- Seizure (HP:0001250): A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:99802)
- Interictal EEG abnormality (HP:0025373): Interictal refers to a period of time between epileptic seizures. Electroencephalographic (EEG) patterns are important in the differential diagnosis of epilepsy, and the EEG is almost always abnormal during a seizure. Some persons with seizures may show EEG abnormalities between seizures, while others do not. In some cases, multiple interictal EEGs must be recorded before an abnormality is observed. In most cases the electrographic pattern of seizure onset is completely different from the activity recorded during interictal discharge. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:99802)
- Hyperintensity of cerebral white matter on MRI (HP:0030890): A brighter than expected signal on magnetic resonance imaging emanating from the cerebral white matter. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:99802)
- Cranial asymmetry (HP:0000267): Asymmetry of the bones of the skull. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Abnormal skull morphology (HP:0000929): An abnormality of the skull, the bony framework of the head which is comprised of the neurocranium (with eight cranial bones) and the viscerocranium (facial skeleton) that comprises fourteen facial bones with the mandible as its largest bone. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Global developmental delay (HP:0001263): 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. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Ventriculomegaly (HP:0002119): An increase in size of the ventricular system of the brain. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Polymicrogyria (HP:0002126): Polymicrogyria is a congenital malformation of the cerebral cortex characterized by abnormal cortical layering (lamination) and an excessive number of small gyri (folds). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- EEG with polyspike wave complexes (HP:0002392): The presence of complexes of repetitive spikes and waves in EEG. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Hemimegalencephaly (HP:0007206): Enlargement of all or parts of one cerebral hemisphere. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- EEG with burst suppression (HP:0010851): The burst suppression pattern in electroencephalography refers to a characteristic periodic pattern of low voltage (<10 microvolts) suppressed background and a relatively shorter pattern of higher amplitude slow, sharp, and spiking complexes. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Focal motor seizure (HP:0011153): A type of focal-onset seizure characterized by a motor sign as its initial semiological manifestation. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- EEG with focal spikes (HP:0011193): EEG with focal sharp transient waves of a duration less than 80 msec. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- EEG with focal sharp slow waves (HP:0011195): EEG with focal sharp transient waves of a duration between 80 and 200 msec followed by a slow wave. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Hemihypsarrhythmia (HP:0011215): Hypsarrhythmia occurring in one hemisphere. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Focal cortical dysplasia (HP:0032046): A type of malformation of cortical development that primarily affects areas of neocortex. It can be identified on conventional magnetic resonance imaging as focal cortical thickening, abnormal gyration, and blurring between gray and white matter, often associated with clusters of heterotopic neurons. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:99802)
- Macrocephaly (HP:0000256): Occipitofrontal (head) circumference greater than 97th centile compared to appropriate, age matched, sex-matched normal standards. Alternatively, a apparently increased size of the cranium. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Optic atrophy (HP:0000648): Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Hemiparesis (HP:0001269): Loss of strength in the arm, leg, and sometimes face on one side of the body. Hemiplegia refers to a complete loss of strength, whereas hemiparesis refers to an incomplete loss of strength. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Pachygyria (HP:0001302): Pachygyria is a malformation of cortical development with abnormally wide gyri with sulci 1,5-3 cm apart and abnormally thick cortex measuring more than 5 mm (radiological definition). See also neuropathological definitions for 2-, 3-, and 4-layered lissencephaly. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Myoclonus (HP:0001336): Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Status epilepticus (HP:0002133): Status epilepticus is a type of prolonged seizure resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms which lead to abnormally prolonged seizures (after time point t1). It is a condition that can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Gliosis (HP:0002171): Gliosis is the focal proliferation of glial cells in the central nervous system. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Gray matter heterotopia (HP:0002282): Heterotopia or neuronal heterotopia are macroscopic clusters of misplaced neurons (gray matter), most often situated along the ventricular walls or within the subcortical white matter. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Functional motor deficit (HP:0004302). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Cranial nerve paralysis (HP:0006824). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Atonic seizure (HP:0010819): Atonic seizure is a type of motor seizure characterized by a sudden loss or diminution of muscle tone without apparent preceding myoclonic or tonic event lasting about 1 to 2 seconds, involving head, trunk, jaw, or limb musculature. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Severe intellectual disability (HP:0010864): Severe intellectual disability (ID) is defined as a type of ID characterized by severely sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) the range of 20-34. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Epileptic spasm (HP:0011097): A sudden flexion, extension, or mixed extension-flexion of predominantly proximal and truncal muscles that is usually more sustained than a myoclonic movement but not as sustained as a tonic seizure. Limited forms may occur: Grimacing, head nodding, or subtle eye movements. Epileptic spasms frequently occur in clusters. Infantile spasms are the best known form, but spasms can occur at all ages. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Focal tonic seizure (HP:0011167): A type of focal motor seizure characterized by sustained increase in muscle contraction, lasting a few seconds to minutes. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Oculomotor nerve palsy (HP:0012246): Reduced ability to control the movement of the eye associated with damage to the third cranial nerve (the oculomotor nerve). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Hemianopia (HP:0012377): Partial or complete loss of vision in one half of the visual field of one or both eyes. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
- Abnormal neuron morphology (HP:0012757): A structural anomaly of a neuron. Neurons are electrically excitable cells that transmit signals throughout the body. Neurons employ both electrical and chemical components in the transmission of information. Neurons are connected to other neurons at synapses and connected to effector organs or cells at neuroeffector junctions. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:99802)
These phenotypes are associated with the disease Hemimegalencephaly (ORPHA:99802).