Facial Nerve Injury

Facial Nerve Injury


FACIAL NERVE INJURY 

CAUSES OF FACIAL NERVE PARALYSIS:

  1. Supranuclear Lesions :

  • Congenital abnormalities, stroke, malignancies, trauma , vascular conditions and other causes .
  • Only lower part of the opposite side of the face is paralyzed.
  • The upper part with the frontalis and orbicularis oculi escapes due to bilateral representation in the cerebral cortex.

  2. Infranuclear Lesions :

  • Malignancy (parotid gland as well as tumors of adjacent structures) , trauma, infections, Bell’s palsy, steopetrosis  and  iatrogenic causes .
  • The whole of the face of the same side gets paralyzed.

  3. FRACTURES:

  • Facial nerve palsy occurs in 20% of longitudinal temporal bone fractures and 50% of transverse temporal bone fractures.
  • Facial nerve palsy is also seen in the fracture of middle cranial fossa.

  4. IATROGENIC:

  • Mastoidectomy commonly.
  • While doing posterior tympanotomy through the facial recess there are chances of injury to the Chorda tympani & Vertical descending part of facial nerve but not Facial nerve horizontal part.
  • Most common nerve injured in face lift surgery is  Frontal branch of facial nerve.

  5. INFECTION:

  • Facial nerve palsy is seen in Malignant otitis externa & also in Chronic suppurative otitis media.
  • Herpes zoster infection recurrence causes facial nerve palsy. 

SIGNS & SYMPTOMS OF FACIAL NERVE PARALYSIS: 

  • The symptoms according to the level of injury of facial nerve.

1. At Internal Auditory Meatus: (injury is at Geniculate ganglion)

  • Loss of lacrimationstapedial reflex(seen in facial nerve swelling within facial canal )taste from most of anterior two-third of tongue, lack of salivation and paralysis of muscles of facial expression.

2.  Below Geniculate Ganglion: (at chorda tympani)

  • Loss of stapedial reflex i.e.inability to dampen loud noises taste from anterior two third of tongue, lack of salivation and paralayis of facial expression muscles.

3. Region Below Stylomastoid Foramen :

  • Paralysis of facial expression muscles., (Loss of corneal reflex at side of lesion).

Upper motor neuron Vs lower motor neuron palsy

  • Part of facial nucleus that supplies muscles of upper part of face receives corticonucleur (cortex to nucleus) fibers from both sides of motor cortex.
  • Incontrast , the facial nucleus that supplies muscles of lower part of face receive corticonuclear fibers only from opposite motor coortex.
  • Thus, if the lesion is proximal (above) the facial nucleus (upper motor neuron lesion), the upper facial muscles are partially sparedbecause of innervation of opposite motor cortex for upper facial muscles.
  • If the lesion is distal to facial nucleus (lower motor neuron lesion), there is involvement of all muscles of the face on ipsilateral side.
  • UMN lesion causes contralateral paresis, while LMN causes ipsilateral paresis.
Upper motor neuron  innervation to forehead muscle is bilateral and for lower facial muscles is unilateral and contralateral→Thus UMN facial palsy causes:
  1. Palsy of contralateral lower half of face
  2. Sparing of upper half of face (because of innervation from other side also)
Lower motor neuron  innervation is unilateral and ipsilateral for both upper and lower facial muscles→ Thus LMN facial palsy causes paralysis of ipsilateral half (both forehead and lower half) of face.
Exam Question
 
  • Facial nerve palsy is seen in Malignant otitis externa.
  • Facial nerve palsy is seen in the fracture Middle cranial fossa.
  • Recurrent facial nerve palsy is a feature of Melkersson Rosenthal syndrome.
  • Iatrogenic traumatic facial nerve palsy is most commonly caused du­ring Mastoidectomy.
  • In supranuclear lesion of facial nerve lower part of the opposite side of the face is paralyzed.
  • A Swelling of the facial nerve within the facial canal resulting from compression of nerve due to an inflammatory process in the temporal bone results in paralysis of stapedius muscle
  • Iatrogenic traumatic facial nerve palsy is most commonly caused du­ring Mastoidectomy
  • A patient with a facial nerve paralysis suffers from inability to dampen loud noises due to denervation of stapedius muscle
  • Facial nerve palsy occurs in 20% of longitudinal temporal bone fractures and 50% of transverse temporal bone fractures.
  • While doing posterior tympanotomy through the facial recess there are chances of injury to the Chorda tympani & Vertical descending part of facial nerve but not Facial nerve horizontal part.
  • Facial nerve palsy is seen in Malignant otitis externa.
  • Facial nerve palsy is seen in Chronic suppurative otitis media(CSOM).
  • Lacrimation is affected when facial nerve injury is at Geniculate ganglion
  • In oedma of facial nerve at the level of geniculate ganglion hyperacusis, loss of lacrimation and loss of taste sensation in the anterior 2/3rd of the tongue are seen
  • In Dryness of mouth with facial nerve injury site of lesion is at Chorda tympani Nerve
  • Level of injury of facial nerve region below Stylomastoid foramen Loss of corneal reflex 
  • Most common nerve injured in face lift surgery is  Frontal branch of facial nerve
Don’t Forget to Solve all the previous Year Question asked on Facial Nerve Injury

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