Nerve and muscle disease Flashcards
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?
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)
what is myotonic dystrophy?
multisystem progressive disease characterised by delayed muscular relaxation and muscle wasting
(just think of name: MYO-muscle TONIC-increased tone DYSTOPHY-wasting)
genetic cause of myotonic dystrophy?
tri-nucleotide repeat on Cr19
clinical features of myotonic dystrophy?
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
what is Lambert-Eaton myasthenic syndrome
neuromuscular junction disorder caused by impaired release of Ach from the presynaptic terminal
what causes Lambert-Eaton myasthenic syndrome?
malignancy (SCLC) or autoimmune disease > autoimmune attack against P/Q-type voltage gated Ca channels
clinical features of Lambert-Eaton myasthenic syndrome?
insidious onset proximal muscle weakness. Mainly lower limbs > waddling gait
Autonomic features > constipation, postural hypotension, impotence, dry mouth
Deep tendon reflexes diminished/ absent
How is Lambert-Eaton myasthenic syndrome diagnosed?
anti-VGCC antibodies
characteristic electrophysiological findings using a 20-50Hz repetitive stimulation
CT to rule out malignancy
treatment of Lambert-Eaton myasthenic syndrome?
Mainly 3,4-diaminopyridine (amifampridine)
More severe cases: immunosuppression or IV immunoglobulins
what is Myasthenia gravis?
autoimmune disease of post-synaptic nicotinic ACh receptors at the NMJ.
Myasthenia gravis
1) sex distribution
2) typical age
1) F>M
2) 20-30
clinical features of myasthenia gravis?
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
thymid hyperplasia, thyoma, hyperthyroidism and SLE are quite common associations with which neuromuscular disease?
myasthenia gravis
myasthenia crisis
1) precipitating factors?
2) best method to monitor for this?
3) treatment?
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
Cholinergic crisis
1) is a potential complication of __ __
2) is common in patients receiving high dose ___ medication
3) symptoms include …
1) myasthenia gravis
2) anticholinesterase
3) SLUDGE syndrome”: Salivation, Lacrimation, Urination, Defecation, Gastrointestinal distress and Emesis
thymic hyperplasia, thyoma, hyperthyroidism and SLE are quite common associations with which neuromuscular disease?
myasthenia gravis
list some drugs which can induce or exacerbate myasthenia?
Gentamicin, beta blockers, verapamil, lithium, penicillamine, phenytoin and chloroquine.
Ix in myasthenia?
anti-AChR Abs (check for anti-MuSK if negative). Repetitive nerve stimulation tests: decremented muscle response. TFTs CT thymus.
management of myasthenia gravis?
symptomatic control: acetylcholinesterase inhibitors e.g. Pyridostigmine
to improve weakness and establish remission: immunosuppression e.g. corticosteroids, azathioprine
Thymectomy
CMT1
1) age of onset?
2) presentation?
3) diagnosis?
1) first decade
2)
3)
most common form of charcot-marie-tooth disease? how is it inherited?
CMT1
autosomal dominant
histopathological features of CMT1?
schwann cells proliferate and form concentric arrays of remyelination around the demyelinated axon > onion bulb appearance
CMT1
1) age of onset?
2) presentation?
3) diagnosis?
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)
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
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
how is guillain-barre syndrome diagnosed?
usually clinical
LP (high CSF protein) and nerve conduction studies (patchy proximal and distal demyelination) sometimes useful
treatment of guillain-barre syndrome?
plasma exchange or IV IGs
what is chronic inflammatory demyelinating polyradiculoneuropathy? (CIDP)
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
CIDP
1) diagnosis
2) treatment
1) clinical, supported by electrophysiological nerve conduction studies and CSF (high protein)
2) oral steroids, IV IGs
what is spinal muscular atrophy (Werdnig-Hoffmann disease)
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)
Poliomyelitis
1) causative pathogen?
2) infection causes destructions of cells where?
3) signs and symptoms?
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
