Please enable JavaScript.
Coggle requires JavaScript to display documents.
Neuromuscular Disorders (i) - Coggle Diagram
Neuromuscular Disorders (i)
Intro
key clinical feature = weakness - can be progressive or static
clinical features
floppiness
unsteadiness
delayed motor milestones
abnormal gait
muscle cramps (suggests metabolic myopathy)
Hx + exam can provide useful clues
waddling gait - myopathy
Gowers sign
proximal muscle weakness
normal until 3y/o
turn prone, 'climb hands up legs' to stand
distal wasting/weakness (esp pes cavus) - hereditary motor sensory neuropathy (HMSN)
increased fatiguability throughout day (diurnal worsening) + opthalmoplegia + ptosis - MG
usually difficult to differentiate myopathy from neuropathy on clinical grounds
weakness, lost reflexes, fasciculations, wasting - ant horn cell
distal Ns affected - neuropathy
motor neuropathy - weakness
sensory neuropathy - impaired perception of pain, touch + temp
loss of reflexes in both sensory + motor
weakness (usually proximal), wasting, gait disturbance - myopathy
Causes
Disorders of ant horn cell
SMA
poliomyelitis
Disorders of peripheral Ns
HMSN
acute post infectious polyneuropathy (Guillain-Barré syndrome - GBS)
Bell palsy
Disorders of NMJ (MG)
Muscle disorders
Dystrophies (Duchenne / Becker / Congenital)
Inflamm myopathies (benign acute myositis, polymyositis, dermatomyositis)
Myotonic disorders (dystrophia myotonica)
Congenital myopathies
Investigations
serum creatinine phosphokinase - elevated in Duchenne, Becker + inflamm myopathies
muscle bx
DNA testing
for Duchenne, SMA, myotonic dystrophy, hereditary neuropathies
allows antenatal testing + genetic counselling
US + MRI of muscles
N conduction studies identify neuropathies
N bx rarely performed
EMG
helps differentiate myopathic from neuropathic disorders
fatiguability on repetitive N stim = MG
Disorders of ant horn cell
weakness, wasting, absent reflexes
SMA
AR
degeneration of ant horn cells
mutations in survival motor neuron (SMN) gene
SMA type 1 (Werdnig-Hoffmann disease)
v severe + progressive
presents in early infancy
diminished foetal movements often noticed
arthrogryposis (positional deformities of limbs with contractures in @ least 2 joints) @ birth
lack of antigravity power in hip flexors
absent deep tendon reflexes
intercostal recession
fasciculations of tongue
never sit unaided
death from resp failure in 12mo
SMA type 2
can sit but never walk independently
SMA type 3 (Kugelberg-Welander)
do walk
present later in life
Peripheral neuropathies
HMSNs
group of disorders
symm slowly progressive distal muscle wasting
Type 1 most common
aka peroneal muscular atrophy / Charcot Marie Tooth disease
AD
affected Ns may be hypertophic due to demyelination followed by attempts @ remyelination
'onion bulb formation' on N bx
onset in 1st decade with distal atrophy, pes cavus, legs more affected than arms
rarely distal sensory loss + diminished reflexes
chronic
only rarely able to walk
GBS
typically 2-3 wks after URTI or campylobacter gastroenteritis
fleeting abnormal sensory sx in legs
less striking than paresis but can unpleasant
main feature = ascending symm weakness, loss of reflexes, autonomic involvement
sometimes bulbar muscles involved
difficulty chewing + swallowing
aspiration risk
resp depression may require artificial ventilation
max weakness 2-4wks after onset
full recovery in 95% but may take up to 2yrs
CSF protein raised, but may not be seen until wk 2 of illness
CSF WCC normal
N conduction velocities reduced
tx = supportive, Ig infusions, plasma exchange
probably due to abs
steroids have no benefit + may delay recovery