Phenotypes associated with the disease Isolated lissencephaly type 1 without known genetic defects (ORPHA:1084):
- 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: Frequent (HP:0040282). (ORPHA:1084)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- 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: Frequent (HP:0040282). (ORPHA:1084)
- Neonatal hypotonia (HP:0001319): Muscular hypotonia (abnormally low muscle tone) manifesting in the neonatal period. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Ventriculomegaly (HP:0002119): An increase in size of the ventricular system of the brain. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Profound intellectual disability (HP:0002187): Profound intellectual disability (ID) is defined as a type of ID characterized by profoundly sub-average adaptive functioning and intellectual functioning, with an intelligence quotient (IQ) below 20. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- 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: Frequent (HP:0040282). (ORPHA:1084)
- Hypsarrhythmia (HP:0002521): 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). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- 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: Frequent (HP:0040282). (ORPHA:1084)
- EEG with changes in voltage (HP:0011201): EEG with abnormal amplitude. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Feeding difficulties (HP:0011968): Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Infantile spasms (HP:0012469): Infantile spasms represent a subset of "epileptic spasms". Infantile Spasms are epileptic spasms starting in the first year of life (infancy). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Neurodevelopmental delay (HP:0012758): Neurodevelopmental delay (NDD) refers to delays in the maturation of the brain and central nervous system; infants and young children with NDD may experience delays in the development of one or more skills including gross motor abilities, fine-motor coordination, language abilities and ability to solve increasingly complex problems. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Motor seizure (HP:0020219): A motor seizure is a type of seizure that is characterized at onset by involvement of the skeletal musculature. The motor event could consist of an increase (positive) or decrease (negative) in muscle contraction to produce a movement. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Agyria (HP:0031882): A congenital abnormality of the cerebral hemisphere characterized by lack of gyrations (convolutions) of the cerebral cortex. Agyria is defined as cortical regions lacking gyration with sulci great than 3 cm apart and cerebral cortex thicker than 5 mm. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)
- Enlarged sylvian cistern (HP:0100952): An increase in size of the subarachnoid space associated with the lateral cerebral sulcus (Sylvian fissure). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1084)