Nerve and muscle disease

Question 1

McArdle’s disease

1) mode of inheritance?
2) underlying cause?
3) usually presents when in life?
4) presentation?
5) __ __ levels are elevated in most cases
6) lifestyle advice?

Answer 1

1) AR
2) myophosphrylase deficiency > impaired glucose release from glycogen in the muscles
3) first decade of life
4) muscle pain soon after commencing exercise (can be severe and cramping). Often a 2nd wind phenomenon where pt may resume exercise again after a period of rest
5) CK
6) avoid vigorous exercise, stop in the presence of pain (increased risk of rhabdomyolysis with myoglobinuria and subsequent AKI)

Question 2

what is myotonic dystrophy?

Answer 2

multisystem progressive disease characterised by delayed muscular relaxation and muscle wasting
(just think of name: MYO-muscle TONIC-increased tone DYSTOPHY-wasting)

Question 3

genetic cause of myotonic dystrophy?

Answer 3

tri-nucleotide repeat on Cr19

Question 4

clinical features of myotonic dystrophy?

Answer 4

SCM and distal limb muscles affect 1st > grip myotonia and =foot drop
facial weakness > haggard appearance
ptosis, ophthalmoplegia and bilateral ‘christmas tree’ cataracts
hallowing of temples (temporalis muscle wasting) and atrophy of jaw muscles
early frontal balding

Question 5

what is Lambert-Eaton myasthenic syndrome

Answer 5

neuromuscular junction disorder caused by impaired release of Ach from the presynaptic terminal

Question 6

what causes Lambert-Eaton myasthenic syndrome?

Answer 6

malignancy (SCLC) or autoimmune disease > autoimmune attack against P/Q-type voltage gated Ca channels

Question 7

clinical features of Lambert-Eaton myasthenic syndrome?

Answer 7

insidious onset proximal muscle weakness. Mainly lower limbs > waddling gait
Autonomic features > constipation, postural hypotension, impotence, dry mouth
Deep tendon reflexes diminished/ absent

Question 8

How is Lambert-Eaton myasthenic syndrome diagnosed?

Answer 8

anti-VGCC antibodies
characteristic electrophysiological findings using a 20-50Hz repetitive stimulation
CT to rule out malignancy

Question 9

treatment of Lambert-Eaton myasthenic syndrome?

Answer 9

Mainly 3,4-diaminopyridine (amifampridine)

More severe cases: immunosuppression or IV immunoglobulins

Question 10

what is Myasthenia gravis?

Answer 10

autoimmune disease of post-synaptic nicotinic ACh receptors at the NMJ.

Question 11

Myasthenia gravis

1) sex distribution
2) typical age

Answer 11

1) F>M

2) 20-30

Question 12

clinical features of myasthenia gravis?

Answer 12

muscle fatiguability: occurs readily after exercise/ at end of day, improves on rest
ocular features most commonly appear first: b/l, asymmetric ptosis and extraocular weakness> diplopia
proximal > distal muscle weakness
jaw and facial muscles, speech, swallow and resp muscles also affected

Question 13

thymid hyperplasia, thyoma, hyperthyroidism and SLE are quite common associations with which neuromuscular disease?

Answer 13

myasthenia gravis

Question 14

myasthenia crisis

1) precipitating factors?
2) best method to monitor for this?
3) treatment?

Answer 14

1) bronchopneumonia, medications, surgery
2) monitor tidal volume and vital capacity
3) urgent intubation and ventilation when vital capacity <15. Treatment: plasmapheresis, IV IGs and systemic steroids

Question 15

Cholinergic crisis

1) is a potential complication of __ __
2) is common in patients receiving high dose ___ medication
3) symptoms include …

Answer 15

1) myasthenia gravis
2) anticholinesterase
3) SLUDGE syndrome”: Salivation, Lacrimation, Urination, Defecation, Gastrointestinal distress and Emesis

Question 16

thymic hyperplasia, thyoma, hyperthyroidism and SLE are quite common associations with which neuromuscular disease?

Answer 16

myasthenia gravis

Question 17

list some drugs which can induce or exacerbate myasthenia?

Answer 17

Gentamicin, beta blockers, verapamil, lithium, penicillamine, phenytoin and chloroquine.

Question 18

Ix in myasthenia?

Answer 18

anti-AChR Abs (check
for anti-MuSK if negative).
Repetitive nerve stimulation tests: decremented muscle response.
TFTs
CT thymus.

Question 19

management of myasthenia gravis?

Answer 19

symptomatic control: acetylcholinesterase inhibitors e.g. Pyridostigmine
to improve weakness and establish remission: immunosuppression e.g. corticosteroids, azathioprine
Thymectomy

Question 20

CMT1

1) age of onset?
2) presentation?
3) diagnosis?

Answer 20

1) first decade
2)
3)

Question 21

most common form of charcot-marie-tooth disease? how is it inherited?

Answer 21

CMT1

autosomal dominant

Question 22

histopathological features of CMT1?

Answer 22

schwann cells proliferate and form concentric arrays of remyelination around the demyelinated axon > onion bulb appearance

Question 23

CMT1

1) age of onset?
2) presentation?
3) diagnosis?

Answer 23

1) first 2 decades
2) motor symptoms in the lower limbs e.g. difficulty walking, foot deformity (pes cavus, hammer toes). Distal muscles are affected, more commonly in lower limbs > inverted champagne bottle appearance. Sensory loss in same pattern. Hyporeflexia and thoracic scoliosis common.
3) clinically _ genetic testing + electrophysiological nerve conduction studies (reduce nerve motor conduction velocity in media or ulnar nerves)

Question 24

guillain-barre syndrome

1) what is it?
2) most patients have a preceding history of what?
3) presentation?
4) progression normally stops __ weeks from its onset

Answer 24

1) acute autoimmune disorder causing demyelination and axonal injury
2) infection with campylobacter (most common), EBV, CMV or HIV.
3) symmetrical scending sensorimotor paralysis with areflexia starting in lower limb
4) 4

Question 25

how is guillain-barre syndrome diagnosed?

Answer 25

usually clinical

LP (high CSF protein) and nerve conduction studies (patchy proximal and distal demyelination) sometimes useful

Question 26

treatment of guillain-barre syndrome?

Answer 26

plasma exchange or IV IGs

Question 27

what is chronic inflammatory demyelinating polyradiculoneuropathy? (CIDP)

Answer 27

acquired, demyelinating PNS disease: progressive or relapsing proximal and distal weakness with
hyporeflexia/areflexia and a distal sensory loss (paraesthesia and numbness).
Tremor also common

Question 28

CIDP

1) diagnosis
2) treatment

Answer 28

1) clinical, supported by electrophysiological nerve conduction studies and CSF (high protein)
2) oral steroids, IV IGs

Question 29

what is spinal muscular atrophy (Werdnig-Hoffmann disease)

Answer 29

AR neuromuscular disorder: congenital degeneration of anterior horns of spinal cord (LMN lesion) > progressive muscular wasting (often early death)
Sever form: “Floppy baby syndrome” in 1st month of life - marked hypotonia and
tongue fasciculations.

Think of name:

• SPINAL (anterior horn)
• MUSCULAR ATROPHY (muscle wasting)

Question 30

Poliomyelitis

1) causative pathogen?
2) infection causes destructions of cells where?
3) signs and symptoms?

Answer 30

1) poliovirus (faecal-oral transmission)
2) destruction of cell in the anterior horn of the spinal cord (LMN death)
3) LMN signs: weakness, hypotonia, flaccid paralysis, fasciculations, hyporeflexia, muscle atrophy