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ABSTRACT: Background and Study Aims/Object Oral nimodipine is recommended to reduce poor outcome related to aneurysmal subarachnoid hemorrhage (SAH). In addition, animal experiments and clinical trails revealed a beneficial effect of enteral and parenteral nimodipine for the regeneration of cranial nerves following skull base, laryngeal, and maxillofacial surgery. Despite these findings there is a lack of pharmacokinetic data in the literature, especially concerning its distribution in nerve tissue.Patients/Material and Methods Samples were taken from a consecutive series of 57 patients suffering from skull base lesions and treated with nimodipine prophylaxis from the day before surgery until the seventh postoperative day. Both groups received standard dosages for enteral (n = 25) and parenteral (n = 32) nimodipine . Nimodipine levels were measured in serum, cerebrospinal fluid (CSF), and tissue samples, including vestibular nerves.Results Nimodipine levels were significantly higher following parenteral as compared with enteral administration for intraoperative serum (p < 0.001), intraoperative CSF (p < 0.001), tumor tissues (p = 0.01), and postoperative serum (p < 0.001). In addition, nimodipine was significantly more frequently detected in nerve tissue following parenteral administration (Fisher's exact test, p = 0.015).Conclusions From a pharmacokinetic point of view, parenteral nimodipine medication leads to higher levels in serum and CSF. Furthermore, traces are more frequently found in nerve tissue following parenteral as compared with enteral nimodipine administration, at least in the early course.
Journal of neurological surgery. Part A, Central European neurosurgery. 03/2013;
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ABSTRACT: We report on the case of a 52-year-old man who presented with a history of chronic neuropathic pain treated with intrathecal application of morphine for many years. In spite of significant dose escalation, considerable pain relief had not been achieved. Ziconotide had been tried but not only did it not provide pain relief, but it also caused severe side effects in this patient. A combination of morphine and clonidine was delivered by a programmable pump, slowly increasing the clonidine rate over several weeks. For ease of transition and minimization of hospitalization, which was a special concern to this patient, combining clonidine and morphine was chosen over monotherapy with hydromorphone, with both possibilities being described as equal alternatives in the literature. Considerable pain relief was achieved during week 2 at a clonidine dose of 0.040 mg/d, thereby decreasing the visual analog score (VAS) from 10 to 4. Yet, after developing erectile dysfunction and relative hypotension soon after beginning clonidine treatment, the patient decided not to continue with the combined application of morphine and clonidine. Treatment was therefore switched back to the former monotherapy with morphine. Thereafter, erectile dysfunction disappeared and blood pressure returned to habitual high levels. Although common in systemic application, erectile dysfunction caused by the intrathecal application of clonidine has not been described yet in the literature. In this patient, this rare side effect decisively impaired life quality, subjectively outweighing the considerable pain relief which could be achieved after formerly inefficacious treatment. Further and prospective investigation might be needed to estimate the connection of erectile dysfunction to intrathecal application of clonidine.
Pain physician 07/2012; 15(4):E523-6. · 10.72 Impact Factor
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ABSTRACT: Continuous electromyography (EMG) monitoring is a standard method for intraoperative monitoring of facial nerve function. Typically, only two or three bipolar channels are recorded from needle electrodes to detect pathologic activity, which may provide an incomplete sample. Therefore, we evaluated the influence of channel number on monitoring quality.
The EMG data of 30 patients undergoing surgery for vestibular schwannoma were recorded using 9 bipolar channels from subdermal needle electrodes located in the orbicular oculi, oris, and nasal muscle. Pathologic A-train activity was evaluated in regard to correlation to postoperative nerve function. Channel combinations with different channel numbers were compared.
A-train quantity showed high correlations to postoperative nerve function: Spearman rank correlation of 0.58 for 2, 0.61 for 3 channels. It increased further with every additional channel to 0.69 for all 9 channels (48% of variance accounted for). Single channels with more than one-third of total A-train activity ("hot spots") were observed in 17 patients, which did not show consistent spatial patterns and could only be completely detected with a high number of channels.
Few channels as used in conventional monitoring setups yield acceptable results. However, correlation between train time and postoperative functional results improves with every additional EMG channel.
Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society 06/2012; 29(3):226-9. · 1.47 Impact Factor
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ABSTRACT: An understanding of the normal topography during cerebellopontine angle surgery is necessary to obviate the anatomical distortions caused by tumors.
The aim of this study was to analyze the morphological features of the nervus intermedius (NI) and its related structures in the cerebellopontine angle (CPA).
Forty-three isolated human brainstems were examined to collect comprehensive morphometric and topographical data of the NI in its course from the brainstem to the ganglion geniculi, and discover its anatomical relationship with the other neurovascular structures in the CPA as well as within the meatus acusticus internus.
A total of 84 NI were analyzed. The number of bundles comprising the NI varied from one to five. The mean length of the cisternal segment of the NI was 11.47 mm. In most cases, a vein between the root entry/exit zones of the facial and the vestibulocochlear nerve (VN) was documented. In all cases the NI joined the facial nerve, typically (85 %) distally to the the porus within the meatus acusticus internus. The entry/exit zone of the NI can be categorized into four types: in type A, they arise directly from the brainstem; in type B, they arise solely from the facial nerve; in type C solely from the VN; and in type D, where the bundle or bundles arise from both the brainstem and the VN or the facial nerve.
The anatomical features of the NI can provide an additional variable landmark and critical structure during cerebellopontine microsurgery. Our study of the nerve's anatomy and topographical relations may contribute to preventing intraoperative nerve injuries.
Acta Neurochirurgica 05/2012; 154(7):1263-8. · 1.52 Impact Factor
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ABSTRACT: The interspinous distraction devices are used to treat variable pathologies ranging from facet syndrome, diskogenic low back pain, degenerative spinal stenosis, diskopathy, spondylolisthesis, and instability. The insertion of a posterior element with an interspinous device (ISD) is commonly judged responsive to a relative kyphosis of a lumbar segment with a moderate but persistent increase of the spinal canal and of the foraminal width and area, and without influence on low-grade spondylolisthesis. The consequence is the need of shared specific biomechanical concepts to give for each degenerative problem the right indication through a critical analysis of all available experimental and clinical biomechanical data. We reviewed systematically the available clinical and experimental data about kyphosis, enlargement of the spinal canal, distraction of the interspinous distance, increase of the neural foramina, ligamentous structures, load of the posterior annulus, intradiskal pressure, strength of the spinous processes, degeneration of the adjacent segment, complications, and cost-effectiveness of the ISD. The existing literature does not provide actual scientific evidence over the superiority of the ISD strategy, but most of the experimental and clinical data show a challenging potential. These considerations are applicable with different types of ISD with only few differences between the different categories. Despite-or because of-the low invasiveness of the surgical implantation of the ISD, this technique promises to play a major role in the future degenerative lumbar microsurgery. The main indications for ISD remain lumbar spinal stenoses and painful facet arthroses. A clear documented contraindication is the presence of an anterolisthesis. Nevertheless, the existing literature does not provide evidence of superiority of outcome and cost-effectiveness of the ISD strategy over laminectomy or other surgical procedures. At this time, the devices should be used in clinical randomized independent trials in order to obtain more information concerning the most advantageous optimal indication or, in selected cases, to treat tailored indications.
Neurosurgical Review 05/2012; 35(4):477-84. · 2.04 Impact Factor
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ABSTRACT: The central myelin-peripheral myelin transitional zone, also referred to as the "Obersteiner-Redlich zone (ORZ)" or "glial/Schwann junction" of the nervus intermedius, is thought to play a role in the pathophysiology of nervus intermedius neuralgia (NIN). To evaluate the location and histological features of the ORZ of the nervus intermedius (NI), 10 NI specimens from five fresh cadavers were microscopically analyzed for structural differences between their central and peripheral myelin segments. The ORZ was analyzed under a light microscope, and the exact location of the ORZ was confirmed by immunohistochemical staining using an oligodendroglial antibody. The total diameter of the NI showed a mean of 0.62 mm. The cisternal segment of the NI from the brain stem to the porus acusticus internus had a mean length of 13.97 mm. The mean extent of central myelin was 0.5 mm from the brain stem on the medial side and 0.33 mm on the lateral side. Moreover, the mean length of the ORZ was 0.279 mm on the medial side and 0.134 mm on the lateral side. The distance between the brain stem and the most distal point of central myelin that could be detected was 0.67 mm. Accordingly, the ORZ of the NI appears closer to the brain stem compared to the other cranial nerves. The exact location of the ORZ may play a role in diagnostic preoperative imaging, in the planning of surgical procedures for NIN, and may offer suitable landmarks for surgeons performing microvascular decompression in NIN treatment. Clin. Anat. 25:882-888, 2012. © 2011 Wiley Periodicals, Inc.
Clinical Anatomy 12/2011; 25(7):882-8. · 1.29 Impact Factor
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ABSTRACT: During surgery, lower cranial nerve (CN) electromyography (EMG) may show spontaneous activity without surgical correlate. These episodes have been observed in association with sudden patient movement. In the study presented, this activity was quantified and correlated to the Bispectral Index (BIS) to evaluate the potential of lower CN-EMG for monitoring the depth of anesthesia.
Spontaneous EMG activity in muscles targeted by the CNs IX, X, and XII was quantified and correlated with the BIS measured in 23 patients operated on for posterior fossa pathology. In a blinded retrospective analysis, the time interval from beginning of build-up of the respective parameter (EMG activity and BIS) until extubation was marked. The resulting time intervals were then compared between BIS and EMG.
EMG and BIS build-up was seen 12.3 and 5.9 minutes, respectively, before extubation in median. Thus, EMG provided a longer "warning time" (P=0.026). Isolated lower CN EMG channels preceded BIS in 53%, 62%, and 70% (CN IX, X, and XII). The earliest available EMG channel preceded BIS in 67% of the patients by a median time of 4.3 minutes. The beginning of EMG build-up in the earliest channel was found to be significantly earlier than BIS (P<0.001).
Spontaneous EMG of muscles targeted by lower CNs seems to correlate well with arousal reactions at the end of anesthesia. In many cases, this effect preceded BIS changes. Thus, lower CN EMG monitoring may be a valuable tool in monitoring adequate depth of anesthesia.
Journal of neurosurgical anesthesiology 11/2011; 24(2):139-45. · 2.41 Impact Factor
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ABSTRACT: The authors report surgical and endocrinological results of a series of 73 cases of craniopharyngioma that they treated surgically since 1997 to demonstrate their change in treatment strategy and its effect on outcome compared with a previous series and results reported in the literature.
A total of 73 patients underwent surgery for craniopharyngiomas between May 1997 and January 2005. In patients with poor clinical or neuropsychological condition, even following pretreatment, only stereotactic cyst aspiration took place (8 cases). In the remaining patients, gross-total resection (GTR) was intended and appeared to be possible. The most frequent approaches were subfrontal (27 cases) and transsphenoidal (26 cases); in some cases, a multistep approach was used. The rate of GTR, complications, and functional outcome (comparing pre- and postoperative endocrine and neuropsychological testing) were evaluated. The mean duration of follow-up was 25.2 months.
Gross-total resection was achieved in 88.5% of cases in which a transsphenoidal approach was used and 79.5% of those in which a transcranial approach was used (85.2% of those in which a subfrontal approach was used and 72.7% of those in which a frontolateral approach was used). In the total series, GTR was achieved in 83.1% of cases (vs 49.3% in the authors' former series). The complication rate was 13.8% without any mortality. New endocrine deficits were observed more frequently in patients treated with transcranial approaches over the years (16.3%-66.7% vs 2.6%-50.0%) but were less frequent after transsphenoidal approaches (5.2%-19.2% vs 2.9%-45.7%).
Open surgery with intended total resection remains the treatment of choice in most patients. Initial stereotactic cyst aspiration or medical pretreatment to improve the patients' condition and adequate choice of surgical approach(es) are essential to achieve that goal. Nevertheless, a moderate increase in endocrinological deficits has to be accepted. The authors recommend using radiotherapy only in cases in which there are tumor remnants or disease progression after surgery.
Journal of Neurosurgery 09/2011; 116(2):373-84. · 2.96 Impact Factor
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The Journal of Headache and Pain 09/2011; 12(6):657. · 2.43 Impact Factor
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ABSTRACT: 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.
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.
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.
Tumor origin is an important prognostic factor for cochlear nerve preservation in VS surgery.
Journal of Neurosurgery 07/2011; 115(5):900-5. · 2.96 Impact Factor
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ABSTRACT: Efficacy of radiosurgery in vestibular schwannoma (VS) is usually documented by changes of tumor size and by loss of contrast enhancement in MR imaging within the central portion of the lesion. Until now, however, correlation between contrast enhancement and timing of image acquisition in nontreated VS has not been analyzed systematically. The authors undertook this study to investigate changes in contrast enhancement with respect to latency of image acquisition after contrast agent administration.
The dynamics of contrast medium uptake were evaluated with T1-weighted VIBE MR imaging sequences performed immediately and 1.5, 3.5, 4.5, 9.5, and 11.5 minutes after administration of single dose of Gd in 21 patients with nontreated medium- to large-sized VSs. Signal-to-noise (SNR) and contrast-to-noise ratio (CNR) of tumors were evaluated, and volumes of central nonenhancing areas (NEAs) were determined.
The interior appearance of the tumors changed considerably over time. The NEA significantly diminished in size (p < 0.0001, Friedman test) and almost completely disappeared in all but 2 patients. Compared to images at 1.5 minutes, NEA volumes decreased to a median of 36% at 3.5 minutes and 34% at 4.5 minutes, showing smaller changes after that-9% at 9.5 minutes and 3% at 11.5 minutes. Tumor SNR and CNR increased over time. The maximum change in the median values for SNR and CNR were a 72% increase and 117% increase, respectively; both occurred at 1.5 minutes after Gd administration.
Contrast enhancement in VS MR imaging varies according to the duration of the delay between contrast agent administration and image acquisition. Postradiotherapy changes in contrast enhancement of VS can therefore not be attributed only to effective radiotherapy. So-called "loss of central contrast enhancement" may be falsely detected because of timing. A standardized protocol with defined timing of image acquisition may increase comparability of contrast uptake in VS.
Journal of Neurosurgery 02/2011; 114(2):394-9. · 2.96 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
Journal of Neurosurgery 02/2011; 114(2):426-31. · 2.96 Impact Factor
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ABSTRACT: Although probably identified by Eustachius (1563), the first clearly documented description of the nervus intermedius was completed by Heinrich August Wrisberg at the University of Göttingen in 1777. In 1881, Giuseppe Sapolini defined the nervus intermedius, according to its specific features, as the 13th cranial nerve. In 1908, Ramsay Hunt discovered the correlation between herpes zoster, nervus intermedius and geniculate neuralgia. The combination of venerable accuracy with modern knowledge in electrophysiology, clinical and microsurgical aspects give us an outstanding model of the manner of progress and of the interdisciplinary importance of applied anatomy in medicine. Despite the long history of anatomical description of this small nerve, not all features are well known and the common definition as a purely sensory and parasympathetic root of the facial nerve may not cover all aspects of the nervus intermedius.
Annals of anatomy = Anatomischer Anzeiger: official organ of the Anatomische Gesellschaft 05/2010; 192(3):139-44. · 0.88 Impact Factor
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ABSTRACT: Damage to the facial nerve during surgery in the cerebellopontine angle is indicated by A-trains, a specific electromyogram pattern. These A-trains can be quantified by the parameter "traintime," which is reliably correlated with postoperative functional outcome. The system presented was designed to monitor traintime in real-time.
A dedicated hardware and software platform for automated continuous analysis of the intraoperative facial nerve electromyogram was specifically designed. The automatic detection of A-trains is performed by a software algorithm for real-time analysis of nonstationary biosignals. The system was evaluated in a series of 30 patients operated on for vestibular schwannoma.
A-trains can be detected and measured automatically by the described method for real-time analysis. Traintime is monitored continuously via a graphic display and is shown as an absolute numeric value during the operation. It is an expression of overall, cumulated length of A-trains in a given channel; a high correlation between traintime as measured by real-time analysis and functional outcome immediately after the operation (Spearman correlation coefficient [rho] = 0.664, P < .001) and in long-term outcome (rho = 0.631, P < .001) was observed.
Automated real-time analysis of the intraoperative facial nerve electromyogram is the first technique capable of reliable continuous real-time monitoring. It can critically contribute to the estimation of functional outcome during the course of the operative procedure.
Neurosurgery 04/2010; 66(6):1064-73; discussion 1073. · 2.79 Impact Factor
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ABSTRACT: A retrospective study on solid central nervous system haemangioblastomas was performed to characterize clinical features, treatment strategies and outcome in these rare lesions. Between 1993 and 2006 23, solid haemangioblastomas were surgically removed in 17 patients. Eight lesions were located within pons Varolii and medulla oblongata, six within the cerebellar hemispheres and three in the cerebellopontine angle. Three haemangioblastomas were located supratentorially and three within the spinal cord. All patients except two underwent pre-operative magnetic resonance imaging (MRI). Post-operative digital subtraction angiography and/or MRI was performed in all surviving patients. Except for spinal cord lesions, rather unsystematic clinical symptoms were observed. Twenty-two tumours could be resected completely. Two patients with brainstem lesions died within 10 weeks after surgery from infectious complications. Persistent new neurological deficits occurred in two patients. Three patients underwent radiosurgery prior to or following the surgical procedure. Solid haemangioblastomas represent a surgical challenge due to their arteriovenous malformation-like vascularisation and their frequent location in eloquent areas. Surgery is the therapy of choice. Circumferential dissection with devascularization and en bloc removal yields good functional results. A location within the brainstem carries the most unfavourable prognosis.
Neurosurgical Review 10/2008; 32(1):37-47; discussion 47-8. · 2.04 Impact Factor
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ABSTRACT: Intraoperative monitoring of spontaneous facial nerve electromyographic activity during surgery for microvascular decompression in trigeminal neuralgia was evaluated. Fifteen patients with trigeminal neuralgia underwent surgery for microvascular decompression. During the entire operation, free-running facial nerve electromyographic signals were recorded. The data were analyzed with respect to waveform patterns known from vestibular schwannoma-surgery. Special regard was given to the occurrence of A-trains that are associated with postoperative paresis in patients operated on vestibular schwannoma. The spectrum of the observed activities matched patterns known from surgery of vestibular schwannoma; even A-trains, a pattern known to be an indicator of postoperative deterioration of facial nerve function (Romstöck et al., J Neurosurg 2000;93:586-593), were seen in 3 of the 15 patients with trigeminal neuralgia. The quantity of A-trains observed was much less than it is known from patients operated on tumors of the cerebellopontine angle. None of the trigeminal neuralgia-patients experienced postoperative deterioration of facial nerve function. The present study shows that A-trains do not only occur during tumor surgery, but also during procedures with indirect manipulation of the facial nerve. They do not necessarily lead to postoperative paresis as long as certain thresholds concerning amount and length of these A-trains are not exceeded.
Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society 09/2008; 25(4):225-32. · 1.47 Impact Factor
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ABSTRACT: 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.
Journal of Neurosurgery 08/2008; 109(1):144-8. · 2.96 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
Journal of Neurosurgery 08/2008; 109(1):70-6. · 2.96 Impact Factor
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ABSTRACT: In intraoperative analysis of electromygraphic signals (EMG) for monitoring purposes, baseline artefacts frequently pose considerable problems. Since artefact sources in the operating room can only be reduced to a limited degree, signal-processing methods are needed to correct the registered data online without major changes to the relevant data itself. We describe a method for baseline correction based on "discrete wavelet transform" (DWT) and evaluate its performance compared to commonly used digital filters.
EMG data from 10 patients who underwent removal of acoustic neuromas were processed. Effectiveness, preservation of relevant EMG patterns and processing speed of a DWT based correction method was assessed and compared to a range of commonly used Butterworth, Resistor-Capacitor and Gaussian filters.
Butterworth and DWT filters showed better performance regarding artefact correction and pattern preservation compared to Resistor-Capacitor and Gaussian filters. Assuming equal weighting of both characteristics, DWT outperformed the other methods: While Butterworth, Resistor-Capacitor and Gaussian provided good pattern preservation, the effectiveness was low and vice versa, while DWT baseline correction at level 6 performed well in both characteristics.
The DWT method allows reliable and efficient intraoperative baseline correction in real-time. It is superior to commonly used methods and may be crucial for intraoperative analysis of EMG data, for example for intraoperative assessment of facial nerve function.
Journal of Clinical Monitoring and Computing 09/2007; 21(4):219-26. · 0.89 Impact Factor
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ABSTRACT: The authors describe a quantitative electromyographic (EMG) parameter for intraoperative monitoring of facial nerve function during vestibular schwannoma removal. This parameter is based on the automated detection of A trains, an EMG pattern that is known to be associated with postoperative facial nerve paresis.
For this study, 40 patients were examined. During the entire operative procedure, free-running EMG signals were recorded in muscles targeted by the facial nerve. A software program specifically designed for this purpose was used to analyze these continuous recordings offline. By automatically adding up time intervals during which A trains occurred, a quantitative parameter was calculated, which was named "train time." A strong correlation between the length of train time (measured in seconds) and deterioration of postoperative facial nerve function was demonstrated. Certain consecutive safety thresholds at 0.5 and 10 seconds were defined. Their transgression reliably indicated postoperative facial nerve paresis. At less than a 10-second train time, discrete worsening, and at more than 10 seconds, profound deterioration of facial nerve function can be anticipated.
Train time as a quantitative parameter was shown to be a reliable indicator of facial nerve paresis after surgery for vestibular schwannoma.
Journal of Neurosurgery 06/2007; 106(5):826-32. · 2.96 Impact Factor
