Nerve and Muscle Disease Neuro Revision

Question 1

what is mcardle’s disease?

Answer 1

AR disease caused by myophosphorylase deficiency

leads to impaired glucose release from glycogen in the muscles

Question 2

how does mcardle’s disease present?

Answer 2

usually presents in first decade in life
muscle pain soon after starting exercise (can be severe and cramping causing patient to stop)
second wind phenomenon is common (following a short period of rest the patient can continue exercise)

Question 3

how is CK affected in mcardle’s disease?

Answer 3

elevated

Question 4

advice in mcardle’s disease and why?

Answer 4

avoid vigorous exercise
stop exercise in presence of pain
may increase risk of rhabdomyolysis and myoglobinuria and subsequent AKI

Question 5

what is myotonic dystrophy?

Answer 5

multisystem, progressive disease characterised by delayed muscular relaxation and muscle wasting

Question 6

what causes myotonic dystrophy?

Answer 6

AD inheritance of a tri-nucleotide repeat on chromosome 19

Question 7

clinical features of myotonic dystrophy?

Answer 7

grip myotonia and foot drop
facial weakness (haggard appearance)
ptosis, ophthalmoplegia and bilateral christmas tree like cataracts
hollowing of the temples due to temporalis muscle wasting and atrophy of jaw muscles
early frontal balding

Question 8

what muscles are affected first in myotonic dystrophy?

Answer 8

sternocleidomastoid and distal limb muscles first

proximal limb muscles are affected later in course of disease

Question 9

what is lambert eaton myasthenic syndrome (LEMS)?

Answer 9

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

Question 10

what causes LEMS?

Answer 10

associated with malignancy (small cell lung cancer) or autoimmune disease resulting in an autoimmune attack against the P/Q-type Ca2+ voltage gated channels

Question 11

clinical features of LEMS?

Answer 11

insidious onset of weakness of proximal muscles (mainly lower limbs causing waddling gait)
autonomic features (constipation, postural hypotension, impotence and dry mouth)
deep tendon reflexes are diminished or absent

Question 12

investigations in LEMS?

Answer 12

diagnosis established by presence of anti-VGCC antibodies and characteristic electrophysiological findings using repetitive stimulation
CT scan used to rule out malignancy

Question 13

how is LEMS managed?

Answer 13

3,4 - diaminopyridine (amifampridine) mainly used
- blocks pre-synaptic ca2+ channels to increase amount of ACh released
immunosuppression or IV Ig can be used in more severe causes

Question 14

what is MG?

Answer 14

myasthenia gravis

autoimmune disease affecting the post-synaptic nicotinic ACh receptors at the NMJ

Question 15

who is MG most commonly seen in?

Answer 15

women

2nd or 3rd decade

Question 16

clinical features of MG?

Answer 16

muscle fatigability that occurs readily after exercise or at the end of the day and improves on rest
ocular features most commonly appear first
proximal muscle weakness more marked than distal
jaw, facial muscles, speech and/or swallow and resp muscles also affected

Question 17

what ocular features are seen in MG?

Answer 17

bilateral, asymmetrical ptosis and extra-ocular weakness causing diplopia

Question 18

what is a myasthenic crisis?

Answer 18

complication of MG where weakness of the muscles of repiration causes ventilator failure

Question 19

what can precipitate myasthenic crisis?

Answer 19

bronchopneumonia
medications (gentamicin)
surgery

Question 20

management of myasthenic crisis?

Answer 20

monitor via vital capacity and tidal volume
plasmapheresis
IV Ig
systemic steroids
urgent tracheal intubation and ventilation if vital capacity falls <15

Question 21

what is a cholinergic crisis?

Answer 21

complication of MG causing sweating, hypersalivation, bronchial hypersecretions and miosis which can lead to resp failure

Question 22

cholinergic crisis is common in which MG patients?

Answer 22

those receiving high doses of anticholinesterases

Question 23

what is MG associated with?

Answer 23

thymic hyperplasia
thymoma
hyperthyroidism
SLE

Question 24

what drugs can exacerbate MG?

Answer 24

gentamicin
beta blockers
verapamil
lithium
penicillamine 
phenytoin
chloroquine

Question 25

how is MG investigated?

Answer 25

antibody testing (IgG antibodies against ACh receptor)
- some MG patients can be negative so should be tested for anti-MuSK antibodies
repetitive nerve stimulation tests showing decreased muscle response
thyroid function tests
CT of thymus

Question 26

how is MG managed?

Answer 26

symptomatic control = acetylcholinesterase inhibition (pyridostigmine)
usually combined with immunosuppressive agents (corticosteroids and azathioprine)
thymectomy can also be performed

Question 27

what is charcot marie tooth disease?

Answer 27

refers to a group of hereditary neuropathies which can be inherited as either AD (most common), AR or X linked
most common type = CMT1 (AD)

Question 28

histopathology of charcot marie tooth CMT1?

Answer 28

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

Question 29

features of charcot marie tooth CMT1?

Answer 29

onset usually in first 2 decades of life
motor symptoms in lower limbs (difficulty walking or foot deformity such as pes cavus or hammer toes)
distal muscles more affected especially in lower limb (champagne legs etc)
sensory loss follows same pattern as muscle weakness
hyporeflexia
thoracic scoliosis

Question 30

how is charcot marie tooth CMT1 diagnosed?

Answer 30

clinically
genetic testing
electrophysical nerve conduction studies show low conduction velocity <38 m/s

Question 31

what is guillian barre syndrome?

Answer 31

acute neuromuscular weakness causing demyelination and axonal injury
majority of patients have history of preceeding illness or infection (campylobacter, EBV, CMV, HIV)

Question 32

features of guillian barre syndrome?

Answer 32

patients present with a symmetrical progressive ascending sensorimotor paralysis with areflexia starting in the lower limbs and usually stops progressing after 4 weeks from onset

Question 33

how is guillian barre syndrome diagnosed?

Answer 33

usually clinical
lumbar puncture (shows high CSF protein)
nerve conduction studies (patchy proximal and distal demyelination)

Question 34

management of guillian barre syndrome?

Answer 34

plasma exchange

IV Ig

Question 35

what is chronic inflammatory demyelinating polyradiculoneuropathy?

Answer 35

acquired demyelinating peripheral nervous system disease characterised by progressive or relapsing proximal and distal weakness with hyporeflexia and a distal sensory loss (paraesthesia and numbness)
tremor is common

Question 36

diagnosis of CIDP?

Answer 36

clinical

supported by electrophysical nerve conduction studies and CSF analysis (shows high protein)

Question 37

management of CIDP?

Answer 37

oral steroids

IV Ig

Question 38

what is spinal muscular atrophy?

Answer 38

AR neuromuscular disorder characterised by congenital degeneration of anterior horns of spinal cord (LMN lesion) leading to progressive muscular wasting often leading to early death

Question 39

features of spinal muscular atrophy?

Answer 39

often manifests in first month of life causing floppy baby syndrome with marked hypotonia and tongue fasciculations

Question 40

what is poliomyelitis?

Answer 40

infection with polio virus (faeco-oral transmission) causes destruction of cells in anterior horn of spinal cord

Question 41

signs and symptoms of poliomyelitis?

Answer 41

those of LMN disease
weakness
hypotonia
flaccid paralysis
fasciculations
hyporeflexia
muscle atrophy