Motor deficits: Part 1 (Bell's palsy, Myasthenia gravis, GBS, Inflammatory myopathies/myositis) Flashcards
What is Bell’s palsy? What is characterised by? When is the peak incidence?
Refers to an idiopathic syndrome that causes damage to the facial nerve.
Characterised by unilateral, lower motor neuron facial weakness.
Peak incidence age 15-45 years.
Causes of Bell’s palsy?
Cause unknown.
HSV-1 (herpes simplex virus type 1)
EBV (Epstein-Barr virus)
VZV (varicella-zoster virus)
Presentation of Bell’s palsy?
Acute onset
Unilateral lower motor neuron facial weakness
Mild to moderate postauricular otalgia (may lead to PARALYSIS)
Hyperacusis (reduced tolerance for sound -loud sounds may be uncomfortable)
Altered tast and dry eyes/mouth
Numbness or heaviness
Facial tingling
How is Bell’s palsy diagnosed? Possible investigations?
Clinical diagnosis
FBC
ESR or CRP
Viral serology (HSV-1, EBV, VZV)
Otoscopy
EMG (electromyography)
Imaging studies (MRI, CT)
Management of Bell’s palsy?
Steroids (oral prednisolone) + Aciclovir
Eye patch
Artificial tears
Pain control (analgesia)
Psychological support
Physical therapy, including facial exercises and massage (maintain muscle tone and prevent contractures)
What is myasthenia gravis?
Refers to an autoimmune disease characterised by the production of antibodies against the nicotinic acetylcholine receptors on muscle fibres, leading to muscle weakness.
Presentation of myasthenia gravis?
Facial weakness
Weakness in proximal arm muscles (limb muscle weakness)
Ptosis
Drooping eyelids
Diplopia
Muscle fatigue with repetition of movements
Difficulty in smiling or chewing
Change in speech
Dysphagia
Myasthenic snarl
Head droop
Symptoms typically worsen with prolonged movement or by the end of the day.
What drugs can exacerbate myasthenia gravis?
Beta blockers
Lithium
Penicillamine
Gentamicin
Quinolones
Phenytoin
Management of myasthenia gravis?
Mestinon, pyridostigmine or neostigmine (acetylcholinesterase inhibitor)
Immunosuppressive meds (e.g. azathioprine, methotrexate, mycophenolate, mofetil)
Prednisone
Acute case:
Plasmaphresis
IV immunoglobin (IV IG)
Thymectomy (removal of thymus gland)
Multi-disciplinary approach
How is myasthenia gravis diagnosed?
Blood tests:
- Test for serum acetylcholine receptor antibody
- Test for muscle-specific tyrosine kinase antibodies
EMG
- Repetitive nerve stimulation testing
CT chest
What is Guillain Barré Syndrome (GBS)?
Refers to an acute ascending inflammatory demyelinating polyneuropathy.
Characterised by a rapid, progressive onset of bilateral and roughly symmetric limb weakness.
Causes of Guillain Barré Syndrome (GBS)?
GBS typically occurs 1-3 weeks following an infection.
Common:
Campylobacter
Mycoplasma
EBV
Other:
CMV
HIV
Hepatitis A
Vaccinations (for tetanus, rabies, or swine flu)
Presentation of Guillain Barré Syndrome (GBS)?
Progressive ascending symmetrical limb weakness
Lower back pain due to radiculopathy
Paraesthesia
Potential respiratory muscle involvement in severe cases
Cranial nerve involvement:
- diplopia
- facial droop
- ophthalmoplegia
- facial nerve palsy
- bulbar palsy
Lower motor neurone signs in the lower limbs:
- hypotonia
- flaccid paralysis
- areflexia (absent reflexes)
Questions to ask when considering Guillain Barré Syndrome (GBS)?
- When did your symptoms start?
- Have the symptoms changed? (would
expect progression of symptoms in GBS) - Did you have a recent illness?
- Can you still walk?
- Can you breathe ok?
- Any tingling or other abnormal sensations?
IVx for Guillain Barré Syndrome (GBS)?
FVC (for resp muscle involvement)
Cardiac monitoring (autonomic instability)
Blood tests
ABG
Anti-ganglioside antibodies
Lumbar puncture (albuminocytological dissociation)
Nerve conduction studies
Identification of the underlying cause:
- stool cultures
- serology
- CSF virology
