Gorrie et al (2010) substantively added to the literature with their new article regarding vascular loops (VLs) and microvascular compression (MVC) as a cause of unexplained unilateral auditory symptoms.
Since the 1970s, the pioneering work of Jannetta (with regard to VLs impinging upon cranial nerves) has potentially explained hemi-facial spasm, trigeminal neuralgia. Additionally, some authors have speculated as to the presence of VLs with regard to VIIIth nerve symptoms, such as unilateral tinnitus, vertigo, and unilateral hearing loss.
In their retrospective study, Gorrie et al evaluated 58 patients with asymmetric sensoriuneural hearing loss (SNHL) who had high-resolution, thin-section, T2, fast spin echo magnetic resonance imaging (MRI) studies performed. Two scoring systems were employed to grade the VLs with regard to their anatomic location, as well as the amount of contact between the VL and the VIIIth cranial nerve.
Results included: 58 subjects facilitated 116 sides to be evaluated. VLs (Type I, see article) were present in 83 percent (48) of the symptomatic sides and VLs were also present in 76 percent (44) of asymptomatic sides. For 48 patients with unilateral hearing loss and tinnitus, 84 percent (40) of them had type I VLs on the symptomatic side and 77 percent (37) had Type I VLs on the asymtomatic side.
The authors note that MVC has been accepted as an explanation for hemi-facial spasm and trigeminal neuralgia and they note it is possible the same/similar process is responsible for some asymmetric VIIIth cranial nerve symptoms. Nonetheless, as there is no clearly defined clinical presentation of MVC related to the VIIIth cranial nerve, MVC is often used as a "diagnosis of exclusion." The authors concluded that there was no demonstrated significant relationship between the presence of VLs in the cerebellopontine angle, or VLs within the first 50 percent of the internal auditory canal (IAC), and hearing loss.
Gorrie et al said, "The presence of a loop lying directly adjacent to or displacing the VIIth cranial nerve was not found to be significantly associated with symptoms."
For More Information, References, and Recommendations
Gorrie A, Warren FM, de la Garza AN, Shelton C, Wiggins RH. (2010) Is There a Correlation Between Vascular Loops in the Cerebellopontine Angle and Unexplained Unilateral Hearing Loss?
Otology & Neurotology. 31(1):49-52.