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Cranial Nerve V

From Anonymous

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Facial Onset Sensory & Motor Neuronopathy (FOSMN) ¹

• Epidemiology
  • > 100 sporadic patients: Australia, Japan & France
  • 65% to 70% male
• Genetics ²
  • Inheritance: Usually sporadic
  • TDP-43 mutations: Some patients; A315T, G386E, N390D, N390S
• Clinical
  • Onset
    • Age: Range 7 to 78 years; Mean 54 years
    • Face: Paresthesias & Numbness (Trigeminal distribution)
  • Sensory loss
    • Course
      • Slow progression
      • Early: Face; Bilateral; May be asymmetric
      • Progresses to: Scalp, Neck, Upper trunk & Upper limbs; Legs in 10%
    • Small fiber sensations: Pin reduced > Temperature
    • Taste: Reduced
    • Corneal reflex: Reduced
    • Vibration & Proprioception: Normal
  • Weakness: Later in disease course
    • Bulbar
      • Dysphagia (50%)
      • Hoarseness & Dysarthria (75%)
      • Tongue: Atrophy & Fasciculations
      • Gag reflex: Absent (75%)
    • Diffuse
      • Proximal & Distal
      • Arms > Legs
      • May be asymmetric
      • Neck: Posterior & Anterior
    • Respiratory: Late; Some patients
  • Other muscle features
    • Cramps
    • Fasciculations
    • Wasting: Masseter; Temporalis; Neck
  • Reflexes
    • Tendon: Reduced or Absent
    • Plantar: Flexor
  • Upper motor neuron signs: 28%
  • Cognitive or behavioral dysfunction: May be common
  • Bladder & Bowel: Normal
  • Progression
    • Slow to Moderate over years
    • Anatomy: Rostral to Caudal
    • Immunomodulating agents: Little or No response
    • 1 patient with upper motor neuron signs & rapid progression
    • Survival: 14 months to 46 years; Mean 8 years
    • Cause of death: Often respiratory
  • Differential diagnosis: Tangier disease; Gelsolin amyloid
• Laboratory
  • Serum IgG binding to Sulfatide: High in 50%
  • Serum CK: Mildly high; Mean 297; Range 100 to 900
  • CSF: Normal
  • MRI: Atrophy of mid-cervical spinal cord
  • Electrophysiology: Sensory-Motor Neuronopathy
    • SNAPs: Reduced amplitudes in arms more than legs
    • F-wave latencies: Prolonged
    • EMG: Denervation, Chronic partial
      • Distributiontion: Trunk, proximal & distal
      • Motor units: Large
      • Fasciculations
    • Blink & Trigeminal reflexes: Abnormal (94%)
      • Blink: Delayed R2 response or Complete absence
    • No cortical hyperexcitability
• Pathology
  • Cranial nerve atrophy: V & IX-XII
  • Motor
    • Motor neuron loss: Facial & Hypoglossal nucleus; Cervical anterior horns
    • Anterior roots: Atrophic
  • Brain: TDP-43 glial inclusions
  • Sensory nuclei & ganglia: Neuron loss
  • Peripheral nerve: Axon loss
  • Muscle: Denervation
  • Skin biopsy: Trigeminal
    • Myelinated axons: Reduced
    • Unmyelinated epidermal axons: Normal

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Cranial Dysinnervation Disorder, Congenital, with Absent Corneal reflex & Developmental delay (CCDDRD)
  ● Neurogenin 1 (NEUROG1) ; Chromosome 5q31.1; Recessive

• Epidemiology: 3 families
• Genetics
  • Mutations: Missense, Stop, Duplication
• NEUROG1 protein
  • Basic helix-loop-helix (bHLH) protein
  • Transcription factor
  • Astrocyte differentiation
  • Role in cranial sensory ganglia development
  • Formation of Cranial nerves V & VIII
• Clinical
  • Onset: Congenital or Early infant
  • Cornea: Opacities; Reflex reduced
  • Deafness: Sensorineural; Cranial nerve 8 dysgenesis
  • Face
    • Expressionless
    • Dysmorphic
    • Oromotor dysfunction
    • Asymmetry
    • Eyebrows: High arched
    • Palpebral fissures: Elongated
  • Plagiocephaly
  • Developmental delay
• Laboratory
  • Brain imaging: Cochlear & CN8 hypoplasia
  • NCV: Axon loss
  • Agenesis: Cochlea; Cranial Nerve V (1 patient)

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References
1. Brain 2006;129:3384–3390, Muscle Nerve 2010; Online November, Neurology 2012;79:73–79, Neurol Sci 2016;37:1905-1909, Neurology: Clinical Practice 2020, Clin Neurophysiol 2022 May 10
2. Neurol Genet 2024;10:e200160

6/5/2024