More neuropathies

Question 1

Myasthenia gravis signs on examination

Answer 1

Inspection: thymectomy scar
Eyes: Bilateral ptosis, worse on sustained upwards gaze. Complex ophthalmoplegia.
Facial movements: myasthenia snarl on smiling (can’t lift corners of mouth).
Voice: nasal, deterioration - ask patient to count to 50.
Limbs: fatiguability - repeatedly flap arm.

Question 2

Completion of myasthenia gravis examination

Answer 2

Spirometry for respiratory muscle function

Question 3

Investigations for myasthenia gravis

Answer 3

Antibodies: Anti-nAChR, Anti-mAChR
EMG: reduced response to titanic train of impulses
Tension test: improvement with edrophonium (anticholinesterase)
TFTs: Graves in 5%
CT mediastinum: thymoma in 10%

Question 4

Conditions associated with myasthenia gravis

Answer 4

Patient <50yo, female:
AI disease - DM, RhA, Graves, SLE
Patient >50yo, male:
Thymoma

Question 5

Acute management of myasthenia gravis

Answer 5

Plasmapheresis or IVIg

Monitor FVC: consider ventilation

Question 6

Chronic management of myasthenia gravis

Answer 6

Pyridostigmine
Immunosuppression: steroids and azathioprine
Thymectomy: benefit even if no thymoma

Question 7

Pathophysiology of Lambert-Eaton myasthenia syndrome

Answer 7

Antibodies against voltage-gated calcium channels

Often paraneoplastic e.g. SCLC

Question 8

Symptoms in Lambert-Eaton myasthenia syndrome

Answer 8

Lower limb girdle weakness

Weakness improves on repetitive testing

Question 9

Investigation to differentiate LEMS from MG

Answer 9

Tensilon test (edrophonium) will improve muscle strength in MG but not in LEMS

Question 10

Differential for bilateral ptosis

Answer 10

Myasthenia gravis
Myotonic dystrophy
Congenital
Senile
Bilateral Horner's (rare)

Question 11

What is Miller-Fisher subtype of Guillan-Barre Syndrome

Answer 11

More pronounced ophthalmoplegia + ataxia + areflexia

Question 12

Pathophysiology of Guillan Barre Syndrome

Answer 12

Antibody cross-reactivity between microorganism and gangliosides (found on peripheral nerves)
There is also an axonal type: AMAN (“Chinese paralytic syndrome”)

Question 13

Common organisms causing Guillan Barre syndrome

Answer 13

Bacteria: Campylobacter jejuni, mycoplasma
Viruses: CMV, EBV

Question 14

Features of Guillan Barre syndrome

Answer 14

Symmetrical ascending flaccid paralysis
Sensory disturbance: paraesthesia
Autoimmune neuropathy: labile BP

Question 15

Investigations for Guillan Barre syndrome

Answer 15

Evidence of infection, e.g. stool MC+S
Anti-ganglioside antibodies
Lumbar puncture: very high CSF protein
Nerve conduction studies: demyelination

Question 16

Management of Guillan Barre syndrome

Answer 16

1. Supportive: “AAAA”
   ABCDE: ITU if FVC <1.5L
   Analgesia: NSAIDs, gabapentin
   Autonomic: may need inotropes, catheter
   Antithrombotic: TEDS, LMWH
2. Immunosuppression: IVIg, plasma exchange
3. Physiotherapy (prevent flexion contractors)

Question 17

Prognosis in Guillan-Barre syndrome

Answer 17

85% complete recovery
10% unable to walk unaided at 1 year
5% mortality