Management of Motor Fluctuations in Parkinson's Disease

Management of Motor Fluctuations in Parkinson's Disease Fifteen–Twenty High-Yield Points Definition and types

Motor fluctuations are predictable or unpredictable changes in motor performance in relation to levodopa dosing, appearing after several years of treatment. They occur together with involuntary movements — chorea, athetosis and dystonia.

Wearing-off (end-of-dose deterioration) is the earliest and commonest form — return of parkinsonian symptoms before the next dose is due.

Delayed-on and dose failure (no-on) result from impaired gastric emptying and competition with dietary protein for absorption.

On-off phenomenon is abrupt, unpredictable switching between mobility and immobility, unrelated to dose timing.

Early-morning akinesia and early-morning/off-period dystonia (typically painful foot dystonia) reflect overnight levodopa washout.

Freezing of gait may be off-period (levodopa-responsive) or on-period (levodopa-resistant); the distinction determines whether more drug will help.

Dyskinesias are classified by their timing: peak-dose dyskinesia (commonest, choreiform), diphasic dyskinesia (at the beginning and end of dose, often dystonic and painful in the legs), and off-period dystonia.

Non-motor fluctuations parallel the motor ones — anxiety, panic, pain, sweating, akathisia, breathlessness and mood swings in the off state — and are frequently missed.

Fluctuations arise from a narrowing therapeutic window: progressive loss of nigrostriatal terminals removes the buffering capacity to store and release dopamine, so the striatum becomes directly dependent on the short plasma half-life of levodopa. This pulsatile stimulation induces post-synaptic changes that generate dyskinesia.

Assessment begins with a patient-completed diary recording on time, off time, and dyskinesia against each dose, together with meal timing and constipation.

Exclude malabsorption and delayed gastric emptying, including Helicobacter pylori infection and severe constipation, before concluding that the disease has advanced. Also review any newly added dopamine-blocking drug.

First step — manipulate levodopa: revise the timing of administration, fractionate the dose (smaller doses given more frequently), and give doses 30 minutes before meals to avoid protein competition.

Dispersible levodopa (dispersible Madopar) reaches peak plasma concentration faster and is used as a rescue dose for early-morning akinesia and delayed-on, allowing the standard dose to be taken at the same time.

COMT inhibitors — entacapone and tolcapone — decrease dopamine degradation, increasing and prolonging the effect of levodopa, and are specifically useful in older patients with motor fluctuations and/or levodopa-induced dyskinesia. Entacapone 200 mg is given with each levodopa dose.

Adding a controlled-release levodopa preparation at night helps nocturnal akinesia and early-morning off dystonia.

Amantadine is the best-established antidyskinetic drug, acting through NMDA antagonism, but must be used cautiously in the elderly because it causes delirium, hallucinations and livedo reticularis and is renally excreted, requiring dose reduction in renal impairment.

Dopamine agonists and MAO-B inhibitors smooth fluctuations in younger patients but are generally avoided in the elderly because of neuropsychiatric adverse effects.

Reducing the individual levodopa dose while increasing frequency is the standard manoeuvre for peak-dose dyskinesia; diphasic dyskinesia, paradoxically, may improve by increasing the dose.

Continuous dopaminergic delivery is the definitive answer to refractory fluctuations: intrajejunal levodopa-carbidopa gel via PEG-J, or continuous subcutaneous apomorphine infusion.

Bilateral DBS of STN or GPi is offered to cognitively intact patients with severe disability from motor complications refractory to best medical therapy; it gives sustained improvement in levodopa-responsive symptoms and reduces drug-induced involuntary movements.