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Chapter 7: Parkinson’s disease and other movement disorders 321

Clinical features Incidence
Features that suggest other causes of parkinsonism 1in 20,000
include:
Symmetry of signs (Parkinson’s disease is usually Age

asymmetrical). Peak presentation in middle age.
History of drug use, in particular dopamine antago-

nists.
Sex
Additional neurology such as upgoing plantars or

M = F
cerebellar signs.
Earlydementia,prominenthallucinations,autonomic

Geography
neuropathy and axial rigidity are signs of Parkinson’s
Worldwide
plus syndromes:
Aetiology
Management
Huntington’s disease is an autosomal dominant condi-
Levodopa and other treatments used in Parkinson’s dis-
tion with full penetrance.
ease tend to have little or no effect, therefore withdrawal
of the causative drug, or supportive treatment. PSP and
MSA may respond to dopamine agonists, but postural Pathophysiology
hypotension tends to be exacerbated by medication. There is an expanded trinucleotide repeat sequence
(CAG) mutation on the short arm of chromosome 4.
Normally, the number of repeats is less than 35, but once
Benign essential tremor
this increases to over 36, the gene product called hunt-
Definition ingtin causes the disease. The more repeats there are,
An action tremor without features of parkinsonism. the earlier and the more severe the disease is, and the
expansion tends to increase in subsequent generations
Aetiology/pathophysiology (genetic anticipation). It is not clear how the abnormal
Often inherited as an autosomal dominant trait. It tends protein causes the neuropathological effects, but it is
to present in the teens or in the elderly and affects males thought that the mutant protein may cause biochem-
and females equally. ical effects, increase apoptosis and also (by interfering
withthenormalprotein)downregulateneuronalgrowth
Clinical features factors:
Asymmetrical, flexion-extension tremor, affecting the There is atrophy of the caudate nucleus and putamen
hands and head in particular, and sometimes the voice. in particular (these basal ganglia nuclei are important
Oscillations are not usually present at rest, but occur in control of movement). There is also diffuse cerebral
posturally, e.g. holding a newspaper, and are increased atrophy (which would account for dementia).
by anxiety and movement. There are neurochemical effects, such as a depletion
of acetylcholine and GABA but an increase in somato-
Management statinandotherhormonesinthestriatum.Thisresults
Treatment is often unnecessary, small doses of a β adren- in a loss of inhibition of the dopaminergic pathway,
ergic blocker such as propranolol or primidone often re- i.e. release of dopamine which leads to chorea.
duce the tremor. The condition is slowly progressive and
may cause some disability. Clinical features
The disease usually manifests as progressive cognitive
impairment and increasing movement disorder. Chorea
Huntington’s disease
consists of jerky, quasi-purposeful and sometimes ex-
Definition plosive movements, following each other but flitting
Genetically inherited progressive chorea and dementia. from one part of the body. When seen in middle age