Long-term Observation On Curative Effect Of Hemifacial Spasm Treated By Microvascular Decompression And Facial Nerve Root Combing

Background and ObjectHemifacial spasm (HFS) is a peripheral movement disorder caused by direct or indirect compression or distortion of the root exit zone of the seventh cranial nerve, which is most commonly compressed by an arterial loop, but also may be compressed by a tumor, cyst, or aneurysm. HFS is a peripherally induced movement disorder characterized by involuntary and unilateral contractions involving the upper and lower facial muscles.Even if HFS begins in the orbicularis oculi or another muscle innervated by the facial nerve, it usually spreads to involve most divisions with time. Although some patients are not bothered by the spasms, others complain that it interferes with vision or speaking and it often causes embarrass- ment.Hemifacial spasm is a long-term disease from which patients rarely recover spontaneously. Primary HFS is commonly attributed to vascular loops compressing the seventh cranial nerve at its exit zone from the brainstem. The facial nerve compression is thought to lead to ephaptic transmission and to hyperactivity of the facial nucleus, resulting in the involuntary facial movements. Secondary HFS frequently follows peripheral facial palsy or may arise from facial nerve damage produced by tumors, demyelinating disorders, traumatisms, and infections. A study about Prevalence of hemifacial spasm in Oslo, Norway shows that Fifty patients with HFS were treated. The total prevalence was 9.8 per 100,000. Incidence and prevalence rates were highest in those ages 40 to 79.Usually without any identifiable etiology, this peripheral movement disorder has been most frequently attributed to compression of the facial nerve at the root exit zone (REZ) by an ectopic anatomical or pathological structure resulting in―ephaptic transmission.‖Antidromic stimulation of the facial nucleus has been thought to produce a―kindling‖effect. Compression by an atherosclerotic,aberrant,or ectatic intracranial artery near the REZ,first described in 1947 by Campbell and Keedy,14 has been recognized as one of the most common mechanisms of this condition. Other sources of compression include arteriovenous malformation(AVM),aneurysm, different types of brain tumors,meningioma,and bony abnormalities of the skull localized in the ipsilateral cerebellopontine angle (CPA) or on the contralateral side, distorting the normal anatomy of the ipsilateral facial nerve. All patients with HFS should undergo magnetic resonance imaging, with particular attention to the seventh cranial nerve.A number of studies have suggested that the most frequent etiology of HFS is compression of the facial nerve at its REZ by aberrant or ectatic blood vessels. The anterior inferior cerebellar artery or PICA are most commonly involved and unusual tortuosity of these vessels has been frequently found during microvascular decompressive procedures; an ectatic vertebral artery, aneurysm of the basilar artery, and AVM are some of the other vascular abnormalities noted in patients with HFS.Microvascular surgical decompression has the advantage of being potentially curative.Surgery carries much greater availability than botulinum toxin and Oral medications,and lower risk of recur than other therapeutics. Spasm is believed to be caused by compression of both the facial nerves by an abnormal anatomical structure.Microvascular decompression(MVD) for HFS relieves both conditions. Both microvascular decompression and facial nerve root combing(FNRC) were perfo- rmed to reduce recurrence. The other cases with perforating artery or without any compressing vessels underwent the FNRC.So we choose the more reason- able surgical methods according to the surgical findings,But in most case we performed in both of the two: facial nerve root combing assisted microvascular decompression(MVDC).In order to explore the effective intracranial surgical method for HFS which can be operated more safely and easily,and the causes of hemifacial spasm and the curative effects of retrosegmoid approach facial nerve root combing and microvascular decompression on it. In this study, we retrospective analysis the circumstances during Cerebello- pontine Angle Laparotomy of 82 cases of patients with HFS, follow-up the long-term effect of them. Evaluation and comparative the long-term effect of MVD or FNRC and their integrated operation——MVDC,to guide the clinical treatment of HFS and improve surgery effect,to enable the surgical with better efficacy be applied further universal,and analysis the factors to find which may affect the long-term effect.Materials and MethodsThere are 82 patients with complete medical records who had HFS and underwent MVD in the First Hospital of Jilin Univercity had been colected from January 1992 to February 2007. Retrosegmoid approach MVD was performed in 22patients,FNRC in 9 patients and MVDC in 51 patients.Total of 82 patients (41 male,41female),the mean age at onset was 44.90±10.98 years (range: 14–71), with a disease course ranging from 0.5 to 180 months, and the mean duration of symptoms was 52.79±43.54months was enrolled in the study,of whom 43 had facial spasm on the left side and 39 on the right side and no patients had bilateral HFS. Comparing the long-term curative of three types surgical operations, analysing the influence of age,sex,cause,disease course,Cohen grading the pressure point number of corresponding vessels to facial nerve operations prognostic.ResultIn this group of the short term(one year after operation) efficacy was 96.3 %, and the long term efficacy of which had a short term efficacy was 83.5%.The evaluation of the long-term effect of 79 patients who was effective one year after operation:To compare with MVD and FNRC: Of 21 MVD,giving a 71.4% long-term effective rate,and a 28.6% recurrence rate; Of 8 FNRC, giving a 75.0% long-term effective rate,and a 25.0% recurrence rate.These two groups giving a 72.4% long-term effective rate and a 27.6% recurrence rate as a whole.The long-term effective rate of MVDC in 50 patients is 90.0%, and the recurrence rate is 10.0%.The long- term effective rate of MVDC is far higher than MVD or FNRC treated (P<0.05),MVDC is characterized by its higher curative rate,low complications and stable long-term effect.The influence factors of the long-term effect of FNRC assisted MVD:①Cause:There were 73 caused by vascular factors,giving a 82.2% long-term effective rate,6 non-vascular factors giving a 100% long-term effective rate.②Offender:The anterior inferior cerebellar artery (AICA) in 40,giving a 85.7% long-term effective rate,the posterior inferior cerebellar (PICA) in 12,giving a 91.7% long-term effective rate, vein in 6,giving a 100% long-term effective rate, both of AICA and PICA in 7, giving a 57.1% long-term effective rate,AICA passing through the facial and acoustic nerves or the t rigeminal nerve in 8, giving a 50% long-term effective rate,the prognostic of the first three was good and the latter two was bad, the fewer pressure point number of corresponding vessels to facial nerve will get a better curative effect(P<0.05).③Sex:Among the 79 patients , there were 41 male ,giving a 82.9% long- term effective rate,38 female , giving a 84.2% long-term effective rate (p>0.05).④Age: the mean age at onset was 45.18±11.09 years ,the patients who obtained a good efficacy the mean age was 44.74±13.31 years and who obtained a bad efficacy the mean age was 47.38±10.66 years (P>0.05).⑤Cohen grading preoperative: preoperative,the Cohen grading2～3 in 67,giving a 82.1% long-term effective rate;Cohen grading 4 in 12,giving a 91.7% long-term effective rate (P>0.05).⑥Disease course:The patients enrolled in the studywith a disease course ranging from 0.5 to 180 months, and the mean duration of symptoms was 52.79±43.54 months, the patients who obtained a good efficacy the mean duration of symptoms was 53.38±45.36months and who obtained a bad efficacy the mean duration of symptoms was 49.79±34.17months (P>0.05).ConclusionMVD can remove the oppression pathological of vascular to the facial nerve or relieve the trigger role of the corresponding vessels, and stop the facial spasm onset, has high curative effect,stable effective rate and few complication. FNRC can reduce the nerve impulse of fibers,with satisfactory effect in long run,and low operative risk,but often complicated with varying degrees facial paralysis,mainly applicable to some patients not suitable for MVD.MVDC aims at neurovascular compression and abnormal function motor nucleus of facial nerve, has higher curative effect than MVD or FNRC,it is the most effective treatment of HFS.The three operation types all existing problems about complication and recurrence, but rare occurrence severe complications. With the application of new technologies, the efficacy improving and complications reducing. Correctly judge the corresponding vessels, sufficiently shift and septal the vessels, cold and effectively combing facial nerve root to reduce recurrence. According to the situation choose the operative mode to achieve the best effect. Only one corresponding vessels compression point to facial nerve will get a better long-term effect than multi ompression points;age, gender, disease duration, Cohen grading preoperative have no influence to the long-term effect of HFS.