Neuromuscular Disorders Flashcards
What is GBS (Guillain-Barré Syndrome)?
An acute paralytic polyneuropathy that affects the peripheral nervous system. It causes acute, symmetrical, ascending weakness and can also cause sensory symptoms. It is usually triggered by an infection
What organisms cause GBS?
Campylobacter jejuni
Cytomegalovirus (CMV)
Epstein-Barr virus (EBV)
Sx of GBS?
Sx usually start within 4 wks of triggering infx:
* Symmetrical ascending weakness (starting w/lower limbs)
* Reduced reflexes
* Lower back pain
* Paraesthesia
* Cranial nerve involvement and facial weakness (diplopia and facial droop)
Recovery can take months to years.
Ix for GBS
Clinically: Brighton criteria
Other Ix:
* Nerve conduction studies - reduced nerve signal
* Lumbar puncture for CSF - raised proteins
Mx of GBS?
Supportive care
VTE prophylaxis (as PE is leading cause of death)
1st line: IV immunoglobulins (IVIG)
Plasmapheresis (IVIG alternative)
What is bulbar palsy?
Subtype of LMN lesion impacting 9th (glossopharyngeal), 10th (vagus) and 12th (hypoglossal) CN.
The resultant impairments primarily involve mechanisms of speech (dysarthria) and swallowing (dysphagia).
Causes of bulbar palsy
- MND - Progressive bulbar palsy
- Myasthenia gravis
- GBS
- Brainstem stroke
Sx of bulbar palsy
Absent or normal jaw jerk reflex
Absent gag reflex
Flaccid, fasciculating tongue
Nasal speech, often described as “quiet”
Ix for bulbar palsy
Neuro examination - asses CN
Electromyography (EMG) + nerve conduction studies
Bloods
Mx of bulbar palsy?
Speech + swallowing therapy - manage dysarthria + dysphagia
Nutrition support
Tx of underlying cdtn
What is muscular dystrophy? What are two different types of this disease?
A group of inherited genetic disorders characterised by progressive degeneration and weakening of body’s muscles.
Two Types:
1. Duchenne muscular dystrophy (DMD)
2. Becker muscular dystrophy
What kind of genetic inheritence are muscular dystrophies?
X-linked recessive disorders, males are predominantly affected while females are usually carriers
Sx in Duchenne’s muscular dystrohpy compared to Becker’s MD?
Duchenne:
* Early childhood
* Muscle wasting + weakness
* Children usually wheelchair bound before puberty and have resp failure by early twenties
* Hypertrophic calves (degenerated muscle replaced by fat)
* +ve Gower’s manoeuvre
* Difficulty lifting the child due to proximal muscle weakness
Becker’s:
* Later in childhood
* Muscle wasting + weakness
* Become wheelchair bound in teens and can survive into thirties
Ix for Duchenne’s and Becker’s dystrophy?
GS - genetic testing
1st line - Creatine kinase
Mx of muscular dystrophies?
- Glucocorticoids - slow muscle degeneration
- Physio - maintain mobility
- Genetic counselling for affected family members
What are the main causes of mortality for muscular dystrophies like Duchenne’s?
Resp complications and dilated cardiomyopathy.
What is myasthenia gravis?
Autoimmune disease marked by production of antibodies that target nicotinic acetylcholine receptors on muscle fibres. This reduces ability of acetylcholine to trigger muscle contraction resulting in muscle weakness.
What are the drugs that can exacerbate Myasthenia Gravis?
Beta blockers
Lithium
Penicillamine
Gentamicin
Quinolones
Phenytoin
Sx of Myasthenia Gravis?
- Limb muscle weakness
- Drooping eyelids or diplopia
- Difficulty smiling or chewing
- Change in speech or difficulty swallowing
- Myasthenic snarl
- Head droop
- Fatigable muscle weakness
Sx worsen w/prolonged movement or by end of the day
Ix for myasthenia gravis?
Bloods - serum acetylcholine receptor antibody and muscle-specific tyrosine kinase antibodies
CT chest - thymoma (identify thymic hyperplasia)
EMG or nerve conduction studies
In myasthenic crisis - Spirometry
Tx of Myasthenia Gravis?
- Acute cases - intravenous immunoglobulin (IVIG) or plasmapheresis in severe
- Immunosuppressive therapy (steroids)
- Anticholinesterase inhibitor (pyridostigmine or neostigmine)
If pts have thmic hyperplasia or thymoma - thymectomy
