Hemifacial Spasm Caused by Vascular Compression in the Cisternal Portion of the Facial Nerve: Report of Two Cases with Review of the Literature

Figure 1

Magnetic resonance imaging (MRI) and intraoperative findings of hemifacial spasm (HFS) caused by distal offender (the meatal loop of AICA, case 1).

(a) In the axial CISS image of left cerebellopontine angle, there was no vascular structure in the REZ of the facial nerve (arrowhead). A meatal loop of the anterior inferior cerebellar artery (AICA) is in close approximation with the cisternal portion of the facial nerve (arrow)

(b) An intraoperative photography showing an absence of any vascular offender in the root exit zone (REZ) of the facial nerve (arrow). Note the indentation of the distal facial nerve by the loop of the AICA (asterisk). : the seventh (facial) nerve, : the eighth (vestibulocochlear) nerve

(c) An intraoperative photography showing decompression of distal facial nerve with a small piece of Teflon felt from the loop of AICA (asterisk)

(d) Immediate disappearance of lateral spread response (LSR) of the facial EMG (mentalis muscle) following decompression of distal, cisternal portion of the facial nerve (left). Brainstem auditory evoked potential (BAEP) was stable (right)