Hemifacial spasm caused by vascular compression of the distal portion of the facial nerve

Abstract

It is generally accepted that hemifacial spasm (HFS) and trigeminal neuralgia are caused by compression of the facial nerve (seventh cranial nerve) or the trigeminal nerve (fifth cranial nerve) at the nerve's root exit (or entry) zone (REZ); thus, neurosurgeons generally perform neurovascular decompression at the REZ. Neurosurgeons tend to ignore vascular compression at distal portions of the seventh cranial nerve, even when found incidentally while performing neurovascular decompression at the REZ of that nerve, because compression of distal portions of the seventh cranial nerve has not been regarded as a cause of HFS. Recently the authors treated seven cases of HFS in which compression of the distal portion of the seventh cranial nerve produced symptoms. The anterior inferior cerebellar artery (AICA) was the offending vessel in five of these cases. Great care must be taken not to stretch the internal auditory arteries during manipulation of the AICA because these small arteries are quite vulnerable to surgical manipulation and the patient may experience hearing loss postoperatively. It must be kept in mind that compression of distal portions of the seventh cranial nerve may be responsible for HFS in cases in which neurovascular compression at the REZ is not confirmed intraoperatively and in cases in which neurovascular decompression at the nerve's REZ does not cure HFS. Surgical procedures for decompression of the distal portion of the seventh cranial nerve as well as decompression at the REZ should be performed when a deep vascular groove is noticed at the distal site of compression of the nerve.

Microvascular decompression for atypical hemifacial spasm: lessons learned from a retrospective study of 12 cases

“…4). 17 The characteristics of the case (Case 3) in which the REZ was compressed by the VA and PICA (Fig. 5) are consistent with those seen in typical hemifacial spasm as described by Mathur et al 12 …”

“…The present findings of our study demonstrate that distal compression of the seventh cranial nerve by blood vessels plays an important role. 17 Partial demyelination and axonal degeneration of the seventh cranial nerve in typical HFS with neurovascular compression have been also reported. 15 The same mechanism might be appropriate for interpreting the cause of AHFS with compression of a distal portion of the seventh cranial nerve.…”

“…Thus, we concluded that more force might be produced in inducing HFS at the distal area of the facial nerve. 17 As such, the incidence rate of AHFS is less than that of typical HFS. When facing patients with HFS, every neurosurgeon should carefully take the patient's history to identify typical or atypical HFS.…”

“…The entire intracranial segment of the facial nerve can be classified into 3 portions, including proximal (REZ), middle (between the REZ and the internal auditory canal), and distal (around the internal auditory canal). 17 Among our 12 patients, 2 patients suffered from proximal compression, 6 distal, 3 middle, and 1 both REZ and middle.…”

Infranuchal Infrafloccular Approach to the More Vulnerable Segments of the Facial Nerve in Microvascular Decompressions for the Hemifacial Spasm

“…Recently, there have been reports that not only the TRZ/CNS but also the other segments of the facial nerve can cause the HFS 8,10,18,28,31,36) . The distal cisternal segment and even the extracranial portion of the facial nerve have been reported to be sites causing HFS 2,7,8,10,18,28,31) . In patients with the HFS, both partial demyelination and axonal degeneration of the seventh cranial nerve may be essential to produce the hyperactivity of the facial motor nucleus.…”