Normal Facial Nerve Enhancement on Volumetric Interpolated Breath-Hold Examination MRI Sequence

Area of Science:

• Neuroradiology
• Medical Imaging
• Neuroscience

Background:

• Facial nerve enhancement on MRI can be attributed to its vascular plexus.
• Traditionally, enhancement beyond the geniculate ganglion was considered normal, while canalicular and labyrinthine segments were deemed abnormal.

Purpose of the Study:

• To investigate whether enhancement of the canalicular and labyrinthine segments of the facial nerve is a normal finding.
• To evaluate this finding on postcontrast T1-weighted, fat-saturated volumetric interpolated breath-hold examination (VIBE) sequences using both 1.5T and 3T MRI scanners.

Main Methods:

• Retrospective analysis of 50 patients (100 facial nerves) without facial nerve symptoms who underwent MRI with an internal auditory canal protocol.
• Two neuroradiologists independently assessed facial nerve segment enhancement on postcontrast T1-weighted, fat-saturated VIBE sequences from 1.5T and 3T scanners.

Main Results:

• On 1.5T MRI, enhancement was observed in 80% of canalicular and 92% of labyrinthine segments.
• On 3T MRI, enhancement was seen in 60% of canalicular and 84% of labyrinthine segments.
• High rates of enhancement were noted in tympanic, mastoid, and intraparotid segments on both scanners.

Conclusions:

• Enhancement of the canalicular and labyrinthine segments of the facial nerve is a normal finding on postcontrast T1-weighted, fat-saturated VIBE MRI sequences.
• Clinicians should consider clinical history and asymmetry to avoid misinterpreting this normal enhancement as facial nerve abnormality.