MDCT Assessment of the Cochlear-Carotid Interval

Carotid-cochlear dehiscence: a dangerous mimicker of inner ear pathologies

A 67-year-old woman was referred to the otolaryngology service after presenting to the emergency department for dizziness and loss of balance. She reported several similar episodes over the past years. Physical examination was unremarkable. A temporal bone CT scan revealed dehiscence between the bony carotid canal and the cochlea resulting in the diagnosis of carotid-cochlear dehiscence (CCD). CCD is an extremely rare condition involving the thinning of the bony canal separating the internal carotid artery from the cochlea. CCD is best diagnosed with temporal bone CT scan. Treatment options include observation as well as chemical or surgical labyrenthectomy. Despite similar clinical and diagnostic characteristics of reported CCD cases, general trends and consensus on treatment options cannot be ascertained due to the extreme rarity of this condition. Regardless of these limitations, CCD is a critical diagnosis as it mimics other inner ear conditions and poses a potential, significant surgical risk for the otolaryngologist.

The impact of the cochlear-carotid interval on tinnitus perception

PURPOSE

We hypothesized that the cochlear-carotid interval (CCI), which is defined as the smallest distance along the petrous segment of the internal carotid artery and basal turn of cochlea, may be associated with direct stimulation of hair cells, thereby affecting tinnitus perception. The aim of this study was to investigate the relationships between the CCI, tinnitus perception, and accompanying hearing loss in patients with tinnitus.

METHODS

The CCI on both sides was measured independently by two observers from the temporal 3D b-FFE MR images of 25 patients with tinnitus and 20 age/gender matched control subjects. The relationships between CCI, tinnitus visual analog scale (VAS), and tinnitus handicap inventory (THI) were investigated.

RESULTS

CCI ranged 0.2-5.6 mm (1.9 ± 1.5) on the right and 0.1-5.4 mm (2.2 ± 1.6) on the left side in the patient group and 0.5-5.4 (1.9 ± 1.4) mm on the right and 0.3-6.7 (2.3 ± 1.7) on the left side in the control group. The differences between the two groups were not statistically significant (p > 0.05). CCI showed a strong negative correlation with THI and VAS scores on both sides. Correlation of audiologic findings with CCI revealed a significant negative correlation with pure tone average of the ipsilateral ear most affectedly at high frequencies.

CONCLUSION

The strong negative correlation of CCI with tinnitus-related distress and accompanying sensorineural hearing loss predominantly at high frequencies suggests that further studies on patients with tinnitus that focus on this small area may help to improve the knowledge of tinnitus pathophysiology.