Surgical anatomy of the transtemporal approaches to the petrous apex.
OBJECTIVE
This study was undertaken to compare the subcochlear and infralabyrinthine approaches to the petrous apex.


BACKGROUND
Both approaches are advocated to drain cholesterol granuloma or biopsy lesions of the petrous apex. There is little data directly comparing these approaches.


METHODS
Anatomic dissections were performed on 20 preserved temporal bones. The anatomic distances were measured to the nearest quarter millimeter using a two-point needle caliper. Measurements were repeated three times and averaged.


RESULTS
The average window created through the subcochlear approach was 9.41 x 7.33 mm. The approach is performed between the carotid artery, jugular bulb, and basal turn of the cochlea, and gives a roughly triangular window in most cases. The cochlear aqueduct and glossopharyngeal nerve may be exposed during this approach. The subcochlear approach provided a more consistent exposure (SD of 3.5 x 1.9) and was always possible. Still, the exposure obtained through this approach may be limited if the hypotympanic air cell tract is sclerotic. The infralabyrinthine approach gave adequate exposure in most cases, but a high-lying jugular bulb obstructed this approach completely in eight of 20 cases. The average window created was 4.99 x 7.23 mm (SD 4.4 x 1.3).


CONCLUSIONS
The availability of a particular approach to the petrous apex and the exposure obtained varies considerably in individual cases. The choice of a surgical approach to the petrous apex should be influenced by the location of disease, the type of disease, the existing anatomy, and the experience of the surgeon.
Haberkamp
T J
TJ
Department of Otolaryngology and Human Communication, Medical College of Wisconsin, Milwaukee 53226, USA.
D003051:Cochlea / Q000601:surgery; D046508:Culture Techniques; D007758:Ear, Inner / Q000601:surgery; D006801:Humans; D010579:Petrous Bone / Q000033:anatomy & histology* / Q000601:surgery*; D013701:Temporal Bone / Q000601:surgery*