Hemifacial spasm etiology

Hemifacial spasm etiology

Although classical hemifacial spasm (HFS) has been attributed to an atraumatic pulsatile vascular compression around the root exit zone (REZ) of the facial nerve, rare tumor-related HFS associated with meningiomas, epidermoid tumors, lipomas, and schwannomas in the cerebellopontine angle have been reported. The exact mechanism and the necessity of microvascular decompression for tumor-induced HFS is not clear, especially for vestibular schwannomas.

In clinical pediatric neurosurgery practice, fourth ventricle tumor and cerebellar tumors are not rare. However, reports of secondary refractory hemifacial spasm are very rare. No report is currently available on the treatment of hemifacial spasm secondary to fourth ventricle and cerebellar tumors in China. Zamponi et al. [Childs Nerv Syst 2011 Jun;27(6):1001-5] reported that these lesions can occur in neonates and infants, and surgical resection is effective 1).


Imaging data of 341 patients with a HFS who underwent microvascular decompression were reviewed retrospectively and compared with 360 controls. The hemodynamics of typical anatomical variations of the vertebral artery (VA) were analyzed using computational fluid dynamics (CFD) software.

Asymmetry of the left and right VAs was prevalent, and the left VA was the most dominant VA. A dominant VA was more prevalent in the HFS group than in the control group (p=0.026). A Left HFS had a significantly higher proportion of a left dominant VA, and a right HFS had a significantly higher proportion of right dominant VA (p<0.001). CFD models showed that angulation and tortuosity of vessels caused remarkable pressure difference between vascular walls of opposite sides. Dynamic clinical observations showed the mode of vessel transposition coincided with biomechanical characteristics.

Anatomical variations and hemodynamics of the vertebrobasilar arterial system are likely to contribute to vascular compression formation in a HFS2).


Liu et al. retrospectively analyzed 10 patients with vestibular schwannomas out of 5218 cases of hemifacial spasm between 2004 and 2014.

Hemifacial spasm occurred ipsilateral to the vestibular schwannoma in 9 patients and contralateral to the lesion in 1 patient. The mean follow-up period was 86 months (range, 22-140 months). All patients underwent surgery for resection of the vestibular schwannoma. Following the principle of neurovascular compression, offending vessels were found in 7 patients, no offending vessels in 2 patients, and a tumor with the displacement of brain stem contributing to contralateral facial nerve compression in 1 patient. HFS was relieved immediately postoperatively in 9 patients, whereas it improved gradually and then resolved after one month in one patient with a contralateral vestibular schwannoma.

For HFS induced by vestibular schwannomas in this study, the majority of cases are caused by a combination of tumor and vascular co-compression at the REZ. Surgical intervention resulted in resolution of symptoms. For HFS with ipsilateral vestibular schwannoma, exploration of the facial nerve root for vascular compression should be performed routinely after tumor resection. It is critical to check that no vessel is contact with the entire nerve root 3).


During the period from October 1984 to October 2008, Han et al. treated 6,910 HFS patients using a microsurgical procedure. Of these HFS patients, 55 cases were associated with cerebellopontine angle tumors. A small craniectomy was performed in order to excise the tumor. All tumors were found to compress the root exit zone (REZ) of the facial nerve to different extents, but concomitant vascular compression of the facial nerve was observed in a majority of cases, and microvascular decompression of the facial nerve at REZ was conducted in 43 of 55 patients (78.2%) by displacing the co-compressing vasculature away from the REZ and retaining it using a Teflon pad. Intraoperative findings and postoperative pathological examinations suggested that the tumors were epidermoid cysts, meningiomas, and Schwannomas. Follow-up in 48 of 55 patients for 4-230 months after surgery showed that the clinical symptoms of HFS disappeared in 43 cases, improved in two cases, and recurred in three cases. Ten patients had sequelae associated with the operation. They concluded from this study that the majority of cases of tumor-related HFS are caused by combined tumor and vascular co-compression at the REZ, and tumor removal and microvascular decompression are required in order to relieve the symptoms 4).


Kindling-like hyperactivity of the facial motor nucleus induced by constant stimulation of compressing artery is considered as the predominant mechanism underlying the pathogenesis of Hemifacial spasm (HFS).

Trigeminal neuralgia, hemifacial spasm, vestibulocochlear neuralgia and glossopharyngeal neuralgia represent the most common neurovascular compression syndromes.

In nearly all cases, primary hemifacial spasm is related to arterial compression of the facial nerve at root exit zone (REZ). The offending arterial loops originate from the posterior inferior cerebellar artery (PICA), anterior inferior cerebellar artery (AICA), or vertebrobasilar artery (VB). In as many as 40% of the patients, neurovascular conflicts are multiple. The cross-compression is almost always seen on magnetic resonance imagingcombined with magnetic resonance angiography.


Hemifacial spasm (HFS) associated with type 1 Chiari malformation is particularly uncommon and is limited to isolated case report.

Li et al retrospectively evaluated 13 patients who had simultaneously HFS and type 1 Chiari malformation among 675 HFS patients. Clinical features and radiological findings were collected from each patient and analyzed. All these 13 patients were surgically treated with MVD through retro-mastoid microsurgical approach, and postoperative outcomes were evaluated. A review of literature about this association was also provided. In this study, the frequency of type 1 Chiari malformation in HFS patients was 1.9 %. The clinical profile of this series of patients did not differ from typical form of primary HFS. MVD achieved satisfactory results in 11 patients (85 %) in short- and long-term follow-up. There was no mortality or severe complication occurred postoperatively. Although rare, clinician should be aware of the association of HFS and type 1 Chiari malformation and consider MVD as an effective surgical management 5).

References

1)

Cai Y, Ge M, Qi X, Sun H, Zhang D. Ocular Dyskinesia and Hemifacial Spasm Secondary to Fourth Ventricular Tumor: Report of 4 Cases and Review of the Literature. Pediatr Neurosurg. 2019 Aug 22:1-8. doi: 10.1159/000501915. [Epub ahead of print] PubMed PMID: 31437843.
2)

Wang QP, Yuan Y, Xiong NX, Fu P, Huang T, Yang B, Liu J, Chu X, Zhao HY. Anatomical variation and hemodynamic evolution of vertebrobasilar arterial system may contribute to the development of vascular compression in hemifacial spasm. World Neurosurg. 2018 Dec 26. pii: S1878-8750(18)32897-3. doi: 10.1016/j.wneu.2018.12.074. [Epub ahead of print] PubMed PMID: 30593967.
3)

Liu J, Liu P, Zuo Y, Xu X, Liu H, Du R, Yu Y, Yuan Y. Hemifacial Spasm as Rare Clinical Presentation of Vestibular Schwannomas. World Neurosurg. 2018 Aug;116:e889-e894. doi: 10.1016/j.wneu.2018.05.124. Epub 2018 May 28. PubMed PMID: 29852302.
4)

Han H, Chen G, Zuo H. Microsurgical treatment for 55 patients with hemifacial spasm due to cerebellopontine angle tumors. Neurosurg Rev. 2010 Jul;33(3):335-9; discussion 339-40. doi: 10.1007/s10143-010-0250-0. Epub 2010 Mar 9. PubMed PMID: 20217169.
5)

Li N, Zhao WG, Pu CH, Yang WL. Hemifacial spasm associated with type 1 Chiari malformation: a retrospective study of 13 cases. Neurosurg Rev. 2016 Jul 15. [Epub ahead of print] PubMed PMID: 27422274.

Neuromelanin magnetic resonance imaging

Neuromelanin magnetic resonance imaging

Neuromelanin-sensitive MRI (NM-MRI) purports to detect the content of neuromelanin (NM), a product of dopamine metabolism that accumulates with age in dopamine neurons of the substantia nigra (SN). Interindividual variability in dopamine function may result in varying levels of NM accumulation in the SN; however, the ability of NM-MRI to measure dopamine function in nonneurodegenerative conditions has not been established.


Neuromelanin sensitive MRI may be the method of choice for the follow-up of meningeal melanocytoma 1).


Cassidy et al. validated that NM-MRI signal intensity in postmortem midbrain specimens correlated with regional NM concentration even in the absence of neurodegeneration, a prerequisite for its use as a proxy for dopamine function. They then validated a voxelwise NM-MRI approach with sufficient anatomical sensitivity to resolve SN subregions. Using this approach and a multimodal dataset of molecular PET and fMRI data, they further showed the NM-MRI signal was related to both dopamine release in the dorsal striatum and resting blood flow within the SN. These results suggest that NM-MRI signal in the SN is a proxy for function of dopamine neurons in the nigrostriatal pathway. As a proof of concept for its clinical utility, we show that the NM-MRI signal correlated to severity of psychosis in schizophrenia and individuals at risk for schizophrenia, consistent with the well-established dysfunction of the nigrostriatal pathway in psychosis. The results indicate that noninvasive NM-MRI is a promising tool that could have diverse research and clinical applications to investigate in vivo the role of dopamine in neuropsychiatric illness 2).


A study aimed to evaluate the accuracy and diagnostic test performance of the U-net-based segmentation method in neuromelanin magnetic resonance imaging (NM-MRI) compared to the established manual segmentation method for Parkinson’s disease diagnosis.

NM-MRI datasets from two different 3T-scanners were used: a “principal dataset” with 122 participants and an “external validation dataset” with 24 participants, including 62 and 12 PD patients, respectively. Two radiologists performed SNpc manual segmentation. Inter-reader precision was determined using Dice coefficients. The U-net was trained with manual segmentation as ground truth and Dice coefficients used to measure accuracy. Training and validation steps were performed on the principal dataset using a 4-fold cross-validation method. We tested the U-net on the external validation dataset. SNpc hyperintense areas were estimated from U-net and manual segmentation masks, replicating a previously validated thresholding method, and their diagnostic test performances for PD determined.

For SNpc segmentation, U-net accuracy was comparable to inter-reader precision in the principal dataset (Dice coefficient: U-net, 0.83 ± 0.04; inter-reader, 0.83 ± 0.04), but lower in external validation dataset (Dice coefficient: U-net, 079 ± 0.04; inter-reader, 0.85 ± 0.03). Diagnostic test performances for PD were comparable between U-net and manual segmentation methods in both principal (area under the receiver operating characteristic curve: U-net, 0.950; manual, 0.948) and external (U-net, 0.944; manual, 0.931) datasets.

U-net segmentation provided relatively high accuracy in the evaluation of the SNpc in NM-MRI and yielded diagnostic performance comparable to that of the established manual method 3)

References

1)

Matsuno H, Takasu S, Seki Y. Usefulness of Neuromelanin Sensitive MRI for En Plaque Meningeal Melanocytoma Involving the Cavernous Sinus: A Case Report. NMC Case Rep J. 2019 Mar 21;6(2):43-46. doi: 10.2176/nmccrj.cr.2018-0211. eCollection 2019 Apr. PubMed PMID: 31016099; PubMed Central PMCID: PMC6476814.
2)

Cassidy CM, Zucca FA, Girgis RR, Baker SC, Weinstein JJ, Sharp ME, Bellei C, Valmadre A, Vanegas N, Kegeles LS, Brucato G, Jung Kang U, Sulzer D, Zecca L, Abi-Dargham A, Horga G. Neuromelanin-sensitive MRI as a noninvasive proxy measure of dopamine function in the human brain. Proc Natl Acad Sci U S A. 2019 Mar 12;116(11):5108-5117. doi: 10.1073/pnas.1807983116. Epub 2019 Feb 22. PubMed PMID: 30796187; PubMed Central PMCID: PMC6421437.
3)

Le Berre A, Kamagata K, Otsuka Y, Andica C, Hatano T, Saccenti L, Ogawa T, Takeshige-Amano H, Wada A, Suzuki M, Hagiwara A, Irie R, Hori M, Oyama G, Shimo Y, Umemura A, Hattori N, Aoki S. Convolutional neural network-based segmentation can help in assessing the substantia nigra in neuromelanin MRI. Neuroradiology. 2019 Aug 10. doi: 10.1007/s00234-019-02279-w. [Epub ahead of print] PubMed PMID: 31401723.

Recurrent hemifacial spasm after microvascular decompression

Recurrent hemifacial spasm after microvascular decompression

Microvascular decompression (MVD) is a highly effective treatment for hemifacial spasm (HFS), but even if the root exit zone (REZ) from the brainstem is adequately decompressed, residual spasms after surgery or early reappearance of spasms are not uncommon 1) 2) 3) 4) 5)

Return of symptoms after a period of complete resolution of hemifacial spasm occurs in up to 10% of patients, 86% of recurrences happen within 2 yrs of surgery, and the risk of developing recurrence after 2 yrs of post-op relief is only ≈ 1% 6).


Among more than 2500 patients who underwent microvascular decompression for hemifacial spasm, 23 patients received a second MVD in the Kyung Hee University Hospital from January 2002 to December 2017. Three-dimensional time of flight magnetic resonance angiography and reconstructed imaging were used to identify the culprit vessel and its conflict upon root exit zone (REZ) of the facial nerve. They reviewed patients’ medical records and operation videos to identify the missing points of the first surgery.

8 patients had incomplete decompression, such as single-vessel decompression of multiple offending vessels. Teflon was not detected at the REZ, but was found in other locations in 12 patients. Three patients had severe adhesion with previous Teflon around the REZ. Nineteen patients had excellent surgical outcomes at immediate postoperative evaluation; 20 patients showed spasm disappearance at 1 year after surgery and 3 patients showed persistent symptoms. Neuro-vascular contacts around REZ of facial nerve were revealed on MRI of incomplete decompression and Teflon malposition patient groups. There were no clear neuro-vascular contacts in the patients with severe Teflon adhesion.

The decision on secondary MVD for persistent or recurrent spasm is troubling. However, if the neurovascular contact was observed in the MRI of the patient and there were offending vessels, the surgical outcome might be favorable 7).

References

1)

Fukushima T: Microvascular decompression for hemifacial spasm: results in 2890 cases, in Carter LP, Spetzler RF, editors. (eds): Neurovascular Surgery. New York, McGraw-Hill, 1995, pp 1133–1145
2)

Huang CI, Chen IH, Lee LS: Microvascular decompression for hemifacial spasm: analyses of operative findings and results in 310 patients. Neurosurgery 30: 53– 56; discussion 56–57, 1992.
3)

Ishikawa M, Nakanishi T, Takamiya Y, Namiki J: Delayed resolution of residual hemifacial spasm after microvascular decompression operations. Neurosurgery 49: 847– 854; discussion 854–856, 2001.
4)

Li CS: Varied patterns of postoperative course of disappearance of hemifacial spasm after microvascular decompression. Acta Neurochir (Wien) 147: 617– 620; discussion 620, 2005.
5)

Shin JC, Chung UH, Kim YC, Park CI: Prospective study of microvascular decompression in hemifacial spasm. Neurosurgery 40: 730– 734; discussion 734–735, 1997.
6)

Payner TD, Tew JM. Recurrence of Hemifacial Spasm After Microvascular Decompression. Neurosurgery. 1996; 38:686–691
7)

Park CK, Lee SH, Park BJ. Surgical Outcomes of Revision Microvascular Decompression for Persistent or Recurrent Hemifacial Spasm after Surgery: Analysis of radiological and intraoperative findings. World Neurosurg. 2019 Aug 2. pii: S1878-8750(19)32107-2. doi: 10.1016/j.wneu.2019.07.191. [Epub ahead of print] PubMed PMID: 31382068.
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