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.

Practice in the perioperative prevention of deep vein thrombosis in german neurosurgical departments: is there a trend towards homogenization?

OBJECTIVE

There was no consensus on the most suitable perioperative prophylaxis of deep vein thrombosis (DVT) in neurosurgical patients. The aim of this work was to review the current practice and search for a standard protocol in the prophylaxis of DVT.

METHODS AND MATERIAL

Questionnaires addressing the routine prophylaxis of perioperative DVT for 4 groups of neurosurgical procedures and the estimation of risks and benefits of perioperative heparin (unfractionated and/or low-molecular-weight) administration were sent to 130 neurosurgical departments in Germany.

RESULTS

103 of 130 questionnaires were returned and suitable for analysis. The use of heparin (unfractionated and/or low-molecular-weight) is common, with some variation depending on the type of operation (83.5-99%). In spinal procedures, heparin administration is commonly started early, i. e., between the preoperative and first postoperative day (90.3-97.1%). This differs in intracranial procedures. In most neurosurgical departments heparin administration is stopped at the day of discharge (69.6-77.4% depending on procedure). Enoxaparin is the most commonly used heparin. In spinal as well as in cranial procedures, thrombosis risk reduction is unanimously assumed to be lesser the later administration starts. The estimation of the risks related to heparin injection are considered to be higher in cranial than in spinal operation in the early postoperative period. Most departments use antithrombotic stockings (ATS) irrespective of the type of surgery. However, 11% never use ATS.

CONCLUSIONS

In spinal surgery, a trend towards homogenization is observed with the early use of heparin. In intracranial procedures, practice is more heterogenous. The heterogeneity is due to the fact that the data available in the literature does not allow for the identification of an optimal protocol.

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.

Magnetic resonance imaging dynamics of contrast medium uptake in vestibular schwannomas

OBJECT

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

A Real-Time Monitoring System for the Facial Nerve

OBJECTIVE

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.

METHODS

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.

RESULTS

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 [ρ] = 0.664, P &lt; .001) and in long-term outcome (ρ = 0.631, P &lt; .001) was observed.

CONCLUSION

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.

History of the nervus intermedius of Wrisberg

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.

Ultracold triplet molecules in the rovibrational ground state

We report here on the production of an ultracold gas of tightly bound Rb2 triplet molecules in the rovibrational ground state, close to quantum degeneracy. This is achieved by optically transferring weakly bound Rb2 molecules to the absolute lowest level of the ground triplet potential with a transfer efficiency of about 90%. The transfer takes place in a 3D optical lattice which traps a sizeable fraction of the tightly bound molecules with a lifetime exceeding 200 ms.

Solid haemangioblastomas of the CNS: a review of 17 consecutive cases

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.

Hemorrhage into cystic vestibular schwannoma following stereotactic radiation therapy

The occurrence of a hemorrhage into a vestibular schwannoma is a rare phenomenon. Several reports, however, indicate a risk profile for a subgroup of patients with vestibular schwannoma which show hypervascularity in the histopathological examination. Cystic formation, large size, mixed Antoni type and anticoagulation therapy seem to enhance the risk of tumor hemorrhage. We report on a patient with a large cystic vestibular schwannoma who died from fatal bleeding into the tumor 15 months following stereotactic radiation therapy. Since hemorrhage seems to be a relevant risk in large cystic vestibular schwannomas, a surgical treatment should be preferred whenever possible.

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.

Intraoperative brainstem auditory evoked potential pattern and perioperative vasoactive treatment for hearing preservation in vestibular schwannoma surgery

OBJECTIVE

In vestibular schwannoma surgery, four different intraoperative brainstem auditory evoked potential (BAEP) patterns (stable BAEP, abrupt loss, irreversible progressive loss, reversible loss) can be identified and correlated with postoperative hearing outcome. Patients with reversible loss significantly benefit from postoperative vasoactive treatment consisting of hydroxyethyl starch and nimodipine. The present study investigates the treatment effect in the remaining three BAEP patterns.

METHODS

A retrospective analysis was performed in 92 patients operated on for vestibular schwannoma between 1997 and 2005. Between 1997 and 2001, only patients with reversible loss of BAEP received vasoactive medication. Subsequently, all patients operated on between 2001 and 2005 received a 10 day course of therapy, regardless of the BAEP pattern. Serial audiological examinations before, after surgery and after 1 year were performed in all patients.

RESULTS

All 30 patients with reversible loss of BAEP received medication, and postoperative hearing preservation was documented in 21 patients. All 13 patients with stable waves showed hearing preservation, regardless of treatment. In all 24 patients with abrupt loss and in all 25 patients with irreversible progressive loss, postoperative anacusis was documented, regardless of treatment.

CONCLUSION

In patients with reversible loss of BAEP, a disturbed microcirculation of the cochlear nerve seems to be the underlying pathophysiological factor. In patients with abrupt or irreversible progressive loss, additional mechanical injury of nerve fibres determines hearing outcome. The study provides evidence that for the purpose of hearing preservation, only patients with reversible loss of BAEP benefit from vasoactive treatment.

Baseline correction of intraoperative electromyography using discrete wavelet transform

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Train time as a quantitative electromyographic parameter for facial nerve function in patients undergoing surgery for vestibular schwannoma

Object

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.

Methods

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.

Conclusions

Train time as a quantitative parameter was shown to be a reliable indicator of facial nerve paresis after surgery for vestibular schwannoma.

Keratinocyte transcriptional regulation of the human c-Myc promoter occurs via a novel Lef/Tcf binding element distinct from neoplastic cells

The proto-oncogene c-Myc is involved in early neoplastic transformations. Two consensus Lef/Tcf binding elements (TBE) were found to be prerequisite for transcriptional transactivation by the armadillo proteins beta-catenin and plakoglobin (PG) together with Tcf4 in human neoplastic cells. In epidermal keratinocytes, c-Myc was reported to be repressed by Lef-1 and PG. Using reporter gene assays, here we demonstrate that deletion of the two consensus TBE fails to abrogate transcriptional regulation by Lef-1/PG in wildtype and beta-catenin-/- keratinocytes, while it reduces transcription in pre-neoplastic PG-/- keratinocytes. We identified a TBE sequence variant downstream of the major transcriptional initiation site that binds Lef-1 in vitro and in vivo, and its mutation compromised transcriptional regulation by Lef-1/PG. Collectively, this study demonstrates that the two consensus TBE's reported in neoplastic cells are dispensable for c-Myc regulation in normal keratinocytes, which instead use a novel TBE sequence variant. This unprecedented finding may have important implications for armadillo target genes involved in carcinogenesis.