MDCT ASSESSMENT OF THE COCHLEAR-CAROTİD INTERVAL

H.Pınar Gunbey, M.D. ¹Huseyin Aydın, M.D.²Huseyin Cetin, M.D¹

¹Ataturk Education and Research Hospital, Ankara,² Gulkent Hospital, Isparta

Turkey

Background

The cochlea and the carotid canal are among a number of crucial anatomic structures that extremely close one to another in the petrous pyramid of temporal bone

Anatomic knowledge of these vital structures and relations between them provides an important key to approach this complex region

This close anatomic course represents possible surgical risk during

petrosectomy apporach to the clivus brainstem or the middle fossa apporach to the internal

acustic meatus or most recentlly increasingly popular the cohlear

implant surgery. Especially internal carotid artery (ICA) lesion

transoperative bleeding risk difficult to control serius results associated with the irrigation of the central nervous system

In cochlear implant surgery the risk of potential injury to the

carotid artery may be seen during drilling of the basal turn of the cochlea and improper placement of the electrode

The instance between the cochlea and the carotid artery may be also a possible reson for auditory and vestibular symptoms such as tinnitus and hearing loss.

Purpose

investigate the normal range of the this region called ‘‘ cohlear- carotid interval’’ (CCI) in a wide population by 64-slice multi-detector computed tomography (MDCT).

Materials and Method A retrospective study who had undergone a

temporal MDCT between September 2008 and March 2010

1105 patients (510 M and 595 F) 0,5 mm thickness coronal images by 64-

slice MDCT The bony interval for right and left sides

confirming from axial and sagittal planes of multiplanar reformat images

Measured independently by 2 observers

Mann Whitney U test and Sperman correlation test were used to assess differences between readers ,sides and gentles

Results

All subjects (mm)

Female (mm)

Male (mm)

Right Range 0,0-6 0,0-5,8 0,0-6 Mean ± SD

0,9 ± 0.8 1.0 ± 0.8 1.0 ± 0.8

Left Range 0.0-5.9 0.0-5.9 0,1-5,4 Mean ± SD

1.0 ± 0.8 1.0 ± 0.8 1.0 ± 0.8

Carotid-cochlear interval measures

CCI measured 0.0 mm unilateraly in 8 patients (0.7%) (Young et al.2006)

bilateraly in 2 patients (0.1%) (Modugno et al.2004)

a score of 10 in total population (0.9%) CCI scores of total population a range

of 0,0 to 6 mm for the right side (mean 0,9 ± 0.8) and 0,0 to 5.9 mm for the left side (mean 1.0 ± 0.8;)

CCI dehisence

3D reconstruction

Bilateral dehisence

No relation CCI measures and subject gender

Positive correlation Right and left side CCI mesures

Conclusion The cochlea- carotid interval represents a wide

variation independently from gender and the distance can be in microns

The dehisence can be seen unilateraly and more less bilateraly in a large population.

It is a developmental defect like superior semisircular canal dehisence and may be related with defects on maturation stages.

In preoperative CT imaging special attention to this close relationship may allow the radiologist :

to play a crucial role in alerting the surgeon to prevent the penetration of the carotid canal during cochlear surgery and the cochlear injury during vasculary surgery.

Possible surgical risk may result in unexpected tragic damage