Bell Palsy: Quantitative Analysis of MR Imaging Data as a Method of Predicting Outcome

Abstract

Quantitative analysis of ROI MR imaging data is a valid method of predicting the outcome of acute facial nerve palsy during the first days after onset of symptoms and thus at a time when it is not yet possible to obtain valuable prognostic information by using electrophysiologic methods.

Enhancement pattern of the normal facial nerve at 3.0 T temporal MRI

“…In the labyrinthine segment, the nerve occupies nearly the entire fallopian canal, and at the tympanic and mastoid segment it occupies approximately 30-50% of its bony canal [14,15]. In patients with Bell's palsy, oedema and haemorrhagic infarction occur regularly in the labyrinthine segment [10,14]. This may indicate that the labyrinthine segment might be more vulnerable to ischaemic damage, consistent with the previously demonstrated narrowness of the labyrinthine and fallopian canal [13][14][15].…”

“…The markedly reduced flow of contrast material into the compressed endoneural capillaries in the labyrinthine segment may prevent flow of contrast material into this segment, resulting in minimal enhancement [2]. The intense enhancement of the meatal segment is considered pathological and is observed in Bell's palsy [3][4][5][6][7][8][9][10]. In this condition, enhancement of the facial nerve is caused by a breakdown of the blood-peripheral nerve barrier and subsequent diffusion of contrast material into the endoneural space.…”

“…In addition to normal enhancement of the facial nerve, the facial nerve may also enhance in association with many pathological conditions, including acute idiopathic peripheral facial paralysis (Bell's palsy), infections, inflammation (e.g. post-radiation injury), cholesteatoma, trauma, previous surgery, neoplasms and neurofibromatosis [3][4][5][6][7][8][9][10]14]. In our experience with Bell's palsy, the distal meatal and labyrinthine segments are characteristically intensely enhanced; therefore, intense enhancement of these segments is considered pathological.…”

“…The gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) contrast pulse sequence is the most informative MRI procedure for evaluation of facial nerve pathology [1]. Although many studies involving MRI of normal and paralysed facial nerves have been performed [2][3][4][5][6][7][8][9][10], there are no reports on the enhancement pattern of normal and abnormal facial nerves with 3.0 T MR scanning. The 3.0 T MR scan provides a higher signal-tonoise ratio (SNR), which allows a higher imaging matrix, thinner slices and a shorter time for scanning [11].…”

MR Diagnosis of Facial Neuritis: Diagnostic Performance of Contrast-Enhanced 3D-FLAIR Technique Compared with Contrast-Enhanced 3D-T1-Fast-Field Echo with Fat Suppression

“…However, the major disadvantage of EPS is its inability to detect diagnostic abnormalies of the nerve distal to the stylomastoid foramen within 1 week of symptom onset. 1 Although the potential of MR imaging has been studied as part of the effort to find other helpful diagnostic techniques over the past 20 years, [2][3][4][5][6][7][8][9][10] its results have been largely disappointing. Gd-DTPA-enhanced T1-weighted spin-echo and 3D spoiled gradient-echo sequences have shown significant limitations in diagnosing and predicting outcomes in patients with facial neuritis; the geniculate ganglion, tympanic, or mastoid segment of the normal facial nerve can be significantly enhanced in up to 76% of patients due to the distribution of arteriovenous plexus along the facial nerve, which, in turn, may inhibit evaluation of the pathologic enhancement of the nerves resulting from breakdown of the blood nerve barrier.…”