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

Figure 2

Magnetic resonance imaging (MRI) and intraoperative findings of the right-sided hemifacial spasm (HFS) caused by distal offender (the postmeatal segment of AICA, case 2).

(a) An axial CISS MRI image of left cerebellopontine angle. Although the PICA (black arrowhead) is close to the REZ of the facial nerve (white arrowhead), there is no compression in the REZ (white arrowhead). The postmeatal segment of AICA (white arrow) is passing horizontally between the vestibulocochlear and facial nerves. The black arrow indicates the meatal segment of AICA

(b) An intraoperative photography showing an absence of any vascular offender in the root exit zone (REZ) of the facial nerve (arrow). There was no compression of the REZ from the loop of PICA. : the seventh (facial) nerve, : the eighth (vestibulocochlear) nerve, FL: flocculus

(c) The postmeatal segment of AICA (white arrow) is interposed between the vestibulocochlear and facial nerves. Although a small piece of Teflon (asterisk) was interposed below the loop of PICA, LSR did not disappear (Figure 2(e), black asterisk). Note the premeatal segment of AICA (arrowhead) behind the PICA

(d) After mobilization of the postmeatal segment of AICA (arrow) with dissection from the distal facial nerve, LSR disappeared (Figure 2(e), white asterisks)

(e) Disappearance of LSR of the facial EMG (orbicularis oculi muscle) following decompression of distal facial nerve (white asterisks) from the postmeatal segment of AICA. Teflon insertion beneath the PICA did not affect the LSR (black asterisk)