[Preoperative etiological diagnosis of hemifacial spasm: a comparative study between magnetic resonance tomographic angiography and intra-operative findings].

Objective: To summarize retrospectively the value of magnetic resonance tomographic angiography (MRTA) in the preoperative etiological diagnosis for hemifacial spasms (HFS).

Methods: 336 cases of HFS, 127 male and 209 female, aged 46.2 (16-75), with a course of 1-29 years (6.2 years on average) and with the unilateral symptoms except one case were subjected to routine MRTA check up preoperatively. The MRTA findings were compared with the operative findings.

Results: Pre-operative evaluation by MRTA discerned 273 offending vessels with a positive rate of 81.3%, which were completely consistent with the intra-operative findings. The false positive and false negative rates were 8.0% and 9.8% respectively. Three cases of HFS due to secondary cause were found: one of CPA meningioma at the cerebellopontine angle and two cases of cholesteatoma.

Conclusion: MRTA imaging provides more useful information concerning the etiology of hemifacial spasm than any other available diagnostic modalities. It is an effective and reliable means for pre-operative evaluation of the existence and sources of offending vessels in hemifacial spasm patients, and thus benefits the planning and guiding of intra-operative manipulation.