A condition in which the stomach contents leak backwards from the stomach into the esophagus through the lower esophageal sphincter.

Underdevelopment of the external ear.

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.

Severe mental retardation is defined as an intelligence quotient (IQ) in the range of 20-34.

A shaky or wobbly manner of walking.

A failure to achieve the ability to walk at an appropriate developmental stage. Most children learn to walk in a series of stages, and learn to walk short distances independently between 12 and 15 months.

A delay in the acquisition of the ability to understand the speech of others.

A degree of language development that is significantly below the norm for a child of a specified age.

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.

A type of ataxia characterized by the impairment of the ability to coordinate the movements required for normal walking. Gait ataxia is characteirzed by a wide-based staggering gait with a tendency to fall.

Delayed myelination.

A type of Developmental delay characterized by a delay in acquiring motor skills.

Areas of brighter than expected signal on magnetic resonance imaging emanating from the cerebral white matter that surrounds the cerebral ventricles.

Bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline.

The postnatal development of an abnormally large skull (macrocephaly).

Generalized muscular hypotonia (abnormally low muscle tone).

Recurrent episodes of decreased concentration of glucose in the blood.

Facial height (length) is more than 2 standard deviations above the mean (objective); or, an apparent increase in the height (length) of the face (subjective).

Width of the forehead or distance between the frontotemporales is more than two standard deviations above the mean (objective); or apparently increased distance between the two sides of the forehead.

An eye that is more deeply recessed into the plane of the face than is typical.

A manifest or latent ocular deviation in which one or both eyes tends to deviate nasally.