Surgical markings for finding the facial nerve is are?

Ans. is 'a' i.e., Tympano-mastoid suture Surgical landmarks to identify main trunk of the facial nerve are as follows: Tympanomastoid suture line - it is located between the mastoid and the tympanic bones. The main facial trunk lies 6 -8 mm distal to the end of the suture. Tragal pointer - the main nerve trunk lies 1.0 to 1.5 cm deep and slightly anterior and inferior to the tip of the external ear canal cailage. Posterior belly of digastric -the main nerve trunk lies 1 cm deep to the medial attachment of the posterior belly of digastric muscle to the digastric groove (mastoid notch) of the mastoid bone. Mastoid bone - main nerve trunk is identified inside the mastoid bone by mastoidectomy.