Neuro - Parkinson's, Trigeminal Neuralgia, MS Flashcards
Parkinson’s Disease (PD) - what is it?
Progressive reduction in amount of dopamine in the basal ganglia
Degeneration of dopaminergic neurons in the substantia nigra
Lead to disorders of movement
PD - what are the characteristic featurs?
Triad:
- Bradykinesia
- Cog-wheel rigidity
- Resting tremor (unilateral)
Characteristically asymmetrical, one side affected more than the other
PD - pathophysiology
The basal ganglia are a group of structures situated in the middle of the brain
Responsible for coordinating habitual movements such as walking or looking around, controlling voluntary movements and learning specific movement patterns
Part of the basal ganglia called the substantia nigra produces a neurotransmitter called dopamine
Dopamine is essential for the correct functioning of the basal ganglia
In Parkinson’s disease, there is a gradual but progressive fall in the production of dopamine
PD - what are the features of the characteristic resting tremor?
The tremor in Parkinsons has a frequency of 4-6 Hz, meaning it occurs 4-6 times a second
“pill rolling tremor”
More pronounced when resting and improves on voluntary movement
The tremor is worsened if the patient is distracted
PD - what are the features of the characteristic bradykinesia?
Bradykinesia describes how their movements get slower and smaller
This presents in a number of ways:
- Their handwriting gets smaller and smaller
- They can only take small steps when walking (“shuffling gait”)
- They have difficulty initiating movement
- They have difficulty in turning around when standing, having to take lots of little steps
- They have reduced facial movements and facial expressions (hypomimia)
PD - what are some other features?
- Depression
- Sleep disturbance and insomnia
- Loss of the sense of smell (anosmia)
- Postural instability
- Cognitive impairment and memory problems
PD - how to distinguish between PD and drug-induced parkinsonism?
In drug-induced parkinsonism:
- Motor symptoms are generally rapid onset and bilateral
- Rigidity and rest tremor are uncommon
PD - what are two drug examples which can cause drug-induced parkinsonism?
Metaclopramide - can cross BBB
Antipsychotics
PD - how do you distinguish between Parkinson’s tremor and Benign essential tremor?
Parkinson’s tremor - asymmetrical, worse at rest, improves with intentional movement, no change with alcohol
Benign essential tremor - symmetrical, improves at rest, worse with intentional movement, improves with alcohol
Opposite to one another
PD - what is Multiple System Atrophy?
This is a rare condition where the neurones of multiple systems in the brain degenerate
Affects basal ganglia as well as multiple other areas
Degeneration of the basal ganglia lead to a Parkinson’s presentation
Degeneration in other areas lead to autonomic dysfunction (causing postural hypotension, constipation, abnormal sweating and sexual dysfunction) and cerebellar dysfunction (causing ataxia).
PD - what is Progressive Supranuclear Palsy and what are the clinical features?
It is a ‘Parkinson Plus’ syndrome
Features
- postural instability and falls
- patients tend to have a stiff, broad-based gait
- impairment of vertical gaze (down gaze worse than up gaze - patients may complain of difficultly reading or descending stairs)
- parkinsonism
- bradykinesia is prominent
- cognitive impairment
- primarily frontal lobe dysfunction
PD - how do you diagnose?
Clinical diagnosis based on symptoms and examination
PD - 1st line management?
For first-line treatment:
if the motor symptoms are affecting the patient’s quality of life: levodopa
if the motor symptoms are not affecting the patient’s quality of life: dopamine agonist (non-ergot derived), levodopa or monoamine oxidase B (MAO‑B) inhibitor
PD - what is levodopa?
synthetic dopamine given orally to boost their own dopamine levels
PD - what is levodopa combined and taken with?
It is usually combined with a drug that stops levodopa being broken down in the body before it gets the chance to enter the brain
These are peripheral decarboxylase inhibitors - examples are carbidopa and benserazide.
Combination drugs are:
- Co-benyldopa (levodopa and benserazide)
- Co-careldopa (levodopa and carbidopa)
PD - what is the main side effect when the dose is too high, and there is too much dopamine?
Main side effect of dopamine is when the dose is too high patients develop dyskinesias
Abnormal movements associated with excessive motor activity
Examples are:
- Dystonia: This is where excessive muscle contraction leads to abnormal postures or exaggerated movements.
-
Chorea: These are abnormal involuntary movements that can be jerking and random.
- Athetosis: These are involuntary twisting or writhing movements usually in the fingers, hands or feet
PD - what are COMT inhibitors, how do they work, and what is the main example?
Entacapone
Inhibitors of catechol-o-methyltransferase (COMT)
The COMT enzyme metabolises levodopa in both the body and brain
Entacapone is taken with levodopa (and a decarboxylase inhibitor) to slow breakdown of the levodopa in the brain - it extends effective duration of the levodopa
PD - what are examples of dopamine agonists, how do they work and what is their main side effect?
These mimic dopamine in the basal ganglia and stimulate the dopamine receptors
Used to delay the use of levodopa and are then used in combination with levodopa to reduce the dose of levodopa that is required to control symptoms
SE - with prolonged use, pulmonary fibrosis
- Bromocryptine
- Pergolide
- Carbergoline
PD - what are MOA-B inhibitors, how do they work, and what are some examples?
Monoamine oxidase enzymes break down neurotransmitters such as dopamine, serotonin and adrenaline
The monoamine oxidase-B enzyme is more specific to dopamine and does not act on serotonin or adrenalin
These medications block this enzyme and therefore help increase the circulating dopamine
Similarly to dopamine agonists, they are usually used to delay the use of levodopa and then in combination with levodopa to reduce the required dose
- Selegiline
- Rasagiline
Trigeminal Neuralgia (TN) - what is it?
Trigeminal neuralgia is a pain syndrome characterised by severe unilateral pain
The vast majority of cases are idiopathic but compression of the trigeminal roots by tumours or vascular problems may occur
TN - what is the presentation of the pain?
Unilateral disorder characterised by brief electric shock-like pains, abrupt in onset and termination, limited to one or more divisions of the trigeminal nerve
TN - how is the pain evoked?
The pain is commonly evoked by light touch, including washing, shaving, smoking, talking, and brushing the teeth (trigger factors), and frequently occurs spontaneously
TN - what are red flag symptoms?
- Age of onset before 40 years
- Sensory changes
- Deafness or other ear problems
- History of skin or oral lesions that could spread perineurally
- Pain only in the ophthalmic division of the trigeminal nerve (eye socket, forehead, and nose), or bilaterally
- Optic neuritis
- A family history of multiple sclerosis
TN - management?
1st line - Carbamazepine
Failure to respond to treatment or atypical features (e.g. < 50 years old) should prompt referral to neurology
