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. 2017 Apr 26:8:67.
doi: 10.4103/sni.sni_8_17. eCollection 2017.

Lower cranial nerve palsy after the infrafloccular approach in microvascular decompression for hemifacial spasm

Kenichi Amagasaki  1 , Nobuhiko Kurita  2 , Saiko Watanabe  1 , Naoyuki Shono  1 , Atsushi Hosono  1 , Kazuaki Naemura  1 , Hiroshi Nakaguchi  1
Affiliations

Lower cranial nerve palsy after the infrafloccular approach in microvascular decompression for hemifacial spasm

Kenichi Amagasaki et al. Surg Neurol Int. .

Abstract

Background: The infrafloccular approach was introduced as a variation in microvascular decompression (MVD) for hemifacial spasm. However, the rate of postoperative lower cranial nerve (CN) palsy can be high. This study investigated the surgical factors in relation to the occurrence of postoperative lower CN palsy.

Methods: The case records of 103 patients who underwent MVD were reviewed. Dissection around the lower CNs to approach the root exit zone of CN VII was divided into two steps - incision of the rhomboid lip at the root of the lower CNs and separation of CN IX and flocculus/choroid plexus. The correlations of these steps and other characteristics to the occurrence of lower CN palsy were analyzed.

Results: Ten of the 103 patients suffered from postoperative transient lower CN palsy. The rhomboid lip was incised in 30 cases (29.1%), separation of CN IX and flocculus or choroid plexus was necessary in 24 cases (23.3%), and both steps were required in 7 cases (6.8%). The steps showed no correlation with postoperative lower CN palsy. Posterior inferior cerebellar artery (PICA) as the offending vessel was significantly correlated with postoperative lower CN palsy (P < 0.05).

Conclusions: Our study showed that the offending PICA was the only significant factor for postoperative lower CN palsy. Therefore, correct dissection around the lower CNs, particularly for complicated PICA, is necessary to reduce the risk of postoperative lower CN palsy.

Keywords: Infrafloccular approach; PICA; lower cranial nerve palsy; microvascular decompression.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Illustrations showing surgical exposure of the root exit zone (REZ) of the CN VII. Left: REZ of the CN VII (asterisk) approached through the angle formed with CN VIII and CN IX. Right: Dissection (purple arrow) along the rootlets of the lower CN. Dissection (red arrow) along the rostral margin of CN IX. Labels VII, VIII, IX, X, and XI show CN VII (facial nerve), VIII (vestibulocochlear nerve), IX (glossopharyngeal nerve), X (vagus nerve), and XI (accessory nerve), respectively. F = Flocculus; CP = Choroid plexus; Rho-L = Rhomboid lip
See this image and copyright information in PMC

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