Bridge technique for hemifacial spasm with vertebral artery involvement

Abstract

Background: To assess efficacy and safety of a newly developed decompression technique in microvascular decompression for hemifacial spasm (HFS) with vertebral artery (VA) involvement.

Methods: A rigid Teflon (Bard^® PTFE Felt Pledget, USA) with the ends placed between the lower pons and the flocculus creates a free space over the root exit zone (REZ) of the facial nerve (bridge technique). The bridge technique and the conventional sling technique for VA-related neurovascular compression were compared retrospectively in 60 patients. Elapsed time for decompression, number of Teflon pieces used during the procedure, and incidences of intraoperative manipulation to the lower cranial nerves were investigated. Postoperative outcomes and complications were retrospectively compared in both techniques.

Results: The time from recognition of the REZ to completion of the decompression maneuvers was significantly shorter, and fewer Teflon pieces were required in the bridge technique than in the sling technique. Lower cranial nerve manipulations were performed less in the bridge technique. Although statistical analyses revealed no significant differences in surgical outcomes except spasm-free at postoperative 1 month, the bridge technique is confirmed to provide spasm-free outcomes in the long-term without notable complications.

Conclusions: The bridge technique is a safe and effective decompression method for VA-involved HFS.

Keywords: Bridge technique; Hemifacial spasm; Microvascular decompression; Supraolivary fossette; Surgical technique; Vertebral artery.

Fig. 1

Participant flow diagram. MVD, microvascular decompression; HFS, hemifacial spasm; VA, vertebral artery

Fig. 2

Schematic illustration of the bridge technique. a A schematic illustration of the vertebral artery (VA)-involved neurovascular compression (NVC). The anterior inferior cerebellar artery (AICA) and/or the posterior inferior cerebellar artery (PICA) are concomitantly involved in most cases. b, c The NVC is located at the supraolivary fossette (SOF), which is deeper than the lower pons and the flocculus. A Teflon bridge is first inserted parallel with the brainstem surface, then rotated 90 degrees (blue curved arrow) to reinforce holding the offenders and create free space on the root entry zone (REZ). The edges of the bridge are placed on the brainstem and the flocculus. d A schematic figure of a failed transposition. When a bridge is not rotated, the bridge may bend by compression force from the VA, resulting in re-compression onto the nerve root (blue arrow)

Fig. 3

Figure presentation of the bridge technique. a A Teflon bridge cut out from a Teflon sheet (Bard^® PTFE Felt Pledget, nominal thickness 1.65 mm). Appropriate length of 15–18 mm and width of 3–4 mm. b A schematic figure elevating the VA (red tube) with a single Teflon bridge. c A dual bridge for high-compression force from the VA. One of the bridges can be placed either above or below the lower cranial nerves. d A folded bridge is another method for high-compression force from the VA. A longitudinally folded Teflon bridge can reinforce supporting the VA. e A brainstem figure with a Teflon bridge shows the typical placement of a bridge over the SOF. The medial edge is placed on the brainstem near the abducens nerve (black arrowhead). The lateral edge is placed on the bottom of the flocculus (yellow arrowhead). A small free space is created over the REZ of the facial nerve (white asterisk). f The same figure looking from the lateral shows a free space (white asterisk) created over the REZ on the SOF

Fig. 4

Data analyses of operative manipulations. a Decompression time (blue column, sling technique; orange column, bridge technique) from identification of the REZ to completing the decompressive maneuvers in a single procedure. (*, significant difference) b Number of Teflon pieces used for decompression in a single MVD. c Number of cases requiring lower cranial nerve manipulation among 30 patients in each technique. LCN, lower cranial nerves

Fig. 5

Case presentation (Case 1). A 70-year-old woman with HFS on the right caused by the VA and AICA compression. a An intraoperative photograph of MVD for hemifacial spasm on the right side. A Teflon bridge (TB) is inserted to reposition the offenders, the VA, and the AICA. The lateral edge is placed on the base of the flocculus (FL), and the other edge is placed on the brainstem near the exit of the abducens nerve. b A photo from the caudal side shows a free space over the root exit zone (REZ) of the facial nerve (white asterisk) created under the bridge. c A postoperative computed tomography (CT) taken postoperative1 week indicates the location of the bridge (white rectangular shape) and a free space over the REZ (white arrowhead). d Magnetic resonance imaging (MRI) taken 6 months after surgery shows a free space (white arrowhead) maintained in front of the REZ and the transposed offenders in place on the Teflon bridge

Fig. 6

Case presentation (Case 2). A 54-year-old man with HFS on the left due to the VA and the AICA. a An MRI slice shows neurovascular compression by the AICA in combination with the VA on the facial nerve on the left side. b An MRI taken 1 year after MVD demonstrates the inserted bridge in place and a free space maintained over the REZ (asterisk). c A pre-operative three-dimensional (3D) image shows a relationship between the facial nerve and the adjacent structures. The AICA is the direct compression onto the REZ. The VA should be repositioned simultaneously to obtain sufficient decompression. d An intraoperative photograph indicating a single Teflon bridge inserted just above the ninth cranial nerve root to reposition the offenders, the VA, and the AICA. The lateral edge is placed on the flocculus, and the other edge is placed on the brainstem near the exit of the abducens nerve

Fig. 7

Case presentation (Case 3). A 44-year-old man with HFS on the left. The VAs on both sides, the PICA, and the AICA are involved. a A Gadolinium-enhanced MRI shows multiple offenders present near the REZ of the facial nerve on the left side. b A three-dimensional (3D) image looking from the lower-left clarifies the anatomical relationships of the offending arteries and the facial and vestibular nerves. c An intra-operative photograph shows the cistern is occupied with the offenders and the stretched cranial nerves. The hypoglossal nerve (XII) is at an unusual location stretched by the PICA orifice from the left VA. d A photo showing identification of the REZ of the facial nerve (black asterisk) after elevating both vertebral arteries and the PICA away from the brainstem. The AICA is still deeply impinging onto the REZ of the facial nerve. The AICA is relocated laterally (yellow arrow) together with other offenders, and then, a Teflon bridge is inserted into the gap (green arrow). e All offenders are held with a Teflon bridge (colored in light green). Two additional small Teflon pieces are placed on both edges to secure the position of the bridge. f A post-operative 3D-CT demonstrates the bridge (green) is holding all offenders. g An enhanced MRI shows the offenders elevated away from the facial nerve with a free space over the REZ (white arrowhead). h An MRI with fast imaging employing steady-state acquisition shows cerebrospinal intensity over the REZ of the facial nerve (white arrowhead)