Write down the difference in the anatomical relationship of facial nerve in adult and children.
At birth, the normal temporal bone has no mastoid process process and an incomplete tympanic ring. The ‘U’ shaped tympanic ring has nodular prominence on each arm, which separates the annulus from the further External Auditory Canal (EAC) and the foramen of Huschke.
By the end of the first post natal year these processes fuse, lengthening the canal. The foramen usually closes sometime later ~4 years.
In the new born the chorda tympani and the facial nerve may exist through the stylomastoid foremen. The mastoid process and EAC are undeveloped so the nerve is very superficial.
The mastoid process develops and reaches adult proportion by the age of 12 years.
In neonates and small children: the second genu of the facial nerve is more acute and course more laterally.
The most common variation in the course of the facial nerves canal involves the tympanic segment.
The bony wall may be dehiscent in 35-55%of population particularly in the above the oval window.
Acute suppurative otitis media in neonates and children may therefore present with the facial paralysis from neuroparxia or bacterial infiltration of the facial nerve sheath-within an enclosed middle ear.
Dehiscence of this segment of facial nerve may be associated with a persistent stapedial artery in its course from the tympanic cavity to the middle cranial fossa where this become the middle meningeal artery. The foramen spinosum is absent on the side of the persistent stapedial artery on plain x-ray or CT.
On leaving the slylomastoid foramen, the facial nerves enters the parotid gland in the more anterior location than in the adult as the parotid gland in smaller and more anteriorly placed.
The nerve divides into two main divisions:
The lower division of the facial nerve in young children runs very superficially over the angle of the mandible and can be damaged by a skin incision during surgery.
Absent mastoid process and incomplete tympanic ring
The chord tympani may exit through the stylomastoid foramen with the main trunk in the neonate.
2nd genu of the facial is more acute and more lateral.
Nerve trunk on exit from slylomastoid foramen is more anterior and lateral.
Nerve very superficial over the angle of mandible.
Mastoid process present and tympanic ring is completed by adolescent.
The chords tympanic exist separately and proximal to the stylomastoid foramen.
Second genu of facial nerve less acute and more medial.
Parotid is most posteriorly placed and the nerve trunk is anterior and deeper.