by myoclonus in association with other seizure types. Myoclonic epilepsy syndromes are divided into three subtypes based on etiology: familial, cryptogenic, and symptomatic. [from MeSH]

A type of epilepsy with only generalized onset epileptic seizures. [from SNOMEDCT_US]

The action myoclonus-renal failure syndrome, also known as progressive myclonic epilepsy-4 with or without renal failure (EPM4), is an autosomal recessive progressive myoclonic epilepsy associated with renal failure. Cognitive function is preserved (Badhwar et al., 2004). Some patients do not develop renal failure (Dibbens et al., 2009). For a discussion of genetic heterogeneity of progressive myoclonic epilepsy, see EPM1A (254800). [from OMIM]

Progressive myoclonic epilepsy-8 (EPM8) is a rare autosomal recessive form of progressive myoclonic epilepsy with phenotypic variability including ataxia and other movement disorders in addition to myoclonus (summary by Godeiro et al., 2018). For a discussion of genetic heterogeneity of progressive myoclonic epilepsy, see EPM1A (254800). [from OMIM]

Focal seizure with eyelid myoclonia, not eyelid myoclonias in the context of absence seizures. [from HPO]

An absence with eyelid myoclonia seizure is a type of generalized non-motor (absence) seizure characterized by forced upward jerking of the eyelids during an absence seizure. [from HPO]

PEHO is a severe autosomal recessive neurodevelopmental disorder characterized by extreme cerebellar atrophy due to almost total loss of granule neurons. Affected individuals present in early infancy with hypotonia, profoundly delayed psychomotor development, optic atrophy, progressive atrophy of the cerebellum and brainstem, and dysmyelination. Most patients also develop infantile seizures that are often associated with hypsarrhythmia on EEG, and many have peripheral edema (summary by Anttonen et al., 2017). [from OMIM]