Photobiomodulation enhances facial nerve regeneration via activation of PI3K/Akt signaling pathway-mediated antioxidant response.

Facial nerve dysfunction is a common clinical condition that leads to disfigurement and emotional distress in the affected individuals. This study aimed to evaluate whether photobiomodulation can enhance regeneration of crushed facial nerves and attempt to investigate the possible underlying mechanism of neuroprotective function and therapeutic target. Various parameters of photobiomodulation were assigned to the facial nerves and Schwann cells (SCs) separately during crushed injury in rats. Axonal regeneration, functional outcomes, and SC apoptosis, proliferation, and underlying mechanisms of action were evaluated by morphological, histopathological, and functional assessments, flow cytometry, western blotting, real-time PCR, and IncuCyte. The results showed that photobiomodulation improved axonal regeneration and functional recovery, and also promoted proliferation, and inhibited apoptosis of SCs, both of these were considered as the most effective parameters in 250mW group. In addition, the neuroprotective effects of photobiomodulation (500mW) were likely associated with oxidative stress-induced SC apoptosis via activation of the PI3K/Akt signaling pathway. Our results revealed that photobiomodulation significantly promoted axonal regeneration, functional recovery, and regeneration of the facial nucleus, and its mechanism was related to the up-regulation of the PI3K/Akt signaling pathway. These findings provide clear experimental evidence of photobiomodulation as an alternative therapeutic strategy for peripheral nerve damage.

Twelve-year results of LINAC-based radiosurgery for vestibular schwannomas.

PURPOSE: To report long-term outcomes of 53 patients with vestibular schwannomas (VS) submitted to a single high-dose LINAC-based radiosurgery (SRS) in our institution. METHODS: 48 (92%) patients were evaluable for clinical and MRI response as well as late toxicity. At a median follow-up of 12 years (range 2-16 years), local control (LC), hearing capacity, trigeminal and facial nerve function, and toxicity were assessed. Hearing capacity was classified according to the Gardner-Robertson scale, where class I-II patients had "serviceable hearing." RESULTS: Median dose of SRS was 16.5 Gy (range 13-20 Gy) and median tumor volume 1.7 cm3 (range 0.09-7.4 cm3). 35 (73%) patients were treated with SRS alone, in the remaining 13 (27%) patients, SRS was performed as salvage therapy for recurrent or progressive tumors after previous microsurgery. Before SRS, 44 patients (92%) had hearing loss and 25 (52%) had "non-serviceable" hearing. Tumor extension, classified with Koos categories, was grade I-II in 27 (56%) and grade III-IV in 21 (44%) cases. LC was 100% and hearing preservation in "serviceable hearing" patients was 91%. 4 (11%) patients developed incomplete and intermittent ipsilateral facial nerve palsy which regressed in a median time of 6 months. Trigeminal toxicity was registered in 11 (23%) patients, reversible in 6 (13%) and permanent in 5 (10%). Only Koos tumor grade III-IV significantly influenced late toxicity (p = 0.01). CONCLUSION: LC and hearing preservation after SRS were excellent. Toxicity proved acceptable. Although the median administered dose (16.5 Gy) was rather high, the only factor which significantly influenced late toxicity was Koos tumor grade III-IV.

Advance in Functional Restoration of Injured Nerve with Low Level Laser and its Utilization in the Dental and Maxillofacial Region.

The inferior alveolar nerve and facial nerve are the two most important nerves in the dental and maxillofacial region. The injury to them is one of the major postoperative complications after alveolar surgery and orthognathic surgery. However, recovering the nerve function after injury takes a long time and the recovery effect tends to be unsatisfactory. In recent years, an intensively investigated technique, low level laser which has been applying in assisting the recovery of nerve function, has been gradually proved to be effective in clinically treating postoperative nerve injury. In this article we review in terms of the mechanisms involved in low level laser-assisted functional restoration of nerve injury and its clinical application in the recovery of nerve function in the dental and maxillofacial area as well.

Three-Dimensional Printed Plate-Guided 125I Brachytherapy for Malignant Parotid Tumors.

PURPOSE: The treatment of malignant parotid tumors with 125I brachytherapy is rarely reported. This study evaluated the efficacy and dose and response of 125I brachytherapy in patients with malignant tumors. MATERIALS AND METHODS: From July 2014 through August 2017, 39 patients with malignant parotid tumors were treated with 125I brachytherapy. Thirty-five patients were treated with conservative surgical resection before brachytherapy. Four patients were treated with brachytherapy alone. Clinical outcomes and side effects were evaluated. Clinical factors were investigated to determine correlations with local control (LC) and side effects. RESULTS: Mean follow-up was 25 months (range, 7 to 47 months). The LC rate was 87.2% and the overall survival rate was 97.4%. High tumor grade and large tumor showed a propensity for local recurrence. Acute skin toxicity occurred in 87.2% of patients and grade 3 and 4 radioepidermitis was found in 20.5% of patients. In total, 89.7% of patients with facial nerve dysfunction recovered within 12 months. CONCLUSIONS: 125I brachytherapy was a feasible treatment option for patients with malignant parotid tumors. Although side effects were minimal, strict follow-up was necessary for patients treated with a high dose.

Percutaneous Selective Neuromodulation via Monopolar Radiofrequency for Glabellar Lines: A Case Study.

INTRODUCTION: Injectable botulinum toxin is a safe, effective, and popular therapy that blocks neural impulses to achieve a desired effect. Using monopolar RF, percutaneous selective neuromodulation can achieve a similar but more persistent effect. METHODS: Bilateral treatment was performed on a woman (48 years of age) to ablate the angular nerves of the face, inhibiting muscular function and reduce the appearance of glabellar lines. The cannula was inserted at the mid-pupillary line and advanced toward the lateral border of the nose. After isolating the nerve via low-level stimulation, anesthetic was given through a port in the cannula and energy was applied; tissue temperature of 85 °C was maintained for 70 seconds. RESULTS: Full ablative lesioning of the angular nerve of the patient was achieved and function was therapeutically inhibited with minimal pain. Results have persisted for more than two years.

The new heterologous fibrin sealant in combination with low-level laser therapy (LLLT) in the repair of the buccal branch of the facial nerve.

This study aimed to evaluate the effects of low-level laser therapy (LLLT) in the repair of the buccal branch of the facial nerve with two surgical techniques: end-to-end epineural suture and coaptation with heterologous fibrin sealant. Forty-two male Wistar rats were randomly divided into five groups: control group (CG) in which the buccal branch of the facial nerve was collected without injury; (2) experimental group with suture (EGS) and experimental group with fibrin (EGF): The buccal branch of the facial nerve was transected on both sides of the face. End-to-end suture was performed on the right side and fibrin sealant on the left side; (3) Experimental group with suture and laser (EGSL) and experimental group with fibrin and laser (EGFL). All animals underwent the same surgical procedures in the EGS and EGF groups, in combination with the application of LLLT (wavelength of 830 nm, 30 mW optical power output of potency, and energy density of 6 J/cm(2)). The animals of the five groups were euthanized at 5 weeks post-surgery and 10 weeks post-surgery. Axonal sprouting was observed in the distal stump of the facial nerve in all experimental groups. The observed morphology was similar to the fibers of the control group, with a predominance of myelinated fibers. In the final period of the experiment, the EGSL presented the closest results to the CG, in all variables measured, except in the axon area. Both surgical techniques analyzed were effective in the treatment of peripheral nerve injuries, where the use of fibrin sealant allowed the manipulation of the nerve stumps without trauma. LLLT exhibited satisfactory results on facial nerve regeneration, being therefore a useful technique to stimulate axonal regeneration process.

Long-term outcomes of facial nerve function in irradiated and nonirradiated nerve grafts.

OBJECTIVES: We reviewed the long-term results of facial nerve repair in a tertiary head and neck institution in the north of England. METHODS: We performed a case notes review of patients who had facial nerve repair over a 10-year period and had completed 24 months of follow-up. RESULTS: The study population comprised 18 female patients and 24 male patients, with an overall mean age of 53.2 years (range, 16 to 80 years). Of the 24 patients who had a cable nerve graft, the greater auricular nerve was used in 15 cases. The sural nerve was used as the donor in a cross-facial nerve graft in 9 patients. Sixteen patients had transposition nerve repair: hypoglossal and ansa cervicalis in 7 and 9 cases, respectively. Two patients had primary anastomosis after surgery for extensive malignant tumors. In this series, no patients achieved a House-Brackmann (HB) grade of II. Overall, the HB grades III, IV, and V were the best postoperative facial nerve functions achieved in 11.9%, 33.3%, and 26.2% of patients, respectively. Failure (HB grade VI) was observed in 28.6% of patients. More than half of patients (62.5%) who had either a sural nerve cable graft or a faciohypoglossal transposition had a good outcome (HB grade III or IV). CONCLUSIONS: In the present series, 45% of patients had an HB grade of III or IV at long-term follow-up. The best outcome (HB grade III) was observed after cross-facial grafting with the sural nerve.

[First experience of stereotactic radiation therapy for vestibular schwannoma using CyberKnife].

Currently stereotactic radiosurgery has become the treatment of choice in small vestibular schwannomas. This paper discusses our first experience of application of CyberKnife system for stereotactic irradiation of these tumors. From April 2009 till June 2011 we treated 62 patients (35 female and 27 male) with vestibular schwannomas. Stereotactic radiosurgery using CyberKnife system was performed in 33 patients. Mean tumor volume was 2 +/- 1.4 cm3. Hypofractionated treatment was used in 30 cases (31 tumor). Mean tumor volume reached was 7 +/- 6.2 cm3 (range - 0.5-31.3 cm3). In a case of a patient with NF2 simultaneous irradiation of bilateral tumors was performed. Most frequently we applied 3 fractions 6 Gy each (17 observations of 31, or 55%) and 5 fractions with mean dose 5 Cy (10 cases, or 32%). Follow-up period varied from 1 to 26 months (mean 9 +/- 4.5 months). By the end of this study (June 30, 2011) surgical resection was required in the only case of 47-years old male patient with cystic schwannoma of left vestibular nerve 5 months after radiation treatment, due to progressive growth of the cyst and increased brainstem compression. Tumor growth control was established in 97.5% of cases. Stabilization of auditory function was achieved in 77.5% of series. Effective hearing was preserved in 75% of patients. Facial nerve palsy after stereotactic radiation treatment was observed in 2 cases (3%). Incidence of trigeminal nerve dysfunction was significantly higher: sensation disturbances occurred in 6 (10%) patients: 3% after radiosurgery and 16.7% after hypofractionation. We did not obtain significant correlations between risk of cranial nerve complications and dosimetric or demographic factors. However we observed stable tendency: larger initial volume of the tumor and presence of trigeminal nerve dysfunction before treatment were poor prognostic factors for trigeminal neuropathy. Stereotactic irradiation using CyberKnife system is effective and sufficiently safe technique for management of vestibular schwannoma. The paper demonstrates high rates of tumor stabilization, hearing preservation and minimal incidence of complications associated with trigeminal or facial nerve.

Photobiomodulation Therapy to Treat Facial Paralysis of 8 Years: Case Report.

Background: Paralysis of the facial muscles produces functional and aesthetic disturbance that has a negative impact for the patient's quality of life. Objective: To evaluate the effects of a photobiomodulation (PBM) with low-level laser (LLL) on the treatment of a patient with 8 years of facial paralysis. Methods: PBM with two different wavelengths of LLL (660 and 808 nm), applied only on the affected side, three times a week for 8 consecutive weeks. Evaluations were performed before starting treatments, after the 12th session of treatment and after the 24th session, using the House-Brackmann scale and electroneuromyography. Results: The House-Brackmann and electroneuromyography tests showed improvements in the movement of the facial muscles when tested in the middle and at the end of the treatment with LLL. Conclusions: PBM with LLL at the wavelength of 660 and 808 nm with the parameters used in this case report was an effective and noninvasive treatment for facial paralysis in this long-standing, chronic case of 8 years.

Facial nerve preservation after vestibular schwannoma Gamma Knife radiosurgery.

OBJECTIVE: Facial nerve preservation is a critical measure of clinical outcome after vestibular schwannoma treatment. Gamma Knife radiosurgery has evolved into a practical treatment modality for vestibular schwannoma patients, with several reported series from a variety of centers. In this study, we report the results of an objective analysis of reported facial nerve outcomes after the treatment of vestibular schwannomas with Gamma Knife radiosurgery. MATERIALS AND METHODS: A Boolean Pub Med search of the English language literature revealed a total of 23 published studies reporting assessable and quantifiable outcome data regarding facial nerve function in 2,204 patients who were treated with Gamma Knife radiosurgery for vestibular schwannoma. Inclusion criteria for articles were: (1) Facial nerve preservation rates were reported specifically for vestibular schwannoma, (2) Facial nerve functional outcome was reported using the House-Brackmann classification (HBC) for facial nerve function, (3) Tumor size was documented, and (4) Gamma Knife radiosurgery was the only radiosurgical modality used in the report. The data were then aggregated and analyzed based on radiation doses delivered, tumor volume, and patient age. RESULTS: An overall facial nerve preservation rate of 96.2% was found after Gamma Knife radiosurgery for vestibular schwannoma in our analysis. Patients receiving less than or equal to 13 Gy of radiation at the marginal dose had a better facial nerve preservation rate than those who received higher doses (13 Gy = 94.7%, P < 0.0001). Patients with a tumor volume less than or equal to 1.5 cm(3) also had a greater facial nerve preservation rate than patients with tumors greater than 1.5 cm(3) (1.5 cm(3) 95.5%, P < 0.0001). Superior facial nerve preservation was also noted in patients younger than or equal to 60 years of age (96.8 vs. 89.4%, P < 0.0001). The average reported follow up duration in this systematic review was 54.1 +/- 31.3 months. CONCLUSION: Our analysis of case series data aggregated from multiple centers suggests that a facial nerve preservation rate of 96.2% can be expected after Gamma knife radiosurgery for vestibular schwannoma. Younger patients with smaller tumors less than 1.5 cm(3) and treated with lower doses of radiation less than 13 Gy will likely have better facial nerve preservation rates after Gamma Knife radiosurgery for vestibular schwannoma.

Qualitative effect on mRNAs of injury-associated proteins by cell phone like radiation in rat facial nerves.

Rats were exposed to cell phone radiation for 6 hours per day for 18 weeks. The buccal and mandibular branches of the facial nerve were evaluated for this study. The mRNA levels of four proteins that are usually up regulated when an injury has occurred were investigated; included were Calcium ATP-ase, Endothelin, Neural Cell Adhesion Molecule, and Neural Growth Factor. These isolated mRNAs were subjected to RT-PCR and all four were up regulated. The mandibular nerve showed a higher and broader level of up regulation than the buccal nerve. All four mRNA up regulations for the mandibular nerve and two for the buccal nerve were also statistically significant. These specific injury-related findings were mild. As the use of these cell phones continues, there most likely will be permanent damage to these tissues over the years and the likelihood of tumors, cancers, and system failures will potentially increase.

Axonal excitability properties in hemifacial spasm.

Hemifacial spasm (HFS) is characterized by involuntary, irregular contractions of muscles innervated by the facial nerve. Whether the facial nerve has a relative predisposition for ectopic activity has not been clarified. Nerve excitability techniques, which provide information about membrane potential and axonal ion channel function, were initially measured in 12 control subjects looking for biophysical differences that may predispose the facial nerve to generate ectopic activity. In a second series of studies, facial nerve excitability was assessed in nine HFS patients. In both series, stimulus-response behavior, threshold electrotonus, a current threshold relationship, and the recovery of excitability following supramaximal stimulation were recorded following stimulation of the facial nerve. When compared to normative data from nerves in the upper and lower limbs, there was a relative "fanning-in" of threshold electrotonus, reduced superexcitability, and increased subexcitability in facial nerve studies from control subjects (P < 0.05), consistent with relative axonal depolarization. These findings may underlie the propensity for the facial nerve to develop ectopic impulse activity in motor axons. In the HFS patient study, there were no significant differences in distal facial nerve excitability properties from the affected side in HFS patients when compared either to the unaffected side or to normative facial nerve data. It is concluded that the impulse generator underlying HFS must consequently be sited more proximally and does not cause a generalized disturbance of motor axon excitability.

Experimental study on the correlation between abnormal muscle responses and F waves in hemifacial spasm.

OBJECTIVES: To investigate the correlation between abnormal muscle response (AMR) and F wave by establishing an animal model of hemifacial spasm (HFS). METHODS: Both demyelination in the main trunk of the facial nerve just distal to stylomastoid foramen and vascular compression were used to duplicate animal model of HFS in ten New Zealand white rabbits. AMR and F waves were elicited from the orbicularis oculi and mentalis muscles respectively by stimulating marginal mandibular branch of the facial nerve 6 weeks post-operatively. Correlation analyses were used to compare the relationship between AMR/M and F/M amplitude ratio and between the duration of AMRs and F waves. RESULTS: There was a linear correlation between the mean values of the AMR/M and F/M amplitude ratio (r=0.8602, p<0.01), which can also be found between the duration of AMRs and F waves (r=0.7702, p<0.01). DISCUSSION: Enhanced F waves and AMRs may have the same origin. The F wave can be regarded as a more direct index in the diagnosis pre-operatively, monitoring intraoperatively and follow-up post-operatively in patients with HFS.

Optical stimulation of the facial nerve: a new monitoring technique?

OBJECTIVES/ HYPOTHESIS: One sequela of skull base surgery is iatrogenic damage to cranial nerves, which can be prevented if the nerve is identified. Devices that stimulate nerves with electric current assist in nerve identification. Contemporary devices have two main limitations: 1) the physical contact of the stimulating electrode and (2) the spread of the current through the tissue. In contrast to electrical stimulation, pulsed infrared optical radiation can be used to safely and selectively stimulate neural tissue and might be valuable for screening. METHODS: The gerbil facial nerve was exposed to 250 microsecond pulses of 2.12 microm radiation delivered via a 600-microm-diameter optical fiber at a repetition rate of 2 Hz. With use of 27 GA, 12-mm intradermal electrodes, muscle action potentials were recorded. Nerve samples were examined for possible tissue damage. RESULTS: Eight facial nerves were stimulated with radiant exposures between 0.71 and 1.77 J/cm, resulting in compound muscle action potentials (CmAPs) that were simultaneously measured at the m. orbicularis oculi, m. levator nasolabialis, and m. orbicularis oris. Resulting CmAP amplitudes were 0.3 to 0.4 mV, 0.15 to 1.4 mV, and 0.3 to 2.3 mV, respectively, depending on the radial location of the optical fiber and the radiant exposure. Individual nerve branches were also stimulated, resulting in CmAP amplitudes between 0.2 and 1.6 mV. Histology revealed tissue damage at radiant exposures of 2.2 J/cm but no apparent damage at radiant exposures of 2.0 J/cm. CONCLUSIONS: The experiments showed that selective muscle action potentials can be evoked optically in the gerbil facial nerve without direct physical contact.

Efficacy of Laser Photobiomodulation on Morphological and Functional Repair of the Facial Nerve.

OBJECTIVE: Evaluate the efficacy of low-level laser therapy (LLLT) on qualitative, quantitative, and functional aspects in the facial nerve regeneration process. MATERIALS AND METHODS: Forty-two male Wistar rats were used, randomly divided into a control group (CG; n = 10), in which the facial nerve without lesion was collected, and four experimental groups: (1) suture experimental group (SEG) and (2) fibrin experimental group (FEG), consisting of 16 animals in which the buccal branch of the facial nerve was sectioned on both sides of the face; an end-to-end epineural suture was performed on the right side, and a fibrin sealant was used on the left side for coaptation of the stumps; and (3) laser suture experimental group (LSEG) and (4) laser fibrin experimental group (LFEG), consisting of 16 animals that underwent the same surgical procedures as SEG and FEG with the addition of laser application at three different points along the surgical site (pulsed laser of 830 nm wavelength, optical output power of 30 mW, power density of 0.2586 W/cm2, energy density of 6.2 J/cm2, beam area of 0.116 cm2, exposure time of 24 sec per point, total energy per session of 2.16 J, and cumulative dose of 34.56 J). The animals were submitted to functional analysis (subjective observation of whisker movement) and the data obtained were compared using Fisher's exact test. Euthanasia was performed at 5 and 10 weeks postoperative. The total number and density of regenerated axons were analyzed using the unpaired t-test (p < 0.05). RESULTS: Laser therapy resulted in a significant increase in the number and density of regenerated axons. The LSEG and LFEG presented better scores in functional analysis in comparison with the SEG and FEG. CONCLUSIONS: LLLT enhanced axonal regeneration and accelerated functional recovery of the whiskers, and both repair techniques allowed the growth of axons.

Long-term outcome of stereotactic radiosurgery (SRS) in patients with acoustic neuromas.

PURPOSE: To evaluate the effectiveness and long-term outcome of stereotactic radiosurgery (SRS) for acoustic neuromas (AN). PATIENTS AND METHODS: Between 1990 and 2001, we treated 26 patients with 27 AN with SRS. Two patients suffered from neurofibromatosis type 2. Before SRS, a subtotal or total resection had been performed in 3 and in 5 patients, respectively. For SRS, a median single dose of 13 Gy/80% isodose was applied. RESULTS: The overall actuarial 5-year and 10-year tumor control probability in all patients was 91%. Two patients developed tumor progression after SRS at 36 and 48 months. Nineteen patients (73%) were at risk of treatment-related facial nerve toxicity; of these, 1 patient developed a complete facial nerve palsy after SRS (5%). A total of 93% of the lesions treated were at risk of radiation-induced trigeminal neuralgia. Two patients (8%) developed mild dysesthesia of the trigeminal nerve after SRS. The hearing preservation rate in patients with useful hearing before SRS was 55% at 9 years. CONCLUSION: Stereotactic radiosurgery results in good local control rates of AN and the risk of cranial nerve toxicities is acceptable. As toxicity is lower with fractionated stereotactic radiotherapy, SRS should be reserved for smaller lesions.

Nervus Intermedius Symptoms following Surgical or Radiation Therapy for Vestibular Schwannoma.

OBJECTIVES: This study compares the functional outcomes of nevus intermedius impairment following surgery, radiation, or observation for the treatment of vestibular schwannoma. STUDY DESIGN: Retrospective cohort study. SETTINGS: Tertiary care medical center. SUBJECTS AND METHODS: We retrospectively examined 141 charts of patients with a vestibular schwannoma seen in the Dartmouth-Hitchcock Acoustic Neuroma Clinic between 2012 and 2014. Seventy-one patients underwent intervention (including radiation) as their primary treatment, and 70 were treated with observation. As part of routine care, patients were interviewed at clinic visits and with a questionnaire assessing nervus intermedius impairment. RESULTS: At presentation, 25 patients (19%) reported nervus intermedius impairment. Most common disturbances were xerophthalmia (dry eyes, 13%) and dysgeusia (taste alteration, 7.6%). Postintervention, 35 patients (53%) had ≥1 symptoms of nervus intermedius dysfunction, which is increased in comparison with patients in the observation group (17 patients, 26.5%, P < .05). Twelve intervention patients had symptoms resolve postoperatively, making no long-term difference between the observation and intervention groups (P = .20). Motor function of the facial nerve postoperatively is correlated with nervus intermedius symptoms. Surgical approaches were compared with radiation therapy, and no significant difference in nervus intermedius outcomes was found. CONCLUSION: This study demonstrates the clinical importance of monitoring nervus intermedius symptoms, since a high percentage of all patients undergoing intervention will be symptomatic during management. Patients with motor dysfunction are at a higher risk of developing nervus intermedius sequelae and need close follow-up. Although impairment is common, many symptoms will improve over time with no long-term difference between intervention patients and those under observation.

The implications of improved treatment of malignant salivary gland tumors by fast neutron radiotherapy.

The conventional treatment for cancer of the salivary glands is surgery, with or without X ray therapy. In advanced tumors (Stage III and IV), local control and 5-year survival rates are less than 35%. Radical surgery severs the facial nerve in the majority of operations on parotid gland tumors. Local control of unresectable salivary gland tumors was achieved, in 74% of cases, by fast neutron therapy. From the MRC cyclotron at Hammersmith Hospital neutrons were given to 65 patients, with locally advanced or recurrent tumors, 89% of which were Stage IV. Local control and 5-year survival rates were 72% and 50%, respectively. The facial nerve was not damaged by neutron therapy. In patients with parotid gland tumors, 77% regained or maintained function. Function was lost in 14% through recurrence and 9% remained paralyzed. The results were achieved using beams from primitive machines with serious disadvantages. The results from neutrons implicate improvements for locally advanced tumors of non-epidermal origin in other sites of the body, especially with the high energy neutrons now available from modern cyclotrons.

Decrease in cranial nerve complications after radiosurgery for acoustic neuromas: a prospective study of dose and volume.

PURPOSE: To determine whether tumor control can be maintained, and cranial nerve complications decreased by reducing the radiosurgical dose to acoustic neuromas. METHODS AND MATERIALS: Forty-two consecutive patients with acoustic neuromas were treated prospectively using an initial standard-dose protocol in which the tumor-margin dose (50% isodose) was 20, 18, and 16 Gy for tumor diameters < or =2 cm, 2.1-3 cm, and 3.1-4 cm, respectively. After analysis of tumor control and complications, the next 40 patients were treated using a reduced-dose protocol in which the tumor-margin dose was 16, 14, and 12 Gy for tumor volumes < or =4.2 cm3, 4.2-14.1 cm3, and > or =14.1 cm3, respectively. RESULTS: Median follow-up was 2.3 years (range 0.1-6) for 80 of 82 patients. The actuarial incidence (Kaplan-Meier) of facial neuropathy at 2 years was 38% (95% confidence interval [CI], 23-53%) for the standard-dose protocol and 8% (95% CI, 0-17%) for the reduced-dose protocol (p = 0.006). Univariate analysis revealed an association between risk of facial neuropathy and use of CT planning, higher radiosurgical dose, and neurofibromatosis, type 2. Multivariate analysis revealed that the only factor associated with increased risk of post-treatment facial neuropathy was a tumor margin dose > or =18 Gy. The incidence of trigeminal neuropathy at 2 years was 29% (95% CI, 15-43%) for the standard-dose protocol and 15% (95% CI, 3-27%) for the reduced-dose protocol (p = 0.17). Univariate analysis revealed an association between maximal tumor diameter and increased risk of trigeminal neuropathy; multivariate analysis revealed no additional statistically significant associations between tumor and dosimetric and patient characteristics and risk of trigeminal neuropathy. Two tumors in the standard-dose protocol required salvage surgery for progression. To date, no tumor in the reduced-dose protocol has shown progression. CONCLUSION: Our analysis suggests that a tumor margin dose of > or =18 Gy is the most significant risk factor for facial nerve complications after acoustic neuroma radiosurgery. Patients receiving a minimal tumor dose of < or =16 Gy are at significantly lower risk for permanent facial neuropathy after radiosurgery. Longer follow-up is required before definitive conclusions can be made about the ultimate rate of tumor control using reduced radiosurgical doses.

Treatment of acoustic neuroma: stereotactic radiosurgery vs. microsurgery.

PURPOSE: Two major treatment options are available for patients with acoustic neuroma, microsurgery and radiosurgery. Our objective was to compare these two treatment modalities with respect to tumor growth control, hearing preservation, development of cranial neuropathies, complications, functional outcome, and patient satisfaction. METHODS AND MATERIALS: To compare radiosurgery with microsurgery, we analyzed 96 patients with unilateral acoustic neuromas treated with Leksell Gamma Knife or microsurgery at Memorial Hermann Hospital, Houston, Texas, between 1993 and 2000. Radiosurgery technique involved multiple isocenter (1-30 single fraction fixed-frame magnetic resonance imaging) image-based treatment with a mean dose prescription of 14.5 Gy. Microsurgery included translabyrinthine, suboccipital, and middle fossa approaches with intraoperative neurophysiologic monitoring. Preoperative patient characteristics were similar except for tumor size and age. Patients undergoing microsurgery were younger with larger tumors compared to the radiosurgical group. The tumors were divided into small <2.0 cm, medium 2.0-3.9 cm, or large >4.0 cm. Median follow-up of the radiosurgical group was longer than the microsurgical group, 48 months (3-84 months) vs. 24 months (3-72 months). RESULTS: There was no statistical significance in tumor growth control between the two groups, 100% in the microsurgery group vs. 91% in the radiosurgery group (p > 0.05). Radiosurgery was more effective than microsurgery in measurable hearing preservation, 57.5% vs. 14.4% (p = 0.01). There was no difference in serviceable hearing preservation between the two groups. Microsurgery was associated with a greater rate of facial and trigeminal neuropathy in the immediate postoperative period and at long-term follow-up. The rate of development of facial neuropathy was significantly higher in the microsurgical group than in the radiosurgical group (35% vs. 0%, p < 0.01 in the immediate postsurgical period and 35.3% vs. 6.1%, p = 0.008, at long-term follow-up). Similarly, the rate of trigeminal neuropathy was significantly higher in the microsurgical group than in the radiosurgical group (17% vs. 0% in the immediate postoperative period, p < 001, and 22% vs. 12.2%, p = 0.009, at long-term follow-up). There was no significant difference in exacerbation of preoperative tinnitus, imbalance, dysarthria, dysphagia, and headache. Patients treated with microsurgery had a longer hospital stay (2-16 days vs. 1-2 days, p < 0.01) and more perioperative complications (47.8% vs. 4.6%, p < 0.01) than did patients treated with radiosurgery. There was no correlation between the microsurgical approach used and postoperative symptoms. There was no difference in the postoperative functioning level, employment, and overall patient satisfaction. There was no correlation between the radiation dose, tumor size, number of isocenters used, and postoperative symptoms in the radiosurgical group. CONCLUSION: Radiosurgical treatment for acoustic neuroma is an alternative to microsurgery. It is associated with a lower rate of immediate and long-term development of facial and trigeminal neuropathy, postoperative complications, and hospital stay. Radiosurgery yields better measurable hearing preservation than microsurgery and equivalent serviceable hearing preservation rate and tumor growth control.