Hemifacial Spasm Caused by Epidermoid Tumor at Cerebello Pontine Angle

Abstract

Hemifacial spasm (HFS) is almost always induced by vascular compression but in some cases the cause of HFS are tumors at cerebellopontine angle (CPA) or vascular malformations. We present a rare case of hemifacial spasm caused by epidermoid tumors and the possible pathogenesis of HFS is discussed. A 36-year-old female patient presented with a 27-month history of progressive involuntary facial twitching and had been treated with acupuncture and herb medication. On imaging study, a mass lesion was seen at right CPA. Microvascular decompression combined with mass removal was undertaken through retrosigmoid approach. The lesion was avascular mass and diagnosed with an epidermoid tumor pathologically. Eventually, we found a offending vessel (AICA : anterior inferior cerebellar artery) compressing facial nerve root exit zone (REZ). In case of HFS caused by tumor compression on the facial nerve REZ, surgeons should try to find an offending vessel under the mass. This case supports the vascular compression theory as a pathogenesis of HFS.

Epidermoid cyst causing hemifacial spasm epidermoid cyst in cerebellopontine angle presenting with hemifacial spasm

“…[8] As for HS induced by benign tumors in many cases, as in our patient, previous researchers suggested that the vascular compression under the tumor is the main cause of the HS. [9,10] Typical MRI appearance of an epidermoid tumor is hypo to slight hyperintense on T1W images, iso to hyperintense on T2W images, and hyperintense on DWI. [11,12] Arachnoid cysts and schwannomas also appear as hyperintense on T1W images and hyperintense on T2W images.…”

Hemifacial Spasm Developed after Contralateral Vertebral Artery Ligation

“…Offending vessels are most often found on preoperative radiologic evaluation or during surgery; MVD of these offending vessels has yielded successful outcomes in large serial studies 1 , 8) . In several rare secondary causes of HFS, including CPA tumors, aneurysms, and AVMs, compression of the facial nerve REZ by altered vasculature is also considered the etiology of HFS 5 , 7 , 10 , 13 , 17 , 18) .…”

“…Although the mechanism of HFS is not yet well established, vascular compression of the facial nerve root exit zone (REZ) is one likely mechanism given the effectiveness of microvascular decompression (MVD) in the treatment of the disorder 1 , 7 , 9) . Moreover, the vascular compression theory has been accepted as the etiology of rare secondary HFS in some cases of cerebellopontine angle (CPA) tumors, aneurysms, and arteriovenous malformations (AVMs) 5 , 7 , 10 , 13 , 17 , 18) . However, another theory for the mechanism of HFS, hyperexcitability of the facial nucleus, has also been suggested.…”

Commentary

“…[ 5 ] Among 2050 HFS patients, CPA tumors were detected in 9 (0.4%) and 2 of them were epidermoids. [ 6 ]…”

“…[ 4 ] Recently, arterial compression at the root exit zone was also reported in the majority of HFS cases with CPA epidermoids. [ 5 6 ]…”