Abstract:

Objective　To provide evidence for the morphological diagnosis on the oppression and contact of the cisternal segment of facial nerve with its surrounding vessels.　Methods　140 normal and 70 patients with unilateral hemifacial spasm were selected by MRI 3D-FIESTA and 3D-TOF sequence scanning. The following parameters were observed in the MPR reconstruction image, including the vascular diameter, distance to brainstem vascular self angle and included angle at the intersection of the cisternal segment of facial nerve with its surrounding vessels, and its relationship with the morbidity of hemifacial spasm.　Results　The vascular diameter, distance to brainstem, vascular self angle and included angle at the intersection of the cisternal segment of facial nerve with its surrounding vessels were (0.48±0.03)mm, (0.49±0.04)mm, (0.71±0.06) mm and (8.69±0.62) mm, (8.66±0.75)mm, (5.93±0.47) mm and (74.39±2.33) °, (72.66±2.54) °, (48.57±3.28) ° and (85.60±3.07) °, (86.75±2.73) °, (88.41±3.76) ° on the normal group, uninjured group of hemifacial spasm, ipsilateral group of hemifacial spasm， respectively. There were significant difference between the ipsilateral group of hemifacial spasm to the normal group, uninjured group of hemifacial spasm at the vascular diameter, to brainstem distance and vascular self angle at the intersection of the cisternal segment of facial nerve with its surrounding vessels (P<0.05), there was no significant difference at the included angle(P>0.05). The morbidity decreased with the increase of intersection to brainstem distance, increased with the enlargement of vascular diameter and the reduction of vascular self angle. There was no significant change between the included angle to morbidity.　Conclusions　The vascular diameter, distance to brainstem and vascular self angle at the intersection of the cisternal segment of facial nerve with its surrounding vessels are important diagnostic markers whether the oppression or contact exists. The lesser of the vascular self angle, the larger of the vascular diameter and the shorter of the distance between the intersection and brainstem, the more prone the patient is to hemifacial spasm lesions.

Key words: Facial nerve, 　Brain vessel, 　Magnetic resonance imaging, 　Multiplanar reconstruction, 　Hemifacial spasm