Cranial Nerve Palsies

Question 1

Bell’s Palsy

Answer 1

• Definition:
  
  • idiopathic disorder of the facial nerve (CN VII)
• Pathophys:
  
  • acute inflammation of the facial nerve from an infectious or immune cause; reactivation of HSV-1 in geniculate ganglion responsible for most cases
• Risks:
  
  • pregnancy, hypothyroidism, DM, intranasal flu vaccines, viruses (varicella, etc. )
• Epidemiology:
  
  • : most common form of facial paralysis; 1 in 60 persons in a lifetime.
• Max weakness by 48 hours
• S/sxs:
  
  • *Sudden onset
  • -Unilateral paralysis of facial muscles
  • -Eyebrow saggingwith inability to close the eye on affected side
  • -Disappearance of nasolabial fold
  • -Drooping of affected corner of the mouth which is drawn to the affected side
• Bell’s Palsy vs Stroke:
  
  • Bell’s Palsy: peripheral lesions, affect brow & forehead, asymmetrical elevation of eyebrows
  • -Stroke: central lesions, spare forehead muscles on affected side, symmetric elevation of eyebrows & forehead
• Dx:
  
  • Clinical dx in pts with: typical presentation, no Red flags or preexisting symptoms, no cutaneous HSV lesions in external ear canal, normal neuro exam
  • Labs & imaging usually not indicated
  • If uncertain: ESR/CRP, blood glucose, lyme titer, ACE, & CXR (r/o sarcoidosis), LP (Guillain-Barre)
  • -MRI: swelling of facial nerve
  • -EMG: denervation
• Tx:
  
  • *80 % of patients recover within a few weeks-months. Some people will have permanent facial weakness
  • -Glucocorticoids: prednisone 60-80mg qday x 5 days then taper
  • -Antivirals: valacyclovir 1000mg qday x 5-7 days or acyclovir 400mg 5x/day x 10 days
  • -Patching the affected eye at night & lubricating drops

Question 2

CN III Palsy

Answer 2

• Etiology:
  
  • Vascular ischemia, trauma, tumor, hemorrhage, congenital, idiopathic, DM, HTN
• S/sxs:
  
  • Ptosis: d/t paralysis of levator palpebrae muscle
  • -Ocular deviation: “down & out” position
  • -Diplopia: d/t deviation but may not be a complaint d/t ptosis
  • -Pupil fixed & dilated: d/t paralysis of sphincter pupillae, pipil spared in ischemic cause
• Tx:
• Conservative: short-term in acute palsy for patients > 50yo with a hx of HTN, DM, f/u q 3 months
• Diplopia: eye patch or opaque contact lens
• Surgery: after 6 months in pupil sparing acquired palsies

Question 3

CN IV Palsy

Answer 3

• Etiology:
  
  • -congenital: trochlear nerve congenitally absent + superior oblique muscle atrophied OR trochlear nerve normal + abnormal tendon of superior oblique
  • -Acquired: closed head injury or infarction, DM
• S/sxs:
  
  • Paresis of vertical gaze (in one or both eyes)
  • -Torsional Diplopia: double images with one above & slightly to the side of the other; compensate by tilting head
  • -Paralytic strabismus
• Dx:
  
  • CT or MRI
  • LP: if suspect meningeal process
• Tx:
  
  • Tx the underlying etiology
  • -oculomotor exercises or prism glasses
  • -Surgery: if palsy does not resolve (mainly for congenital strabismus)

Question 4

Cranial Nerve VI Palsy (Abducens Nerve)

Answer 4

• Etiology:
  
  • neoplasm, trauma, stroke, metabolic conditions, demyelinating lesions, increased ICP, OM, mastoiditis, viral illness, basilar skull fracture, orbital lesions; reported following LP
• S/sxs:
  
  • Binocular Horizontal Diplopia: double vision when with objects looking side-by-side
  • -Vision loss
  • -HA
  • -N/V
  • -hearing loss
• Dx:
  
  • MRI
  • CBC/CMP
  • ESR/CRP
• Tx:
  
  • Children: alternate patching, prism therapy, strabismus surgery, botulism toxin
  • -Adults: most are self-limited, tx underlying causes, if persistent then treat like children