Objective       To investigate the measurement method of posterior fossa volume

and to determine whether occurrence of hemifacial spasm is related to posterior fossa volume.       Methods       Sixty female patients with hemifacial spasm hospitalized in our department from 2008 to 2009 and 60 healthy controls were enrolled. All the subjects had no intracranial tumor

hydrocephalus or head injury

and they all received head MRI examination (slice thickness=1 mm). AW4.4 workstation and 3D reconstruction software were applied to measure posterior fossa volume. No significant difference of height and age existed between the patients with hemifacial spasm and healthy controls (P0.05).       Results       There was no significant difference of posterior fossa volume between the patients with h

emifacial spasm [(165.682±12.474) cm

3

and the healthy controls [(159.151±18.798) cm

3

]

(P0.05).       Conclusion       Application of MRI scanning and 3D reconstruction software can measure posterior fossa volume

which is not related to hemifacial spasm.