Fig. 1

The surgical approach to the right bulla. (a) Place the mouse into the head holder and incise the skin along the white line, approximately 2 cm. (b) Retract the skin to expose the submandibular glands (SMG). Identify the anterior belly of the digastric muscle (AD). Separate the right and left SMG along the white dashed line by blunt dissection. (c) Retract the right SMG and identify the anterior and posterior bellies of the digastric muscle, AD, and PD, respectively. The location of the bulla is below the PD (white arrow). (d) Detach the intermediate tendon from the hyoid bone and elevate the PD to expose the bulla region (box) and outer ear canal (thin white arrow). Avoid manipulating the facial nerve (thick arrow). Further, retract the muscles to expose the bulla.