Total Facial Paralysis after Vestibular Schwannoma Surgery: Probability of Regaining Normal Function

Accuracy and outcomes of diffusion tensor imaging tractography in resection for vestibular schwannoma for facial nerve preservation

BACKGROUND

Impairment of facial nerve (FN) function is a common postoperative complication in surgical resections of Vestibular Schwannomas (VS). Diffusion tensor imaging (DTI) tractography creates in vivo imaging of the anatomical location of white matter tracts that can be preoperatively used to visualize the displaced FN. We present an analysis of patients who underwent DTI tractography imaging prior to VS resection.

METHODS

Patient charts were reviewed from March 2012 to April 2015 who underwent DTI tractography prior to surgical resection for VS. Reliability of this measure was compared to the intraoperative FN location as determined by the surgeon. House Brackmann (HB) score was used to assess facial nerve function.

RESULTS

A total of 11 patients were included with a mean age of 43 years (range: 19-64) and mean follow-up length of 11.9 months (range: 3.1-34.2). The average maximum tumor diameter was 2.82 cm (range: 1.7-4.2). DTI tractography was accurate in 90.9% (10/11) of patients. Postoperatively, 72.7% (8/11) had a HB score of I or II, 18.2% (2/11) had a HB score of III, and 9.1% (1/11) had a HB score of IV.

CONCLUSIONS

Facial nerve visualization for VS resection can be accurately visualized using DTI tractography. This modality may lead to reduction of postoperative FN damage.

A Systematic Analysis of the Reliability of Diffusion Tensor Imaging Tractography for Facial Nerve Imaging in Patients with Vestibular Schwannoma

Surgeons need to visualize the facial nerve reliably in relation to the vestibular schwannoma (VS) in surgical planning. Diffusion tensor imaging (DTI) tractography has enabled unprecedented in vivo preoperative visualization. We collected data to measure the accuracy of DTI for an accurate location of the nerve in preoperative VS resection planning. A PubMed search for relevant studies was conducted. Inclusion criteria were gross total resection of VS, preoperative DTI identification of the facial nerve, and intraoperative cranial nerve localization by the surgeon. Exclusion criteria were tumors other than VS and unsuccessful preoperative location of the cranial nerve. Accuracy rate was calculated by comparing the intraoperative and preoperative locations detailed by DTI. The query identified 38 cases of VS that fit our inclusion criteria. Overall, 89% had surgical findings that agreed with the DTI location of the facial nerve. Of these cases, 32 patients had a postoperative House-Brackmann grade I or II. Our findings suggest that DTI is a reliable method for facial nerve imaging. Implementation of this technique may help decrease facial nerve injury during surgery. Limitations and further studies are needed to better understand what factors correlate with successful location of the facial nerve and DTI in patients with VS.

Evolution of Patients With Immediate Complete Facial Paralysis Secondary to Acoustic Neuroma Surgery

OBJECTIVE

To study the evolution of patients with immediate complete facial paralysis after acoustic neuroma surgery in different scenarios and assess different facial reanimations techniques.

METHODS

This study included 50 patients with complete facial paralysis immediately after acoustic neuroma surgery. Data were analyzed into 4 groups according to the need and type of reconstruction of the facial nerve, either none, immediate, or on a deferred basis. All patients had intraoperative facial nerve monitoring, and facial nerve function was evaluated according the House-Brackmann (HB) scale.

RESULTS

Of all patients with immediate total paralysis, no patients achieved totally normal facial function (grade I), and only 5 (10%) recovered to a grade II. For all groups included, the majority of patients (82%) achieved an acceptable final facial function (grade III HB). In this series, only 2 patients remained with a grade VI facial function.

CONCLUSIONS

The possibility of recovering near normal facial function after a grade VI facial paralysis is very low. Procedures like the immediate repair of the facial nerve with an interposed donor graft may provide better facial function in patients with partially injured facial nerve. Even in cases of total section, there are other procedures that can improve the results.

Facial nerve preservation with preoperative identification and intraoperative monitoring in large vestibular schwannoma surgery

BACKGROUND

Microsurgery is an option of choice for large vestibular schwannomas (VSs). Anatomical and functional preservation of facial nerve (FN) is still a challenge in these surgeries. FNs are often displaced and morphologically changed by large VSs. Preoperative identification of FN with magnetic resonance (MR) diffusion tensor tracking (DTT) and intraoperative identification with facial electromyography (EMG) may be desirable for improving functional results of FN.

METHOD

In this retrospective study, eight consecutive cases with large VS (≥30 mm in maximal extrameatal diameter) were retrospectively studied. FN DTT was performed in each case preoperatively. All the cases underwent microsurgical resection of the tumor with intraoperative FN EMG monitoring. Correctness of prediction for FN location by DTT was verified by the surgeon's inspection. Postoperative FN function of each patient was followed up.

RESULTS

Preoperative identification of FN was possible in 7 of 8 (87.5 %) cases. FN location predicted by preoperative DTT agreed to surgical finding in all the 7 cases. FN EMG was helpful to locate and protect the FN. Total resection was achieved in 7 of 8 (87.5 %). All FNs were anatomically preserved. All cases had excellent facial nerve function (House-Brackmann Grade I-II).

CONCLUSIONS

FN DTT is a powerful technique in preoperatively identification of FN in large VS cases. Continuous intraoperative FN EMG monitoring is contributive to locating and protecting FNs. Radical resection of large VSs as well as favorable postoperative FN outcome is available with application of these techniques.

Facial nerve function after vestibular schwannoma surgery

OBJECT

The object of this study was to evaluate long-term postoperative facial nerve (FN) function in patients undergoing vestibular schwannoma (VS) surgery.

METHODS

The authors retrospectively reviewed the clinical course of patients affected by isolated VSs with normal preoperative FN function, with no previous surgical or radiotherapeutic treatment, and who underwent surgery between 1987 and 2007. Facial nerve function was clinically evaluated according to the House-Brackmann (HB) scale. The minimum postoperative follow-up was 12 months.

RESULTS

Among the 1550 patients surgically treated at the authors' center, 1151 matched inclusion criteria for the present study. The FN was anatomically interrupted in 48 cases (4.2%), and 51 patients (4.4%) underwent subtotal tumor removal and were considered separately. Among the 1052 patients with anatomically preserved FNs and total tumor removal, 684 (65%) enjoyed postoperative HB Grade I or II and 309 (29.4%) enjoyed Grade III, with the remaining 59 cases (5.6%) suffering unsatisfactory results (HB Grades IV-VI). As expected, FN function results deteriorated in cases of larger tumors.

CONCLUSIONS

The main factor influencing postoperative FN function was tumor size. Although there was a progressive deterioration in FN function outcome in relation to tumor size, a cutoff point between satisfactory and unsatisfactory results could be identified at around 2 cm in maximum extrameatal tumor diameter, with the "optimal size" for surgery identified at < 1 cm. This finding emphasizes the importance of an early diagnosis and should be kept in mind when selecting the correct timing for VS removal. For small lesions, the results following a middle cranial fossa approach were significantly worse as compared with those following the translabyrinthine and retrosigmoidretrolabyrinthine approaches.

Displacement of the facial nerve course by vestibular schwannoma: Preoperative visualization using diffusion tensor tractography

PURPOSE

To preoperatively visualize the course of the facial nerve, which is displaced by vestibular schwannoma, using diffusion tensor (DT) tractography, and to evaluate the agreement with surgical findings.

MATERIALS AND METHODS

The subjects were eight patients with vestibular schwannoma who had undergone removal surgery. DT MR images were obtained and tracts that were considered to represent the facial nerve were constructed. We assessed the success rate for tract construction and evaluated the agreement between tractography findings and surgery.

RESULTS

We obtained a tract that connected the internal auditory meatus and brainstem, and was considered to represent the facial nerve in seven of eight cases. The course of the constructed tract agreed with surgical findings in five of these seven cases. One exception was a case in which the tumor was too large to enable intraoperative observation of the facial nerve; however, the facial nerve appeared to be displaced anteriorly at intracapsular resection, in agreement with tractography. In the other case, the schwannoma was mostly cystic.

CONCLUSION

Tractographs constructed using MR tensor images enabled us to identify tracts considered to represent facial nerves. We consider DT tractography to be a useful tool for preoperatively predicting facial nerve displacement in vestibular schwannoma.