Clonus is an involuntary tendon reflex that causes repeated flexion and extension of the foot. Ankle clonus is tested by rapidly flexing the foot upward.

Reduced strength and weakness of the muscles of the arms and legs.

A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).

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.

Weakness of all four limbs.

Tendon reflexes that are noticeably more active than usual (conventionally denoted 3+ on clinical examination). Brisk reflexes may or may not indicate a neurological lesion. They are distinguished from hyperreflexia by the fact that hyerreflexia is characterized by hyperactive repeating (clonic) reflexes, which are considered to be always abnormal.

Bulbar weakness (or bulbar palsy) refers to bilateral impairment of function of the lower cranial nerves IX, X, XI and XII, which occurs due to lower motor neuron lesion either at nuclear or fascicular level in the medulla or from bilateral lesions of the lower cranial nerves outside the brain-stem. Bulbar weakness is often associated with difficulty in chewing, weakness of the facial muscles, dysarthria, palatal weakness and regurgitation of fluids, dysphagia, and dysphonia.

A disorder of bone growth affecting the vertebrae and the ends of the long bones (epiphyses).

Spondylolysis is an osseous defect of the pars interarticularis, thought to be a developmental or acquired stress fracture secondary to chronic low-grade trauma.

Muscular atrophy involving the muscles of the hand.

Partial dislocation of the atlantoaxial joint.

Abnormally increased movement at the junction between the first cervical (atlas) and the second cervical (axis) vertebrae as a result of either a bony or ligamentous anomaly.

A decreased rate of skeletal maturation. Delayed skeletal maturation can be diagnosed on the basis of an estimation of the bone age from radiographs of specific bones in the human body.

An abnormal accentuation of the inward curvature of the spine in the lumbar region.

Underdevelopment of the proximal epiphysis of the femur.

The capability that a joint (or a group of joints) has to move, passively and/or actively, beyond normal limits along physiological axes.

Separation of the odontoid process from the body of the axis.

Complete bilateral fractures of the pars interarticularis resulting in the anterior slippage of the fifth lumbar vertebral body (L5) onto the sacrum (level S1).

A severe form of respiratory insufficiency characterized by inadequate gas exchange such that the levels of oxygen or carbon dioxide cannot be maintained within normal limits.

Fasciculations or fibrillation affecting the tongue muscle.