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FACIAL (VII) NERVE DISORDERS

Anatomy
Bell's palsy
Differential diagnosis

Facial nerve: Anatomy +

  • 2 roots
    • Motor
      • Origin: From facial nucleus
      • Muscle Projections
        • Facial
        • Stapedius
        • Digastric & Stylohyoid
    • Nervus intermedius (of Wrisberg)
      • Sensory afferents
        • Origin: Cell bodies in geniculate nucleus
        • Projections
          • Skin: To spinal nucleus of cranial nerve V
          • Taste: To nucleus tractus solitarius
      • Preganglionic parasympathetics
        • Origin: Superior salivatory nucleus
        • Ganglion innervation
          • Submandibular
          • Pterygopalatine
  • Branches
    • Greater & Lesser petrosal
      • To: Pterygopalatine & Otic ganglia
      • Parasympathetic
      • Lacrimation & Salivation
    • Nerve to stapedius muscle
      • Origin: Tympanic canal
      • Ends in: Inner ear
    • Chorda tympani
      • Joins lingual nerve
      • Taste in anterior 2/3 of tongue
      • Preganglionic Parasympathetic fibers
        • To submandibular ganglion
        • To sublingual & submaxillary salivary glands
    • Sensory (Posterior) auricular branch
      • Sensation
        • Posterior external auditory canal
        • Inferior ear pinna
      • Some axons may arise from vagus (Arnold's nerve)
    • Motor innervation
      • Exits skull: Stylomastoid foramen
      • Neck
        • Stylohyoid muscle
        • Digastric muscles
      • Facial muscles (Facial expression): Branches
        • Temporal
        • Zygomatic
        • Buccal
        • Mandibular
        • Cervical
  • Facial nerve: Anatomy
    • Diagram
    • Neighboring nerves
      • VI: VII nerve Internal genu around VI nucleus
      • VIII: With VII nerve in internal acoustic canal
  • EMG: Motor units vs Limbs
    • Amplitude: Smaller
    • Duration: Shorter
    • Firing rate: Faster

From: Eichhorst

Facial nerve paralysis

  • Clinical features
    • Facial asymmetry
    • Eyebrow droop
    • Loss of forehead & nasolabial folds
    • Drooping of corner of mouth
    • Uncontrolled tearing
    • Inability to close eye
    • Lips not held tightly together: Difficulty keeping food in mouth
    • Facial muscle atrophy (Late)
  • Electrophysiology
    • EMG
      • Denervation
      • Synkinesis: Late
    • Blink reflex
      • Abnormal ipsilateral
        • R1 (early, disynaptic)
        • R2 (late multisynaptic) responses
      • Synkinesis (Late)
   

Bell's Palsy 8


Sir Charles Bell
Duchenne
Bell's palsy (19th cent)

Facial Paresis: Left
VII disorders: Differential Diagnosis

Melkersson-Rosenthal syndrome

  Chromosome 9p11; Dominant

Möbius & Congenital facial syndromes

Möbius syndrome: General Features 4 Möbius & Congenital facial syndromes: Types



Facial Nerve Trauma & Tumors


Hemifacial Spasm

  • Onset
    • Adults
      • Typically 5th or 6th decade
      • Younger patients: Rule out brainstem disease, MS
    • Location: Orbicularis oculi muscle
    • More common in women
  • Contraction pattern
    • Synchronous contraction of facial nerve innervated muscles
    • Paroxysmal
    • Involuntary
    • Duration: Up to 1 minute
    • May persist during sleep
    • Usually unilateral
  • Weakness: Unusual
  • Triggers: Aggravating factors
    • Emotion
    • Fatigue
  • Causes
    • Recovery from Bell's palsy
      • Associated with synkinesis & contracture
    • Dolichoectatic brainstem artery
      • Frequency: 30%
      • Mechanism: Pressure on VII root entry zone
      • Vessels: PICA; AICA; Vertebral
    • Brainstem disease
    • Idiopathic
  • Course: Usually permanent without treatment
  • Electrophysiology
    • Brief bursts of action potentials
      • High frequency (150-400 Hz)
      • Normal motor units
    • Variable rhythm & amplitude
    • Lateral spread response 3
      • Stimulation: Facial nerve branch
      • Response: In muscles not normally innervated by branch  
      • Related to cross transmission of facial nerve fibers
        • Location: Probably at site of compression
  • Treatment
    • Botulinum toxin
    • Microvascular decompression of VII nerve
      • Morbidity & Mortality 5%
    • Anticonvulsants


Bright 1831

Barker

T2 image: Brainstem & Cerebellum


MRA: AP view
Dolichoectasia of vertebral arteries
Deviation to right (Arrows)

Patient syndrome: R hemifacial spasm

Return to Cranial nerve disorders
Go to Facial Paralysis (Baylor)

References
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2. Neurology 2000;54:1217
3. Muscle Nerve 2002;25:845849
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9. JNNP 2007 Online May
10. JNNP 2007;78:659-660
11. Lancet Neurology 2008;7:976-977 & 2008;7:993-1000
12. Otol Neurotol 2008;29:397-400
13. Otolaryngol Head Neck Surg 2007;137:858-861
14. Ann Neurol 2010;68:404408
15. Am J Human Genet 2012; Online July

3/30/2018