Nerve and Muscle Disease Flashcards
McArdle’s disease is autosomal recessive - T/F?
TRUE
pathophysiology behind McArdle’s disease
myophosphorylase deficiency leading to impaired glucose release from glycogen in the muscles
how does McArdle’s disease present?
1st decade of life
pt presents with muscle pain shortly after they exercise
CK is decrease in McArdle’s disease - T/F?
FALSE
why must pt stop vigorous exercising when they get pains?
it could lead to rhabdomyolysis + myoglobinuria = AKI
What is myotonic dystrophy?
Multisystem progressive disease with delayed muscular relaxation and muscle wasting
What is the inheritance of myotonic dystrophy?
Autosomal dominant
Tri nucleotide repeat on chromosome 19
Clinical features of myotonic dystrophy
Sternocleidomastoid muscle + Distal limb affected 1st
Proximal limb affected later
Facial weakness (‘haggard’’ appearance
Ptosis, ophthalmoplegia & bilateral Christmas tree-like cataracts
Hollowing of temples due to temporalis muscle wasting & atrophy of jaws
Early frontal balding
Lambert-Eaton myasthenic syndrome pathophysiology
Impaired release of acetylcholine by the pre-synaptic terminal
what voltage gated channels does Lambert-Eaton syndrome affect?
Ca2+
what malignancy is lambert-eaton syndrome associated with?
Small cell lung cancer
clinical features of lambert-eaton syndrome
insidious onset of weakness of PROXIMAL muscles
Autonomic features - constipation, postural hypotension, dry mouth
Deep tendon reflexes diminished
the upper extremities are most affected in L-E syndrome - T/F?
FASLE.
Lower extremities are predominantly affected - this causes a waddling gait
Ix L-E syndrome
presence of anti -VGCC antibodies
repetitive electrical stimulation at 20-50Hz
CT scan to rule out malignancy (SCC)
Tx L-E syndrome
MOA of drug
Amifampridine
Blocks pre-synaptic Ca2+ channels & increases quantity of ACh released
If L-E is very severe, what medication may be used?
Immunosuppression or IV immunoglobulins
What is myasthenia gravis (MG) ?
autoimmune disease affecting post-synaptic nicotinic acetylcholine receptors
who does MG affect?
F>M
10-30 y/o
clinical features of MG?
muscle fatigability occurring quickly after exercise or end of day. improves with rest
ocular features can be presenting complaint - bilateral asymmetrical ptosis & extraocular weakness causing diplopia
Proximal muscle weakness > Distal
one complication of MG is Myasthenia crisis - what is this?
weakness of respiratory muscles causing ventilator failure
bronchopneurmonia - medications can precipitate this
how to monitor the respiratory complications of MG?
measure vital cap & tidal volume
at what stage do you need an intervention for the respiratory complications of MG?
when vital capacity falls below 15mL/kg
what tx do you give to pt when their vital capacity falls below 15mL/kg
plasmapheresis
IV immunoglobulins
systemic steroids
what is cholinergic crisis
too much anticholinesterase given
symptoms = sweating, hypersalivation, bronchial hypersecretions & miosis - can lead to resp failure
what conditions are associated with myasthenia gravis?
thymic hyperplasia
thyoma
hyperthyroidism
SLE
drugs that can induce MG
gentamicin b-blockers verapamil lithium penicillamine phenytoin chloroquine
Ix MG
antibody test - IgG against ACh receptor (anti-AChR)
NOTE - in some pt this is -ve so they should be checked for anti-MuSK antibodies
Repetitive nerve stimulation
Thyroid function test
CT thymus
Mx of MG
symptomatic control - acetylcholinesterase inhibition using pyridostigmine
Immunosuppression with corticosteroid & azathioprine to improve myasthenic weakness
Thymectomy if thyoma is present
Is Charcot Marie tooth (type 1) autosomal dominant - T/F?
TRUE
What is Charcot Marie Tooth Disease (CMT)
A group of diseases affecting the peripheral nerves
Histopathology of Charcot Marie Tooth Disease
Schwann cells proliferate and form concentric arrays of remyelination around the demyelinated axon resulting in ‘onion bulb’ appearance
When does CMT present
1st or 2nd decade of life
Clinical features of CMT
Motor symptoms affecting distal muscles - ‘inverted champagne bottle’ appearance
Sensory loss follows same pattern
Hyporeflexia
Thoracic scoliosis
Diagnosis of CMT
Genetic testing
Electrophysiological nerve conduction study (low conduction rate <38 m/s)
What is Guillian-Barre Syndrome
Acute neuromuscular weakness causing demyelination and axonal injury
What often precedes GB syndrome?
Campylobacter
also EBV, CMV, HIV
Presentation of GB Syndrome?
Symmetrical progressive ascending sensorimotor paralysis
Areflexia in lower limbs
Usually stops progressing after 4 weeks from its onset
Diagnosis of GB syndrome
Clinical
Lumbar puncture - high protein
Nerve conduction studies
Mx of GB syndrome
Plasma exchange of IV immunoglobulins
What is chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)?
Acquired demyelinating peripheral nervous system disease
Progressive proximal & distal weakness with hyporeflexia
Distal sensory loss (numbness)
Tremor
Diagnosis of CIDP
Clinical
Nerve conduction studies
CSF - high protein
Treatment of CIDP
Oral steroids or IV Immunoglobulins
What is spinal muscular atrophy
congenital degeneration of anterior horns of spinal cord (LMN lesion)
leads to progressive muscular wasting & early death
‘floppy baby syndrome’ - hypotonia and tongue fasciculations
is spinal muscular atrophy X-linked recessive?
NO - it is autosomal recessive
what is poliomyelitis?
caused by polio virus
infections causes destruction of cells in anterior horn of spinal cord (LMN death)
how is the polio virus transmitted?
faecal-oral transmission
symptoms of poliomyelitis
LMN signs basically: weakness hypotonia flaccid paralysis fasciculations hyporeflexia muscle atrophy
