A Study Of Arachnoid Architecture In Root Exit Zone Of Facial Nerve And Its Clinical Significance In Hemifacial Spasm Patients

Objective To explore arachnoid architecture in facial nerve root exit zone with primary hemifacial spasm patients, To find out the root reasons for blood vessels compresses nervous, To further improve operative techniques of microvascular decompression.Methods To select 119 cases with microvascular decompression for the first time in the second hospital of Lanzhou University neurosurgery-centre from January 2013 to March 2015,54 cases of primary hemifacial spasm as study group,65 cases of primary trigeminal neuralgia as the control group, to do case-control study. Through imaging examination, operation observation, intraoperative neurophysiological monitoring, pathological examination, treatment outcome and complications observation etc, to further investigate the arachnoid architecture in facial nerve root exit zone and clinical significance with hemifacial spasm patients.Results 1. Arachnoid architecture in facial nerve root exit zone makes adhesion, pulling, fixing, tieing, covering, wrapping effects for the facial nerve and blood vessels around the brain stem area. As the change of arachnoid architecture by surgical operation, intraoperative neurophysiological monitoring show lateral spread response also changing at the same time. The responsible vessels as oppressing the facial nerve, including anterior inferior cerebellar artery, posterior inferior cerebellar artery, superior cerebellar artery, vertebral artery, basilar artery, anterior inferior cerebellar veins, etc.2. Intraoperative neurophysiological monitoring of 54 cases with primary hemifacial spasm,50 cases(93%) successfully recorded lateral spread response. With surgery operation changing arachnoid architecture in facial nerve root exit zone, the lateral spread response was disappeared completely in 12 cases (24%), the lateral spread response was not completely disappeared in 20 cases (40%) only with the waveform changed and amplitude lower, the lateral spread response without change there were 18 cases (36%).Then place teflon washers, the lateral spread response was disappears completely with 46 cases (92%) at the end of surgery, there was not disappears completely 3 cases (6%), and only 1 cases (2%) waveform without change.3. The pathology results of the arachnoid in facial nerve root exit zone had 110 cases (92%) normal.9 cases (8%) arachnoid had pathological abnormalities, including inflammatory cell infiltrate, calcification, edema and so on. Case Control Study proved the facial spasm groups and the trigeminal neuralgia groups which arachnoid in facial nerve root exit zone had not significant differences.4. In 54 cases with primary hemifacial spasm,43 (80%) cases which symptom immediately disappeared, including lateral spread response was completely disappeared in 40 cases,1 case was not disappear completely, and 2 cases failed to draw out waveforms.6 cases (11%) symptom disappeared completely about a week when they discharged from hospital, including lateral spread response was completely disappeared in 4 cases,1 case was not disappear completely, and 1 case facial muscles continued to produce spontaneous electrical interference.5 cases (9%) have different degrees of hemifacial spasm symptom until after leaving hospital, including 2 cases lateral spread response was disappeared completely,1 case was not disappear completely,1 case facial muscles continued to produce spontaneous electrical interference, and 1 case was not change throughout. TO follow-up survey 6-24 months these 5 cases with hemifacial spasm symptoms still exist after leaving hospital,4 cases symptoms disappeared or got better,1 case is not valid. Lateral spread response disappeared completely groups which has more obvious short term effect. Primary hemifacial spasm treated by microvascular decompression which has the long-term overall effective rate about 98%. There are some related complications after operation, including 1 case with cerebrospinal fluid leakage,2 cases with delayed facial paralysis, 3 cases with facial muscles slight numbness,6 cases with hearing loss,1 case with slight tinnitus and vertigo.Conclusions 1.The arachnoid architecture in facial nerve root exit zone is the root reason to cause disease of primary hemifacial spasm.2. There is obvious relevance between operation changing the arachnoid architecture in facial nerve root exit zone and the change of the lateral spread response. To release the arachnoid in facial nerve root exit zone can achieve the aim of decompression. Intraoperative neurophysiological monitoring can help in determining the liability blood vessel whether decompression has adequacy, and protect facial nerve and auditory nerve to avoid damage. Whether lateral spread response was disappeared has very important value of judging prognosis that primary hemifacial spasm patients treated by microvascular decompression. 3. To emphasize explore arachnoid architecture in facial nerve root exit zone, and enough release arachnoid which play a role of pulling and fixing responsible vessels or facial nerve, that is an important improvement for microvascular decompression.4. Through pathological examination, the vast majority of arachnoid in facial nerve root exit zone is normal, and not to find pathological abnormalities including inflammatory cell infiltrate, calcification, edema, etc. The cause of hemifacial spasm symptom associated with normal arachnoid architecture, which is not arachnoid pathological abnormalities lead to adhesion between relevant vessels and facial nerve.