Surgical anatomy of tympano-mastoid segment of facial nerve.

OBJECTIVE

Facial nerve is known to have a considerable variations more so in the temporal bone. An otologist with inadequate familiarity with facial nerve usually have a tendency to do incomplete surgery in chronic suppurative otitis media. The present study was conducted to explore the microanatomy of tympanic and mastoid segments of facial nerve.

SETTING

Temporal bone lab.

MATERIALS AND

METHODS

This study was conducted at PGIMS Rohtak in 25 wet temporal bones which were dissected under the microscope. Various parameters studied included the length of tympanic and mastoid segments of facial nerve, various anomalies, depth from the cortex and relation to various important structures.

RESULTS

The mean length of tympanic segment was 11.1 mm±0.88 and mastoid segment was 15.4 mm±2.4. The angle at second genu was 95-125° and the facial canal was dehiscent in 12% cases.

CONCLUSIONS

The tympanomastoid segment of facial nerve has variations in length and in its relation with various middle ear structures. Further the nerve, in Indians is also at variance as compared to Japanese and Americans probably because of different racial configuration of the skull.