Early infantile epileptic encephalopathy 1

Also known as: early infantile epileptic encephalopathy-1; EIEE1; epileptic encephalopathy, early infantile, 1; infantile epileptic-dyskinetic encephalopathy; ISSX; ISSX1; X-linked infantile spasm syndrome; X-linked infantile spasm syndrome 1; X-linked Ohtahara syndrome; X-linked West syndrome


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Early infantile epileptic encephalopathy 1 (EIEE1) is a seizure disorder characterized by a type of seizure known as infantile spasms. The spasms usually appear before the age of 1. Several types of spasms have been described, but the most commonly reported type involves bending at the waist and neck and extending the arms and legs (sometimes called a jackknife spasm). Each spasm lasts only seconds, but they occur in clusters several minutes long. Although individuals do not usually have spasms while they are sleeping, the spasms commonly occur just after awakening. Infantile spasms usually stop by age 5, but many children then develop other types of seizures that recur throughout their lives.

Most babies with EIEE1 have characteristic results on an electroencephalogram (EEG), a test used to measure the electrical activity of the brain. The EEG of these individuals typically shows an irregular pattern known as hypsarrhythmia, and this finding can help differentiate infantile spasms from other types of seizures.

Because of the recurrent seizures, babies with EIEE1 stop developing normally and begin to lose skills they have acquired (developmental regression), such as sitting, rolling over, and babbling. Most affected individuals also have intellectual disability throughout their lives.

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West syndrome (or infantile spasms) is characterised by the association of clusters of axial spasms, psychomotor retardation and an hypsarrhythmic interictal EEG pattern. It is the most frequent type of epileptic encephalopathy. It may occur in otherwise healthy infants and in those with abnormal cognitive development.

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Medical Term Other Names Description
Seizures Epilepsy Seizures are an intermittent abnormality of the central nervous system due to a sudden, excessive, disorderly discharge of cerebral neurons and characterized clinically by some combination of disturbance of sensation, loss of consciousness, impairment of psychic function, or convulsive movements. The term epilepsy is used to describe chronic, recurrent seizures.
Encephalopathy Encephalopathy is a term that means brain disease, damage, or malfunction. In general, encephalopathy is manifested by an altered mental state.
Infantile spasms Infantile spasms represent a subset of "epileptic spasms". Infantile Spasms are epileptic spasms starting in the first year of life (infancy).
Epileptic encephalopathy
Hypsarrhythmia Hypsarrhythmia by EEG Hypsarrhythmia is abnormal interictal high amplitude waves and a background of irregular spikes. There is continuous (during wakefulness), high-amplitude (>200 Hz), generalized polymorphic slowing with no organized background and multifocal spikes demonstrated by electroencephalography (EEG).
Developmental regression Psychomotor regression, Psychomotor regression in infants, Psychomotor regression beginning in infancy, Loss of developmental milestones, Mental deterioration in childhood, Psychomotor regression, progressive, Neurodevelopmental regression [more] Loss of developmental skills, as manifested by loss of developmental milestones.
Global developmental delay Psychomotor developmental delay, Psychomotor retardation, Developmental delay, Lack of psychomotor development, Cognitive delay, Delayed intellectual development, Delayed milestones, Psychomotor development deficiency, Developmental retardation, Motor and developmental delay, Developmental delay in early childhood, Retarded psychomotor development, Retarded mental development, Delayed cognitive development, Retarded development, Delayed developmental milestones, Delayed development, Psychomotor development failure, Mental and motor retardation, Psychomotor delay, Delayed psychomotor development [more] A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Intellectual disability Nonprogressive intellectual disability, Poor school performance, Mental-retardation, Dull intelligence, Nonprogressive mental retardation, Mental deficiency, Mental retardation, nonspecific, Low intelligence [more] Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.
Epileptic spasms West syndrome, Salaam convulsions, Salaam seizures [more] A sudden flexion, extension or mixed extension-flexion of predominantly proximal and truncal muscles which is usually more sustained than a myoclonic movement but not as sustained as a tonic seizure.

Other Classifiers and IDs

  • OrphaNet: ORPHA:3451
  • MedDRA: 10021750
  • UMLS: C0037769