An unintentional, oscillating to-and-fro muscle movement about a joint axis.

A type of ataxia characterized by the inability to carry out movements with the correct range and motion across the plane of more than one joint related to incorrect estimation of the distances required for targeted movements.

A tonic seizure is a type of motor seizure characterized by unilateral or bilateral limb stiffening or elevation, often with neck stiffening.

Underdevelopment of the corpus callosum.

Hyperactivity is a condition characterized by constant and unusually high levels of activity, even in situations where it is deemed inappropriate.

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

A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase.

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.

Incapability to ambulate.

The term gait disturbance can refer to any disruption of the ability to walk. In general, this can refer to neurological diseases but also fractures or other sources of pain that is triggered upon walking. However, in the current context gait disturbance refers to difficulty walking on the basis of a neurological or muscular disease.

Cerebellar atrophy is defined as a cerebellum with initially normal structures, in a posterior fossa with normal size, which displays enlarged fissures (interfolial spaces) in comparison to the foliae secondary to loss of tissue. Cerebellar atrophy implies irreversible loss of tissue and result from an ongoing progressive disease until a final stage is reached or a single injury, e.g. an intoxication or infectious event.

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.

The absence of wakefulness and consciousness, but in contrast to a coma, there is involuntary opening of the eyes and movements such as teeth grinding, yawning, or thrashing of the extremities.

Loss of developmental skills, as manifested by loss of developmental milestones.

A type of motor delay characterized by a delay in acquiring the ability to control the large muscles of the body for walking, running, sitting, and crawling.

Underdevelopment of the vermis of cerebellum.

Complete lack of development of speech and language abilities.

A generalized myoclonic seizure is a type of generalized motor seizure characterized by bilateral, sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus.

A failure to meet one or more age-related milestones of social behavior.

A type of motor delay characterized by a delay in acquiring the ability to control the fingers and hands.

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

Continuous involuntary sustained muscle contraction. When an affected muscle is passively stretched, the degree of resistance remains constant regardless of the rate at which the muscle is stretched. This feature helps to distinguish rigidity from muscle spasticity.

Habitual flow of saliva out of the mouth.