Nerve and Muscle Disease Neuro Revision Flashcards
what is mcardle’s disease?
AR disease caused by myophosphorylase deficiency
leads to impaired glucose release from glycogen in the muscles
how does mcardle’s disease present?
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)
how is CK affected in mcardle’s disease?
elevated
advice in mcardle’s disease and why?
avoid vigorous exercise
stop exercise in presence of pain
may increase risk of rhabdomyolysis and myoglobinuria and subsequent AKI
what is myotonic dystrophy?
multisystem, progressive disease characterised by delayed muscular relaxation and muscle wasting
what causes myotonic dystrophy?
AD inheritance of a tri-nucleotide repeat on chromosome 19
clinical features of myotonic dystrophy?
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
what muscles are affected first in myotonic dystrophy?
sternocleidomastoid and distal limb muscles first
proximal limb muscles are affected later in course of disease
what is lambert eaton myasthenic syndrome (LEMS)?
neuromuscular junction disorder caused by impaired release of Ach by the presynaptic terminal
what causes LEMS?
associated with malignancy (small cell lung cancer) or autoimmune disease resulting in an autoimmune attack against the P/Q-type Ca2+ voltage gated channels
clinical features of LEMS?
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
investigations in LEMS?
diagnosis established by presence of anti-VGCC antibodies and characteristic electrophysiological findings using repetitive stimulation
CT scan used to rule out malignancy
how is LEMS managed?
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
what is MG?
myasthenia gravis
autoimmune disease affecting the post-synaptic nicotinic ACh receptors at the NMJ
who is MG most commonly seen in?
women
2nd or 3rd decade
clinical features of MG?
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
what ocular features are seen in MG?
bilateral, asymmetrical ptosis and extra-ocular weakness causing diplopia
what is a myasthenic crisis?
complication of MG where weakness of the muscles of repiration causes ventilator failure
what can precipitate myasthenic crisis?
bronchopneumonia
medications (gentamicin)
surgery
management of myasthenic crisis?
monitor via vital capacity and tidal volume
plasmapheresis
IV Ig
systemic steroids
urgent tracheal intubation and ventilation if vital capacity falls <15
what is a cholinergic crisis?
complication of MG causing sweating, hypersalivation, bronchial hypersecretions and miosis which can lead to resp failure
cholinergic crisis is common in which MG patients?
those receiving high doses of anticholinesterases
what is MG associated with?
thymic hyperplasia
thymoma
hyperthyroidism
SLE
what drugs can exacerbate MG?
gentamicin beta blockers verapamil lithium penicillamine phenytoin chloroquine
how is MG investigated?
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
how is MG managed?
symptomatic control = acetylcholinesterase inhibition (pyridostigmine)
usually combined with immunosuppressive agents (corticosteroids and azathioprine)
thymectomy can also be performed
what is charcot marie tooth disease?
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)
histopathology of charcot marie tooth CMT1?
schwann cells proliferate and form concentric arrays of remyelination around the demyelinated axon resulting in an onion bulb appearance
features of charcot marie tooth CMT1?
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
how is charcot marie tooth CMT1 diagnosed?
clinically
genetic testing
electrophysical nerve conduction studies show low conduction velocity <38 m/s
what is guillian barre syndrome?
acute neuromuscular weakness causing demyelination and axonal injury
majority of patients have history of preceeding illness or infection (campylobacter, EBV, CMV, HIV)
features of guillian barre syndrome?
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
how is guillian barre syndrome diagnosed?
usually clinical
lumbar puncture (shows high CSF protein)
nerve conduction studies (patchy proximal and distal demyelination)
management of guillian barre syndrome?
plasma exchange
IV Ig
what is chronic inflammatory demyelinating polyradiculoneuropathy?
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
diagnosis of CIDP?
clinical
supported by electrophysical nerve conduction studies and CSF analysis (shows high protein)
management of CIDP?
oral steroids
IV Ig
what is spinal muscular atrophy?
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
features of spinal muscular atrophy?
often manifests in first month of life causing floppy baby syndrome with marked hypotonia and tongue fasciculations
what is poliomyelitis?
infection with polio virus (faeco-oral transmission) causes destruction of cells in anterior horn of spinal cord
signs and symptoms of poliomyelitis?
those of LMN disease weakness hypotonia flaccid paralysis fasciculations hyporeflexia muscle atrophy
