Facial Nerve Intraoperative Monitoring in Otologic Surgeries under Sedation and Local Anesthesia - A Case Series and Literature Review

Abstract Introduction Local anesthesia with sedation has been employed for an increasingly number of otolaryngology procedures, and might be associated with lower surgical morbidity and costs. Facial nerve monitoring is often advisable in otology to minimize the risks of injuries to this cranial nerve, but the principles, techniques and parameters involved have only been studied for procedures under general anesthesia. Objective To report the preliminary outcomes of intraoperative facial nerve moni- toring during otologic procedures under sedation and local anesthesia. Methods A total of five procedures and their respective intraoperative electrophysi- ological main findings were described. Facial neuromonitoring was performed using the same device by an electrophysiologist. The monitor sensitivity was set at 100 mV, and a stimulating probe was used whenever needed. Results Progressively decreasing low-amplitude baseline values were usually obtained as the level of anesthesia increased, with isolated oscillations possibly related to some degree of voluntary muscular activity. These oscillations could be easily distinguished from those of the surgical manipulation or electrical stimulation of the nerve, which tended to be of much greater amplitude and shorter latency, occurring during specific surgical steps. Conclusion With a surgical team with proper procedural knowledge and broad expertise regarding the technique, intraoperative facial nerve monitoring under local anesthesia with sedation seemed both feasible and reliable. Thus, the need for intraoperative neuromonitoring should not be an obstacle for otologic procedures under less aggressive anesthetic management.

Muscle reinnervation in one or two stages?: experimental study in rats with end-to-side nerve graft / Reinervação muscular em um ou dois estágios?: estudo experimental em ratos com enxerto de nervo término-lateral

PURPOSE: To compare muscle reinnervation in one and two surgical stages using end-to-side neurorrhaphy (ESN) without donor nerve injury. METHODS: The experiment was performed on four groups of 20 rats. Group 1 (G1), one stage, received the graft which was sutured to the tibial nerve, with ESN, and its free stump was sutured end-to-end to the distal stump of the sectioned peroneal nerve (PN), all in the same operation. In Group 2 (G2), two stages, the nerve graft was sutured to the tibial nerve, with ESN. Two months later the PN was sectioned and its distal stump connected to the distal stump of the graft as in G1. Normal control group (Gn) received the graft only sutured to the tibial nerve, with ESN. Denervated control group (Gd), as well received the graft and had the PN sectioned and its two stumps buried in adjacent musculature, with the aim of denervating the cranial tibial muscle (CTM), the target of this study. The parameters used to evaluate CTM reinnervation were muscle mass, muscle fiber's minimum diameter and area. RESULTS: The mean CTM mass, the average of the muscular fibers areas and the average of the muscular fiber minimum diameters was higher (all p<0.0001) in G2 than in G1. Comparing the four groups, these parameters had their maximum expression in Gn and the minimum in Gd, as expected. CONCLUSION: The two stages showed better muscle reinnervation than one stage.

OBJETIVO: Comparar a reinervação muscular com enxerto de nervo em um e dois tempos operatórios, utilizando a neurorrafia término-lateral (NTL) sem lesão do nervo doador. MÉTODOS: Vinte ratos foram distribuídos em quatro grupos. O grupo 1 (G1), um estágio, recebeu o enxerto que foi suturado ao nervo tibial (NT), por meio de NTL, e seu coto livre foi suturado por NTL ao coto distal do nervo peroneal (NP), seccionado a um centímetro do NT, na mesma cirurgia. O grupo 2 (G2), dois estágios, recebeu o enxerto de nervo na primeira cirurgia, como já descrito. Dois meses depois, na segunda cirurgia, o NP foi seccionado e seu coto distal ligado ao coto distal do enxerto como em G1. O grupo controle de normalidade (Gn) recebeu o enxerto da mesma forma, apenas. E o grupo controle de denervação (Gd), além de receber o enxerto, teve o NP seccionado e seus cotos sepultados na musculatura adjacente, com a finalidade de denervar o músculo tibial cranial (MTC), alvo deste estudo. Os parâmetros utilizados para avaliar a reinervação do MTC foram massa muscular, diâmetro mínimo da fibra muscular e área. RESULTADOS: O grupo G2 apresentou superioridade (p<0,0001) em relação ao G1 na massa do MTC, no diâmetro mínimo e na área das fibras musculares. Na comparação entre os quatro grupos, estes mesmos parâmetros tiveram sua expressão máxima em Gn e mínima em Gd, como era esperado. CONCLUSÃO: A reinervação muscular em dois estágios apresenta melhor resultado quando comparada à técnica em um tempo.

Temporal branch of facial nerve: a normative study of nerve conduction / Ramo temporal do nervo facial: um estudo normativo da condução nervosa

The temporal branch of the facial nerve is particularly vulnerable to traumatic injuries during surgical procedures. It may also be affected in clinical conditions. Electrodiagnostic studies may add additional information about the type and severity of injuries, thus allowing prognostic inferences. The objective of the present study was to develop and standardize an electrophysiological technique to specifically evaluate the temporal branch of the facial nerve. METHOD: Healthy volunteers (n=115) underwent stimulation of two points along the nerve trajectory, on both sides of the face. The stimulated points were distal (on the temple, over the temporal branch) and proximal (in retro-auricular region). Activities were recorded on the ipsilateral frontalis muscle. The following variables were studied: amplitude (A), distal motor latency (DML) and conduction velocity (NCV). RESULTS: Differences between the sides were not significant. The proposed reference values were: A >0.4 mV, DML <3.9 ms and NCV >40 m/s. Variation between hemifaces should account for less than 60 percent for amplitudes and latency, and should be inferior to 20 percent for conduction velocity. CONCLUSION: These measurements are an adequate way for proposing normative values for the electrophysiological evaluation of the temporal branch.

O ramo temporal do nervo facial é particularmente vulnerável a lesões traumáticas nos procedimentos cirúrgicos. Também pode ser acometido em várias condições clínicas. Estudos eletrodiagnósticos podem acrescentar informações quanto ao tipo e severidade das lesões. A pesquisa visa aperfeiçoar técnica eletrofisiológica para avaliação específica daquele ramo. MÉTODO: Voluntários (n=115) foram submetidos a estimulação eletroneurográfica em dois pontos, nas duas hemifaces. Estímulo distal na têmpora, estímulo proximal na região retroauricular. Foram registradas distâncias dos pontos de estímulo até pontos anatômicos da face; assim como variáveis relacionadas com o potencial de ação resultante. RESULTADOS: Houve grande variabilidade nas amplitudes, porém a diferença entre as hemifaces não foi significativa. Valores de referência propostos foram: amplitude (A) >0.4mV, latência motora distal (LMD) <3.9ms e velocidade de condução (VCN) >40m/s. Variabilidade aceitável entre os lados: LMD e A <60 por cento e VCN <20 por cento. CONCLUSÃO: Este estudo pode ser a ferramenta inicial para aplicações futuras no diagnóstico e seguimento de pacientes com lesões no ramo temporal.

Influência do AMP cíclico na regeneração do nervo facial em ratos / Influence of cyclic AMP on facial nerve regeneration in rats

Estimular a regeneração do nervo facial é ainda hoje um desafio. OBJETIVO: Estudar a possível influência neurotrófica do nucleotídeo cíclico adenosina monofosfato (AMPc) na regeneração do nervo facial de ratos Wistar. MÉTODO: Trinta e dois animais foram submetidos à transecção completa com sutura imediata do nervo facial direito, sendo divididos em expostos ou não expostos à aplicação tópica de AMPc, com análises comportamentais (movimentação de vibrissas e fechamento da rima palpebral) e histométrica (contagem de fibras mielinizadas) em dois períodos, 14 e 28 dias após a lesão. RESULTADO: Encontramos diferenças estatísticas (p<0,05) nas análises comportamental e histométrica no 14º dia, sugerindo uma precocidade na regeneração do nervo facial exposto ao AMPc. CONCLUSÃO: Nosso estudo constatou uma possível ação neurotrófica do AMPc na regeneração do nervo facial em ratos.

Promoting facial nerve regeneration is a significant challenge. AIM: To evaluate the possible neurotrophic influence of cyclic AMP on facial nerve regeneration of Wistar rats. METHOD: The right facial nerve of thirty-two animals were completely transected and immediately sutured, followed by exposure or not to topical cyclic AMP. Behavioral and histometric analyses were done at 14 and 28 days. RESULTS: Statistical differences (p<0.05) were found in the behavioral and histometric analyses on the 14th day, suggesting an early regenerative response of the facial nerve to cAMP exposure. CONCLUSION: This study demonstrates a possible neurotrophic effect of cAMP on facial nerve regeneration in rats.

Anastomose do nervo facial de coelhos com cola de fibrina: estudo da velocidade de condução nervosa / Rabbit facial nerve anastomosis with fibrin glue: nerve conduction velocity evaluation

OBJETIVO: Este estudo tem o objetivo de avaliar através da velocidade de condução nervosa com eletrodos de superfície a utilização da cola de fibrina na anastomose nervosa. MÉTODOS: Neste experimento, foram avaliadas as diferenças entre as velocidades de condução nervosa pré e pós-operatória do nervo facial esquerdo de 12 coelhos. Foi verificada a existência de correlação entre a velocidade de condução nervosa e o número de axônios regenerados no pós-operatório. Os nervos transeccionados foram unidos com cola de fibrina. O potencial de ação motora foi obtido com o uso de eletrodos de superfície. O eletrodo de estimulação foi colocado imediatamente à frente do pavilhão auditivo (tronco do nervo facial) e o eletrodo de gravação foi colocado no músculo quadrado do lábio inferior. RESULTADOS: A média normal da velocidade de condução nervosa foi de 36,53 m/seg. Ao final do período, a velocidade de condução nervosa atingiu um valor de aproximadamente 81 por cento do valor normal. Não foi observada correlação significativa entre a velocidade de condução nervosa pós-operatória e o número de axônios regenerados (p=0,146). CONCLUSÃO: A anastomose com cola de fibrina pode ser utilizada para anastomose nervosa no modelo animal e nervo estudados.

AIM: The aim of this study was to evaluate the use of fibrin glue on nerve anastomosis, and study conduction velocity obtained by surface electrodes. METHODS: In this experimental model we evaluated nerve conduction velocity differences in the preoperative and postoperative periods, for the left facial nerve of 12 rabbits. Then, we evaluated whether there were correlations between conduction velocity and the number of postoperative regenerated axons. The sectioned nerves were anastomosed with fibrin glue. The muscle action potentials were obtained from surface electrodes. The stimulation electrode was placed immediately before the ear pinna (facial nerve trunk) and the recording surface electrode was placed on the quadratus labii inferioris muscle. RESULTS: The facial nerve normal conduction velocity mean value was of 36.53 m/sec. On the postoperative period, the mean conduction velocity was approximately 81 percent of the normal mean value. A significant correlation was not observed between the postoperative conduction velocity and the number of regenerated axons (p=0.146). CONCLUSION: The fibrin glue can be used on nerve anastomosis in this animal model and nerve.

Modelo experimental comportamental e histológico da regeneração do nervo facial em ratos / Behavioral and histologic experimental model of facial nerve regeneration in rats

O estabelecimento de modelos experimentais é o passo inicial para estudos de regeneração neural. OBJETIVO: Estabelecer modelo experimental de regeneração do nervo facial. MATERIAIS E MÉTODOS: Ratos Wistar com secção completa e sutura do tronco do nervo facial extratemporal, com análise comportamental e histológica até 9 semanas. FORMA DE ESTUDO: Estudo prospectivo experimental. RESULTADOS: Progressiva recuperação clínica e histológica dos animais. CONCLUSÃO: Estabelecemos um método aceitável para o estudo de regeneração do nervo facial em ratos.

To setup an experimental model is the first step to study neural regeneration. AIM: Setting up an experimental model on facial nerve regeneration. MATERIAL AND METHODS Wistar rats with complete sectioning and suturing of the extratemporal facial nerve trunk; with a behavioral and histological analysis for 9 weeks. STUD DESIGN: Experimental prospective study. RESULTS: Progressive clinical and histological recovery of the animals. CONCLUSION: Our method is acceptable to study facial nerve regeneration in rats.

Regeneração pós-traumática do nervo facial em coelhos / Posttraumatic facial nerve regeneration in rabbits

A paralisia facial periférica traumática constitui-se em afecção freqüente. OBJETIVO: estudo da regeneração pós-traumática do nervo facial em coelhos, por avaliação funcional histológica dos nervos traumatizados comparados aos normais contralaterais. METODOLOGIA: Vinte coelhos foram submetidos à compressão do tronco do nervo facial esquerdo e sacrificados após duas (grupo AL), quatro (BL) e seis (CL) semanas da lesão. A comparação entre os grupos foi feita pelas densidades total e parcial de axônios mielinizados. ESTUDO ESTATíSTICO: método de Tukey (p < 0,05). RESULTADOS: Houve recuperação funcional parcial após duas, e completa após cinco semanas. Na análise qualitativa, verificou-se em AL um padrão degenerativo, com maior processo inflamatório tecidual. Em BL, sinais de regeneração neural, praticamente completa em CL. Os nervos normais (N) apresentaram DT média de 15705,59 e DP média de 21800,75. O grupo BL revelou DT média de 10818,55 e DP média de 15340,56 e o CL, DT média de 13920,36 e DP média de 16589,15. BL obteve 68,88 por cento, e o grupo CL, 88,63 por cento da DT de N. N mostrou DP maior que os lesados; porém, esta não evidenciou diferença estatística entre BL e CL. A DT dos nervos revelou-se um método analítico mais fidedigno do que a DP estudada.

Posttraumatic facial paralysis is a frequent disease. This work studies posttraumatic regeneration of the facial nerve in rabbits. Functional and histological analysis compared injured and normal nerves on opposite sides. The left facial nerve trunk of twenty rabbits were subjectedto compression lesion, and sacrificed after two (subgroup AL), four (BL) and six (CL) weeks. Comparison between groups was made by analysing total and partial densities of myelinated axons. STATISTICAL ANALYSIS: Tukey Method (p<0.05). RESULTS:There was partial functional recovery after two weeks, and complete recovery after five weeks. Qualitative analysis demonstrated a degenerative pattern in the AL group, with an increased tissue inflammatory process. Evident regeneration signs were observed in the BL group, and almost complete regeneration was seen in the CL group. Normal nerves (N) had an average TD of 15705.59 and average PD of 21800.75. The BL group had an average TD of 10818.55 and an average PD of 15340.56. The CL group had an average TD of 13920.36 and an average PD of 16589.15. The BL group had an average TD of N equal to 68.88 percent, and the CL group had an average TD of N equal to 88,63 percent (statistically significant). N showed a significant higher PD than injured nerves. However, this was not statistically different between BL and CL subgroups. Nerve DT was a more reliable method than PD in this study.

Surgery of vestibular schwannomas: an institutional experience.

AIMS: To report management results of vestibular schwannomas (VS) treated surgically in our institute, with particular reference to completeness of tumor excision, facial nerve and hearing preservation and complications of surgery. STUDY DESIGN AND SETTINGS: Retrospective study of 259 patients treated during the years 1988 to 2002. MATERIALS AND METHODS: The facial nerve function and hearing assessment was done according to House-Brackmann [HB] grading and pure tone audiometry (PTA) respectively. All patients were operated by retro-mastoid sub-occipital approach. RESULTS: Most patients had large tumors and had no useful hearing (90%), had disabling cerebellar ataxia (88%) and presented with features of raised intra-cranial pressure (45%). Large sized tumors were in 41.3% and giant sized tumors were in 56% cases. Complete tumor excision was carried out in 96.5% and anatomical preservation of facial nerve was achieved in 79.2% cases. Hearing preservation was achieved in 8 patients. Cerebrospinal fluid leak with or without meningitis and transient lower cranial nerve paresis were common complications. The mortality was 6%. CONCLUSIONS: With experience, complete tumor excision with good facial nerve preservation can be achieved in large tumors. Hearing preservation is difficult in bigger tumors. Prevention and control of infection was a major concern.

Conduction velocity of the rabbit facial nerve: a noninvasive functional evaluation

The aim of this study was to evaluate standardized conduction velocity data for uninjured facial nerve and facial nerve repaired with autologous graft nerves and synthetic materials. An evaluation was made measuring the preoperative differences in the facial nerve conduction velocities on either side, and ascertaining the existence of a positive correlation between facial nerve conduction velocity and the number of axons regenerated postoperatively. In 17 rabbits, bilateral facial nerve motor action potentials were recorded pre- and postoperatively. The stimulation surface electrodes were placed on the auricular pavilion (facial nerve trunk) and the recording surface electrodes were placed on the quadratus labii inferior muscle. The facial nerves were isolated, transected and separated 10 mm apart. The gap between the two nerve ends was repaired with autologous nerve grafts and PTFE-e (polytetrafluoroethylene) or collagen tubes. The mean of maximal conduction velocity of the facial nerve was 41.10 m/s. After 15 days no nerve conduction was evoked in the evaluated group. For the period of 2 and 4 months the mean conduction velocity was approximately 50 percent of the normal value in the subgroups assessed. A significant correlation was observed between the conduction velocity and the number of regenerated axons. Noninvasive functional evaluation with surface electrodes can be useful for stimulating and recording muscle action potentials and for assessing the functional state of the facial nerve

Evoked electromyogram as a function of facial nerve.

Compound muscle action potentials were recorded bilaterally from alae nasi muscles following stimulation of facial nerve in 45 normal subjects in the age group of 20-30 years. Latency, amplitude and total duration of the compound muscle action potential were compared on both sides. A significant positive correlation between the three parameters with the highest for the amplitude was observed. Therefore it is suggested that amplitude is a better parameter for comparison while testing for side to side facial nerve integrity.

Examen clínico de los pares craneales de interés odontológico / Clinical examination of the cranial pairs of dental interest

El objetivo principal de este trabajo consiste en presentar al lector una descripción de las técnicas de examen neurológico de los pares creneales que están en relación con el ejercicio de la odontología, como lo son el nervio oftálmico, trigémino, facial, glosofaríngeo, neumogástrico espinal e hipogloso

Facial nerve electroneurography: variability in normal subjects

Twenty normal individuals were submitted to facial nerve electroneurography using different techniques in order to determine the most accurate to obtain the latencies and amplitudes of the compound muscle action potentials (CMAP) of the facial muscles. First of all it was determined in which muscle or muscle group highest amplitude CMAP could be recorded with the lowest variability between sides and in test-retest. Different techniques were studied in order to determine which could give the best results. This was shown to be an arrangement of bipolar surface electrodes fixed to a plastic bar. The records with higher amplitude where obtained from the nasolabial fold muscles. Therefore 65 normal volunteer were examined using this technique and recording the potentials obtained over the nasolabial fold muscles. Normal values were determined (latency lower than 4.5 ms and amplitude larger than 2 mV - 95 per cent confidence limits).

Arte y anatomía de la sonrisa / The art and anatomy of the smile

En el presente artículo se abordan los distintos tipos de sonrisa existentes, en función a sus características anatómicas y su relación con la patología. Así mismo, se establece un paralelismo entre la clasificación de Rubin y el mundo del Arte y la Literatura.

Evoluçäo do tratamento dos neurinomas do acústico / Evolution of acoustic neuroma treatment

Os autores fazem a revisao da literatura sobre o tratamento dos neurinomas do acústico, enfatizando a evoluçao das técnicas cirúrgicas que possibilitaram, de maneira consecutiva, a diminuiçao da morbidade e mortalidade, a preservaçao da funçao do nervo facial, e a conservaçao da audiçao remanescente. O acesso suboccipital retrossigmóideo transmeatal representa o método de escolha para abordar os neurinomas de diversos tamanhos, com possibilidade de preservar as funçoes dos nervos facial e coclear, com pequenas taxas de mortalidade e morbidade. A evoluçao da técnica microcirúrgica possibilitou a dissecaçao do nervo coclear do tumor, na tentativa de se preservar sua funçao. O tratamento por métodos coadjuvantes tem evoluido, e a radiocirurgia estereotáxica representa uma alteranativa promissora para o tratamento dessas neoplasias.

Eletroneurografia do nervo facial: métodos de estimulaçäo e registro / Electroneurography of the facial nerve: methods of stimulation and records

Neste estudo os autores se propöem a estabelecer os pontos mais adequados para registro do potencial de açäo muscular composto dos múscuulos frontal, orbicular do olho e músculos do sulco nasólabial, após estimulaçäo do nervo facial. Também, o melhor posicionamento do eletrodo estimulador e a variaçäo entre as amplitudes do primeiro e último potencial de açäo muscular composto dos músculos do sulco nasolabial, após 20 estímulos supramáximos sucessivos