Surgical anatomy of the anterior supralabyrinthine air cell tract M B GLUTH 1 , M A COHEN 2 , P L FRIEDLAND 3 , M D ATLAS 3 1 Division of Otology and Neurotology, Department of Otolaryngology, University of Arkansas for Medical Sciences, Little Rock, USA, 2 Department of Otolaryngology, Universidad de Chile, Clinica Las Condes, Santiago, Chile, and 3 Ear Sciences Centre, University of Western Australia School of Surgery and Ear Science Institute Australia, Perth, Australia Abstract Introduction: In order to safely explore the medial wall of the attic, a working knowledge of the anatomy of the anterior supralabyrinthine air cell tract is required. Aim: To clarify the surgically relevant anatomical relationships that comprise the anterior supralabyrinthine air cell tract. Materials and methods: Surgical dissection of 10 fresh cadaveric temporal bones was undertaken, including measurement of distances between the key anterior supralabyrinthine anatomical landmarks. Results: The following mean distances were calculated: the labyrinthine segment between the geniculate ganglion and the ampullated end of the superior semicircular canal, 2.33 mm (range 1.75–2.75); the tympanic segment between the anterior margin of the oval window niche and the geniculate ganglion, 3.58 mm (range 3.25–4); and from the tympanic segment adjacent to the anterior margin of the oval window niche to the labyrinthine segment adjacent to the superior semicircular canal, 3.48 mm (range 3 –4.25). Conclusion: The key anatomical landmarks of the anterior supralabyrinthine air cell tract define a distinct triangular segment of bone, knowledge of which is helpful in surgical dissection. Key words: Mastoid; Temporal Bone; Cholesteatoma; Facial Nerve; Geniculate Ganglion Introduction Otological surgical practice may require drilling and exploration of the medial wall of the attic. Understanding the anatomical relationships and tem- poral bone pneumatisation in this region provides the basis for safe and thorough surgical exploration. Categorisation of temporal bone pneumatisation has classically described five groups of air cell tracts, namely mastoid, perilabyrinthine, apical, peritubal and accessory. 1 –3 The perilabyrinthine air cell tract is encountered during surgical exploration of the medial attic wall. This group is bisected into separate areas of supralabyr- inthine and infralabyrinthine tracts by the bony labyr- inth. The supralabyrinthine area (see Figure 1) is further subdivided into posterosuperior, posteromedial and subarcuate tracts. The former two of these extend parallel to each other immediately posterior to the bony labyrinth adjacent to the junction of the middle and posterior fossa dura. The subarcuate tract runs through the arch of the superior semicircular canal. However, a fourth subset of the supralabyrinthine tract exists – the anterior supralabyrinthine air cells – located immediately anterior to the labyrinth in its superior aspect, and comprising much of the medial attic wall. This anterior supralabyrinthine tract is less often mentioned in classical descriptions of temporal bone pneumatisation. However, in the clinical experience of the authors, this is an area that commonly requires surgi- cal dissection when managing disease processes such as expansile attic cholesteatoma or irreversible mucosa disease. 4 –6 In addition, an intimate understanding of this region is required during surgical management of the facial nerve in cases of trauma or neurotological skull base surgery. Safe negotiation of this tract requires a working knowledge of the relationships between the ampullated end of the superior semicircular canal, the labyrinthine segment of the facial nerve, the geniculate ganglion and the adjacent middle fossa dura. In this report, we aim to better clarify the surgically relevant relationships that comprise the limits of the anterior supralabyrinthine air cell tract. Accepted for publication 6 January 2011 First published online 14 June 2011 The Journal of Laryngology & Otology (2011), 125, 1009–1013. MAIN ARTICLE © JLO (1984) Limited, 2011 doi:10.1017/S0022215111001319