Juvenile HD
Part 7

The symptoms and characteristics of juvenile Huntington’s disease.

How are the symptoms of juvenile HD different from those of adult-onset HD?

The most notable symptomatic distinction between the two forms of HD is that many individuals with juvenile HD do not experience the chorea that is so commonly associated with the adult-onset form. Instead of exhibiting the dance-like movements of chorea, affected children are often rigid and stiff. Generally, children with a younger age of onset are less likely to experience chorea. Chorea is more likely to be present in individuals who have an age of onset from 15-18 years. It seems that individuals with juvenile HD who have a later age of onset are more likely to experience symptoms that resemble those of adult-onset HD.

About 25-30% of individuals with early-onset HD also experience recurring seizures, a symptom that is uncommon in the adult-onset form. Seizures experienced by children with HD are usually generalized, meaning that they are caused by electrical discharges that affect both sides of the brain and often involve a loss of consciousness. However, some children also develop partial seizures, which involve discharges in just one part of the brain and may or may not involve a loss of consciousness.

The generalized seizures experienced by HD children are usually what are called tonic-clonic seizures. Generalized tonic-clonic seizures (or grand mal seizures) consist of both tonic and clonic phases. During the tonic phase the body is rigid, and often the child falls to the ground. The clonic phase follows the tonic phase and is usually associated with convulsive movements or rhythmic jerking motions. The child typically loses consciousness for a variable period of time.

Some children also develop myoclonic seizures, which involve sudden, brief jerking movements, or myoclonus. These seizures vary greatly in their severity and frequency. Myoclonus should not be mistaken for seizures - the term myoclonus refers to the jerking symptom itself, which can have many causes. It is only when myoclonus is caused by abnormal brain activity that it is properly called myoclonic seizure. Many children with HD experience myoclonus that is not related to seizures.

Last Modified: 9-16-02

An educational product of HOPES, not to be used in place of medical care. For more information about HOPES, click on the Logo. To contact HOPES with comments or questions, click here.