What are the principles of therapy and treatment in a 65-year-old patient recently diagnosed with Parkinson's disease who has predominant rigidity and minimal tremor?

Confirm the diagnosis before treating. Apply the Queen Square Brain Bank criteria. An akinetic-rigid presentation with minimal tremor must prompt exclusion of other causes of extrapyramidal syndrome, which account for 20–40% of late-onset parkinsonism — drug-induced parkinsonism (take an exhaustive neuroleptic history), vascular parkinsonism, PSP, MSA and normal pressure hydrocephalus. Ioflupane SPECT is normal in drug-induced parkinsonism and abnormal in PD.

Levodopa is the drug of choice. It is effective in tremor, bradykinesia and rigidity, and is the main and often the only treatment for PD in the elderly. Give it as Madopar or Sinemet with a peripheral decarboxylase inhibitor. Since rigidity and bradykinesia dominate here, levodopa targets exactly the symptoms present.

Start low and titrate slowly. Begin at a low dose and increase very gradually until adequate effect; most patients are controlled in the first years on 300–600 mg/day in 3–4 divided doses given 30 minutes before meals. A good response supports the diagnosis; a negative response to large doses is an exclusion criterion for PD.

Avoid the two prohibited classes. Anticholinergics are never used in older people with PD — and are in any case indicated for tremor, which is minimal in this patient. Dopamine agonists are not used in older people because adverse effects are numerous and can be severe.

Anticipate and monitor adverse effects. Warn about nausea (treat with domperidone, never metoclopramide), and check for orthostatic hypotension at every visit — a fall of 20 mmHg systolic or 10 mmHg diastolic within three minutes, frequently worsened by antiparkinsonian drugs. Watch for sedation, vivid dreams and hallucinations. Counsel that motor fluctuations and dyskinesia appear after several years.

Start non-pharmacological therapy at once and think as a geriatrician. Functional rehabilitation should be started early as it helps preserve motor function, with sessions timed to the peak effect of levodopa, combining joint flexibility, walking, posture, balance and turning exercises against the flexed attitude. Add combined aerobic, strengthening, balance and stretching exercise. Screen for non-motor symptoms (depression, constipation), review polypharmacy for dopamine-blocking drugs, assess falls risk, and provide patient and caregiver education and psychological support.

Levodopa should be started early at the lowest effective dose, not withheld. No agent has proven disease modification — the Phase 3 Exenatide-PD3 trial (Lancet 2025) showed no slowing of progression, and MAO-B inhibitors are no longer claimed to be neuroprotective. Contemporary evidence confirms levodopa is not toxic to nigral neurons and that delaying it does not alter disease course, so "saving levodopa for later" is obsolete — particularly in a 65-year-old with disabling rigidity. Newer formulations (Crexont, August 2024) are available if wearing-off develops later.