Introduction
Despite advances in facial nerve monitoring technology and microsurgical techniques, cerebellopontine angle surgery can still result in varying degrees of facial nerve injury.Reference Harner, Daube, Beatty and Ebersold1, Reference Prass, Kinney, Hardy, Hahn and Lüders2 This can be attributed either to direct nerve trauma during surgery or to the histopathological nature of the lesion. In order to rehabilitate facial nerve function, several surgical techniques have been developed.
Anastomosis of the hypoglossal and facial nerves (i.e. cranial nerves VII and XII) is the treatment of choice for facial reanimation in patients whose facial nerve has been transected in the cerebellopontine angle, and in whom end-to-end anastomosis of the facial nerve is not possible. Anastomosis of cranial nerves VII and XII is considered to achieve a dynamic result, which at best enables static facial symmetry and closure of the eyelid. Thus, both static and dynamic facial functions can be restored.
The aim of this study was to evaluate retrospectively the results of our experience with end-to-end anastomosis of cranial nerves VII and XII, performed due to transection of the facial nerve during acoustic neuroma removal.
Methods
Archival medical records were searched to identify patients who had suffered facial nerve transection during acoustic neuroma excision via a retrosigmoid approach, between 1985 and 2006, and who had subsequently undergone hypoglossofacial end-to-end anastomosis. Forty-three patients were identified. For those patients with adequate follow-up data, details were recorded from the medical record. The remaining patients were contacted via telephone and recalled for an otolaryngological examination. Of the 43 patients identified, eight were lost to follow up, and two had a follow-up period of less than two years. Therefore, 33 patients were included in the study. These patients comprised 24 men and nine women, with ages ranging from 21 to 71 years (mean age 45 years).
Facial function was evaluated according to the House–Brackmann scale.Reference House and Brackmann3 All patients had House–Brackmann grade VI facial weakness after retrosigmoid acoustic neuroma removal. Hypoglossofacial anastomoses were performed one to three months after the posterior fossa surgery, and post-operative facial nerve function was assessed more than 24 months after this surgery. The facial function of patients after short term (i.e. two to three years) and long term (i.e. more than three years) follow up was compared statistically using Fisher's exact test. Patients were also questioned about other possible complications of the anastomosis, i.e. dysarthria, dysphagia and numbness of the tongue.
Results
No patient had a lower cranial nerve deficit after acoustic neuroma removal. House–Brackmann grade III facial function was achieved in 46.2 and 86.4 per cent of the patients after short and long term follow up, respectively. House–Brackmann grade IV facial function was achieved in 53.8 and 13.6 per cent of the patients after short and long term follow up, respectively. The difference between facial recovery results after short and long term follow up was statistically significant (p = 0.03) (Table I).
Table I Patients’ facial reanimation results for hypoglossofacial anastomosis
p = 0.03, Fisher's exact test, comparing results for short and long term follow up. HB = House–Brackmann; post-op = post-operative; yrs = years
Dysarthria was the commonest complication of hypoglossofacial end-to-end anastomosis, being seen in 19 (57.6 per cent) patients; this was described by the patients as ‘difficulty in pronouncing some letters’. The second most common complication was numbness of the tongue, seen in 10 (30.3 per cent) patients. Numbness was described by some patients as a ‘loss of sensitivity’ of the ipsilateral side of the tongue. None of the patients had dysphagia. (difficulty in swallowing).
Discussion
Disruption of the anatomical continuity of the facial nerve beyond its intracranial portion can be treated using a variety of described techniques.Reference Linnet and Madsen4–Reference Spector10 If a central stump of the facial nerve is available, it may be possible to achieve nerve continuity with intracranial–extracranial or intracranial–extratemporal nerve grafting. The functional outcomes of these procedures vary from House–Brackmann grade III to IV.Reference Papel11 Favourable results were reported in a series of 26 patients undergoing hypoglossofacial anastomosis with a modified May technique; House–Brackmann grade II was achieved in 19.2 per cent of patients, while 73.1 per cent had grade IV and 7.7 per cent had grade V facial function at 18 months.Reference Darrouzet, Dutkiewicz, Chambrin, Stoll and Bébéar12 In our series: House–Brackmann grades III and IV were achieved in 71.4 and 28.6 per cent of our patients, respectively, after three years’ follow up.
Malik et al. studied 13 patients, and reported that classical hypoglossofacial end-to-end anastomosis resulted in a House–Brackmann grade of III or less in 25 per cent of patients at 24 months post-operatively; however, some patients showed further improvement in facial function beyond this time period.Reference Malik, Kelly, Ahmed, Saeed and Ramsden13 Similarly, our results also supported the argument that progressive improvement of facial function occurs after facial reanimation. A House–Brackmann grade III was encountered in 46.2 per cent of our patients at two to three years’ follow up, and in 86.4 per cent of patients at more than three years’ follow up; this indicates a significantly better outcome in the long term (i.e. beyond three years post-operatively), compared with earlier assessments.
• Despite technological advances in facial nerve monitoring and microsurgical techniques, cerebellopontine angle surgery can still result in varying degrees of facial nerve injury
• Hypoglossal–facial nerve anastomosis has been the treatment of choice for facial reanimation, when the facial nerve has been transected in the cerebellopontine angle
• Sectioning of the hypoglossal nerve can result in atrophy of the ipsilateral tongue, with swallowing and speech articulation problems
• Significant improvement in facial function can occur more than three years after hypoglossofacial anastomosis
The major drawback of anastomosis of the facial nerve with other cranial nerves (such as the hypoglossal or accessory nerve) is the loss of function of these latter nerves. Sectioning of the hypoglossal nerve can result in atrophy of the ipsilateral tongue and problems with swallowing and speech articulation. In a previous study of hypoglossofacial anastomosis after acoustic neuroma resection, difficulties in articulation and swallowing were noted in 69.6 and 58.7 per cent of patients, respectively.Reference Kunihiro, Higashino and Kanzaki14 In our study, 57 per cent of patients had speech articulation problems and 29 per cent had numbness of the ipsilateral tongue, although none had swallowing problems. Disarticulation generally begins immediately after the operation, and is related to motor denervation of the ipsilateral tongue. This denervation results in atrophy of the tongue muscles, which leads to decreased tongue volume ipsilaterally. Thus, patients may complain of numbness of the tongue.
The oral phase of swallowing may be affected following hypoglossofacial anastomosis. Swallowing problems can decrease patients’ quality of life. However, none of our patients suffered swallowing disorders or dysphagia; this can be attributed to the presence of functioning vagus and glossopharyngeal nerves bilaterally.
In an attempt to preserve tongue function, different anastomosis techniques have been proposed. In a series of 13 patients undergoing end-to-side hypoglossofacial anastomosis using a split hypoglossal nerve technique, Rochkind et al. reported that satisfactory improvement in facial nerve function could be achieved while preserving tongue function.Reference Rochkind, Shafi, Alon, Salame and Fliss15 However, according to a recent meta-analysis, modification of the anastomosis technique seems to avoid the complications of end-to-end anastomosis, although the effect of modified techniques on facial reanimation is still unclear.Reference Yetiser and Karapinar16
Conclusion
Despite morbidities such as disarticulation and tongue numbness, end-to-end hypoglossofacial anastomosis is still an effective procedure for the surgical rehabilitation of static and dynamic facial nerve functions. A significant improvement in facial nerve function can occur more than three years after the reanimation procedure.
