Piezosurgery-, neuroendoscopy-, and neuronavigation-assisted intracranial approach for removal of a recurrent petrous apex cholesteatoma: technical note.

Current approaches for resection of petrous bone cholesteatomas (PBCs), such as canal wall up (closed) and canal wall down (open) mastoidectomies, in the pediatric population present recurrence rates ranging between 17% and 70% with a high rate of postoperative complications involving hearing loss and facial nerve weakness. This technical note illustrates an alternative intracranial approach that was used in combination with the techniques of piezoelectric surgery, neuroendoscopy, and neuronavigation for safe and effective removal in a difficult pediatric case of recurrent PBC. The third recurrence of a PBC in a 14-year-old girl was diagnosed by CT and MRI. A retrosigmoid approach gave access to the petrous apex, allowing for the safe and complete removal of the lesion and decompression of the facial nerve and internal carotid artery. The intraoperative implementation of piezoelectric surgery, neuronavigation, neuroendoscopy, and neuromonitoring ensured better intraoperative visualization, safer bone removal, and preservation of nerve function, facilitating a macroscopically total resection of the pathology without additional neurological damage of the adjacent tissues. Cholesteatoma extension could be clearly verified by intraoperative neuronavigation. Neuroendoscopy and piezoelectric surgery provided good support in the safe bone removal in close vicinity to neurovascular structures and in full vision inside the cholesteatoma cavity beyond the line of sight of the microscope. Hearing and facial nerve function could be preserved. The presented intracranial retrosigmoid approach combined with multiple intraoperative assisting techniques proved to be effective for the safe and complete removal of recurrent PBC, providing excellent intraoperative visualization and the possibility of preserving cranial nerve function.

Mapping the fine structure of cortical activity with different micro-ECoG electrode array geometries.

OBJECTIVE: Innovations in micro-electrocorticography (µECoG) electrode array manufacturing now allow for intricate designs with smaller contact diameters and/or pitch (i.e. inter-contact distance) down to the sub-mm range. The aims of the present study were: (i) to investigate whether frequency ranges up to 400 Hz can be reproducibly observed in µECoG recordings and (ii) to examine how differences in topographical substructure between these frequency bands and electrode array geometries can be quantified. We also investigated, for the first time, the influence of blood vessels on signal properties and assessed the influence of cortical vasculature on topographic mapping. APPROACH: The present study employed two µECoG electrode arrays with different contact diameters and inter-contact distances, which were used to characterize neural activity from the somatosensory cortex of minipigs in a broad frequency range up to 400 Hz. The analysed neural data were recorded in acute experiments under anaesthesia during peripheral electrical stimulation. MAIN RESULTS: We observed that µECoG recordings reliably revealed multi-focal cortical somatosensory response patterns, in which response peaks were often less than 1 cm apart and would thus not have been resolvable with conventional ECoG. The response patterns differed by stimulation site and intensity, they were distinct for different frequency bands, and the results of functional mapping proved independent of cortical vascular. Our analysis of different frequency bands exhibited differences in the number of activation peaks in topographical substructures. Notably, signal strength and signal-to-noise ratios differed between the two electrode arrays, possibly due to their different sensitivity for variations in spatial patterns and signal strengths. SIGNIFICANCE: Our findings that the geometry of µECoG electrode arrays can strongly influence their recording performance can help to make informed decisions that maybe important in number of clinical contexts, including high-resolution brain mapping, advanced epilepsy diagnostics or brain-machine interfacing.

Current practice of external ventricular drainage: a survey among neurosurgical departments in Germany.

BACKGROUND: There are various recommendations, but no generally accepted guidelines, to reduce the risk of external ventricular drainage (EVD)-associated infections. The primary objective of the present study was to evaluate the current practice of EVD in a European country and to set the results in perspective to published data. METHOD: A standardised questionnaire prepared by the Commission of Technical Standards and Norms of the German Society of Neurosurgery was sent to 127 neurosurgical units in Germany. RESULTS: Data were analysed from 99 out of 127 neurosurgical units which had been contacted. Overall, more than 10,000 EVD procedures appear to be performed in Germany annually. There is disagreement about the location where the EVD is inserted, and most EVDs are still inserted in the operation theatre. Most units apply subcutaneous tunnelling. Impregnated EVD catheters are used regularly in only about 20 % of units. Single-shot antibiotic prophylaxis is given in more than half of the units, while continued antibiotic prophylaxis is installed in only 15/99 units at a regular basis. There are discrepancies in the management of prolonged EVD use with regard to replacement policies. Regular cerebrospinal fluid (CSF) sampling is still performed widely. There were no statistical differences in policies with regard to academic versus non-academic units. CONCLUSIONS: This survey clearly shows that some newer recommendations drawn from published studies penetrate much slower into clinical routine, such as the use of impregnated catheters, for example. It remains unclear how different policies actually impact quality and outcome in daily routine.

The value of dynamic radiographic myelography in addition to magnetic resonance imaging in detection lumbar spinal canal stenosis: A prospective study.

OBJECTIVE: MRI is regarded as the study of choice in the diagnosis of lumbar spinal stenosis. In some cases, the supine MRI leads to a misdiagnosis in the extent of lumbar spinal stenosis. Dynamic myelography can detect lumbar spinal stenosis in these cases of where the MRI may not be as sensitive. To compare the sensitivities of dynamic radiographic myelography and supine MRI in lumbar canal stenosis (LCS) patients and to determine whether dynamic radiographic myelography is a valuable diagnostic exam in the work-up of lumbar canal stenosis. PATIENTS & METHODS: Over two years, the imaging data of 100 consecutive patients who were suspected of having LCS were prospectively analyzed. All lumbar intervertebral segments were evaluated in each patient on sagittal MR T2-weighted images and lateral plane images by myelography using a semi-quantitative scoring system. The differences in scores for 5 motion segments under 3 conditions (supine MRI, upright sitting myelography and standing myelography with extension) were analyzed statistically. RESULTS: Of 100 patients with 500 analyzed intervertebral segments, 23 patients with inconclusive supine MRI results had LCS in standing myelography with extension. Compared with upright sitting myelography and supine MRI, standing myelography with extension yielded the highest score for every segment from L1/2 to L5/S1. Compared with the upright sitting myelography position, 61 more patients received a diagnosis of lumbar stenosis in the standing myelography with extension position, and 121 more stenotic segments were diagnosed. Compared with the supine MRI position, standing myelography with extension detected 64 more stenotic patients and 137 more stenotic segments. CONCLUSIO: n Based on a large patient sample, dynamic myelography is a valuable diagnostic tool in detecting lumbar spinal stenosis. Patients with lumbar spinal stenosis may have inconclusive supine MRI in 23% of cases being misdiagnosed as normal. This missed rate of LCS patients with unclear supine MRI results can be avoided with dynamic myelography. The combination of supine MRI and dynamic myelography is critical in the evaluation of LCS, especially if multisegmental findings are detected.

Challenges for Restoration of Lower Urinary Tract Innervation in Patients with Spinal Cord Injury: A European Single-center Retrospective Study with Long-term Follow-up.

UNLABELLED: Xiao and colleagues in China reported successful restoration of bladder control in patients with spinal cord injury (SCI) by establishing a somatic-autonomic reflex pathway through lumbar-to-sacral ventral root nerve rerouting. We evaluated long-term results in eight patients who underwent this procedure at a German university clinic between 2005 and 2007. The primary outcome was the occurrence of voiding upon stimulation of the skin, with normalization of bladder pressure when filling, as assessed with videourodynamics at each visit. Videourodynamic variables, urinary tract infections, and bladder/stool events recorded in a patient diary were stored in a prospective database and reviewed retrospectively. Intraoperative testing indicated successful nerve rerouting in all eight patients. Duration of follow-up was 71 mo (range: 56-86). No patient reached the primary goal of voluntary voiding with normalization of detrusor pressure at any point during follow-up. No improvements in videourodynamic or diary variables regarding bladder function were observed. In view of the lack of short (12-18 mo) and long-term (71 mo) success in our patients and others, the risks of any surgical procedure using general anesthesia, and potential for unmet expectations to wreak havoc on patient emotional well-being, we cannot recommend this procedure for patients with SCI. PATIENT SUMMARY: Although the hope was to improve long-term outcomes of spinal cord injury patients, intraspinal nerve rerouting did not improve or normalize bladder function. In view of the lack of success, we cannot recommend this procedure until proven in clinical studies.

Central skull base osteomyelitis: new insights and implications for diagnosis and treatment.

Central skull base osteomyelitis (SBO) is a life-threatening disease originating from ear and from sinonasal infections. The intention of this study was to evaluate contemporary trends in etiology, diagnosis, management, and outcome of SBO and to draw the clinician's attention on this probably underestimated disease. Over a 6-year period we performed this systematic study in an academic quaternary medical care and skull base center including 20 patients (mean age 63.7 years) with central SBO, which is one of the largest series from a single center. In contrast to previous studies we explicitly excluded infections limited to malignant external otitis only but did not restrict central SBO to conditions unrelated to aural pathology. Fifteen patients had otogenic and five sinugenic SBO; four patients had fungal or mixed fungal infections. Pre-existing illnesses altering bone vascularization were detected in 70 % of the patients and had a negative effect on the improvement of cranial nerve palsies that were found in 14 patients. In relation, patients with otogenic SBO more often had local and systemic predisposing factors. Contrary to previous studies 16 patients (80 %) underwent surgical therapy and none of our patients died. A meta-analysis of five recent studies was done and compared with our own data and two previous meta-analyses. The present study highlights several important aspects with major implications for diagnosis and treatment of SBO that have not been adequately addressed as yet. In contrast to the restrictive attitude towards surgery in literature we recommend early and radical operative treatment to reduce its mortality.

Use of Piezosurgery for removal of retrovertebral body osteophytes in anterior cervical discectomy.

BACKGROUND CONTEXT: The relatively new technique of Piezosurgery is based on microvibrations, generated by the piezoelectrical effect, which results in selective bone cutting with preservation of adjacent soft tissue. PURPOSE: To study the applicability of Piezosurgery in anterior cervical discectomy with fusion (ACDF) surgery. STUDY DESIGN/SETTING: Prospective clinical study at the neurosurgical department of the University of Freiburg, Germany. PATIENT SAMPLE: Nine patients with cervical disc herniation and retrovertebral osteophytes who underwent ACDF surgery. OUTCOME MEASURES: Piezosurgery was evaluated with respect to practicability, safety, preciseness of bone cutting, and preservation of adjacent neurovascular tissue. Pre- and postoperative clinical and radiological data were assessed. METHODS: Piezosurgery was supportively used in ACDF in nine patients with either radiculopathy or myelopathy from disc herniation or ventral osteophytes. After discectomy, osteophytes were removed with Piezosurgery to decompress the spinal canal and the foramina. Angled inserts were used, allowing for cutting even retrovertebral osteophytes. RESULTS: In all nine cases, Piezosurgery cut bone selectively with no damage to nerve roots, dura, or posterior longitudinal ligament. None of the patients experienced any new neurological deficit after the operation. The handling of the instrument was safe and the cut precise. Osteophytic spurs, even retrovertebral ones that generally only can be approached via corpectomies, could be safely removed because of the angled inserts through the disc space. Currently, a slightly prolonged operation time was observed for Piezosurgery. Furthermore, the design of the handpiece could be further improved to facilitate the intraoperative handling in ACDF. CONCLUSIONS: Piezosurgery proved to be a useful and safe technique for selective bone cutting and removal of osteophytes with preservation of neuronal and soft tissue in ACDF. In particular, the angled inserts were effective in cutting bone spurs behind the adjacent vertebra which cannot be reached with conventional rotating burs.

Computational tissue volume reconstruction of a peripheral nerve using high-resolution light-microscopy and reconstruct.

The development of neural cuff-electrodes requires several in vivo studies and revisions of the electrode design before the electrode is completely adapted to its target nerve. It is therefore favorable to simulate many of the steps involved in this process to reduce costs and animal testing. As the restoration of motor function is one of the most interesting applications of cuff-electrodes, the position and trajectories of myelinated fibers in the simulated nerve are important. In this paper, we investigate a method for building a precise neuroanatomical model of myelinated fibers in a peripheral nerve based on images obtained using high-resolution light microscopy. This anatomical model describes the first aim of our "Virtual workbench" project to establish a method for creating realistic neural simulation models based on image datasets. The imaging, processing, segmentation and technical limitations are described, and the steps involved in the transition into a simulation model are presented. The results showed that the position and trajectories of the myelinated axons were traced and virtualized using our technique, and small nerves could be reliably modeled based on of light microscopy images using low-cost OpenSource software and standard hardware. The anatomical model will be released to the scientific community.

Evaluation of µECoG electrode arrays in the minipig: experimental procedure and neurosurgical approach.

Emerging research on brain-machine interfaces (BMIs) requires the development of animal models for testing implantable BMI electrodes. New models are necessary in order to characterize and test newly constructed electrodes in an acute environment, and their properties and performance need to be evaluated in long-term, chronic implantations. Owing to their availability, small size and neuroanatomical similarity to the human brain, minipigs are frequently used for neurological studies. Despite this fact, there are still no standardized experimental and neurosurgical procedures available for recording of cortical potentials using implantable BMI electrodes in minipigs, and, until now, it was unclear whether these animals could also be used for long-term subdural electrode implantations. We have therefore evaluated the potential use of minipigs for acute and chronic implantation of micro-electrocorticogram (µECoG) electrodes we newly developed for BMI applications and we present a standardized neurosurgical approach to the minipig's cerebral cortex. A neurophysiological setup is described which is suitable to perform recordings of somatosensory evoked potentials (SEPs) with high spatial resolution - down to approx. 1-mm inter-electrode distance. Perioperative management, anesthesia and anatomical landmarks for electrode placement are discussed and common surgical pitfalls are described. While, due to their specific cranial anatomy, minipigs appear not optimally suited for chronic subdural implantations, the findings of the present study indicate that µECoG recording from the minipig cortex is a valuable new approach for acute in vivo characterization of subdural BMI electrode function.

Use of piezosurgery for internal auditory canal drilling in acoustic neuroma surgery.

BACKGROUND: Piezosurgery is based on microvibrations generated by the piezoelectrical effect and has a selective bone-cutting ability with preservation of soft tissue. This study examined the applicability of Piezosurgery compared to rotating drills (RD) for internal auditory canal (IAC) opening in acoustic neuroma (AN) surgery. MATERIALS AND METHODS: Piezosurgery was used in eight patients for IAC drilling in AN surgery. After exposition of the IAC and tumor, the posterior wall of the IAC was drilled using Piezosurgery instead of RD. Piezosurgery was evaluated with respect to practicability, safety, preciseness of bone cutting, preservation of cranial nerves, influences on neurophysiological monitoring, and facial nerve and hearing outcome. RESULTS: Piezosurgery was successfully used for selective bone cutting, while cranial nerves were structurally and functionally preserved, which could be measured by means of neuromonitoring. Piezosurgery guaranteed a safe and precise cut by removing bone layer by layer in a shaping way. Compared to RD, limited influence on neurophysiological monitoring attributable to Piezosurgery was noted, allowing for continuous neuromonitoring. No disadvantage due to microvibrations was noticed concerning hearing function. The angled tip showed better handling in right-sided than in left-sided tumors in the hands of a right-handed surgeon. The short, thick handpiece may be improved for more convenient handling. CONCLUSION: Piezosurgery is a safe tool for selective bone cutting for opening of the IAC with preservation of facial nerve and hearing function in AN surgery. Piezosurgery has the potential to replace RD for this indication because of its safe and precise bone-cutting properties.

A Rare Case of Radiologically Not Distinguishable Coexistent Meningioma and Vestibular Schwannoma in the Cerebellopontine Angle - Case Report and Literature Review.

BACKGROUND: The simultaneous occurrence of cerebellopontine angle (CPA) meningioma and vestibular schwannoma (VS) in the absence of neurofibromatosis type 2 or history of irradiation is very rare. We report a case with coexistent CPA meningioma and VS, which were radiologically not distinguishable in preoperative imaging. CASE DESCRIPTION: A 46-year-old female presented with acute hearing loss, tinnitus and gait ataxia. Otorhinolaryngological diagnostic workup and imaging studies showed an intra- and extrameatal homogenous contrast enhancing lesion. The neuroradiological diagnosis was VS. The patient was operated via the retrosigmoid approach. INTRAOPERATIVELY TWO DISTINCT TUMORS WERE FOUND: a small, mainly intrameatally located VS and a larger meningioma originating from the dura of the petrous bone. Both tumors were completely microsurgically removed. The patient experienced no new neurological deficit after surgery; particularly facial nerve function was completely preserved. Histopathological examination revealed a fibromatous meningioma and a VS, respectively. CONCLUSIONS: The coincidental occurrence of CPA meningioma and VS is very rare. Careful interpretation of imaging studies before surgery is crucial. Even such rare cases should be kept in mind when discussing the therapeutic options with the patient. More studies are needed for a better understanding of mechanisms leading to multiple tumor growth.

The impact of tinnitus and vertigo on patient-perceived quality of life after cerebellopontine angle surgery.

BACKGROUND: Quality of life (QOL) has come into focus after treatment for cerebellopontine angle (CPA) lesions. OBJECTIVE: This study compared subjective (tinnitus, vertigo) and objective (hearing loss, facial palsy) results of CPA surgery with patient-perceived impairment of QOL. METHODS: A retrospective analysis of a consecutive series of 48 patients operated on for either a vestibular schwannoma or a meningioma in the CPA was performed. Patient's subjective impairment of QOL by tinnitus, vertigo, hearing loss, and facial nerve palsy was assessed by a visual analog scale (VAS). Objective facial nerve and hearing function were determined using House-Brackmann and Gardner-Robertson classification systems, respectively. RESULTS: The return rate of questionnaires was 64.4%, with mean follow-up time of 417.2 (+/- 46.4) days. Mean preoperative tinnitus score was 2.5 (+/- 0.5) and increased to 4.6 (+/- 0.7) postoperatively (P < .01). The vertigo score increased from 2.0 (+/- 0.3) to 5.8 (+/- 0.6) (P < .001). Pre- and postoperative values for hearing loss were 3.4 (+/- 0.6) and 5.9 (+/- 0.7), respectively (P < .01), and for facial nerve palsy 0.7 (+/- 0.4) compared with 3.1 (+/- 0.6) postoperatively (P < .01). House-Brackmann grade 1 or 2 was determined in 87.1% of patients before and in 80.6% after surgery. Serviceable hearing (Gardner-Robertson classes I-III) was found in 75% before and in 64.3% after surgery. CONCLUSION: Preservation of facial nerve and hearing function are not the only important criteria defining QOL after CPA surgery. Tinnitus and vertigo may have a significant underestimated impact on the patient's postoperative course and QOL.

Microsurgical approach to the spinal canal in rats.

The spinal cord of the rat has become a widely used model for biodynamic, pharmaceutical and neurological experiments. However, no standard procedure to approach the spinal cord in rats has been published in detail. We present a description of a dorsal approach to the spine, spinal canal and myelon of the rat. This approach provides sufficient exposure of the neural structures to perform extended microsurgery at the spinal nerve-roots, the lateral and dorsal myelon and vertebral structures under a surgical microscope. Perioperative management, anaesthesia and anatomical landmarks are discussed and common pitfalls are described.

Surgical removal of a symptomatic paracondylar process.

The paracondylar process is a rare congenital abnormality of the craniocervical junction that has been identified as a causative agent for severe headache, neck pain, and restricted head movement. Although conservative treatment is usually sufficient, the authors report the case of a symptomatic paracondylar process in a young patient who required surgical intervention.

Giant cell reparative granuloma of the temporal bone.

Giant cell reparative granuloma (GCRG) is an uncommon non-neoplastic reactive tumor that occurs almost exclusively within the mandible and maxilla and can be locally aggressive. Only sporadic cases involving the skull base have been reported. However, this lesion is probably underappreciated because it might be unrecognized or misdiagnosed. We present a case of GCRG of the left temporal bone that was treated surgically via a combined transtemporal-subtemporal approach. A short literature review about diagnosis, clinical behavior and treatment of this tumor entity is given.

Auditory rehabilitation after long-term deafness.

OBJECTIVE: The duration of preexisting profound deafness in patients with bilateral retrocochlear lesions is known to correlate negatively to the extent of auditory restoration after auditory brainstem implantation. There is, therefore, a lack of information regarding the potential of the central auditory system to mediate hearing perception after long-term deafness. METHODS: The authors evaluated auditory perception in a case of auditory brainstem implantation after 35 years of deafness. RESULTS: Electrically evoked auditory brainstem potentials could be elicited by both stimulus polarities and were consistent with auditory brainstem origin. Discrimination between temporal and spectral patterns in speech could be achieved. This permitted us to distinguish various voice qualities, especially of familiar speakers in quiet surroundings. CONCLUSION: The potential of the deafferentiated central auditory system to mediate auditory brainstem implant-induced hearing perception even after very long-term deafness has been demonstrated. Those patients with complete dysfunction of Cranial Nerve VIII for a long period may be considered as candidates for auditory brainstem implantation in the future.

Inflammatory myofibroblastic tumor of the ulnar nerve. Case report and review of the literature.

Inflammatory myofibroblastic tumors with involvement of cranial and peripheral nerves are exceedingly rare. The authors present the case of a 67-year-old man with an inflammatory myofibroblastic tumor of the left ulnar nerve, which was identified intraoperatively and mimicked a malignant neoplastic lesion. Histopathological examination revealed loosely structured fibrous tissue and collagen deposits intermingled with patchy infiltrates of lymphocytes, plasma cells, and histiocytes penetrating the endo- and epineurium of the affected nerve fascicles. There was strong expression of vimentin and actin in spindle cells throughout the lesion. The histiocytes were CD68- and major histocompatibility complex class II-positive, but lacked CD1a expression. A review of the literature revealed nine histopathologically confirmed cases of inflammatory myofibroblastic tumors involving peripheral or cranial nerves in which slight differences in histopathological features and surgical management were found, which are discussed here.

Placement of intraventricular catheters using flexible electromagnetic navigation and a dynamic reference frame: a new technique.

BACKGROUND: Catheterization of narrow ventricles may prove difficult resulting in misplacement or inefficient trials with potential damage to brain tissue. MATERIAL AND METHODS: The application of a new module for navigated ventricular catheterization using flexible electromagnetic navigation and a dynamic reference frame is presented. RESULTS: Navigated catheter placement was successful and accurate in a pilot study. Electromagnetic interferences had to be taken into consideration. CONCLUSION: Flexible electromagnetic navigation with a dynamic reference frame is a useful tool for catheter placement as it reduces the risk of misplacement or repeated catheterization trials.