A hole between the two bottom chambers (ventricles) of the heart. The defect is centered around the most superior aspect of the ventricular septum.

Difficulty in swallowing.

A bilateral form of sensorineural hearing impairment.

A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes.

The corpus callosum is the largest fiber tract in the central nervous system and the major interhemispheric fiber bundle in the brain. Formation of the corpus callosum begins as early as 6 weeks' gestation, with the first fibers crossing the midline at 11 to 12 weeks' gestation, and completion of the basic shape by age 18 to 20 weeks (Schell-Apacik et al., 2008). Agenesis of the corpus callosum (ACC) is one of the most frequent malformations in brain with a reported incidence ranging between 0.5 and 70 in 10,000 births. ACC is a clinically and genetically heterogeneous condition, which can be observed either as an isolated condition or as a manifestation in the context of a congenital syndrome (see MOLECULAR GENETICS and Dobyns, 1996). Also see mirror movements-1 and/or agenesis of the corpus callosum (MRMV1; 157600). Schell-Apacik et al. (2008) noted that there is confusion in the literature regarding radiologic terminology concerning partial absence of the corpus callosum, where various designations have been used, including hypogenesis, hypoplasia, partial agenesis, or dysgenesis.

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.

The presence of developmental dysplasia of the cerebral cortex.

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.

Persistent deficits in social interaction and communication and interaction as well as a markedly restricted repertoire of activity and interest as well as repetitive patterns of behavior.

Complete lack of development of speech and language abilities.

Displacement of the femur from its normal location in the hip joint.

A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move.

Generalized muscular hypotonia (abnormally low muscle tone).

An abnormal connection (fistula) between the esophagus and the trachea.