Peripheral motor disorders- neuromuscular disorders

Peripheral motor disorders- neuromuscular disorders

1. any part of the lower motor pathway can be affected by a neuromuscular disorder

   • ant horn cell disorders
   • peripheral neuropathies
   • disorders of neuromuscular transmission
   • primary muscle disease

2. clinical features

   • key feature
     • weakness
       • progressive or static
   • floppiness
   • delayed motor milestones
   • muscle weakness
     • distal wasting & weakness
       • esp in presence of pes anserinus
         • suggests hereditary motor sensory neuropathy
   • unsteady/abnormal gait
   • fatiguability
     • increasing fatiguability throughout the day
       • often w/ ophthalmoplegia & ptosis
         • suggests depletion at the motor end plate
           • i.e. myasthenia gravis
   • muscle cramps
     • suggesting a metabolic myopahty
   • Gower's sign
     • suggestive of proximal mm weakness
     • = the need to turn prone to rise from supine to standing
       • kids climb up the legs with the hands
     • normal til 3 years old

3. ant horn cell

   • signs of denervation
   • weakness
   • fasciculation
   • wasting

4. neuropathy

   • often distal nerves affected
   • motor ->
     • weakness
       • w/ loss of reflexes
   • sensory ->
     • impaired perception of pain, temp, or touch, w/ loss of reflexes

5. neuromuscular junction

   • as end-plate ACh stores become depleted, there is diurnal worsening through the day-> fatigualbility

6. Ix

   • myopathy
     • serum creatine phosphatase
       • markedly raised in Duchenne & Becker muscular dystrophy
     • muscle biopsy, needle or open
       • modern histochem techniques often a definitive diag
     • DNA testing
       • ID abnormal genes
     • ultrasound & MRI of mm
       • used in specialist centre to diag & monitor progress
   • neuropathy
     • nerve conduction
       • ID delayed motor & sensory conduction velocities
     • DNA testing
       • for abnormal genes
     • EMG (electromyography)
       • to differentiate myopathic from neuropathic disordes
         • e.g. fatiguability on repetitive nerve stimulation in myasthenia
       • use selectively in kds
         • use fine needle electrodes