Facial Recess

Definition and Anatomy

The facial recess (also called the posterior tympanotomy) is a triangular space located in the posterior wall of the tympanic cavity, accessible via the mastoid. Its three borders are:

Border	Structure
Medial (posterior)	Facial nerve (vertical/mastoid segment)
Lateral (anterior)	Chorda tympani nerve
Superior	Fossa incudis (incus buttress)

The size of the recess varies among individuals, depending on where the chorda tympani branches from the facial nerve and the degree of pneumatization of the region.

Facial recess anatomy showing incus buttress, chorda tympani nerve, and facial nerve

Illustration of the facial recess - triangular space bordered by the incus buttress superiorly, chorda tympani nerve anterolaterally, and facial nerve posteriorly.

Surgical Landmarks and Approach

Before opening the facial recess, several key landmarks must be identified:

Lateral semicircular canal - lies just superior to the facial nerve at the second genu
Short process of the incus - points directly toward the facial recess and serves as a reliable guide
Digastric ridge - another landmark for the vertical segment of the facial nerve
"Herald" air cell - a single air cell typically encountered just lateral to the second genu of the facial nerve, even in sclerotic bones

Technique:

Thin the posterior canal wall first
Expose the facial nerve using a large diamond burr with copious irrigation, always stroking parallel to the nerve - never perpendicular
Identify the chorda tympani as it branches from the vertical facial nerve segment, and trace it superiorly toward the incus
Open the recess with a 2-mm diamond burr, starting superiorly where the space is widest
Drill in an anteromedial direction, preserving a small bone sliver just inferior to the incus to protect it from the burr

Caution: Even light contact of the drill with the incus (when the ossicular chain is intact) can cause significant sensorineural hearing loss. Using a small curette or pick for the final bone removal near the incus is advisable.

Fully developed facial recess between the facial and chorda tympani nerves (intraoperative view)

Intraoperative view: facial recess fully developed between the facial and chorda tympani nerves.

Structures Visible After Opening

Once the facial recess is opened, the following middle ear structures can be visualized:

Pyramidal process and stapedial tendon
Stapes superstructure
Long process of the incus
Oval and round windows
Promontory
Incudostapedial joint
Cochleariform process
Medial surface of the tympanic membrane
Eustachian tube orifice

The sinus tympani remains hidden and cannot be seen through this approach.

Extended Facial Recess

For greater access to the hypotympanum, the facial recess can be extended by sacrificing the chorda tympani nerve:

The chorda is transected at its origin from the facial nerve
Drilling continues inferiorly along the fallopian canal with a small diamond burr and copious irrigation
The lateral limit of dissection becomes the tympanic annulus
The facial nerve courses laterally at the inferior extent, so superior-to-inferior drilling direction avoids injury

Indications for the extended facial recess include:

Access to the hypotympanum
Jugular bulb region (e.g., resection of glomus tympanicum tumors)

Clinical Uses

Indication	Role of Facial Recess
Cochlear implantation	Standard transmastoid-facial recess approach to reach the round window for electrode insertion
Cholesteatoma (CWU mastoidectomy)	Used when disease extends into the mesotympanum via this route
Ossiculoplasty	Allows accurate disarticulation of the incudostapedial joint
Glomus tympanicum	Extended facial recess for hypotympanum access
Cochlear malformations	Majority can be implanted via the standard transmastoid-facial recess technique

Sources: Shambaugh Surgery of the Ear, p. 534; p. 807 | Cummings Otolaryngology Head and Neck Surgery, Cochlear Implantation chapter

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