Arachnoid cyst alone causes hemifacial spasm: illustrative case

Abstract

BACKGROUND Hemifacial spasm (HFS) due to an arachnoid cyst at the cerebellopontine angle is rare. Here, the authors reported such a case and analyzed the mechanism of facial nerve hyperactivity by reviewing the literature. OBSERVATIONS A 40-year-old man presented with right HFS for the past 3 years. Preoperative magnetic resonance imaging revealed a right cerebellopontine angle cystic mass with high intensity on T2-weighted images, low intensity on T1-weighted and diffusion-weighted images, and no contrast effects. Cyst excision and decompression of the facial nerve using a lateral suboccipital approach to monitor abnormal muscle response (AMR) resulted in permanent relief. The cyst was histologically compatible with an arachnoid cyst. LESSONS In the present case, when the cyst was dissected, the AMR disappeared and no offending arteries were detected around the root exit zone. Therefore, the cyst itself was responsible for HFS, for which AMR was useful. Limited cases of HFS due to arachnoid cysts without neurovascular compression have been previously reported. The authors suggested that pulsatile compression by the cyst results in facial nerve hyperactivity and secondary HFS.

Arachnoid bands in hemifacial spasm: an overlooked etiology? Illustrative case

“…12 Although tumors such as epidermoid tumors, meningiomas, and acoustic neuromas, as well as cysts and aneurysms, have been associated with HFS, they are less frequently observed. [13][14][15] Yang et al 16 reported cases of HFS secondary to arachnoiditis caused by neurocysticercosis. Surprisingly, arachnoid bands have not previously been reported as a primary cause of HFS without any vessel involvement.…”

Lateral Spread Response: Unveiling the Smoking Gun for Cured Hemifacial Spasm

“…However, within the context of tumors originating from the facial nerve, such as facial nerve schwannomas, reports of facial spasm presentation are conspicuously absent [29][30][31]. This discrepancy may be attributed to the propensity of facial nerve If LSR disappears before decompression or persists after decompression, careful exploration is warranted.…”

“…However, within the context of tumors originating from the facial nerve, such as facial nerve schwannomas, reports of facial spasm presentation are conspicuously absent [29][30][31]. This discrepancy may be attributed to the propensity of facial nerve schwannomas to originate, predominantly, from the peripheral aspect of the facial nerve rather than from its Life 2023, 13, 1825 9 of 12 intracranial segment.…”