NERVE DEGENERATIVE DISORDERS -PART-IV

HUNTINGTON'S DISORDER(HD)

HD is a dominantly inherited disorder characterized by the gradual onset of mobility disorders followed by mental insufficiency. The condition is very common at a young age to mid-age.

Symptoms start insidiously either as a mobility disorder or a cognitive and personality disorder or both. The movement disorders consist of a brief jerk like movements of the extremities, trunk, face, and neck(chorea).

Motor incoordination and impairment of rapid eye movements are the early symptoms. If the onset of the disease occurs in the early 20s the choreic movements are less prominent but instead, bradykinesia(slow neuromuscular response) and dystonia (involuntary contract movement of muscles) are the prominent features.

As the disease progresses the dystonic muscle movements are more frequent and severe, leads to dysarthria(Arthritis like pain and speech difficulty), followed by dysphagia(pain and difficulty in swallowing), and balance to stand or walk is impaired.

Cognitive disorder slowly onset by slow mental processing and difficulty in organizing complex tasks.

Memory in distance and long ago may be impaired but short memories and memory of family friends, close relatives, and immediate incidences may be spared. Hence such persons always seem to be irritant anxious and depressed.

Less frequently paranoia and delusions may manifest.

Over a course of 20 to 30 years, the affected person becomes totally disabled and unable to communicate and require full-time care.

Death ensues from the complications of immobility.

Neurology

In general similar to the other neurological disorders, the HD also caused by the neuronal degeneration at the forebrain in which the reward system is present. The damages are mainly at the nerve nucleus known as caudate nucleus along with the round-shaped nerve capsule known as putamen composed parts of the basal ganglia, at the forebrain.HD is purely a genetic disorder due to a single defect on chromosome-4.

Treatments

There is no cure for the disease but medicines are used in a limited sense because of the side effects to control the symptoms.

1. Depression can be treated with antidepressant drugs such as tricyclic antidepressants(Amitriptyline, imipramine) but their anticholinergic effects which may exacerbate chorea. should be excluded.

SSRIs such as Fluoxetine can be employed to treat depression and irritability with a safe profile.

Antiepileptics such as Carbamazepine has also been tried successfully to relieve depression.

Neuroleptics such as clozapine and risperidone can be used but the doses should be lower than their dose employed in psychiatric disorders. At high doses, they may impair cognitive functions and mobility.

For those with large amplitude chorea causing frequent falls and injury can try antidopaminergic drugs such as haloperidol or tetrabenazine or reserpine. During the dopamine depleting drugs treatment patient should be watched for depression and hypotension.

Benzodiazepines like alprazolam, diazepam, or temazepam can be used to relieve anxiety and stress.
Seizures can be controlled by anticonvulsants such as clonazepam or valproic acid