Common trunk anomaly of the anterior and posterior inferior cerebellar artery in hemifacial spasm.

BACKGROUND

The common trunk anomaly of the anterior and posterior inferior cerebellar artery (APC) is a variant artery that causes a hemifacial spasm (HFS). The anatomical characteristics include a large diameter of the trunk and the existence of the bifurcation near the facial nerve root entry zone (REZ). Despite APC being encountered at a constant rate in microvascular decompression (MVD), the anatomical and technical issues of transposing APC have not been entirely focused on yet.

METHODS

We reviewed our 68 cases with APC involvement. Patient background, radiological findings, and operative video recordings were reviewed retrospectively. The location of the bifurcation of APC and the distribution of perforators were investigated. Surgical outcomes were assessed in the long term.

RESULTS

APC involvement was diagnosed preoperatively in all cases by careful observation with MRI. Three-dimensional images determined the anatomical characteristics of APC and depicted the relationship with the facial nerve. All patients had a bifurcation close to the root entry zone that was required to transpose, including the common trunk and the distal branches, to achieve sufficient decompression. While adequate transposition from the REZ was accomplished in most cases, it was difficult to complete transposition due to short perforators in 6 patients (8.8%), resulting in interposition. Fifty-three patients (77.9%) became spasm free immediately after surgery, 66 patients (97.1%) were after 6 months, and all patients (100%) became spasm free within a year. Spasm-free status was maintained during the follow-up period (4.7 years) in all patients except one in whom facial spasm recurred 2 years after the initial surgery.

CONCLUSIONS

Transposing the common trunk with the bifurcation and distal branches contributes to obtaining favorable surgical outcomes in APC-related HFS.