PATHOLOGIES AFFECTING FACIAL NERVE
Oval window stenosis/atresia
The intimate relationship between formation of the oval window and development of the stapes footplate, horizontal segment of the facial nerve canal, and vestibular portion of the otic capsule results in commonly associated anomalies, including facial nerve malposition and incus and stapes malformations.
Facial nerve schwannoma(FNS).
FNSs usually involve more than one segment of the FN. Like schwannomas occurring elsewhere, FNSs are typically fusiform solid tumors with well-circumscribed smooth margins. They usually grow along the path of least resistance. They appear iso to hypo-intense to brain parenchyma on T1-weighted images and hyperintense on T2-weighted images. On diffusion-weighted imaging, there is usually no restriction. They generally show homogeneous postcontrast enhancement; however, cystic degeneration may result in heterogeneous enhancement (2,3). FNSs can show a “target sign” on T2-weighted images; however, this feature is nonspecific, and may be seen in other benign and malignant neurogenic tumors (4)
CHOLESTEATOMA-
In advanced cases, cholesteatoma can erode into the tegmen tympani or facial nerve canal, particularly the tympanic and mastoid segments. Pars tensa cholesteatoma is seen in 10–20% of cases and is centered in the lower two thirds of the tympanic membrane, medial to the auditory ossicles. Lesions can expand to involve the sinus tympani, facial nerve recess, aditus ad antrum, and mastoid air cells.(9)
BELLS PALSY
Bell's palsy a common MRI finding is enhancement of the labyrinthine portion of the facial nerve, where the facial canal is narrowest. in Bell’s palsy, MRI with gadolinium contrast often demonstrates enhancement of the intracanalicular and labyrinthine segments of the facial nerve, as well as a greater degree of enhancement of the geniculate ganglion, tympanic, and mastoid segments(11)
Here are 4 MRI T1 weighted images with contrast of a patient diagnosed with Bell’s palsy
MRI was significant for diffuse abnormal, asymmetric enhancement of the left intracanalicular (
Figures 1 and 2), labyrinthine (Figure 3), geniculate (Figure 1), tympanic (Figure 1) and mastoid (Figure 4) segments of the left facial nerve. There is a moderate left mastoid effusion. Edema is noted involving the left mandibular condyle. There is also edema and enhancement in the soft tissues overlying the left mandibular condyle and preauricular region, compatible with recent trauma (Figures 1 and 4).(10)![](https://epos.myesr.org/posterimage/esr/ecr2020/154176/media/866472?maxheight=300&maxwidth=300)
Fig. 1: Enhancement of intracanalicular, geniculate part and left periauricular region
References: Mumtaz S, Jensen MB. Facial neuropathy with imaging enhancement of the facial nerve: a case report. Future Neurol. 2014 Nov 1;9(6):571-576
![](https://epos.myesr.org/posterimage/esr/ecr2020/154176/media/866473?maxheight=300&maxwidth=300)
Fig. 2: Enhancement of intracanalicular segment and periauricular region
References: Mumtaz S, Jensen MB. Facial neuropathy with imaging enhancement of the facial nerve: a case report. Future Neurol. 2014 Nov 1;9(6):571-576
![](https://epos.myesr.org/posterimage/esr/ecr2020/154176/media/866474?maxheight=300&maxwidth=300)
Fig. 3: Arrows show enhancement of labrynthine segment of facial nerve and periauricular region
References: Mumtaz S, Jensen MB. Facial neuropathy with imaging enhancement of the facial nerve: a case report. Future Neurol. 2014 Nov 1;9(6):571-576
![](https://epos.myesr.org/posterimage/esr/ecr2020/154176/media/866475?maxheight=300&maxwidth=300)
Fig. 4: Arrows show enhancement of mastoid segment of facial nerve and left preauricular region.
References: Mumtaz S, Jensen MB. Facial neuropathy with imaging enhancement of the facial nerve: a case report. Future Neurol. 2014 Nov 1;9(6):571-576