Clinical Case - Parotid Gland & Face
A 14 year old male was brought to the emergency room by his mother. Symptoms of severe headache, photophobia, nausea, vomiting, fever of 103, and nuchal rigidity (resistance to flexion of the neck) began the evening before, and progressed rapidly during the night. Suspecting meningitis, a lumbar puncture was performed. The CSF appeared purulent and turbid.

CSF lab analysis showed increased protein levels, decreased sugar, and many polymorphonuclear leukocytes. This confirmed meningitis, probably bacterial. Culture of the CSF determined the cause to be Streptococcus pneumoniae. The boy was admitted to the hospital for antibiotic therapy and close monitoring.

Subsequently, the boy developed a facial nerve palsy, a complication of the meningitis. His symptoms mimic Bell's Palsy.

Questions to consider:
  1. What is the course of the facial nerve?
    1. Where does it emerge from the brain?
      lower border of the pons
    2. What foramen does it enter and exit from the skull?
      internal auditory meatus, stylomastoid foramen
    3. Name the ganglion it is associated with.
      geniculate ganglion
    4. Name the five end branches.
      temporal, zygomatic, buccal, mandibular, cervical
    5. What muscles does it innervate?
      the muscles of facial expression, platysma, stylohyoid, posterior belly of digastric, and stapedius

  2. What are the clinical signs of Bell's Palsy?
    Unilateral flaccid paralysis of the muscles innervated by the facial nerve, leading to loss of expression. The patient will be unable to smile, lift their eyebrow, or close their eyelid on the affected side of the face.
  3. Hyperacusis is noted. What is this? What motor branch of the facial nerve is affected?
    Hyperacusis is increased sound perception. This happens because the stapedius (a muscle of the middle ear) is innervated by a branch of the facial nerve. Normally, stapedius serves to dampen large vibrations of the tympanic membrane resulting from loud noises by contracting and inhibiting movement of the stapes. So, the "nerve to the stapedius" is affected.
  4. Facial pain or lack of sensation implies that which nerve is affected?
    Sensation of the face is from the trigeminal nerve (CN V).
  5. The physician orders lubricating eye-drops to be applied as needed. Why?
    Because the eyelid cannot close upon reflex or conscious effort (unless it is closed manually i.e. with one's hand), the patient with facial nerve palsy is at risk for corneal irritation. Closing the eye is a function of the orbicularis oculi muscle.
A 65-year-old man complained of inability to shut his right eye, difficulty in moving food around his mouth and weakness on the same side of his mouth with slight numbness on the right cheek. The problem started a few weeks ago following an excisional biopsy of a right facial lump that proved to be a benign parotid tumor. The surgeon was able to verify an area of mild numbness on the right cheek. Upon examining facial muscles, he suspected an injury to facial nerve branches that must have happened during the biopsy. He suggested intensive physiotherapy sessions and regular checkups to monitor the patient's progress.

Questions:
  1. How would you explain the patient's numbness on the right cheek?
    The most likely reason is an injury to the maxillary division of the trigeminal nerve.
  2. Which facial muscles do you think are responsible for the patient's complaints?
    The main muscles are: orbicularis oculi, buccinator, and orbicularis oris.
  3. How would you test for these muscles?
    For the orbicularis oculi: ask the patient to shut his eye as tightly as he can. The affected eye is either not closed at all, in which case the eyeball rolls upward to make up for the failure of the lid to descend. For buccinator and orbicularis oris: ask the patient to whistle. If he is unable to do so, ask him to smile or show his upper teeth, the mouth is then drawn to the healthy side. Ask him to inflate his mouth with air and blow out his cheeks. Tap with a finger in turn on each inflated cheek. Air can be made to escape from the mouth more easily on the weak or paralyzed side.
  4. What other functions of the facial nerve need to be checked?
    Test sense of taste on the anterior part of the tongue and ask the patient to raise his eyebrows.