CRANIAL NERVE V

Facial onset sensory and motor neuronopathy (FOSMN)¹

• Epidemiology
  • 10 sporadic patients: Australia, Japan & France
  • 90% male
• Onset
  • Age: 5th decade; Mean 43 years
  • Face: Paresthesias & Numbness
• Clinical
  • Sensory loss
    • Early: Face, bilateral
    • Progresses to: Scalp, Neck, Upper trunk & Upper limbs
    • Pin & Temperature sensations: Reduced
    • Vibration & Proprioception: Normal
    • Reduced taste sensation
  • Weakness: Later in disease course
    • Bulbar
      • Dysphagia (50%)
      • Hoarseness & Dysarthria (75%)
      • Tongue atrophy
      • Gag reflex: Absent (75%)
    • Diffuse
      • Proximal & Distal
      • Arms > Legs
      • May be asymmetric
    • Respiratory: Late; Some patients
  • Other muscle features
    • Cramps
    • Fasciculations
  • Reflexes
    • Tendon: Reduced or Absent
    • Plantar: Flexor
  • Progression
    • Slow over years
    • No response to immunomodulating agents
    • 1 patient with upper motor neuron signs & rapid progression
  • Bladder & Bowel: Normal
  • Differential diagnosis: Tangier disease
• Laboratory
  • Serum IgG binding to sulfatide: High in 50%
  • Serum CK: Mildly high (Mean 297)
  • CSF: Normal
  • MRI: Atrophy of mid-cervical spinal cord
  • Electrophysiology: Sensory-Motor neuronopathy
    • SNAPs: Reduced in arms
    • F-wave latencies: Prolonged
    • EMG
      • Denervation: Trunk, proximal & distal
      • Motor units: Large
      • Fasciculations
    • Blink reflex: Abnormal
• Pathology
  • Cranial nerve atrophy: V & IX-XII
  • Anterior roots: Atrophic
  • Sensory nuclei & ganglia: Neuronal loss
  • Peripheral nerve: Axonal loss
  • Muscle: Denervation