Morphometrics of the facial nerve following fractionated external irradiation: an experimental study in rats

This study provides morphometric data on radiation-induced alterations of the facial nerve in female Wistar rats. The facial nerves were explanted 3 to 4 or 7 to 9 months after completion of a fractionated external irradiation of the left side of the neck (5 days per week, 6 weeks, total: 60 Gray). Both facial nerves were investigated in order to identify possible effects of scattered irradiation on them. A total of 54 animals were investigated and 11,193 measurements were obtained. The computer-assisted image analysing system CUE-3 Color Image Analyzer (Olympus, Japan) was used. Facial nerves from untreated animals served as controls.

RESULTS

Three to four months after irradiation, the ratio of axon area and total area of the cross-sectioned nerve was shifted towards the axon area. Seven to 9 months after completion of irradiation, both the myelin sheath and the axon were reduced in diameter. The loss of substance affected predominantly the myelin sheath. Peripheral nerves are radiosensitive. Seven to 9 months after irradiation there was an increase of the axon area compared to the total area, both in absolute values and in relative terms. Radiosensitivity of peripheral nerves can be measured morphometrically in suitable animal models. The measurements disclosed temporal and spatial patterns of radiation response of the nerves. These results may partly explain the increased radiosensitivity of the peripheral nervous system observed in the long-term follow-up after completion of radiotherapy of head and neck in humans.

New stereoscopic virtual reality system application to cranial nerve microvascular decompression

PURPOSE

Cranial nerve microvascular decompression is a habitual neurosurgical procedure. Authors describe a new application of the Dextroscope (Volume Interactions, Ltd.), a virtual reality environment, to plan and properly simulate this kind of procedures.

METHODS

In three cases of hemifacial spasm refractory to drugs and botulinum toxin treatment, the authors used a virtual reality workstation (Dextroscope) to develop an interactive simulation of craniotomy, approach, and Gore-Tex implant optimal size and position in order to reach vascular decompression of facial nerve.

RESULTS

Three-dimensional interactive environment allowed the authors to virtually carry out craniotomy, to visualize vascular and nerve relationship, and finally, to select and to simulate best Gore-Tex graft positioning in each case. During surgical procedures, facial nerve vascular compressions were exposed and Gore-Tex grafts were successfully placed as it was virtually planned. Patient outcomes were excellent, with an average improvement of two units (0-4 grades of severity scale).

CONCLUSION

Virtual reality environment can help the neurosurgeon to plan and train vascular decompression procedures. Use of appropriate craniotomy, knowledge of vascular and nerve relationship, and selection of optimum paddy size and position are the main useful applications of the Dextroscope in these procedures.

Adenoid cystic carcinoma of the parotid with facial nerve invasion

BACKGROUND

Adenoid cystic carcinoma comprises approximately 10% of all epithelial salivary neoplasms and most frequently involves the parotid. Perineural invasion is a common feature but intraneural invasion and spread is less common.

AIM

The authors report a case of parotid adenoid cystic carcinoma with invasion and spread via the facial nerve with an emphasis on radiologic features.

OBSERVATION

We report a case of a 47-year-old man presenting with a right submandibular mass evolving for 4 years. On physical examination, the mass was firm painless, well delineated. There was no facial paralysis. The magnetic resonance imaging (MRI) examination showed a right parotid gland solid mass located in the deep lobe of the parotid gland with mastoid bony involvement.The mass was heterogenously enhanced. High resolution non contrast computed tomographie (CT) scan of the temporal bone showed in the axial and coronal cuts, a widening of the mastoid segment of the facial canal with involvement of the facial nerve. Pathologic examination of the resected specimen revealed histological features of adenoid cystic carcinoma with intra neural invasion of the mastoid segment of the facial nerve. The surgical margins were free. The evolution was favourable 5 years later.

CONCLUSION

This study confirms that multiplanar approach of MRI allows rapid detection of adenoid cystic carcinoma. The influence of intraneural invasion and spread on survival remains controversial.

[Neurovascular interactions in hemifacial spasm]

The article describes our results of surgical treatment of 37 patients with hemifacial spasm (HS) as well as results of morphological studies of facial nerve root exit zone (REZ). Morphological studies demonstrated that extension of central myelinated zone differed between 0.9 and 3.6 mm (mean 2.24 mm). This zone did not exceed 1.1 diameter of facial nerve. Intraoperative findings included 27 cases of compression by a single vessel and 9 cases of compression by multiple vessels. In cases of compression by a single vessel the offending artery was AICA in 11 cases, PICA in 12 cases and VA in 4 cases. In 35 patients complete decompression of facial nerve REZ was achieved. In one case complete decompression was not possible due to penetration o vestibular nerve by AICA which prevented safe manipulations of the artery and nerves. Excellent results of surgical treatment were achieved in 33 patients. In 1 described case the outcome was unsatisfactory. We observed no serious postoperative complications. Vascular decompression is highly effective and relatively safe procedure for treatment o HS. HS results from compression of central myelinated zone of facial nerve thus surgical decompression should be preformed close to REZ at the brainstem.

Useful surgical techniques for facial nerve preservation in tumorous intra-temporal lesions

The management of the facial nerve in tumorous temporal lesions is particularly challenging due to its complex anatomic location and potential postoperative complications, including permanent facial paralysis. The most important concern regarding surgical treatment of a tumorous temporal lesion is the inevitable facial paralysis caused by nerve injury during the tumor removal, especially in patients with minimal to no preoperative facial nerve dysfunction. We describe successful four cases in which various surgical techniques were developed for the preservation of the facial nerve in treatment of intratemporal tumorous lesions.

Management of Facial Nerve Schwannoma in Patients With Favorable Facial Function

OBJECTIVE

We report six cases of facial nerve schwannomas in which surgical management allowed the preservation of facial nerve function. Specifically, this paper reports that a stripping surgery may provide favorable functional outcomes.

STUDY DESIGN

A retrospective review of preoperative and postoperative data for six patients with facial nerve schwannoma that had normal facial nerve function or a House-Brackmann grade II facial palsy before the surgery.

METHODS

Stripping surgery, which removed the schwannoma from the remaining nerve fascicle, was attempted on the six patients. Postoperative facial nerve function and imaging (magnetic resonance imaging) were evaluated.

RESULTS

Stripping surgery with gross total tumor removal of the mass was performed in four cases. In the two remaining cases, the stripping surgery was not possible, and decompression alone was performed. Favorable preservation of facial function was achieved in all six cases.

CONCLUSION

It was possible to preserve facial function after surgery to remove facial nerve schwannoma. We suggest that stripping surgery, focused on the preservation of continuity of the facial nerve, may be attempted for facial nerve schwannoma in which favorable facial function has been preserved.

A facial nerve schwannoma masquerading as a vestibular schwannoma

Schwannoma of the facial nerve is an extremely rare condition with an incidence far lower than that of vestibular schwannoma. We discuss the case of a woman who had been diagnosed as having vestibular schwannoma and referred to our hospital. Initially, we concurred with the diagnosis, but on reassessment of magnetic resonance imaging scans before surgery, we revised the diagnosis to facial nerve schwannoma. This allowed us to counsel the patient appropriately preoperatively regarding the expected outcome. We discuss the importance of this case and the lessons to be learned from it.

[Experimental studies for the improvement of facial nerve regeneration]

Using a combination of the following, it is possible to investigate procedures to improve the morphological and functional regeneration of the facial nerve in animal models: 1) retrograde fluorescence tracing to analyse collateral axonal sprouting and the selectivity of reinnervation of the mimic musculature, 2) immunohistochemistry to analyse both the terminal axonal sprouting in the muscles and the axon reaction within the nucleus of the facial nerve, the peripheral nerve, and its environment, and 3) digital motion analysis of the muscles. To obtain good functional facial nerve regeneration, a reduction of terminal sprouting in the mimic musculature seems to be more important than a reduction of collateral sprouting at the lesion site. Promising strategies include acceleration of nerve regeneration, forced induced use of the paralysed face, mechanical stimulation of the face, and transplantation of nerve-growth-promoting olfactory epithelium at the lesion site.

Androgen regulation of axon growth and neurite extension in motoneurons

Androgens act on the CNS to affect motor function through interaction with a widespread distribution of intracellular androgen receptors (AR). This review highlights our work on androgens and process outgrowth in motoneurons, both in vitro and in vivo. The actions of androgens on motoneurons involve the generation of novel neuronal interactions that are mediated by the induction of androgen-dependent neurite or axonal outgrowth. Here, we summarize the experimental evidence for the androgenic regulation of the extension and regeneration of motoneuron neurites in vitro using cultured immortalized motoneurons, and axons in vivo using the hamster facial nerve crush paradigm. We place particular emphasis on the relevance of these effects to SBMA and peripheral nerve injuries.

Pseudotumoural hypertrophic neuritis of the facial nerve

In a retrospective study of our cases of recurrent paralysis of the facial nerve of tumoural and non-tumoural origin, a tumour-like lesion of the intra-temporal course of the facial nerve, mimicking facial nerve schwannoma, was found and investigated in 4 cases. This was defined as, pseudotumoral hypertrophic neuritis of the facial nerve. The picture was one of recurrent acute facial palsy with incomplete recovery and imaging of a benign tumour. It was different from the well-known recurrent neuritis, hypertrophic neuropathy and perineuroma. A portion of the intra-temporal course of the nerve with concurrent dilatation of the osseous walls was diagnosed pre-operatively as facial nerve schwannoma. The pathological picture showed inflammatory hypertrophy which was not a schwannoma but was likely of viral origin, with degeneration-regeneration of fibres and new connective tissue. Resection of the involved portion of the facial nerve and autologous graft in two cases was performed, decompression with biopsy in the other two. No recurrence of new episodes of paralysis after surgery was observed.

The usefulness of clinical findings in localising lesions in Bell's palsy: comparison with MRI

BACKGROUND

Although electrophysiological tests and brain MRI provide information about the site of the lesion in Bell's palsy, clinicians usually depend on clinical data. However, the accuracy of clinical findings in identifying lesions has never been evaluated.

METHOD

A total of 57 patients with idiopathic peripheral facial palsy were included in this study. We determined the sites of the lesions based on associated symptoms and by brain MRI. We then compared the two to assess the value of clinical findings in determining lesion sites.

RESULTS

Of the 57 patients, 27 were men. The mean age of all patients was 50.6+/-16.7 years. The lesion sites determined from clinical findings were as follows: the infrageniculate-suprastapedial segment, 13 (23%); the infrastapedial-suprachordal segment, 9 (16%); and the mastoid segment, 35 (61%). No sites were classified as involving the suprageniculate segment. On brain MRI, 51 (89%) of the 57 patients showed abnormal enhancement of the facial nerve, with the most common area being the suprageniculate segment, including the distal intrameatal, labyrinthine and geniculate ganglion.

CONCLUSIONS

We demonstrate that clinical history is not helpful in determining the site of a lesion in Bell's palsy. The segment most frequently involved in Bell's palsy is the suprageniculate segment.

[Preliminary study of treating parotid gland malignant tumor with saving facial nerve (surgery associated with 125I seed implant brachytherapy)]

OBJECTIVE

To study the clinical effect of treating parotid gland malignant tumor with facial never-preserving surgery combined with 125I seed implant brachytherapy.

METHODS

Thirty-two patients with parotid gland malignancy underwent tumor and parotid gland excision while preserving facial never. According to treating plan system (TPS), 125I seeds were implanted into the target area during or after operation. The patients were followed up after operation and the local tumor control and facial nerve function were observed.

RESULTS

Tumor recurrence was not found in any patient treated after 12 to 44 months of follow up. All patients did not show obvious radiation-related complications. The facial never function of all patients was basically normal 6 months after operation.

CONCLUSIONS

For parotid gland malignant tumor, surgery combined with 125I seeds implant brachytherapy can save facial nerve function, and the short-term effects were satisfactory.

Hemifacial spasm: neurovascular compressive patterns and surgical significance

BACKGROUND

The aim of this study was to report further investigation of neurovascular compression as a cause of hemifacial spasm (HFS) and to provide useful surgical guidelines by describing the compression patterns.

MATERIAL AND METHODS

From January 2004 to February 2006, 236 consecutive patients with HFS underwent microvascular decompression (MVD) in a single centre. Based on the operation and medical records, the intraoperative findings and post-operative outcomes were obtained and analysed.

RESULTS

We found that 95.3% of lesions had accompanying causative factors that made the neurovascular compression inevitable. Based on the contributing factors, compression patterns were categorised into six different types including: loop (n = 11: 4.6%), arachnoid (n = 66: 27.9%), perforator (n = 58: 24.6%), branch (n = 18: 7.6%), sandwich (n = 28: 11.9%), and tandem (n = 52: 22.0%). The compression patterns were significantly correlated with the compressing vessels involved. Thirty-two (86.5%) of 37 lesions where the vertebral artery was the compressing vessel involved the tandem type. Anterior inferior cerebellar artery was the compressing vessel involved in 49 (84.5%) of 58 perforator type compressions, while posterior inferior cerebellar artery was the compressing vessel involved in 8 (72.7%) of 11 loop type compressions.

CONCLUSIONS

Once the compressing vessel responsible for the neurovascular compression are identified, the probable pattern of compression can be anticipated; this knowledge could facilitate the application of the appropriate operative procedures and minimise post-operative complications.

Microsurgery for vestibular schwannoma after gamma knife radiosurgery

BACKGROUND

We evaluated the clinical characteristics of microsurgery for vestibular schwannoma (VS) after failed gamma knife radiosurgery (GKS).

METHOD

Twelve patients, 5 men and 7 women aged 19 to 70 years (mean 54.5 years), who underwent microsurgery after failed GKS for VS were studied retrospectively.

FINDINGS

The median interval between GKS and microsurgery was 28.8 months (range, 6.6-120 months) and 4 patients had undergone previous microsurgery. The mean volume of tumour at GKS was 6.9 cm(3) (range, 0.5-19.7 cm(3)) and the mean prescription dose to the tumour margin was 12.3 Gy. Microsurgery involved the lateral suboccipital approach in all patients. Tumour expansion involved solid enlargement in 7 patients, cystic enlargement in 3, and central necrosis in 2. Bleeding was slight in all patients except in one, probably because of the previous irradiation. Adhesion to the brain stem was severe in 7 patients. Identification of the facial nerve was easy in 5 operations and difficult in 7. Dissection of the tumour from the facial nerve was difficult in most interventions because of severe adhesions or colour change. Severe adhesions between the trigeminal nerve and the tumour was observed in 2 patients. The tumour was subtotally removed except around the internal auditory canal in most patients. Only one residual tumour increased in size and needed second GKS. The function of the facial nerve deteriorated in 3 patients, was unchanged in 7, and improved in 2. All patients had lost hearing on the affected side at the time of microsurgery.

CONCLUSIONS

Microsurgery for VS after failed GKS presents some technical difficulties. Dissection of the tumour from the facial nerve or brain stem is likely to be difficult. We recommend subtotal resection without dissection of the facial nerve and tumour, because growth of the residual tumour was rare in our series.

Prognostic value of electroneurography in Bell's palsy and Ramsay-Hunt's syndrome

OBJECTIVES

This study evaluated the accuracy of electroneurography to predict the prognosis of Bell's palsy and Ramsay-Hunt's syndrome.

DESIGN

A retrospective, institutional review board-approved study.

SETTING

A secondary referral and a university-based centre.

PARTICIPANTS

The patients had been treated for a sudden onset unilateral facial paralysis over the past 10 years (1994-2004). This retrospective study included only those patients who had been followed up for at least 3 months or if they had reached a complete recovery before then.

MAIN OUTCOMES MEASURES

House-Backmann grade versus electroneurography value.

RESULTS

The recovery rates to House-Brackmann grade II or better were 95% in those with Bell's palsy and 84% in those with herpes zoster oticus. The electroneurography value of the recovery and non-recovery groups from those with either Bell's palsy or herpes zoster oticus was similar. The logistic regression model between the electroneurography values and the probability of recovery showed no correlation in those with Bell's palsy or with herpes zoster oticus. This study did not identify the proper electroneurography value that had enough appropriate sensitivity and specificity to predict the prognosis of paralysis accurately in Bell's palsy or in herpes zoster oticus patients.

CONCLUSION

Electroneurography performed between day 7 and 10 for Bell's palsy or day 10 and 14 for herpes zoster oticus does not provide accurate information on the prognosis or recovery rate of the facial paralysis.

Correlation between MRI and operative findings in Bell's palsy and Ramsay Hunt syndrome

PURPOSE

To investigate the correlation between gadolinium enhanced magnetic resonance image (MRI) results and surgical findings of facial nerves in Bell's palsy and Ramsay Hunt syndrome.

MATERIALS AND METHODS

From 1995 to 2004, MRI was performed on 13 patients with Bell's palsy or Ramsay Hunt syndrome, who were offered with surgical decompression of the facial nerve through the middle cranial fossa approach. Gadolinium enhanced MRI was performed on all patients and the enhancement of the facial nerve was evaluated by radiology specialists. Operative findings including the degree of the facial nerve segment swelling were examined. Furthermore, the time interval from the onset of palsy to surgery was evaluated.

RESULTS

Swelling of facial nerve segments was found in patients with enhanced facial nerves from MRI. The swelling of the facial nerve in the labyrinthine segment in particular was identified in all patients with enhanced labyrinthine segments in MRI. The intraoperative swelling of geniculate ganglion of facial nerve was found in 78% of patients with enhanced facial segment in MRI (p=0.01). The intraoperative swelling of tympanic segment was observed from fourth to ninth weeks after the onset of palsy.

CONCLUSION

MRI enhancement of facial nerves in Bell's palsy and Ramsay Hunt syndrome is associated with the extent of intratemporal lesions of facial nerves, especially in the labyrinthine segment.

[Preliminary studies on histological changes after repairing the facial nerve defect with acellular facial nerve]

OBJECTIVE

To investigate the morphological changes after chemically extracted acellular nerve allografts transplant.

METHODS

Seventy-two rabbits were divided into four groups. Acellular allografts of facial nerve were used in experimental group, and facial nerve autografts, acellular peroneal nerve allografts and peroneal nerve autografts respectively used in three control groups. The morphological changes after transplant were evaluated by modified trichrome staining, immunohistological staining and transmission electron microscope.

RESULTS

The two facial nerve grafts showed numerous regenerated nerve fibers, vessels and as well as a spindle schwann cells arranged longitudinally. No significant difference was observed in the fiber number and myelin thickness between the two groups,while the two peroneal nerve groups showed poor regeneration 6 months after operation.

CONCLUSIONS

The facial nerve allografts showed more neurite regeneration six months after transplant, and the regenerated axons passed through the distal stoma and there were well revascularized and proliferated schwann cells in the grafts.