Evaluation of the facial nerve and internal auditory canal cross-sectional areas on three-dimensional fast imaging employing steady-state acquisition magnetic resonance imaging in Bell’s palsy

Abstract

Background/aim: This study aimed to evaluate the facial nerve (FN) and internal auditory canal (IAC) on three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA) magnetic resonance imaging (MRI) to define possible structural differences in cases of Bell's palsy (BP). Materials and methods:Fifty-six patients presenting with BP were included in this study. The measurements of the diameters and the cross-sectional areas (CSAs) of the FNs and IACs obtained on 3D-FIESTA MRI both on the affected and unaffected sides of all patients were compared.Results: A significant difference was found between affected and unaffected sides of the patients in terms of the mean CSA of the FN and IAC (P < 0.001). The CSAs of the FN were larger and the CSAs of the IAC were smaller on the affected sides than the equivalents on the unaffected sides of the patients, respectively. The difference in terms of the ratios of IAC CSA to FN CSA between affected and unaffected sides of the patients was also found to be statistically significant (P < 0.001). Conclusion:We have found that FN and IAC size differ on the affected sides of patients with BP. These anatomical differences may contribute to the risk for this disease.

The etiology of Bell’s palsy: a review

“…From this point, it is accompanied by the CN VIII along its cisternal pathway to the internal auditory meatus. Specifically, its petrous route includes a labyrinthine segment, a horizontal tympanic segment, and a vertical mastoid segment, which extends until it reaches the stylomastoid foramen and the Table 1 Summary of key evidence for the etiological theory about anatomical structure Key references Summary of evidence [9] Yilmaz et al detected lower internal auditory canal (IAC) inlet as well as mid-canal values in the patients with Bell's palsy [10][11][12] The cross-sectional areas (CSAs) of facial nerve (FN) were larger and the CSAs of IAC were smaller on the influenced sides than the equivalents on the uninfluenced sides of the patients, respectively. There is a significant difference between influenced and uninfluenced sides of the patients in terms of the mean CSA of the FN and IAC (p < 0.001).…”

“…Anatomical differences are critical in assessing cases of BP. After Yilmaz et al [9] assessed the lower internal auditory canal (IAC) inlet as well as mid-canal values in patients with BP, Ozan and Arslan [10] compared the diameters and cross-sectional areas (CSAs) of the facial nerve (FN) and IAC between the affected and unaffected sides of 56 patients via three-dimensional fast imaging, employing steady-state acquisition magnetic resonance imaging (MRI). They also found a notable difference between the affected and unaffected sides of the patients in terms of their mean CSAs of the FN and IAC (p < 0.001).…”

Low Field MRI Measurements of the Normal Canine Trigeminal Nerve

“…Neural ratios help to normalize measurements within a population when absolute values vary significantly. In human medicine, cranial nerve neural ratios are increasingly quoted as reference intervals (RIs) and disease markers in MR studies; for example, optic nerve-to-optic tract ratios provide better assessment of pediatric optic pathways than absolute diameters because they do not vary with age (19), a larger facial nerve-tofacial canal ratio conveys increased risk of Bell's Palsy (20,21) and a reduced cochlear nerve-to-facial nerve ratio is associated with sensorineural hearing loss (22).…”

Evaluation of Bell’s palsy in the cerebellopontine angle: An MRI study

“…measurement of the meatal and cisternal segments, several studies have been conducted on the morphometry of the FN. [2][3][4][5][6] The present study focused on the cisternal segment to further analyse the FN swelling through MRI evaluation. Because of the absence of an anatomic barrier as the fallopian canal (FC) in the temporal bone, the possible involvement of all FN segments may be better evaluated in the cisternal and meatal segments with MRI.…”

“…7 Swelling of the meatal segment of the FN in BP was determined by making a comparison with the unaffected side by the 3D Fast Imaging Employing Steadystate Acquisition (FIESTA) sequences of MRI. 2 In this study, it was aimed to delineate the changes in the cisternal segment of FN and compare it with the normal side in BP patients based on the previously conducted preliminary experiment that compared the actual anatomic nerve dimensions with MRI findings for more appropriate radiologic boundaries.…”