Three-dimensional MR volumetric analysis of the posterior fossa CSF space in hemifacial spasm.

BACKGROUND

We hypothesize that a smaller posterior fossa (PF) CSF space may be a risk factor for hemifacial spasm (HFS).

OBJECTIVE

We conducted a case-control 3-dimensional magnetic resonance (MR) volumetric study in patients with HFS and determined the clinical predictive factors of PF CSF volume.

METHODS

Patients with clinically diagnosed HFS and controls matched for age, sex, race, and hypertension underwent MRI/magnetic resonance angiography examination. The PF CSF space was segmented and quantified on a heavily T2-weighted high-resolution 3-dimensional MR volume slab, centered over the porus acusticus.

RESULTS

Eighty-two study subjects (41 patients and 41 controls) were included. The mean PF CSF volume in patients with HFS and controls was 17,303.0 +/- 3,900.0 vs 19,216.0 +/- 3,912.0 mm(3). The mean volume in patients with HFS was 11.4% smaller than in controls (p = 0.015). Analysis of differences between individually matched pairs and controls also revealed that PF CSF for controls was larger than that for patients with HFS (p = 0.007). A multivariate linear regression analysis revealed that a small PF CSF volume was associated with HFS (p = 0.01). Decreasing age (p = 0.001) and female gender (p < 0.0005), but not hypertension (p = 0.892), were also found to be predictors of a low PF CSF volume.

CONCLUSIONS

Our results showed that the posterior fossa (PF) CSF volume was lower in patients with HFS compared with matched controls. HFS, female gender, and younger age were associated with smaller PF CSF volume. These observations could explain the strong female preponderance in both clinic- and population-based epidemiologic studies.