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GERICLINICS

GeriQBank · Paper III · Q1

Parkinson's disease — pathology, pathogenesis and treatment, with emphasis on drug choice, side effects, newer modalities and treatment of non-motor symptoms

Moderate YieldAsked ×115-mark essay
Topic
Parkinsonism & Movement Disorders
Chapter
Parkinson's Disease & Movement Disorders
Years asked
Not recorded in the source
Frequency
Set 1× in Paper III (2009–2025)

As set in the university paper

  • What are the pathology, pathogenesis and treatment of Parkinson’s disease — with emphasis on choice of drug, side effects, newer treatment modalities and the treatment of non-motor symptoms?

    Paper III · Parkinson’s Disease & Movement Disorders · asked ×1 · 15-mark essay · see in paper list

Answer framework

  1. Definition and epidemiology — second commonest neurodegeneration; prevalence and age; course; longstanding disease in geriatric practice; risk and protective factors
  2. Pathology and pathogenesis — nigral loss and dopamine depletion; Lewy bodies; genes; the threshold and the classical triad
  3. Clinical features — onset and asymmetry; other motor features; non-motor features; advanced disease
  4. Diagnosis — Queen Square criteria; DaTSCAN; levodopa challenge
  5. Drug treatment in older people — levodopa and its side effects; agonists and anticholinergics avoided; COMT inhibitors, amantadine, MAO-B inhibitors
  6. Treatment of non-motor symptoms — drug–symptom pairs (Table 53.4)
  7. Newer modalities and non-drug care — DBS; other surgery; rehabilitation; home support
  8. Recent updates — biological definitions; new levodopa formulations; tavapadon; B6 warning; adaptive DBS; disease modification; Indian data

An exam answer plan drawn from the detailed answer below. Use it to attempt the question first.

Detailed answer

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Short revision answer

  • PD is the second commonest neurodegenerative disease after AD: about 1% over 65, median diagnosis at 60 (very late onset after 75 is uncommon), incidence rising to 80 and then falling, and about 15 years from diagnosis to death — so geriatric patients mostly have longstanding, complicated disease. Risks: family history in 6–10%, head injury, rural living, pesticides; smoking and coffee appear protective.
  • Pathology: loss of substantia nigra neurons with striatal dopamine depletion, plus Lewy bodies (ubiquitinated α-synuclein). About 10 genes cause familial, mainly early-onset, PD. Past a dopamine threshold the triad appears — bradykinesia, rest tremor, rigidity — insidiously and asymmetrically; tremor may precede the others.
  • Other motor features: flexed posture, short low steps, reduced arm swing, falls, writing difficulty. Non-motor: bradyphrenia, depression, anxiety, cognitive decline, constipation, bladder and autonomic dysfunction. Advanced PD (10–15 years): severe akinesia, freezing, falls and fractures, dysphagia, drooling, pain, orthostatic hypotension, hallucinations and dementia; fluctuations and dyskinesia are the main challenge.
  • Diagnosis is clinical (Queen Square): bradykinesia plus rigidity, 4–6 Hz rest tremor or postural instability → exclusion criteria → ≥3 supportive features. DaTSCAN is abnormal in PD and other degenerative parkinsonism, normal in essential tremor, drug-induced parkinsonism and AD. A levodopa challenge (150–250 mg) shows responsiveness but isn't diagnostic.
  • Levodopa (with benserazide — Madopar — or carbidopa — Sinemet) is the main and often only drug in older people: start low, usually 300–600 mg/day in 3–4 doses, 30 minutes before meals (dispersible Madopar for morning akinesia). Side effects: nausea, hypotension, sedation, vivid dreams, hallucinations and delirium; later wearing-off, on–off and dyskinesia.
  • Pathy: direct dopamine agonists aren't used in older people (numerous, potentially severe side effects) and anticholinergics are never used (delirium). Adjuncts: COMT inhibitors (entacapone; Stalevo) for fluctuations; amantadine 200–400 mg/day for peak-dose dyskinesia (renal dosing, delirium); MAO-B inhibitors were proposed for neuroprotection.
  • Non-motor drugs (after optimising levodopa): domperidone for nausea (ECG; metoclopramide contraindicated); venlafaxine for depression; clozapine (start 12.5 mg; weekly counts for 2 months; stop if neutrophils <1500/mm3) or pimavanserin for psychosis; rivastigmine for dementia and apathy; droxidopa (or midodrine, fludrocortisone) for orthostatic hypotension; melatonin; macrogol; botulinum toxin for drooling; solifenacin; sildenafil.
  • DBS (subthalamic or GPi) gives sustained benefit for levodopa-responsive, refractory motor complications in cognitively intact patients — with similar results over 70 — but the disease still progresses. Early rehabilitation timed to levodopa peaks (flexibility, walking, posture, balance), speech and swallow therapy, home help and caregiver education.
  • Updates: biological research definitions (NSD-ISS, SynNeurGe; 2024) based on α-synuclein seed amplification plus DAT imaging; new delivery — Crexont (August 2024), Vyalev 24-hour subcutaneous infusion (October 2024), Onapgo (February 2025); tavapadon (D1/D5 partial agonist) awaits an FDA decision; an FDA warning (March 2026) on vitamin B6 deficiency and seizures with all carbidopa/levodopa products.
  • Adaptive DBS (Medtronic BrainSense, ADAPT-PD) was approved in February 2025. No disease modification is proven — Exenatide-PD3 (2025) was negative (Expression of Concern, June 2026); prasinezumab, bemdaneprocel and GDNF gene therapy are in trials. India: earlier onset than in Europe; crude prevalence 7–60 per 100,000 (much higher in Parsis); parkinsonism in 17.8% of residents in one old-age home.

Condensed by GeriClinics from the detailed answer below, with no new facts added.

High-Yield Points (Textbook)

Source: Pathy's 6th ed., Chapter 53 (Oquendo & Belmin); Essentials of Clinical Geriatrics 7th ed., Chapter 10.

Definition and epidemiology

1.

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Despite progress in understanding the neurochemistry, the exact cause remains undetermined.

2.

Prevalence is about 1% in people over 65 years. Median age at diagnosis is 60. Late-onset PD means first symptoms after age 60; very late-onset PD (after 75) is uncommon.

3.

Incidence rises with age up to 80 years and then appears to fall in the ninth decade. Mean duration from diagnosis to death is about 15 years.

4.

Because of this, most PD patients seen in geriatric practice have longstanding disease with lost independence and complications, not new diagnoses.

5.

Risk factors: family history in 6–10%; weak associations with head injury, rural living, obesity and herbicide/pesticide exposure. Male sex is debated. Cigarette smoking and coffee appear protective.

Pathology and pathogenesis

6.

The main pathological finding is loss of neurons in the substantia nigra with profound dopamine depletion in the projection pathways from substantia nigra to the striatum.

7.

The second hallmark is α-synuclein bound to ubiquitin accumulating in damaged neurons to form Lewy bodies, found in substantia nigra cells and other brain areas.

8.

About 10 gene mutations are identified in familial PD, but these operate mainly in early-onset disease and are rarely involved in late-onset PD.

9.

Once dopamine loss crosses a threshold, the classical triad appears: bradykinesia/akinesia, resting tremor and rigidity (Essentials).

Clinical features

10.

Onset is insidious with slow progression. Cardinal signs do not appear together — tremor may precede bradykinesia and rigidity by months to years. Signs are asymmetric or unilateral at onset and become bilateral later.

11.

Other motor features: flexed posture of limbs and trunk on standing, reduced step length and height, reduced arm swing, falls, and writing difficulty.

12.

Non-motor features: bradyphrenia (slowness of mental function), depression, anxiety, memory problems and dementia, constipation, bladder dysfunction and autonomic dysfunction (gastrointestinal, sexual, cardiovascular).

13.

Advanced PD (after 10–15 years): severe akinesia with less prominent tremor and rigidity, expressionless face, freezing, major gait and postural abnormality, repeated falls and fractures, wheelchair dependence, dysphagia, dysarthria, drooling, insomnia, pain, orthostatic hypotension, hallucinations and dementia. Fluctuations and dyskinesia are very frequent and remain the main therapeutic challenge.

Diagnosis

14.

Diagnosis is clinical, using the Queen Square Brain Bank criteria: Step 1 — bradykinesia plus at least one of muscular rigidity, 4–6 Hz rest tremor, or postural instability not due to visual, vestibular, cerebellar or proprioceptive causes; Step 2 — exclusion criteria; Step 3 — three or more supportive features.

15.

Ioflupane SPECT (DaTSCAN) is normal in essential tremor, drug-induced parkinsonism and Alzheimer's disease, and abnormal in PD and other degenerative parkinsonian syndromes.

16.

Levodopa challenge (150–250 mg with a decarboxylase inhibitor in a fasting patient; assess tremor, rigidity and akinesia every 30 minutes for 2–3 hours) indicates dopaminergic responsiveness — it is not a formal diagnostic test. Treatment — drug choice and side effects in the elderly

17.

Levodopa is the main and often the only treatment for PD in the elderly. It crosses the blood–brain barrier and is given with a peripheral decarboxylase inhibitor — Madopar (levodopa + benserazide) or Sinemet (carbidopa + levodopa). It is effective for tremor, bradykinesia and rigidity. Start low, increase very gradually; usual early control on 300–600 mg/day in 3–4 doses, 30 minutes before meals. Dispersible Madopar peaks faster and is used for early-morning akinesia.

18.

Side effects of levodopa: nausea and vomiting, hypotension, sedation, nightmares and vivid dreams, hallucinations, delusions and delirium; after several years, motor fluctuations (delayed effect, wearing-off, on–off) and involuntary movements (chorea, athetosis, dystonia).

19.

Drugs Pathy's says are NOT used in older people with PD: direct dopamine agonists (apomorphine, piribedil, ropinirole, lisuride, pramipexole, pergolide) — useful in the young to delay levodopa but adverse effects are numerous and can be severe; and anticholinergics (trihexyphenidyl, tropatepine), which are never used in the elderly because of delirium and other adverse effects.

20.

Adjuncts: COMT inhibitors (entacapone, tolcapone) prolong levodopa effect and are useful in older patients with motor fluctuations and/or dyskinesia; Stalevo is the fixed combination of levodopa/carbidopa (50/12.5, 100/25, 150/37.5 mg) with entacapone 200 mg for unstabilised end-of-dose fluctuation. Amantadine 200–400 mg/day lessens peak-dose dyskinesia — reduce dose in renal impairment, delirium is frequent in the old. Selegiline and rasagiline (MAO-B inhibitors) have been proposed for neuroprotection in early PD. Treatment of non-motor symptoms (Pathy's Table 53.4 — each considered only after adjusting levodopa)

Problem Best-evidence treatment Other options

Nausea, vomiting Domperidone (ECG monitoring for QT prolongation) Metoclopramide is contraindicated Depression Venlafaxine Other SSRIs, pramipexole (delirium risk — not first choice in elderly), CBT, rTMS Generalised anxiety disorder None established SSRIs, cognitive-behavioural therapy Hallucinations, delusions Clozapine; pimavanserin (5-HT2A inverse agonist) Clozapine 12.5 mg start, 5-day increments to 25–50 mg; FBC weekly × 2 months then twice monthly; stop permanently if neutrophils <1500/mm3 Dementia Rivastigmine Donepezil Apathy Rivastigmine — Mild cognitive impairment None established — Orthostatic hypotension Droxidopa Midodrine, fludrocortisone, elastic compression Insomnia Sleep hygiene Melatonin Constipation Hydration, probiotics and prebiotic fibre, macrogol Lubiprostone if resistant; psyllium; entacapone's diarrhoea can be exploited Drooling Botulinum toxin into salivary glands if severe — Urinary urgency None established Solifenacin (low brain penetration)

Erectile dysfunction Sildenafil —

Newer modalities and non-pharmacological treatment

21.

Bilateral deep brain stimulation of the subthalamic nucleus or globus pallidus interna produces sustained motor improvement, especially for levodopa-responsive symptoms, and reduces drug-induced involuntary movements. It is offered to cognitively intact patients with severe disability from refractory motor complications; severe comorbidity is a limitation. Pathy's states DBS is not currently used in elderly people with PD, but notes observational studies showing similar efficacy in patients over 70 with no age-related increase in adverse effects. Concerns remain about depression and suicide, and disability still progresses because neurodegeneration continues.

22.

Other surgical options (Essentials): thalamotomy, pallidotomy, and rarely intraputaminal fetal mesencephalic allografts.

23.

Rehabilitation should begin early to preserve motor function, with sessions timed to the peak effect of levodopa. It targets joint flexibility, walking, lifting, posture, balance and turns, and counters the flexed attitude. Speech therapy helps dysarthria, drooling and swallowing later. Combined aerobic, strengthening, balance and stretching programmes improve balance in PD.

24.

Loss of independence requires organised help at home — professional carers, caregiver involvement, meals-on-wheels. PD is not a frequent cause of institutional admission except when severe cognitive and behavioural complications occur. Psychological support and patient/caregiver education improve acceptance and optimise use of health resources.

Latest Updates (2023–Present)

Shift to a biological definition. Two research frameworks were published together in Lancet Neurology 2024 — the Neuronal α-Synuclein Disease Integrated Staging System (NSD-ISS) (Simuni et al.) and SynNeurGe (Höglinger et al.). Both anchor diagnosis in CSF α-synuclein seed amplification assay (SAA) plus dopaminergic neurodegeneration on DAT imaging; SynNeurGe adds a genetic component (S–N–G). Both encompass PD and dementia with Lewy bodies. These are explicitly research constructs, not yet for routine clinical diagnosis (JAMA Neurology viewpoint 2024; Cell Death & Disease review 2025).

New levodopa formulations. Crexont (IPX203), extended-release carbidopa/levodopa capsules, FDA-approved August 2024 for motor fluctuations. Vyalev (foslevodopa/foscarbidopa), the first 24-hour subcutaneous continuous infusion, approved October 2024 — delivers levodopa prodrugs by pump and bypasses the gut, an alternative to intestinal gel. Onapgo (subcutaneous apomorphine infusion) approved February 2025 for "off" episodes. ND0612 (subcutaneous levodopa/carbidopa) under FDA review.

New oral agent in the pipeline. Tavapadon, a selective D1/D5 partial agonist — a different mechanism from D2/D3 agonists — met endpoints in the Phase 3 TEMPO-1, -2 and -3 trials; TEMPO-3 gave an extra 1.1 hours of daily "on" time without troublesome dyskinesia. NDA submitted 26 September 2025; FDA decision expected 2026 (AbbVie; MDS Congress 2025).

Safety alert. In March 2026 the FDA required a new label warning for all carbidopa/levodopa products (Sinemet, Rytary, Stalevo, Crexont, Vyalev) regarding vitamin B6 deficiency and seizures — directly relevant to long-treated geriatric patients. Adaptive (closed-loop) DBS. FDA approved Medtronic BrainSense Adaptive DBS and the BrainSense Electrode Identifier in February 2025, based on the ADAPT-PD randomised crossover trial — the world's first commercially available aDBS. Stimulation is adjusted in real time to sensed beta-band local field potentials; the Electrode Identifier cuts initial programming time by about 85%. Disease modification remains unproven. Exenatide-PD3 (Lancet 2025; 194 patients, 96 weeks) found no benefit of weekly exenatide over placebo on motor progression, despite positive Phase 2 exenatide and lixisenatide (NEJM 2024) data. The Lancet issued an Expression of Concern on this trial in June 2026 — quote it cautiously. Pipeline (2026): prasinezumab (anti-α-synuclein antibody, Phase 3), bemdaneprocel (stem-cell, Phase 3), AB-1005 GDNF gene therapy (Phase 2, RMAT designation).

Indian data. A pan-Indian multicentre study of PD (Kishore et al., Movement Disorders 2025) found clinical features, exposures and comorbidities broadly similar to European populations, but an earlier age at onset in Indian patients, suggesting greater genetic contribution. Community prevalence in India varies widely: crude rates 7–60 per 100,000, age-adjusted 53–192 per 100,000; Kolkata age-adjusted 52.85/100,000 with rates rising to 621/100,000 above 80 years (Das et al., Neurology 2010; Khurana & Gourie-Devi, Cureus 2025). The Parsi community of Mumbai has an exceptionally high crude rate of 328/100,000 and cannot be generalised. A Bangalore old-age-home study found parkinsonism in 17.8% of residents with very poor awareness.

Current Practice Update

Aspect Textbook position (Pathy's 6th ed.) Current evidence-based practice Basis of diagnosis Clinical — Queen Square Brain Bank criteria Clinical criteria remain the practice standard, but biological research definitions (NSD-ISS, SynNeurGe) using CSF α-synuclein SAA now exist and dominate trial recruitment Dopamine agonists in the elderly "Not used in older people with PD" Still avoided as first line, but the position is nuanced — tavapadon (D1/D5 partial agonist) is designed for a better tolerability profile; low-dose rotigotine patch is used where oral routes fail Deep brain stimulation "Not currently used in elderly people with PD" Age alone is no longer a bar; outcomes in patients >70 match younger patients. Adaptive closed-loop DBS approved February 2025 Continuous dopaminergic delivery Duodenal levodopa infusion mentioned; Three device-aided options now licensed: Vyalev subcutaneous apomorphine "limited data" (SC levodopa prodrug, 24 h), Onapgo (SC apomorphine), levodopa–carbidopa intestinal gel Long-term levodopa safety Nausea, hypotension, neuropsychiatric effects, Add vitamin B6 deficiency and seizure risk (FDA fluctuations, dyskinesia labelling change, March 2026) and peripheral neuropathy with high-dose/continuous delivery Disease modification Selegiline/rasagiline "proposed for neuroprotective No agent has proven disease modification. effects" Exenatide-PD3 was negative (Lancet 2025); MAO-B neuroprotection is no longer claimed Examiner's Tip — lines that earn marks "The two pathological hallmarks are nigral neuronal loss with striatal dopamine depletion and ubiquitinated α-synuclein forming Lewy bodies."

"In the geriatric population levodopa is the main and often the only drug; dopamine agonists and anticholinergics are avoided." "Levodopa does not improve non-motor symptoms, posture or gait — every non-motor treatment is considered only after levodopa has been optimised."

Name the drug–symptom pairs verbatim: venlafaxine for depression, clozapine or pimavanserin for psychosis, rivastigmine for dementia and apathy, droxidopa for orthostatic hypotension, domperidone for nausea.

Close with one 2025 fact: "Adaptive DBS was FDA-approved in February 2025 on the ADAPT-PD trial, and age over 70 is no longer a contraindication to DBS."

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