Page 324 - Medicine and Surgery

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320 Chapter 7: Nervous system

Dopamine agonists (such as bromocriptine, prami- With initial treatment:

pexole, cabergolide and apomorphine) act directly on ∼1/3 improve markedly;
dopamine receptors, and are useful in patients who re- 1/3 show some improvement;
sponded to l-dopa, but have developed l-dopa related 1/3 show no significant improvement, which should
dyskinesias. These may be considered first-line treat- prompt the search for another cause of the symp-
ment in young patients. They have a neuroprotective toms, as other causes of parkinsonism do not usually
effect in vitro. respond to the treatment for idiopathic Parkinson’s
Anticholinergicagentsmayimprovesymptoms.InPD disease.

there is a relative overstimulation at the basal gan-
glia by cholinergics compared to dopamine. This can
be redressed by anticholinergic drugs such as ben- Other causes of Parkinsonism
ztropine and procyclidine. They tend only to be used
in mild tremor, and they do not help with akinesia or Definition
There are certain disorders that mimic idiopathic
gait.
Parkinson’s disease, i.e. with tremor, bradykinesia and
Selegiline is a monoamine oxidase B inhibitor which

rigidity but do not respond to the usual treatments.
slows the catabolism of dopamine. It is useful in early
Parkinson’s.
Amantadine is an antiviral agent, which is thought to

Aetiology
act by increasing dopamine release and having NMDA
The main causes are cerebrovascular disease, antidopa-
receptor antagonist properties. It may be of value in
minergic drugs such as neuroleptic drugs, e.g. haloperi-
mild early cases and has the advantage of few side-
dol, reserpine and the anti-emetic metoclopramide.
effects.
There are also specific ‘Parkinson’s plus’ syndromes
Depression is common, difficult to treat and makes

where there is evidence of other neurological deficit:
Parkinson’s disease worse. Hallucinations due to med-
Multiple system atrophy (MSA) is parkinsonism in

ication and insomnia also occur frequently.
association with autonomic failure in particular pos-
Surgery:These procedures are reserved for advanced
tural hypotension and urinary dysfunction. It groups
cases.
together the syndromes previously known as olivo-
Stereotactic placement of small lesions in the ventro-

pontocerebellar atrophy, Shy–Drager syndrome and
lateral nucleus of the thalamus can help tremor, but
striatonigral degeneration.
does not help bradykinesia. Unilateral pallidotomy Progressive supranuclear palsy (PSP) is parkinson-
(removal of or lesions made in the globus pallidus)
ism with downward gaze palsy (a loss of the ability
can help tremor, rigidity, bradykinesia and postural
to look downwards). It tends to cause a rapid dete-
instability. However surgery carries the risk of haem-
rioration, with marked postural instability, frequent
orrhage or infarction in 4%, with a 1% mortality.
falls and difficulty swallowing. In later disease, be-
High frequency deep brain stimulation suppresses

havioural changes such as emotional lability and per-
neuronal activity. Bilateral subthalamic nucleus stim-
sonality changes, disordered sleep and cognitive loss
ulation or globus pallidus stimulation is most useful
are features, which may lead to the initial diagnosis of
in those with difficulty with the on-off phenomenon,
dementia.
as it can improve motor function whilst off medica-
tion and dyskinesias whilst on medication. There is a
risk of infection from the equipment. Pathophysiology
Cerebrovascular parkinsonism is likely to be due to pro-
Prognosis gressive loss of dopaminergic neurons due to small vessel
The course of Parkinson’s disease is very variable. The disease. Drugs which interfere with the dopamine path-
averagesurvival is ∼10 years from onset of symptoms. way tend to cause bradykinesia and rigidity, but with
Drugsappearnottoprolonglifebutlevodopahasgreatly less tremor, and the symptoms reverse on stopping the
improved quality of life. medication.