Parkinsonism

Parkinsonism (extrapyramidal syndrome) is a clinical syndrome, not a disease. Akinesia is the defining and obligatory feature, comprising bradykinesia (slowness in initiation and performance of movement) and hypokinesia (small amplitude of movement).

Rigidity is the increase in resistance to passive movement that is constant throughout the range of joint displacement ("lead-pipe") and not related to the velocity of movement — this distinguishes it from spasticity.

Tremor and postural abnormality, along with rigidity, may also occur as cardinal features of the syndrome.

Operational definition used in population studies: two or more of bradykinesia, gait disturbance, rigidity and tremor. In the East Boston community study of 467 people over 65, 159 had parkinsonism, and prevalence increased with age.

The neuropathological correlate of these age-related findings is the progressive spread of α-synuclein-immunopositive Lewy bodies and Lewy neurites, reported in the brains of ageing but asymptomatic individuals.

Distinguish rigidity from paratonia (gegenhalten) — "superadded hypertonus of a quasi-volitional nature due to the patient's failure to relax". Its anatomical correlate is bilateral frontal lobe pathology, usually diffuse small-vessel ischaemic disease; some classify it as a release sign.

Upward conjugate gaze becomes restricted with age, a finding also observed in parkinsonism — beware over-interpreting it in the very old.

Idiopathic Parkinson's disease is the commonest cause, but in very late-onset parkinsonism other causes account for 20–40% of new cases.

Frequently observed in the elderly: drug-induced parkinsonism, Lewy body dementia, Alzheimer's disease, progressive supranuclear palsy, cerebrovascular disease, normal pressure hydrocephalus.

Very rarely observed as very late-onset parkinsonism: multiple system atrophy, corticobasal degeneration, Huntington's disease, Wilson's disease, and miscellaneous causes (toxic, post-encephalitic, repeated skull trauma).

Drug-induced parkinsonism is defined by exposure to neuroleptics or other drugs before onset; dyskinesia is frequent, tremor is absent, and ioflupane SPECT is normal. Many elderly patients, especially in long-term care, have undiagnosed, treatable drug-induced parkinsonism from the extrapyramidal effects of antipsychotics.

Drugs implicated in tremor and extrapyramidal effects include neuroleptics (haloperidol, fluphenazine, olanzapine), metoclopramide, prochlorperazine, lithium, valproate, amiodarone, calcium channel blockers and antidepressants.

In most cases medical history and physical examination allow identification of the cause. Past or current neuroleptic exposure must be sought carefully by interviewing patients, proxies, physicians and pharmacists.

Apply the Queen Square Brain Bank criteria: Step 1 establishes the parkinsonian syndrome; Step 2 lists exclusions (repeated strokes with stepwise progression, repeated head injury, definite encephalitis, oculogyric crises, neuroleptic treatment at onset, more than one affected relative, sustained remission, strictly unilateral features after three years, supranuclear gaze palsy, cerebellar signs, early severe autonomic involvement, early severe dementia, Babinski signs, cerebral tumour or communicating hydrocephalus, negative response to large doses of levodopa, MPTP exposure); Step 3 requires three or more supportive features.

Parkinsonian syndromes other than PD respond poorly to levodopa — assessed from history or by levodopa challenge.

Ioflupane SPECT (DaTSCAN) shows a normal pattern in essential tremor, drug-induced parkinsonism and Alzheimer's disease, and abnormalities in PD and other parkinsonian syndromes.

MRI identifies midbrain atrophy (PSP), multiple lacunae and leukoaraiosis (vascular), and ventriculomegaly out of proportion to atrophy (NPH).

Where diagnosis remains uncertain, follow-up usually clarifies it as new signs and symptoms appear.

Treat the cause. Stop the offending drug in drug-induced parkinsonism (improvement is slow, over weeks to months; about 20% have persistent signs; there is no satisfactory treatment). Shunt for NPH; vascular risk factor control for vascular parkinsonism; levodopa for PD.

Prevention of drug-induced parkinsonism is a crucial issue in geriatric care — avoid neuroleptics in older people, especially those with dementia, in whom they are ineffective for behavioural symptoms. If untreated, parkinsonian patients eventually become immobile and develop flexion contractures, pressure sores, malnutrition and aspiration pneumonia.