Objective: We report delayed resolution of hemifacial spasm (HFS), 11 years after suboccipital decompression for Arnold-Chiari type I malformation (ACM) with brainstem compression.

Background: Hemifacial spasm is a neuromuscular disorder characterized by involuntary synchronous spasms of one side of the face. It is usually caused by vascular compression of the facial nerve root entry zone. We report a case of HFS secondary to ACM with brainstem compression which resolved completely 11 years after suboccipital craniectomy for ACM. Although a few cases of microvascular decompression led to delayed resolution of HFS (L, 2015) (MY, 2017), to our knowledge this is the first reported case of delayed resolution of HFS following brainstem decompression in ACM.

Method: Case report.

Results: 82 year old woman presented with moderate left HFS with predominant orbicularis oculi and zygomaticus involvement, along with synkinesia. MRI of the brain and cervical spine showed ACM causing brainstem compression with syringomyelia extending from the cervical medullary junction to C5 vertebral body.
Suboccipital craniectomy and resection of C 1 arch with insertion of a dural patch graft for tonsillar herniation was successful in ameliorating symptoms and halting progression, but two subsequent surgeries were needed for progression of her large syringomyelia which extended down to the T4 level.
OnabotulinumtoxinA injections were successful in transiently treating her moderate HFS for about 9 years, but with wearing off she would have debilitating spasms. Ultimately, 11 years after surgical brainstem decompression, HFS spontaneously remitted such that the patient discontinued botulinum toxin injections. HFS has not recurred in the subsequent months.

Conclusion: HFS may resolve spontaneously over a decade after suboccipital craniectomy for ACM, which in this case may have caused traction of the facial nerve or compression of the CN7 nucleus by downward displacement of cerebellar tonsils. Clinicians should consider ACM as a possible cause for HFS when accompanied by other brainstem signs and symptoms. Further study is needed to better delineate the prognosis of HFS following surgical treatment of ACM.

References: 1. Xia L, Zhong J, Zhu J, Dou NN, Liu MX, Li ST. J Craniofac Surg. 2015 Mar;26(2):408-10. doi: 10.1097/SCS.0000000000001406. Review. PMID: 25668113 2. Lv MY, Deng SL, Long XF, Liu ZL. Br J Neurosurg. 2017 Jun;31(3):322-326. doi: 10.1080/02688697.2017.1297368. Epub 2017 Mar 13. PMID: 28288523

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MDS Abstracts - https://www.mdsabstracts.org/abstract/delayed-resolution-of-hemifacial-spasm-following-suboccipital-craniectomy-in-a-patient-with-arnold-chiari-malformation-type-i/