Microvascular decompression for hemifacial spasm involving the vertebral artery: A modified effective technique using a gelatin sponge with a FuAiLe medical adhesive

Microvascular Decompression for Hemifacial Spasm Involving the Vertebral Artery (VA): A Modified Effective Technique Using a Gelatin Sponge with a FuAiLe Medical Adhesive. (a)The VA pushes the anterior inferior cerebellar artery (AICA) which compressed the root exit zone (REZ) of the facial nerve. (b) The VA was adhered to the petrous dura, and the AICA was decompressed from the REZ by a Teflon pad.


Microvascular decompression for hemifacial spasm involving
In HFS, the most common offending vessels (OVs) in 75% of cases are the posterior inferior cerebellar artery (PICA) and anterior inferior cerebellar artery (AICA). For such patients, the MVD technique is used to achieve satisfactory results with Teflon taps. The REZ of the facial nerve is from the pontomedullary sulcus to the pontine surface and is close to the vertebral artery (VA). Therefore, a quarter of the OVs of HFS are VAs. 4 If adding the numbers involving the VA (OVs are due to pushing by the VA or branching of the VA and only a transfer of the VA can achieve decompression), the rate of the VA as the OV of HFS is higher. When the VA is the OV, the diameter is larger; thus, the high blood flow in the above vessel also increases the pressure on the vessel wall. A curved OV experiences high tension due to the strong impact of blood flow. Additionally, the room for transfer is narrow. However, the Teflon decompression technique remains a challenge. Moreover, many previous studies have shown that MVD of HFS involving VA will exhibit higher rates of an incomplete cure and complications than those with the AICA or PICA. 5 Many methods have been used to solve the above problem in recent years. However, these techniques are often dangerous, complex, time-consuming, and increase the risk of surgical complications; therefore, they are not practical enough. [6][7][8][9][10][11] We introduce a simple and effective method using a gelatin sponge absorbed with a  Table 1. Magnetic resonance imaging was performed preoperatively. Pure tone audiometry was carried out to identify any hearing impairments before and after surgery. All of the patients were correctly diagnosed, and serious primary diseases were excluded. All 87 patients had at least a 1-to

5-year follow-up.
A conventional retrosigmoid approach was used in the MVD for HFS with a patient in the lateral decubitus position. The inferior basal aspect of the cerebellum was retracted from caudal to rostral.
The arachnoid membrane between the acoustic nerve and the Ⅸ, Ⅹ, and Ⅺ cranial nerves was dissected to expose the REZ of the facial nerve at the pons. The location of the OV was identified at the REZ.
The Teflon group used a conventional Teflon pad to decompress between the brain stem and the OV. The Fourth, the VA was pushed to the dura and held for several seconds to make sure that the VA firmly adhered to the dura. The last step was examining the ample space to decompress the REZ of the facial nerves from the OV (Figure 1).

Follow-up information was obtained through phone interviews and a review of the medical records from clinic visits. The efficacy
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. of MVD was categorized into 5 levels: early remission (complete and immediate disappearance of spasms), delayed remission (complete disappearance of spasms in 1 year), partial remission (slight spasms but better than that preoperatively after 1 year), failure (the same as that preoperatively after 1 year), and recurrence (spasms again after 1 year). A comprehension analysis of the surgical complications was performed postoperatively (in-patient) and after 1 year (follow-up visit). Permanent complications were compared, and transient complications were defined those as appearing in the patient postoperatively but that resolve after 1 year.
The complications included facial paralysis, hearing loss (>20 dB), and symptoms from the Ⅸ-Ⅺ cranial nerves (hoarseness, dysphagia, and choking). Statistical analyses were performed using SPSS version 18.0. Continuous variables are presented as the mean ±standard deviation, and categorical variables are presented as frequency (%). Age, sex, Cohen grade, duration, follow-up, surgical outcomes, and complications were compared across groups using chi-square tests, unpaired t tests, and Wilcoxon rank sum tests. A P-value less than 0.05 was considered to indicate significant differences between groups.

FAL (n = 33)
Teflon (n = 54) Other reported complications were as follows. Table 1. General accident characteristics, surgical complications, and operative outcomes of the two groups.
No significant differences were observed in terms of gender, age, Cohen grade, and duration or in the postoperative follow-up or complications between the two groups. The Wilcoxon rank sum test was used to compare the operative outcomes of the two groups, and the significance was calculated as Z = 2.53, p = 0.01.
Since Jenetta in 1966, it has been generally accepted that HFS is caused by a compression of the facial nerve at the REZ; thus, neurosurgeons generally perform neurovascular decompression at the REZ. In recent decades, MVD has been widely applied in clinical practice owing to its safety and efficacy. 1,12 The key for MVD is achieving a sufficient decompression. By exploring the REZ area of the cranial nerve, the OV is found, transferred, and fixed to prevent it from nearing the REZ. The most commonly used method to achieve decompression is the use of some material (usually a Teflon pad) as a fulcrum and raising the OV. The method of decompression for HFS is different from that for trigeminal neuralgia (TGN). MVD for TGN can be achieved only by separating the nerves from the OV by the Teflon pad. However, MVD for HFS requires the use of the Teflon pad as a bridge pier and the brain stem surface as the ground; in this way, the OV is lifted from the brain stem through the Teflon pier and becomes the bridge deck. The bridge needs to maintain a certain height so that the REZ of the facial nerve can flow smoothly, like water in a river. When appropriate decompression is provided, long-term spasm relief is achieved. 13,14 If the bridge pier is not high enough, collapses or is improperly distanced between the two piers, it may collapse, similar to a bridge, and then recompress the REZ of the facial nerve, which is the main cause of failure and recurrence.
When the OV is a smaller artery such as the AICA or PICA, the bridge using the above method is easy to build, and the surgical out- In addition, although bioprotein glue has better tissue compatibility and is safer than liquid chemical glue, the adhesion of FAL (a chemical glue) is stronger and adheres firmly. This is the key for decompression.
Avoiding the shortcomings of FAL as a chemical liquid and giving full consideration to the advantages of strong adhesion is similar to changing rocket fuel from a liquid to a solid to improve safety. We managed to achieve this through the use of a piece of gelatin sponge as a carrier that absorbed FAL. After transferring the VA from the REZ of the facial nerve, a FAL-absorbed gelatin sponge was placed between the dura and the VA, and then, pressure was administered for several seconds. The VA stuck tightly to the dura, and the decompression purpose was successful. This method avoids the uncontrollable flow of liquid glue, and the technique is simple, efficient, and safe. Compared with the control group using conventional Teflon decompression during the same period, the FAL technique shows a higher efficiency and fewer complications, making it an ideal technique to prevent the VA from approaching the facial nerve REZ.
Technical notes: 1. The gelatin sponge should be cut to a suitable size according to the adhesion space; furthermore, the area that is clipped by forceps must contain no FAL. Otherwise, it is difficult to withdraw the forceps.
2. If some surgical instruments are stuck to the FAL, then there can be no touching of the brain tissue, nerves, or blood vessels before being wiped and cleaned.
3. Sometimes, the operator must add in a drop of FAL to enhance the fixation. A plastic dropper must be used instead of a syringe because a syringe cannot precisely control the volume.
In most cases, one drop is enough. An excessive amount of FAL can flow to the subarachnoid space, and the chemical stimulation will cause meningitis and cranial nerve damage. 4. The OV and their artery perforators must be carefully protected from damage during transferring. All arteries must not be bent at such an angle that it affects blood flow after being adhered. If the distance between the OV and the dura is too great, then the thickness of the gelatin sponge should be increased, which will help protect and avoid artery perforators.