The Influence of Prophylactic Vasoactive Treatment on Cochlear and Facial Nerve Functions after Vestibular Schwannoma Surgery

Postoperative hematoma can be a risk factor in delayed facial palsy after vestibular schwannoma resection via a retrosigmoid approach: a retrospective single-center cohort study

PURPOSE

Delayed facial palsy (DFP) is a rare postoperative complication after vestibular schwannoma (VS) surgery. The exact mechanism of DFP remains uncertain and the risk factors for DFP are still controversial. The authors aimed to investigate the characteristics, risk factors, and etiology of DFP after VS resection retrospectively.

METHODS

Ninety-one consecutive surgeries with VS were analyzed. Patients with neurofibromatosis 2 in eight surgeries and postoperative facial palsy House-Brackmann (HB) grade more than 3 in two surgeries were excluded. Eighty-one surgeries were included in this research. Facial nerve function was evaluated using the HB grade. Delayed facial palsy was defined as deterioration in the facial function of at least 1 HB grade more than 1 day after undergoing VS resection. The characteristics of patients with VS and risk factors for DFP were analyzed.

RESULTS

All surgeries were performed via a retrosigmoid approach. DFP was observed in nine patients. There were no statistically significant differences between the DFP group and non-DFP group in terms of the following characteristics: sex, age, side, size, Koos grading system, postoperative facial palsy, or extent of resection. Postoperative hematoma in the cerebellopontine angle (CPA) cistern was significantly higher in the DFP group than in the non-DFP group (p = 0.0023), and was significantly associated with DFP after VS surgery (odds ratio 18.40, p < 0.001). DFP improved in seven patients, but two patients did not improve.

CONCLUSION

DFP occurred in 11.1% of patients after VS surgery. This study revealed that postoperative hematoma in the CPA cistern was significantly associated with DFP after VS surgery.

[Utility of the intraoperative neurophysiological monitoring as a prognostic value of postoperative facial paresis in vestibular schwannomas]

BACKGROUND AND OBJECTIVE

Intraoperative neurophysiological monitoring allows us to predict the functional status of the facial nerve after vestibular schwannoma surgery. Due to the great variability of the neurophysiological protocols used for it, the goal of this study is to determine the prognostic ability of our neurophysiological protocol.

MATERIAL AND METHODS

We have performed a statistical analysis of the neurophysiological monitoring data collected from patients operated between March 2009 and July 2021 at the Neurosurgery Service of Salamanca according to their functional status, both in the immediate post-surgical period and one year after surgery.

RESULTS

A number of 51 patients between 46 and 63 years old (median: 54) were analyzed. We have found significant differences studying the threshold value of the stimulation intensity of the facial nerve and the variation of the Cortico-bulbar Evoked Motor Potentials (P=0.043 and P=0.011, respectively) between the patients with good and bad clinical situation after surgery. The most discriminating intensity threshold value was 0.35mA (Sensitivity: 85%; Specificity: 48%). No statistical relationship was found in the study group one year after surgery.

CONCLUSIONS

Our intraoperative monitoring protocol allows us to predict the clinical situation of patients in the immediate postoperative period and improve information for the patient and her relatives after surgery. We cannot, however, use these parameters to predict the functional situation one year after surgery and make clinical decisions in this regard.

Delayed Facial Nerve Paralysis After Vestibular Schwannoma Resection

OBJECTIVE

To report the long-term outcome of delayed facial nerve paralysis (DFNP) after surgical resection of vestibular schwannoma and evaluate the influence of various factors on the prognosis of facial nerve function.

METHODS

Of 265 patients who underwent surgical excision of VS through a retrosigmoid approach between April 2019 and October 2021, 15 (5.7%) developed DFNP and were retrospectively studied. Preoperative and postoperative data were collected and analyzed.

RESULTS

The mean age of patients with DFNP was 42.6 years (range, 27-63 years), and 11 (73.3%) were male. Tumor size ranged from 12 to 37 mm (mean 24 mm) in largest dimension. All patients had normal (House-Brackmann [HB] I) facial nerve function preoperatively. Immediate postoperative facial nerve function was HB I in 12 patients (80%) and HB II in 3 patients (20%). The mean severity of DFNP onset was HB 4.7 (range, HB III-V). The average day of onset was postoperative day 12.6 (range, day 5-28). At 1-year follow-up, 12 patients (80%) were HB I, 1 patient (6.7%) was HB III, and 2 patients (13.3%) were HB IV. All patients who were HB III and IV at the last follow-up had immediate postoperative facial nerve function of HB II.

CONCLUSIONS

Most patients who develop DFNP have a favorable prognosis. However, a small proportion of patients with deteriorated facial nerve function immediately after surgery have poor long-term outcomes, despite confirmation of their facial nerve integrity anatomically and by electrical stimulation.

Nimodipine reduces delayed cerebral vasospasm after intracranial tumour surgery: A Retrospective Study

Cerebral vasospasm (CVS) is a frequent and serious neurosurgical complication, without sufficient therapy. This retrospective study was performed to analyze if nimodipine can improve prognosis and reduce ischaemia secondary to delayed CVS after intracranial tumour surgery. A retrospective review was performed over the years 2011 to 2012 for patients with an anterior cranial fossa tumour and underwent intracranial tumour surgery. The surgical field was soaked with nimodipine solution or normal saline. Transcranial Doppler ultrasonography was used to measure velocity in the middle cerebral artery (MCA) and the distal extracranial internal carotid artery (eICA). Follow-up was performed using the Glasgow Outcome Scale (GOS) after discharge. There were 94 patients that met the inclusion criteria. They included 50 males and 44 females, with a mean age of 49.6 years. In the nimodipine group, CVS occurred in 13 patients; 9 patients had CVS between 4 and 7 days, and 4 had CVS between 8 and 14 days. In the normal saline group, 19 patients had CVS, 3 presented with CVS within 3 days, 11 between 4-7 days and 5 between 8-14 days. A significant difference in the occurrence of CVS was observed between the two groups. Preoperative and postoperative the MCA velocities were compared, revealing a significant change in the normal saline group but not in the nimodipine group. Nimodipine markedly improves prognosis and significantly reduces ischaemia secondary to delayed CVS after intracranial tumour surgery, as well as the risks of mortality and morbidity.

Prophylactic nimodipine treatment for hearing preservation after vestibular schwannoma surgery: study protocol of a randomized multi-center phase III trial-AkniPro 2

Background

A previously performed phase III trial on 112 subjects investigating prophylactic nimodipine treatment in vestibular schwannoma (VS) surgery showed no clear beneficial effects on preservation of facial and cochlear nerve functions, though it should be considered that protection of facial nerve function was the primary outcome. However, the risk for postoperative hearing loss was halved in the nimodipine group compared to the control group (OR 0.49; 95% CI 0.18–1.30; p = 0.15). Accordingly, this phase III extension trial investigates the efficacy and safety of prophylactic nimodipine for hearing preservation in VS surgery.

Methods

This is a randomized, multi-center, two-armed, open-label phase III trial with blinded expert review and two-stage with interim analysis. Three hundred thirty-six adults with the indication for microsurgical removal of VS (Koos I–IV) and serviceable preoperative hearing (Gardner-Robertson scale (GR) 1–3) are assigned to either the therapy (intravenous nimodipine 1–2 mg/h from the day before surgery until the fifth postoperative day and standard of care) or the control group (surgery only and standard of care). The primary endpoint of the trial is postoperative cochlear nerve function measured before discharge according to GR 1–3 versus GR 4–5 (binary). Hearing function will be determined by pre- and postoperative audiometry with speech discrimination, which will be evaluated by a blinded expert reviewer. Furthermore, patient-reported outcomes using standardized questionnaires will be analyzed.

Discussion

Prophylactic parenteral nimodipine treatment may have a positive effect on hearing preservation in VS surgery and would improve patient’s quality of life. Further secondary analyses are planned. Except for dose-depending hypotension, nimodipine is known as a safe drug. In the future, prophylactic nimodipine treatment may be recommended as a routine medication in VS surgery. VS can be considered as an ideal model for clinical evaluation of neuroprotection, since hearing outcome can be classified by well-recognized criteria. The beneficial effect of nimodipine may be transferable to other surgical procedures with nerves at risk and may have impact on basic research.

Trial registration

EudraCT 2019-002317-19, DRKS00019107. 8th May 2020.

Intraoperative Auditory Brainstem Response Results Predict Delayed Sensorineural Hearing Loss After Middle Cranial Fossa Resection of Vestibular Schwannoma

OBJECTIVE

To identify intraoperative neurophysiologic measures predictive of delayed progressive sensorineural hearing loss in the operative ear after a middle fossa approach (MCF) for resection of vestibular schwannoma (VS).

STUDY DESIGN

Retrospective review.

SETTING

Academic, tertiary referral center.

PATIENTS

Subjects with vestibular schwannoma who underwent a MCF microsurgical resection of VS were analyzed for individuals whose hearing was initially preserved but subsequently developed progressive sensorineural hearing loss in the operative ear. Thirty-seven patients were identified for whom audiologic and neurophysiologic data was available.

INTERVENTION

Intraoperative neurophysiologic changes will correlate with delayed sensorineural hearing loss in the operative ear.

MAIN OUTCOME MEASURES

Audiometric evaluations, intraoperative electrocochleography (ECoG), and auditory brainstem response (ABR) measures.

RESULTS

Twenty-five subjects experienced stable hearing or hearing loss in the operative ear comparable to the contralateral ear. Twelve subjects suffered a significant increase in the hearing asymmetry between ears. Deterioration in the amplitude of wave V of the ABR persisting at the close of tumor resection correlated with delayed sensorineural hearing loss in the operative ear (p 0.02, 5% mean improvement in the stable hearing group, versus a 14% decline with progressive asymmetry), but changes in ECoG or other auditory brainstem response parameters (p > 0.05) were not predictive.

CONCLUSIONS

Persisting amplitude reduction of wave V of the intraoperative ABR best correlates with delayed progressive sensorineural hearing loss in the operative ear. Neither persistent changes in ECoG, other ABR parameters, nor transient changes, correlated with delayed progressive sensorineural hearing loss in the operative ear.

Perioperative Nimodipine to Improve Cranial Nerve Function: A Systematic Review and Meta-Analysis

OBJECTIVE

Nimodipine has emerged as a promising strategy for protection of cranial nerves following vestibular schwannoma (VS) resections. Our goal was to conduct a comprehensive analysis of clinical studies to determine the therapeutic efficacy of nimodipine in improving facial nerve and cochlear nerve function.

DATABASE REVIEWED

We searched PubMed, Scopus, Cochrane Clinical Trial Registry, Clinicaltrials.gov, World Health Organization's International Clinical Trials Registry Platform, and EU Clinical Trials Registry to identify clinical studies up to May 11, 2020.

METHODS

We included studies evaluating perioperative administration of nimodipine as a strategy to prevent or treat facial nerve or cochlear nerve dysfunction following VS resections. Primary outcomes included preservation or recovery of House-Brackman scale for facial nerve function and Hearing and Equilibrium Guidelines for cochlear nerve function at the latest follow-up visit. Secondary outcomes included adverse events and administration strategies of nimodipine.

RESULTS

Nine studies (603 patients) met inclusion, of which seven studies (559 patients) were included in the quantitative analysis. Overall, nimodipine significantly increased the odds of cranial nerve recovery compared with controls (odds ratio [OR] 2.87, 95% confidence intervals [CI] [2.08, 3.95]; I2 = 0%). Subgroup analysis demonstrated that nimodipine was only effective for cochlear nerve preservation (OR 2.78, 95% CI [1.74, 4.45]; I2 = 0%), but not for facial nerve function (OR 4.54, 95% CI [0.25, 82.42]; I2 = 33%).

CONCLUSION

Although there is evidence supporting the perioperative role of nimodipine for VS resections, more studies are warranted to help clarify the effects of nimodipine therapy on cranial nerve preservation.

Assessment of eye closure and blink with facial palsy: A systematic literature review

Facial palsy can cause the impairment of eye closure and affect blink, ocular health, communication, and esthetics. Dynamic surgical procedures can restore eye closure in patients with decreased facial nerve function. There are no standardized measures of voluntary and spontaneous eye closure that are used to evaluate the outcomes of blink restoration procedures. The purpose of this systematic literature review was to identify the measures used to assess normal and abnormal eye closure and blinking in patients with facial palsy. A literature search of the PubMed database using the keyword "facial nerve/surgery" was conducted. Only English language articles that pertain to the use of facial paralysis assessment systems published in the past 20 years, which involve eyelid closure were included. There were 57 articles that used a facial paralysis classification system with an eyelid closure component: House-Brackmann Facial Nerve Grading Scale (n = 43, 67%); Sunnybrook Facial Grading Scale (n = 9); palpebral fissure heights (n = 4), and the electronic clinician-graded facial function tool (n = 3) and three additional measures were reported once. Although the Terzis and Bruno Scoring System, blink ratio, and electronic, clinician-graded facial function scale(eFACE) Clinician-Graded Scoring System were valid measures of eyelid closure, there was no one comprehensive eye assessment that demonstrated all aspects of eye closure in facial palsy, which include closure amplitude, spontaneity, and quality of life. For blink assessment, eFACE is the most comprehensive tool currently available and recommended to be used with a patient-reported quality of life supplement that captures the specific domains related to facial nerve dysfunction.

Prophylactic nimodipine treatment improves hearing outcome after vestibular schwannoma surgery in men: a subgroup analysis of a randomized multicenter phase III trial

A 2016 published randomized multicenter phase III trial of prophylactic nimodipine treatment in vestibular schwannoma surgery showed only a tendency for higher hearing preservation rates in the treatment group. Gender was not included in statistical analysis at that time. A retrospective analysis of the trial considering gender, preoperative hearing, and nimodipine treatment was performed. The treatment group received parenteral nimodipine from the day before surgery until the seventh postoperative day. The control group was not treated prophylactically. Cochlear nerve function was determined by pure-tone audiometry with speech discrimination preoperatively, during in-patient care, and 1 year after surgery and classified according to the Gardner-Robertson grading scale (GR). Logistic regression analysis showed a statistically significant effect for higher hearing preservation rates (pre- and postoperative GR 1–4) in 40 men comparing the treatment (n = 21) and the control (n = 19) groups (p = 0.028), but not in 54 women comparing 27 women in both groups (p = 0.077). The results were also statistically significant for preservation of postoperative hearing with pre- and postoperative GR 1–3 (p = 0.024). There were no differences in tumor sizes between the treatment and the control groups in men, whereas statistically significant larger tumors were observed in the female treatment group compared with the female control group. Prophylactic nimodipine is safe, and an effect for hearing preservation in 40 men with preoperative hearing ability of GR 1–4 was shown in this retrospective investigation. The imbalance in tumor size with larger tumors in females of the treatment group may falsely suggest a gender-related effect. Further investigations are recommended to clarify whether gender has impact on nimodipine’s efficacy.

Electrophysiological predictors of hearing deterioration based on AEP monitoring during petroclival meningioma resection

The objective of this study was to calculate the risk of postsurgical hearing deterioration as a function of changes in the amplitude and latency of the most stable components (waves III and V) of the auditory evoked potential (AEP) during petroclival meningioma resection surgery. We retrospectively analyzed intraoperative AEP monitoring results and pre- and postsurgical hearing status in 40 consecutive patients who were surgically treated for petroclival meningiomas. Statistical analyses were conducted to identify the most sensitive and specific way to predict hearing dysfunction after surgery. Patients' mean age was 59 ± 10 years, and 31 (77.5%) were women. Twelve (30%) patients presented with clinically detectable hearing impairment preoperatively. At the first postoperative assessment, four of those 12 patients reported subjective improvement, and eight reported hearing deterioration. Of those eight, four remained stable and four recovered hearing by the last assessment. Wave III latency reached its highest specificity (100%) and sensitivity (71.43%) at x = 143%. Wave V latency, on the other hand, reached its highest sensitivity (71%) and specificity (93%) at x = 124%. Finally, wave V amplitude reached its highest sensitivity (100%) and specificity (79%) at x = 74%. Intraoperative alterations of wave III latency and wave V amplitude seem to be highly sensitive and specific at predicting the risk of auditory dysfunction in patients undergoing petroclival meningioma resection and should be used to determine maximum resection with preservation of function.

Nimodipine-Dependent Protection of Schwann Cells, Astrocytes and Neuronal Cells from Osmotic, Oxidative and Heat Stress Is Associated with the Activation of AKT and CREB

Clinical and experimental data assumed a neuroprotective effect of the calcium channel blocker nimodipine. However, it has not been proven which neuronal or glial cell types are affected by nimodipine and which mechanisms underlie these neuroprotective effects. Therefore, the aim of this study was to investigate the influence of nimodipine treatment on the in vitro neurotoxicity of different cell types in various stress models and to identify the associated molecular mechanisms. Therefore, cell lines from Schwann cells, neuronal cells and astrocytes were pretreated for 24 h with nimodipine and incubated under stress conditions such as osmotic, oxidative and heat stress. The cytotoxicity was measured via the lactate dehydrogenase (LDH) activity of cell culture supernatant. As a result, the nimodipine treatment led to a statistically significantly reduced cytotoxicity in Schwann cells and neurons during osmotic (p ≤ 0.01), oxidative (p ≤ 0.001) and heat stress (p ≤ 0.05), when compared to the vehicle. The cytotoxicity of astrocytes was nimodipine-dependently reduced during osmotic (p ≤ 0.01), oxidative (p ≤ 0.001) and heat stress (not significant). Moreover, a decreased caspase activity as well as an increased proteinkinase B (AKT) and cyclic adenosine monophosphate response element-binding protein (CREB) phosphorylation could be observed after the nimodipine treatment under different stress conditions. These results demonstrate a cell type-independent neuroprotective effect of the prophylactic nimodipine treatment, which is associated with the prevention of stress-dependent apoptosis through the activation of CREB and AKT signaling pathways and the reduction of caspase 3 activity.

Intraoperative Monitoring of the Cochlear Nerve during Neurofibromatosis Type-2 Vestibular Schwannoma Surgery and Description of a "Test Intracochlear Electrode"

Objectives  A decision on whether to insert a cochlear implant can be made in neurofibromatosis 2 (NF2) if there is objective evidence of cochlear nerve (CN) function post vestibular schwannoma (VS) excision. We aimed to develop intraoperative CN monitoring to help in this decision. Design  We describe the intraoperative monitoring of a patient with NF2 and our stimulating and recording set up. A novel test electrode is used to stimulate the CN electrically. Setting  This study was set at a tertiary referral center for skull base pathology. Main outcome measure  Preserved auditory brainstem responses leading to cochlear implantation. Results  Electrical auditory brainstem response (EABR) waveforms will be displayed from different stages of the operation. A cochlear implant was inserted at the same sitting based on the EABR. Conclusion  Electrically evoked CN monitoring can provide objective evidence of CN function after VS excision and aid in the decision-making process of hearing rehabilitation in patients who will be rendered deaf.

Nimodipine for the treatment of otolaryngic indications

PURPOSE

The uses of nimodipine for otolaryngic indications are reviewed, and recommendations for its use in clinical practice are provided.

SUMMARY

Nimodipine is currently indicated for the improvement of neurologic outcomes in adult patients with aneurysmal subarachnoid hemorrhage (aSAH). However, other oral and i.v. calcium channel blockers have not exhibited the same beneficial effects in patients with aSAH, leading clinicians to believe that nimodipine possesses unique neuroprotective effects in addition to its calcium channel-blocking and vasodilatory properties. Consequently, clinical investigations of nimodipine have been conducted for cochlear and facial nerve preservation after vestibular schwannoma (VS) surgery, symptomatic management of Ménière's disease and peripheral vertigo, and recovery of vocal cord paralysis after laryngeal nerve injury. Three prospective randomized studies have investigated nimodipine for hearing and/or nerve preservation in patients undergoing VS resection, the results of which have suggested a potential benefit of initiating nimodipine during the perioperative period. Several studies of Ménière's disease and/or peripheral vertigo have reported improved symptom control with nimodipine. For vocal fold paralysis associated with recurrent laryngeal nerve (RLN) injury, nimodipine may increase the recovery rate based on the results of 1 nonrandomized prospective study that used nimodipine in a protocolized manner. One small pilot study found that nimodipine improved facial nerve function after maxillofacial surgery.

CONCLUSION

Due to its proposed vasoactive and neuroprotective effects, nimodipine may play a role in the treatment of a number of otolaryngic pathologies including VS, Ménière's disease, peripheral vertigo, RLN injury, and facial weakness after maxillofacial surgery. Small studies have shown improved symptom control and recovery after surgery. Since all of the aforementioned indications are still considered off label, clinicians and patients should collaboratively assess the risks and benefits before initiating treatment.

Delayed Facial Nerve Paralysis after Vestibular Schwannoma Resection

Objective  To describe the incidence and clinical course of patients who develop delayed facial nerve paralysis (DFNP) after surgical resection of vestibular schwannoma. Setting  Tertiary skull base center. Methods  Retrospective chart review. Results  Two hundred and forty six consecutive patients, who underwent surgical resection for vestibular schwannoma at a single center between 2010 and 2015, were analyzed. Of these patients, 22 (8.9%) developed DFNP, defined here as deterioration of function by at least 2 House-Brackmann (HB) grades within 30 days in patients with immediate postoperative HB ≤ 3. The mean age of DFNP patients was 47.2 years (range: 17-67) and 16 (73%) were female. The mean tumor size in greatest dimension was 2.1 cm (range: 0.7-3.5 cm). At the conclusion of each case, the facial nerve stimulated at the brainstem. Mean immediate postoperative facial nerve function was HB 1.8 (range: 1-3). Average facial nerve function at the 3-week-postoperative visit was 4.4 (range: 2-6). In 1-year, 8 patients (36%) recovered HB 1 function, 10 patients (46%) recovered to HB 2, and 2 patients (9%) were HB 3. The remaining 2 patients did not recover function and were HB 6 at last follow-up. Initial postoperative facial nerve function (HB 1 or HB 2) was associated with improved recovery to normal (HB 1) function ( p  = 0.018). Conclusion  A majority of patients that develop delayed paralysis will recover excellent facial nerve function. Patients should be counseled; however, a small percentage of patients will not recover function long-term, despite having a previously functioning and anatomically intact nerve.

Recovery of Voice After Reconstruction of the Recurrent Laryngeal Nerve and Adjuvant Nimodipine

Background

Transection injury to the recurrent laryngeal nerve (RLN) has been associated with permanent vocal fold palsy, and treatment has been limited to voice therapy or local treatment of vocal folds. Microsurgical repair has been reported to induce a better function. The calcium channel antagonist nimodipine improves functional recovery after experimental nerve injury and also after cranial nerve injury in patients. This study aims to present voice outcome in patients who underwent repair of the RLN and received nimodipine during regeneration.

Methods

From 2002–2016, 19 patients were admitted to our center with complete unilateral injury to the RLN and underwent microsurgical repair of the RLN. After nerve repair, patients received nimodipine for 2–3 months. Laryngoscopy was performed repeatedly up to 14 months postoperatively. The Voice Handicap Index (VHI) was administered, and patients’ maximum phonation time (MPT) was recorded during the follow-up.

Results

All patients recovered well after surgery, and nimodipine was well tolerated with no dropouts. None of the patients suffered from atrophy of the vocal fold, and some patients even showed a small ab/adduction of the vocal fold on the repaired side with laryngoscopy. During long-term follow-up (>3 years), VHI and MPT normalized, indicating a nearly complete recovery from unilateral RLN injury.

Conclusions

In this cohort study, we report the results of the first 19 consecutive cases at our center subjected to reconstruction of the RLN and adjuvant nimodipine treatment. The outcome of the current strategy is encouraging and should be considered after iatrogenic RLN transection injuries.

Microvascular Brainstem Ischemia After Vestibular Schwannoma Surgery: A Clinical and Microanatomic Study

OBJECTIVE

To identify a potential microvascular etiology in patients who underwent vestibular schwannoma surgery (VSS) complicated by postoperative microvascular brainstem ischemia.

METHODS

Charts were retrospectively reviewed of all patients who had an MRI within 14 days of VSS in years 2005-2016. Patient characteristics, preoperative and postoperative imaging features, clinical course and potential predictors of brainstem ischemia were recorded. Cadaveric dissections of 4 cerebellopontine angle (CPA) cisterns with focus on the anterior inferior cerebellar artery (AICA) microvascular were also performed to identify candidate vessels and potential etiology.

RESULTS

Fifty-four of 258 patients had an MRI within 14 days of VSS. Retrosigmoid approach was used in 61.1% of patients, translabyrinthine approach in 25.9%, and middle fossa approach in 13.0%. Four patients (7.4%) had acute microvascular ischemia involving the middle cerebellar peduncle (MCP) adjacent to the cranial nerve (CN) VII-VIII complex demonstrated on postoperative MRI. A statistically significant association was found between the translabyrinthine approach and acute brainstem ischemia (odds ratio, 10.6; 95% confidence interval, 1.004-112.7). Dissection of CPAs revealed 10-20 perforating arteries per specimen originating from the lateral pontine and the flocculopeduncular segments of the AICA. Most microvessels travelled in retrograde fashion along the anteroinferior surface of the CN VII-VIII complex to perforate the cisternal surface of the MCP. No patient had residual or delayed neurologic deficits related to brainstem ischemia at final follow-up.

CONCLUSIONS

While effort should be made to preserve perforating vessels, microvascular brainstem ischemia is often asymptomatic and did not lead to permanent neurologic deficits in our series.

Non-invasive intraoperative monitoring of cochlear function by cochlear microphonics during cerebellopontine-angle surgery

In vestibular-schwannoma (VS) surgery, hearing-preservation rate remains low. Besides damage to the cochlear nerve, intraoperative cochlear ischemia is a potential cause of hearing loss. Here, we used non-invasive cochlear microphonic (CM) recordings to detect the cochlear vascular events of VS surgery. Continuous intraoperative CM monitoring, in response to 80-95 dB SPL, 1-kHz tone-bursts, was performed in two samples of patients undergoing retrosigmoid cerebellopontine-angle surgery: one for VS (n = 31) and one for vestibular neurectomy or vasculo-neural conflict causing intractable trigeminal neuralgia, harmless to hearing (n = 19, control group). Preoperative and postoperative hearings were compared as a function of intraoperative CM changes and their chronology. Monitoring was possible throughout except for a few tens of seconds when drilling or suction noises occurred. Four patterns of CM time course were identified, eventless, fluctuating, abrupt or progressive decrease. Only the VS group displayed the last two patterns, mainly during internal-auditory-canal drilling and the ensuing tumor dissection, always with postoperative loss of hearing as an end result. Conversely, eventless and fluctuating CM patterns could be associated with postoperative hearing loss when the cochlear nerve had been reportedly damaged, an event that CM is not meant to detect. Cochlear ischemia is a frequent event in VS surgery that leads to deafness. The findings that CM decrease raised no false alarm, and that CM fluctuations, insignificant in control cases, were easily spotted, suggest that CM intraoperative monitoring is a sensitive tool that could profitably guide VS surgery.

New Treatment in Facial Nerve Palsy Caused by Sagittal Split Ramus Osteotomy of Mandible

A 25-years-old woman with mandibular prognathism underwent a mandibular setback by way of mandibular sagittal split ramus osteotomy (MSSRO). After 2 days of operation, she developed difficulty of closing her right eye. The blink reflex test and motor nerve conduction study of the right orbicularis oris muscle were revealed right facial neuropathy of unknown origin and House-Brackmann facial nerve grading system (HBFNGS) grade V. For treatment, we initially prescribed oral prednisolone and nimodipine including physical therapy. The samples consisted of 11 facial nerve palsy patients caused by MSSRO and were analysed about onset of facial nerve palsy, postoperative HBFNGS, final HBFNGS, treatment method and recovery time. At 10 weeks of treatment of nimodipine, she had completely regained normal function (HBFNGS grade I) of the right facial nerve. The clinical results lead to assume a fast recovery of facial nerve function by the nimodipine medication, whereas average time of recovery is 16.32 weeks in references. Despite of the limited one patient treated, the result was very promising with respect to a faster recovery of the facial nerve function. Considering the use of nimodipine treatment for peripheral facial nerve palsy following a surgical approach with an anatomically preserved nerve can be recommended.

[Neuroprotective medication in vestibular schwannoma surgery]

BACKGROUND

Except for glucocorticoids there is a lack of neuroprotective medication in neurosurgical interventions.

OBJECTIVE

An overview of clinical trials investigating administration of the calcium antagonist nimodipine and hydroxyethyl starch (HES) in vestibular schwannoma (VS) surgery is given. Basic research is addressed and potential neuroprotective effect mechanisms are discussed, as are perspectives for application of the concept to other types of surgery with a risk postoperative impairment of nerve function.

MATERIALS AND METHODS

A selective PubMed search was performed and all 10 clinical trials corresponding to the search criteria were included.

RESULTS

Four trials with an intraoperative start of the medication showed a positive effect for the preservation of facial nerve function and hearing preservation. A pilot study showed superiority of prophylactic treatment over intraoperative application. There were no significant results in a prospective multicenter phase III trial. After 1 year, postoperative facial nerve preservation rates were excellent in both groups. However, the risk of hearing loss was twice as high in the control group. A combined analysis of the phase III trial with its pilot study showed significant results for better hearing preservation rates in the treatment group (probably by increasing the case load).

CONCLUSION

Prophylactic nimodipine can be recommended in VS surgery in patients with good preoperative hearing. The effect mechanisms of nimodipine and modifications to prophylaxis should be clarified in basic research.

Calcium-channel blockers as therapeutic agents for acquired sensorineural hearing loss

Acquired sensorineural hearing loss represents a challenging clinical scenario. Currently, there are few approved therapies for treating this type of hearing loss, and diagnosis is often made after permanent damage has occurred. There are numerous etiologies for acquired hearing loss, with complex mechanisms underlying each cause. Despite these complexities, apoptosis of the structures within the inner ear, is a theme common to many forms of acquired hearing loss. Apoptosis is a calcium-dependent process, and within the inner ear, L- and T-type calcium channels are believed to contribute to calcium availability during this process. There are few studies limited to animal models evaluating the role of calcium-channel blockers (CCBs) as otoprotective agents in the setting of acquired hearing loss. Here, I hypothesize that CCBs will provide utility as a therapy against acquired forms of sensorineural hearing loss by preventing calcium influx that occurs during inner ear cellular apoptosis.

Nimodipine but Not Nifedipine Promotes Expression of Fatty Acid 2-Hydroxylase in a Surgical Stress Model Based on Neuro2a Cells

Nimodipine is well characterized for the management of aneurysmal subarachnoid hemorrhage and has been shown to promote a better outcome and less delayed ischemic neurological deficits. Animal and clinical trials show neuroprotective efficacy following nerve injuries. We showed a neuroprotective effect on Neuro2a cells. Subsequent microarray analysis revealed—among others—fatty acid 2-hydroxylase (FA2H) upregulated by nimodipine in vitro, which is a component of myelin synthesis. Differentiated Neuro2a cells were analyzed for nimodipine-mediated survival considering stress treatment in comparison to nifedipine-treatment. Cell survival was determined by measurement of LDH activity in the culture medium. Nimodipine decreased surgery-like stress-induced cell death of differentiated Neuro2a cells. Neuro2a cell culture was analyzed for changes in FA2H expression induced by nimodipine or nifedipine in surgery-like stress conditions. We analyzed expression levels of FA2H mRNA and protein by qPCR using fa2h specific primers or a FA2H-specific antibody in nimodipine or nifedipine non- and pre-treated Neuro2a cell culture, respectively. Nimodipine but not nifedipine increases FA2H protein levels and also significantly increases mRNA levels of FA2H in both undifferentiated and differentiated Neuro2a cells. Our findings indicate that higher expression of FA2H induced by nimodipine may cause higher survival of Neuro2a cells stressed with surgery-like stressors.

Influencing Factors Analysis of Facial Nerve Function after the Microsurgical Resection of Acoustic Neuroma

Objective

To explore and analyze the influencing factors of facial nerve function retainment after microsurgery resection of acoustic neurinoma.

Methods

Retrospective analysis of our hospital 105 acoustic neuroma cases from October, 2006 to January 2012, in the group all patients were treated with suboccipital sigmoid sinus approach to acoustic neuroma microsurgery resection. We adopted researching individual patient data, outpatient review and telephone followed up and the House-Brackmann grading system to evaluate and analyze the facial nerve function.

Results

Among 105 patients in this study group, complete surgical resection rate was 80.9% (85/105), subtotal resection rate was 14.3% (15/105), and partial resection rate 4.8% (5/105). The rate of facial nerve retainment on neuroanatomy was 95.3% (100/105) and the mortality rate was 2.1% (2/105). Facial nerve function when the patient is discharged from the hospital, also known as immediate facial nerve function which was graded in House-Brackmann: excellent facial nerve function (House-Brackmann I–II level) cases accounted for 75.2% (79/105), facial nerve function III–IV level cases accounted for 22.9% (24/105), and V–VI cases accounted for 1.9% (2/105). Patients were followed up for more than one year, with excellent facial nerve function retention rate (H-B I–II level) was 74.4% (58/78).

Conclusion

Acoustic neuroma patients after surgery, the long-term (≥1 year) facial nerve function excellent retaining rate was closely related with surgical proficiency, post-operative immediate facial nerve function, diameter of tumor and whether to use electrophysiological monitoring techniques; while there was no significant correlation with the patient’s age, surgical approach, whether to stripping the internal auditory canal, whether there was cystic degeneration, tumor recurrence, whether to merge with obstructive hydrocephalus and the length of the duration of symptoms.

Prophylactic nimodipine treatment and improvement in hearing outcome after vestibular schwannoma surgery: a combined analysis of a randomized, multicenter, Phase III trial and its pilot study

OBJECTIVE In clinical routines, neuroprotective strategies in neurosurgical interventions are still missing. A pilot study (n = 30) and an analogously performed Phase III trial (n = 112) pointed to a beneficial effect of prophylactic nimodipine and hydroxyethyl starch (HES) in vestibular schwannoma (VS) surgery. Considering the small sample size, the data from both studies were pooled. METHODS The patients in both investigator-initiated studies were assigned to 2 groups. The treatment group (n = 70) received parenteral nimodipine (1-2 mg/hour) and HES (hematocrit 30%-35%) from the day before surgery until the 7th postoperative day. The control group (n = 72) was not treated prophylactically. Facial and cochlear nerve functions were documented preoperatively, during the inpatient care, and 1 year after surgery. RESULTS Pooled raw data were analyzed retrospectively. Intent-to-treat analysis revealed a significantly lower risk for hearing loss (Class D) 12 months after surgery in the treatment group compared with the control group (OR 0.46, 95% CI 0.22-0.97; p = 0.04). After exclusion of patients with preoperative Class D hearing, this effect was more pronounced (OR 0.38, 95% CI 0.17-0.83; p = 0.016). Logistic regression analysis adjusted for tumor size showed a 4 times lower risk for hearing loss in the treatment group compared with the control group (OR 0.25, 95% CI 0.09-0.63; p = 0.003). Facial nerve function was not significantly improved with treatment. Apart from dose-dependent hypotension (p < 0.001), the study medication was well tolerated. CONCLUSIONS Prophylactic nimodipine is safe and may be recommended in VS surgery to preserve hearing. Prophylactic neuroprotective treatment in surgeries in which nerves are at risk seems to be a novel and promising concept. Clinical trial registration no.: DRKS 00000328 ( https://drks-neu.uniklinik-freiburg.de/drks_web/ ).

Auditory Monitoring in Vestibular Schwannoma Surgery: Intraoperative Development and Outcome

OBJECTIVE

The auditory brainstem response (ABR) may be a predictor of postoperative cochlear nerve function. In this study, the course of intraoperative ABR monitoring was analyzed to find predictive markers for postoperative hearing function.

PATIENTS AND METHODS

From 2010 to 2012, 46 patients who had had vestibular schwannoma surgery were investigated by intraoperative ABR monitoring. The type of ABR development was identified: type A, improved or stable ABR; type B, fluctuating or deteriorated ABR; and type C, slow or sudden ABR loss. Hearing function was correlated with ABR monitoring.

RESULTS

The different types of ABR development showed a strong correlation with postoperative hearing (P < 0.001). ABR quality after 60% tumor removal was independently significant for hearing outcome. Possible interpretations are: 1) Independent of positive factors at the start of surgery at the final phase of tumor resection, what mattered for hearing outcome was the ABR quality (P < 0.001). 2) Dependence on ABR quality in the last phase might be a result of what the cochlear nerve has endured during resection. 3) The importance of ABR quality in the last phase might be because the tumor capsule is dissected from the nerves in that final phase.

ANALYSIS

of critical actions with incidence of ABR impairment showed that dissection in the internal auditory canal and drilling were most critical.

CONCLUSIONS

Intraoperative ABR development is a predictive factor for postoperative hearing outcome. Deterioration should be avoided, because ABR improvement as a result of good status at the beginning of surgery could not be assumed.

When Does Hearing Loss Occur in Vestibular Schwannoma Surgery? Importance of Auditory Brainstem Response Changes in Early Postoperative Phase

OBJECTIVE

Some patients suffer postoperative hearing loss even when the intraoperative auditory brainstem response (ABR) is preserved during vestibular schwannomas surgery. This study was conducted to evaluate whether there are dynamic changes of the ABR after surgery.

PATIENTS AND METHODS

In a prospective study from 2010-2012, 46 patients (24 female and 22 male) with vestibular schwannomas were investigated by intraoperative and postoperative ABR monitoring. Development of ABR quality during and after surgery (Class 1 normal, Class 5 complete loss) was correlated to auditory outcome.

RESULTS

At the end of surgery, 17 patients had an ABR Class 1-4 and 29 had Class 5. Four hours after surgery, 9 of 23 (39%) patients showed an ABR quality change, and 24 hours after surgery, 15 of 30 (50%) had undergone ABR quality changes. Four different types of postoperative ABR courses could be distinguished-Course 1: stable with reproducible ABR, Course 2: unstable with reproducible ABR, Course 3: unstable with ABR loss, and Course 4: stable with ABR loss. These courses correlated highly significantly with the intraoperative development (P < 0.001) and with hearing outcome (P = 0.003).

CONCLUSION

The study identifies ongoing changes of ABR quality and hearing function after the end of vestibular schwannoma surgery. Therefore it seems worthwhile to continue ABR monitoring in the postoperative phase in order to identify patients who are at risk of a secondary hearing deterioration and start therapeutic interventions in a timely manner.

Surgery for sporadic vestibular schwannoma. Part IV. Predictive factors influencing facial nerve function after surgery

OBJECTIVE

To analyze the impact of various clinical, radiological and perioperative factors that could influence the facial nerve intraoperative disruption risk (CNVII-IDR) and its long-term function (CNVII-LTF) after vestibular schwannoma (VS) surgery.

MATERIAL AND METHODS

The study included 212 patients operated on for sporadic VS with no history of previous treatment for VS or CNVII palsy. The mean size of the tumor was 30 mm. Gross (210) or near-total (2) resections were carried out using the retrosigmoid (210) or translabyrinthine (2) approach. Correlation studies and multivariate regression analysis (RA) were performed.

RESULTS

In correlation studies, the CNVII-IDR was increased by: headaches and cerebellar ataxia if one of them was the first symptom of the tumor (33% and 29%, respectively, p=0.008); preoperative hydrocephalus (40% vs. 9%, p=0.01), tumor size >3 cm (18% vs. 5%, p<0.01), tumor volume >10 cm(3) (19% vs. 4%, p<0.01), right-sided location 15% vs. 6%, p=0.047), lateral "park-bench" position (19% vs. 5% for supine position, p<0.01) and the procedure order (16% for the first 106 procedures vs. 6% for the last 106 procedures, p<0.05). In RA the tumor volume (p=0.012), side of the tumor (p=0.028) and patient's position during surgery (p=0.016) independently affected the CNVII-IDR. The following factors correlated significantly with satisfactory CNVII-LTF (HB grades I-III): tumor stage <T4 (p=0.000), tumor size ≤3 cm (p=0.000), tumor volume ≤10 cm(3) (p=0.001), and left-sided location (p=0.048). Additional factors correlated significantly with very good CNVII-LTF (HB grades I-II): anterior CNVII displacement (p=0.044), nimodipine use (p=0.016), the absence of postoperative complications (p=0.019), CNVII responsive on final intraoperative EMG stimulation (p=0.000) and supine position during surgery (p=0.018). However, an independent impact on very good CNVII-LTF proved to be the tumor size (p=0.0000), side (p=0.0175), and nimodipine use (p=0.0349).

CONCLUSIONS

In our series, the factors related to size and side of the tumor confirmed an independent impact on CNVII-IDR and CNVIILTF. The significance of patient positioning may reflect the impact of learning curve as only the first 91 patients were operated on using the lateral "park-bench" position. An independent impact on CNVII-LTF was exerted by the perioperative use of nimodipine.

Prophylactic nimodipine treatment for cochlear and facial nerve preservation after vestibular schwannoma surgery: a randomized multicenter Phase III trial

OBJECTIVE

A pilot study of prophylactic nimodipine and hydroxyethyl starch treatment showed a beneficial effect on facial and cochlear nerve preservation following vestibular schwannoma (VS) surgery. A prospective Phase III trial was undertaken to confirm these results.

METHODS

An open-label, 2-arm, randomized parallel group and multicenter Phase III trial with blinded expert review was performed and included 112 patients who underwent VS surgery between January 2010 and February 2013 at 7 departments of neurosurgery to investigate the efficacy and safety of the prophylaxis. The surgery was performed after the patients were randomly assigned to one of 2 groups using online randomization. The treatment group (n = 56) received parenteral nimodipine (1-2 mg/hr) and hydroxyethyl starch (hematocrit 30%-35%) from the day before surgery until the 7th postoperative day. The control group (n = 56) was not treated prophylactically.

RESULTS

Intent-to-treat analysis showed no statistically significant effects of the treatment on either preservation of facial nerve function (35 [67.3%] of 52 [treatment group] compared with 34 [72.3%] of 47 [control group]) (p = 0.745) or hearing preservation (11 [23.4%] of 47 [treatment group] compared with 15 [31.2%] of 48 [control group]) (p = 0.530) 12 months after surgery. Since tumor sizes were significantly larger in the treatment group than in the control group, logistic regression analysis was required. The risk for deterioration of facial nerve function was adjusted nearly the same in both groups (OR 1.07 [95% CI 0.34-3.43], p = 0.91). In contrast, the risk for postoperative hearing loss was adjusted 2 times lower in the treatment group compared with the control group (OR 0.49 [95% CI 0.18-1.30], p = 0.15). Apart from dose-dependent hypotension (p < 0.001), no clinically relevant adverse reactions were observed.

CONCLUSIONS

There were no statistically significant effects of the treatment. Despite the width of the confidence intervals, the odds ratios may suggest but do not prove a clinically relevant effect of the safe study medication on the preservation of cochlear nerve function after VS surgery. Further study is needed before prophylactic nimodipine can be recommended in VS surgery.

Recovery of laryngeal function after intraoperative injury to the recurrent laryngeal nerve

Loss of function in the recurrent laryngeal nerve (RLN) during thyroid/parathyroid surgery, despite a macroscopically intact nerve, is a challenge which highlights the sensitivity and complexity of laryngeal innervation. Furthermore, the uncertain prognosis stresses a lack of capability to diagnose the reason behind the impaired function. There is a great deal of literature considering risk factors, surgical technique and mechanisms outside the nerve affecting the incidence of RLN paresis during surgery. To be able to prognosticate recovery in cases of laryngeal dysfunction and voice changes after thyroid surgery, the surgeon would first need to define the presence, location, and type of laryngeal nerve injury. There is little data describing the events within the nerve and the neurobiological reasons for the impaired function related to potential recovery and prognosis. In addition, very little data has been presented in order to clarify any differences between the transient and permanent injury of the RLN. This review aims, from an anatomical and neurobiological perspective, to provide an update on the current understandings of surgically-induced injury to the laryngeal nerves.

Neuroprotective and neuroregenerative effects of nimodipine in a model system of neuronal differentiation and neurite outgrowth

Nimodipine is a Ca2+-channel antagonist mainly used for the management of aneurysmal subarachnoid hemorrhage (aSAH) to prevent cerebral vasospasms. However, it is not clear if the better outcome of nimodipine-treated patients is mainly due to vasodilatation or whether other cellular neuroprotective or neuregenerative effects of nimodipine are involved. We analysed PC12 cells after different stress stimuli with or without nimodipine pretreatment. Cytotoxicity of 200 mM EtOH and osmotic stress (450 mosmol/L) was significantly reduced with nimodipine pretreatment, while nimodipine has no influence on the hypoxia-induced cytotoxicity in PC12 cells. The presence of nimodipine also increased the NGF-induced neurite outgrowth in PC12 cells. However, nimodipine alone was not able to induce neurite outgrowth in PC12 cells. These results support the idea that nimodipine has general neuroprotective or neuregenerative effect beside its role in vasodilatation and is maybe useful also in other clinical applications beside aSAH.

Nimodipine enhances neurite outgrowth in dopaminergic brain slice co-cultures

Calcium ions (Ca(2+)) play important roles in neuroplasticity and the regeneration of nerves. Intracellular Ca(2+) concentrations are regulated by Ca(2+) channels, among them L-type voltage-gated Ca(2+) channels, which are inhibited by dihydropyridines like nimodipine. The purpose of this study was to investigate the effect of nimodipine on neurite growth during development and regeneration. As an appropriate model to study neurite growth, we chose organotypic brain slice co-cultures of the mesocortical dopaminergic projection system, consisting of the ventral tegmental area/substantia nigra and the prefrontal cortex from neonatal rat brains. Quantification of the density of the newly built neurites in the border region (region between the two cultivated slices) of the co-cultures revealed a growth promoting effect of nimodipine at concentrations of 0.1μM and 1μM that was even more pronounced than the effect of the growth factor NGF. This beneficial effect was absent when 10μM nimodipine were applied. Toxicological tests revealed that the application of nimodipine at this higher concentration slightly induced caspase 3 activation in the cortical part of the co-cultures, but did neither affect the amount of lactate dehydrogenase release or propidium iodide uptake nor the ratio of bax/bcl-2. Furthermore, the expression levels of different genes were quantified after nimodipine treatment. The expression of Ca(2+) binding proteins, immediate early genes, glial fibrillary acidic protein, and myelin components did not change significantly after treatment, indicating that the regulation of their expression is not primarily involved in the observed nimodipine mediated neurite growth. In summary, this study revealed for the first time a neurite growth promoting effect of nimodipine in the mesocortical dopaminergic projection system that is highly dependent on the applied concentrations.

Investigation of the neuroprotective impact of nimodipine on Neuro2a cells by means of a surgery-like stress model

Nimodipine is well characterized for the management of SAH (subarachnoid hemorrhage) and has been shown to promote a better outcome and less DIND (delayed ischemic neurological deficits). In rat experiments, enhanced axonal sprouting and higher survival of motoneurons was demonstrated after cutting or crushing the facial nerve by nimodipine. These results were confirmed in clinical trials following vestibular Schwannoma surgery. The mechanism of the protective competence of nimodipine is unknown. Therefore, in this study, we established an in vitro model to examine the survival of Neuro2a cells after different stress stimuli occurring during surgery with or without nimodipine. Nimodipine significantly decreased ethanol-induced cell death of cells up to approximately 9% in all tested concentrations. Heat-induced cell death was diminished by approximately 2.5% by nimodipine. Cell death induced by mechanical treatment was reduced up to 15% by nimodipine. Our findings indicate that nimodipine rescues Neuro2a cells faintly, but significantly, from ethanol-, heat- and mechanically-induced cell death to different extents in a dosage-dependent manner. This model seems suitable for further investigation of the molecular mechanisms involved in the neuroprotective signal pathways influenced by nimodipine.

Middle fossa approach: indications, technique, and results

This article discusses the indications, surgical technique, results, and complications of middle fossa craniotomy (MFC) for vestibular schwannoma surgery, focusing on issues such as serviceable hearing, tumor characteristics, and patient-specific factors that help determine options for therapy. MFC is suitable for intracanalicular vestibular schwannomas that extend less than 1 cm into the cerebellopontine angle in patients with good hearing. With the expanding use of modern imaging, many small tumors are being identified in patients with no or minimal symptoms. Patients with these tumors have three therapy options: (1) stereotactic radiotherapy, (2) microsurgery, and (3) observation (ie, wait-and-scan approach).

Facial nerve damage following surgery for cerebellopontine angle tumours. Prevention and comprehensive treatment

Facial nerve (CN VII) palsy or even its transient paresis causes physical disability but is also a psychosocial problem. Immediately after vestibular schwannoma removal, different degrees of CN VII paresis occur in 20-70% of patients. Facial nerve paresis is observed in 10-40% after surgery of cerebellopontine angle meningiomas. Postoperative facial nerve weakness significantly reduces or completely withdraws with time in the majority of cases. However, even if prognosis for CN VII regeneration is good, proper management is needed because of the potential for serious ophthalmic complications. In this paper, the authors raise the issue of perioperative prophylaxis and comprehensive treatment of postoperative paresis of CN VII. Prophylaxis and treatment of ophthalmic complications are discussed. Current trends in the treatment of intraoperative loss of facial nerve continuity, management of facial paresis with good prognosis and dealing with facial palsy with no spontaneous recovery are also described in the paper.

Chemical priming for spinal cord injury: a review of the literature part II-potential therapeutics

INTRODUCTION

Spinal cord injury is a complex cascade of reactions secondary to the initial mechanical trauma that puts into action the innate properties of the injured cells, the circulatory, inflammatory, and chemical status around them, into a non-permissive and destructive environment for neuronal function and regeneration. Priming means putting a cell, in a state of "arousal" towards better function. Priming can be mechanical as trauma is known to enhance activity in cells.

MATERIALS AND METHODS

A comprehensive review of the literature was performed to better understand the possible chemical primers used for spinal cord injuries.

CONCLUSIONS

Taken together, many studies have shown various promising results using the substances outlined herein for treating SCI.

Tumor origin and hearing preservation in vestibular schwannoma surgery

OBJECT

Preservation of cochlear nerve function in vestibular schwannoma (VS) removal is usually dependent on tumor size and preoperative hearing status. Tumor origin as an independent factor has not been systematically investigated.

METHODS

A series of 90 patients with VSs, who underwent surgery via a suboccipitolateral route, was evaluated with respect to cochlear nerve function, tumor size, radiological findings, and intraoperatively confirmed tumor origin. All patients were reevaluated 12 months after surgery.

RESULTS

Despite comparable preoperative cochlear nerve status and larger tumor sizes, hearing preservation was achieved in 42% of patients with tumor originating from the superior vestibular nerve, compared with 16% of those with tumor originating from the inferior vestibular nerve.

CONCLUSIONS

Tumor origin is an important prognostic factor for cochlear nerve preservation in VS surgery.

Botulinum toxin for temporary corneal protection after surgery for vestibular schwannoma

Object

High-grade postoperative facial nerve paresis after surgery for vestibular schwannoma with insufficient eye closure involves a risk for severe ocular complications. When conservative measurements are not sufficient, conventional invasive treatments include tarsorrhaphy and eyelid loading. In this study, injection of botulinum toxin into the levator palpebrae muscle was investigated as an alternative for temporary iatrogenic eye closure.

Methods

Injection of botulinum toxin was indicated by an interdisciplinary decision (neurosurgery and ophthalmology) in patients with a postoperative facial nerve paresis corresponding to a House-Brackmann Grade of IV or greater and documented abnormalities concerning corneal status such as keratopathia or conjunctival redness. Twenty-five IUs of botulinum toxin were injected transcutaneously and transconjunctivally.

Results

Six of 11 patients with high-grade paresis showed abnormal corneal findings in the early postoperative period. In 4 of these patients, botulinum toxin was injected; 1 patient declined the treatment, and in 1 patient it was not performed because of contralateral blindness. Temporary eye closure was achieved for 2 to 6 months in all cases. In all cases, facial nerve function had recovered sufficiently in terms of eye closure when the effect of botulinum toxin subsided.

Conclusion

The application of botulinum toxin for temporary iatrogenic eye closure is an excellent low-risk and temporary alternative to other invasive measures for the treatment of postoperative high-grade facial nerve paresis when the facial nerve is anatomically intact.

Standards for reporting randomized controlled trials in neurosurgery

OBJECT

The Consolidated Standards for Reporting of Trials (CONSORT) criteria were published in 1996 to standardize the reporting and improve the quality of clinical trials. Despite having been endorsed by major medical journals and shown to improve the quality of reported trials, neurosurgical journals have yet to formally adopt these reporting criteria. The purpose of this study is to evaluate the quality and reporting of randomized controlled trials (RCTs) in neurosurgery and the factors that may affect the quality of reported trials.

METHODS

The authors evaluated all neurosurgical RCTs published in 2006 and 2007 in the principal neurosurgical journals (Journal of Neurosurgery; Neurosurgery; Surgical Neurology; Journal of Neurology, Neurosurgery, and Psychiatry; and Acta Neurochirurgica) and in 3 leading general medical journals (Journal of the American Medical Association, Lancet, and the New England Journal of Medicine). Randomized controlled trials that addressed operative decision making or the treatment of neurosurgical patients were included in this analysis. The RCT quality was evaluated using the Jadad score and the CONSORT checklist.

RESULTS

In 2006 and 2007, 27 RCTs relevant to intracranial neurosurgery were reported. Of these trials, only 59% had a Jadad score ≥ 3. The 3 major medical journals all endorsed the CONSORT guidelines, while none of the neurosurgical journals have adopted these guidelines. Randomized controlled trials published in the 3 major medical journals had a significantly higher mean CONSORT score (mean 41, range 39-44) compared with those published in neurosurgical journals (mean 26.4, range 17-38; p < 0.0001). Jadad scores were also significantly higher for the major medical journals (mean 3.42, range 2-5) than neurosurgical journals (mean 2.45, range 1-5; p = 0.05).

CONCLUSIONS

Despite the growing volume of RCTs in neurosurgery, the quality of reporting of these trials remains suboptimal, especially in the neurosurgical journals. Improved awareness of the CONSORT guidelines by journal editors, reviewers, and authors of these papers could improve the methodology and reporting of RCTs in neurosurgery.

Intraoperative neurophysiological monitoring in vestibular schwannoma surgery: advances and clinical implications

OBJECT

Intraoperative neurophysiological monitoring has become an integral part of vestibular schwannoma surgery. The aim of this article was to review the different techniques of intraoperative neurophysiological monitoring in vestibular schwannoma surgery, identify the clinical impact of certain pathognomonic patterns on postoperative outcomes of facial nerve function and hearing preservation, and highlight the role of postoperative medications in improving delayed cranial nerve dysfunction in the different reported series.

METHODS

The authors performed a review of the literature regarding intraoperative monitoring in acoustic/vestibular schwannoma surgery. The different clinical series representing different monitoring techniques were reviewed. All the data from clinical series were analyzed in a comprehensive and comparative model.

RESULTS

Intraoperative brainstem auditory evoked potential monitoring, direct cochlear nerve action potential monitoring, and facial nerve electromyography are the main tools used to assess the functional integrity of an anatomically intact cranial nerve. The identification of pathognomonic brainstem auditory evoked potential and electromyography patterns has been correlated with postoperative functional outcome. Recently, perioperative administration of intravenous hydroxyethyl starch and nimodipine as vasoactive and neuroprotective agents was shown to improve vestibular schwannoma functional outcome in few reported studies.

CONCLUSIONS

Recent advances in electrophysiological technology have considerably contributed to improvement in functional outcome of vestibular neuroma surgery in terms of hearing preservation and facial nerve paresis. Perioperative intravenous nimodipine and hydroxyethyl starch may be valuable additions to surgery.

Hearing preservation in medial vestibular schwannomas

Object

Vestibular schwannomas (VSs) with no or little extension into the internal auditory canal have been addressed as a clinical subentity carrying a poor prognosis regarding hearing preservation, which is attributed to the initially asymptomatic intracisternal growth pattern. The goal in this study was to assess hearing preservation in patients who underwent surgery for medial VSs.

Methods

A consecutive series of 31 cases in 30 patients with medial VSs (mean size 31 mm) who underwent surgery between 1997 and 2005 via a suboccipitolateral route was evaluated with respect to pre- and postoperative cochlear nerve function, extent of tumor removal, and radiological findings. Intraoperative monitoring of brainstem auditory evoked potentials was performed in all patients with hearing. Patients were reevaluated at a mean of 30 months following surgery.

Results

Preoperative hearing function revealed American Academy of Otolaryngology–Head and Neck Surgery Foundation Classes A and B in 7 patients each, Class C in 4, and D in 9. Four patients presented with deafness. Hearing preservation was achieved in 10 patients (Classes A–C in 2 patients each, and Class D in 4 patients). Tumor removal was complete in all patients with hearing preservation, except for 2 patients with neurofibromatosis. In 4 patients a planned subtotal excision was performed due to the individual's age or underlying disease. In 1 patient a recurrent tumor was completely removed 3 years after the initial procedure.

Conclusions

The cochlear nerve in medial VSs requires special attention due to the atypical intracisternal growth pattern. Even in large tumors, hearing could be preserved in 37% of cases, since the cochlear nerve in medial schwannomas may not exhibit the adherence to the tumor capsule seen in tumors with comparable size involving the internal auditory canal.

Schwannoma of the intermediate nerve

The intermediate nerve is seldom identified as the site of tumor origin in cerebellopontine angle schwannomas. A 29-year-old man presented with a 6-month history of slowly progressive hearing loss and dizziness; facial nerve weakness was not observed clinically. Magnetic resonance imaging revealed a tumor in the left cerebellopontine angle region extending up to the geniculate ganglion and along the course of the superficial petrosal nerve. A CT scan showed enlargement of the facial nerve canal. Microsurgery was performed via an extended retrosigmoid approach. Intraoperative and electrophysiological findings identified the intermediate nerve as the site of tumor origin.