NMJ, Muscle: MG, LES, DMD/BMD, MD, GBS, MND, Botulism, Tetanus Flashcards
MG
-epidemiology
-pathophysiology
-presentation
Not common
-young women, older men
AI -ACh rec AB => muscle contraction reduced
Gradual/rapid onset after illness, stress, pregnancy
Fatiguable, painless muscle weakness that improves with rest
-eyes, eyelid, facial, speech muscles
-limbs, resp muscles
No impact on GU, heart
MG
-investigations, diagnosis
Blood
-AChR - negative does not rule out possibility
-MuSK AB
-high association with other AI (T1DM, thyroiditis)
Imaging
-thymus hyperplasia - overactivity
-thymoma => rarely malignant but removed eventually
Diagnostic - rep EMG stimulation
-decreased amplitude over time
MG
-management
Lifestyle - avoid triggers
-sufficient rest, stress reduction
-flu/pneumonia jab
Symptomatic - pyridostigmine (AChesterase inh)
Immune system control - CS (induce remission, taper down eventually)
2nd line - DMARD (Aza, metho)
Crisis - breathing and swallowing problems => ICU resp support, plasmapheresis, IVIG
LES
-pathophysiology
-presentation
AI AB against presynaptic VGCC in PNS
Repeated muscle contractions => increased muscle strength
-limb girdle weakness (mainly in legs)
Autonomic involvement - urination/defecation issues, impotence
Hyporeflexia
Eye symptoms not a feature
LES
-investigations
EMG => incremental response to repetitive electrical stimulation
Autoantibody electrical stimulation
Chest CT - small cell lung cancer association
LES
-management
SCLL management
AChinh or aminopyridines (block K channels => increases Ca influx) - diaminopyridine/pyridostigmine
Severe - CS +DMARD (pred + aza)
Plasmapheresis
IVIG
Polymyositis and dermatomyositis
-pathophysiology, presentation
-epidemiology
Inflammatory => symmetrical proximal muscle weakness
-tender
-resp muscle weakness, IDL
-dysphagia, dysphonia
-Raynauds
P - no skin signs
D - heliotrope rash on cheeks, eyelids
-photosensitivity
-red papules over finger extensors
-dry, scaly, cracked hands on palmar
-nailfold capillaries
Middle age females
Polymyositis, dermatomyositis
-investigations
-management
High CK
-other muscle enzymes high (LDH, aldolase, AST, ALT)
AB - more specific
P - anti Jo
D - anti Mi
EMG
Definitive - muscle biopsy
Definitive - pred
Supportive - sun protection, exercise
DMD and BMD
-pathophysiology
-presentation
X recessive - mutated dystrophin gene
-needed to connect muscle membrane to actin
DMD - frameshift => severe
BMD - non frameshift => milder form
DMD
-progressive proximal muscle weakness
-calf pseudohypertrophy
-Gowers sign - arms needed to stand up
-Waddling gait
-loss of walk by 12
-intellectual impairment common
BMD
-10y/o+
-intellectual impairment less common
DMD and BMD
-investigations
-management
High CK -released in muscle damage
Definitive - molecular diagnosis
1st line - CS
-Improve motor and lung function
-delay loss of ambulation, cardiomyopathy
Physio, OT input
Myotonic dystrophy
-epidemiology, pathophysiology
-presentation
Inherited AD myopathy - 20-30 y/o
Affects skeletal, cardiac, smooth muscle
Myotonic dystrophy - contracted muscle destruction
-frontal balding
-arrythmias
-early cataracts
-DM
DM1 - distal weakness
DM2 - proximal weakness
Myotonic dystrophy
-investigations
-management
Definitive - genetics
-DM1 CTG repeat C19
-DM2 repeat expansion C3
No cure, focus on managing symptoms
Physio - maintain strength and endurance, control MSK pain
OT - canes, braces, walkers
Symptomatic management
-arrythmias
-cataracts
GBS
-presentation
-pathophysiology
Adults, males
Immune mediated attack on Schwann cells in PNS
-often triggered by infection - campylobacter jejuni
Leg, back pain => progressive ascending symmetrical weakness of all limbs
More motor than sensory loss
Reduced reflexes
Resp muscle weakness
Urinary retention, constipation
Diplopia
Bilateral facial palsy
Dysphagia
GBS
-investigations, diagnosis
-management
Definitive
-nerve conduction - demyelination => slow conduction
-lumbar puncture - normal WCC, high protein
ABG - resp acidosis
Spirometer - restrictive (muscle weakness)
-May require ventilation
IVIG - stop harmful AB from causing further damage
Plasmapheresis
Resp failure support
Complete recovery in 1 year
-long term rehab needed
GBS differentials
-timeframe and management
Chronic inflammatory demyelinating polyneuropathy
-AB mediated inflammation => demyelination of peripheries
-insidious onset over months
-treated with IC
Investigations used for suspected muscle conditions
EMG neurophysiology - good to rule out other neuropathies
Muscle biopsy analysis - immunohistology, staining
MRI muscle
DNA analysis - gold standard for direct mutation detection
MND
-presentation
-investigations
-management
60-70s males
LMN and UMN
-fasciculations
-wasting of intrinsic hand muscles, tibialis anterior (foot drop, high steppage gait)
-eye sparing
-no cerebellar, sensory signs
Clinical diagnosis
EMG - reduced action potentials with increased amplitude
Riluzole
Respiratory care
-NIV BIPAP used at night
Botulism
-causative organism
-pathophysiology
-presentation
-investigations
-management
Clostridium botulinum => neurotoxin blocks ACh release at NMJ
Affects bulbar muscles and ANS
Contaminated food
IVDU
No sensory disturbance
Flaccid paralysis
Diplopia
Ataxia
Bulbar palsy - dysphagia, dysphonia, dysarthria
Clinical diagnosis
Botulinum antitoxin - only works if given early, toxin binding is irreversible
Supportive care
Tetanus
-causative organism
-pathophysiology
-presentation
-investigations
-management
Clostridium tetani - exotoxin prevents release of GABA => spreads and affects CNS
Soil
IVDU
Prodrome - fever, lethargy, headache
Lockjaw, risus sardonicus
Opisthotonus - arched back, hyperextended neck
Spasms
Clinical diagnosis
Supportive - ventilatory support, muscle relaxants
IM tetanus IG for high risk wounds
Metronidazole
Tetanus vaccination
-type
-when is it given
-wound classification
-management of injuries
Toxin
-2, 3, 4 months
-3, 5, 13-18 years
Clean - U6hrs old, non penetrating, minimal damage
Tetanus prone
-puncture wound in contaminated environment
-foreign body contamination
-compound fracture
-wounds, burns with systemic sepsis
-animal bites and scratches
High risk
-heavy contamination with soil
-wounds or burns with extensive devitalised tissue
-wounds or burns needing surgical intervention
Full course + last dose U10 years ago => no vaccine or IG needed
Full course + last dose 10+ years ago
Tetanus prone => vaccine
High risk => vaccine + IG
Vaccination Hx unknown/uincomplete => vaccine
Tetanus prone/high risk => add IG
