Neurology Flashcards
(100 cards)
Define Parkinson’s disease
Degenerative movement disorder caused by a reduction of dopamine in the substantia nigra in the basal ganglia.
What is the epidemiology of Parkinson’s?
- Increasing prevalence with age
- Peak onset is 55-65 years
- More common in males
- Higher prevalence in West
Name some potential causes of Parkinson’s disease
- Idiopathic
- Drug induced - reversible cause of parkinsonism; Dopamine antagonists, CCB, atypical neuroleptics
- Environmental factors - pesticides, herbicides, heavy metals
- Parkinson genes - Parkin gene, alpha-synuclein gene mutation
What are the risk factors of Parkinson’s disease?
Male
Increasing age (median age is 60)
Family history
Higher risk in non-smokers
What is the pathophysiology of Parkinson’s?
Progressive degeneration of dopaminergic neurones in the substantia nigra in the midbrain that project to the striatum of the basal ganglia. This leads to reduced dopamine levels which means the thalamus will be inhibited, causing decrease in movement.
Describe the direct and indirect pathway of the basal ganglia?
How are the direct and indirect pathways of the basal ganglia affected in Parkinson’s
Direct Pathway: Reduced dopamine leads to less activation of the direct pathway (via D1 receptors). This decreases movement-promoting signals.
Indirect Pathway: Reduced dopamine leads to overactivity of the indirect pathway (via D2 receptors), increasing inhibitory signals that reduce movement.
Overall Effect: Increased inhibition of the thalamus results in less cortical stimulation, leading to the bradykinesia and rigidity characteristic of Parkinson’s disease.
How is gait affected in Parkinson’s?
Reduced asymmetrical arm swing
Narrow gait
Small steps and stooped posture
Shuffling steps, drags feet
What are the motor symptoms of Parkinson’s?
Unilateral tremor
Rigidity
Bradykinesia
What are the non-motor symptoms of Parkinson’s?
Falls, dizziness, orthostatic hypotension
Sleep/fatigue
Mood/cognition - high and lows, depression, anxiety
Vision disturbance/hallucinations
Constipation/swallowing difficulty
Urinary urgency
Sexual function - ED/high sex drive
Anosmia/excessive sweating
How is Parkinson’s diagnosed?
- Clinically based on history and exam
- May be confirmed in response to Levodopa
- MRI head: Initially normal but will show atrophy
What is the gold standard treatment for Parkinson’s? What are the side effects?
Oral Levodopa - usually combined with a peripheral decarboxylase inhibitor (prevents breakdown of dopamine in the body before it reaches the brain)
e.g co-careldopa or co-beneldopa.
Side effects - Dyskinesias when dose is too high; dystonia (excessive muscle contraction), chorea (involuntary movements), athetosis (writhing hand movements)
Name other potential drug treatments for Parkinson’s?
COMT inhibitor - Inhibits Catechol-O-methyltransferase which breaks down dopamine e.g oral Entacapone or Tolcapone.
Monoamine Oxidase B inhibitor - Inhibit MAO-B enzymes which breaks down dopamine. e.g Oral Selegiline or Rasagiline
Dopamine agonists - Used to delay starting L-dopa in early stages
Side effects - Long term use may cause pulmonary fibrosis
What are the non-drug treatments for Parkinson’s?
Deep Brain Stimulation - works best in patients who have on/off fluctuations of drug treatment effectiveness
Surgical ablation - of overactive basal ganglia structures
What are the Parkinson plus syndromes?
Multiple system atrophy
Progressive supranuclear palsy
Corticobasal degeneration
Lewy-body dementia
Define Parkinson plus syndrome
Group of neurodegenerative movement disorders that have a similar presentation to Parkinson’s. However they have a limited response to levodopa and a poor prognosis.
How does an essential tremor differ from a parkinsonian tremor?
Bilateral fine tremor
5-8 cycles per second
Improves at rest, worse on intentional movement
Improves with alcohol
No other features of Parkinson’s
What are the differentials for an essential tremor?
Parkinson’s - most important to rule out
Hyperthyroidism
MS
Huntington’s
Iatrogenic - e.g salbutamol
How is essential tremor treated?
Propanolol - non selective BB
Primidone - Barbituate used in epilepsy, dose increased slowly to reduced SE (drowsiness, ataxia, nausea - all common SEs)
Describe Multiple System Atrophy and its pathophysiology
Rare condition where neurones in multiple areas of the brain degenerate, including the basal ganglia (leading to parkisonian features). Also leads to autonomic and cerebellar dysfunction. Caused by the spread of alpha synuclein and inclusions of tau and ubiquitin proteins.
How does Multiple System Atrophy present? How does it differ from Parkinsons?
Two types, MSA-P which has predominantly parkinsonian features or MSA-C which has predominantly features of cerebellar ataxia. May change through disease course.
Dysautonomia - ED (usually presents 6-8 months before motor symptoms, unlike parkinsons), constipation, urinary frequency, incontinence, abnormal sweating and late onset orthostatic hypotension.
Cognitive function is well maintained
How does corticobasal degeneration affect the brain?
Tau astrocytic plaque and inclusions in the glia (non-nerve cells), leading to severe gliosis (proliferation of glial cells in response to injury causing scarring) and nerve loss. Involving parts of cerebrum and basal ganglia.
How does corticobasal degeneration present?
Asymmetric movement disorder:
Extreme rigidity, muscle jerking, dystonia, alien limb.
Cognitive impairment:
Aphasia
Executive dysfunction
Visuospatial deficits
Behavioural change
How does PSP affect the brain?
Neurofibrillary tangle of tau proteins form (different to Alzheimers) in various structures including basal ganglia, oculomotor nucleus, cerebral cortex.