Timothy C. Hain, M • Page last modified: July 26, 2014
Huntington's chorea is a dominantly inherited disease typified by choreoathetosis, rigidity, dementia, ataxia, and ophthalmoplegia. It was first described by George Huntington in 1872. Incidence is 5-10/100,000. Genetically, it is an autosomal dominant disorder with complete penetrance. The mutation, CAG-trinucleotide repeats, may expand in descendent generations explaining anticipation. A similar syndrome has been reported in SCA-17, another CAG repeat disease (Toyoshima et al, 2004).
HD is a basal ganglia disease; the portions most severely affected are caudate and putamen. The most significant neuropathological change is a preferential loss of medium spiny neurons in the neostriatum. Biochemically there is marked loss of GABA, substance P, enkephalin, angiotension converting enzyme. Neuronal changes begin very early in life, perhaps even from birth. There is no known treatment that will stop progression, but there are symptomatic treatments such as haloperidol.
|Prolonged latency of saccades in a patient with mild Huntington's chorea. Blue-target, Red-horizontal. Dashed lines are 1 second apart.|
Huntingtons can be diagnosed on MRI by caudate atrophy with appropriate history, and also by genetic testing.
On ENG testing, patients may show slow saccades and/or prolonged latency of saccades (Lasker and others; 1987, 1988). The anti-saccade test is sensitive to Huntingtons disease. This is a test where subjects are asked to look away from a newly presented target -- it requires the individual to suppress their impulse to look at the target.
Differential diagnosis of Huntington includes hepatocerebral degeneration (Wilson's disease), schizophrenia with tardive dyskinesia, other chorea's such as SCA-17, and drug reactions.
Treatment is presently symptomatic. Animal work (Duan et al, 2004) suggests that SSRI type antidepressants may be worth considering, but of course, it is unlikely that any medication will reverse a genetic disorder such as HD.
Huntington's disease is associated with very poor performance on tests of driving ability; Devos et al (2014) suggested that monitoring of driving fitness should be initiated early.