Endoscopic treatment of lumbar degenerative disc disease: a narrative review of Full-Endoscopic and Unilateral Biportal Endoscopic Spine Surgery.

BACKGROUND: Degenerative lumbar spine disease is the leading cause of disability and work absenteeism worldwide. Lumbar microdiscectomy became the standard treatment for herniated discs and stenotic disease. With the evolution of different techniques, endoscopic spinal surgery emerged to minimize the surgical footprint while providing at least non-inferior results. Currently, two different types of endoscopic spine procedures are dominating the surgical scenario: "Full-Endoscopic" (FE) and Unilateral Biportal Endoscopic"(UBE) Spine Surgery. The aim of this study is to describe and analyze their indications, their technical characteristicswithitsadvantagesanddisadvantagesofbothtechniquesandtheirfuture trends. METHODS: We performed a narrative review of the most relevant articles published up to August 2023 through a Pub Med search. The search terms "Full-Endoscopic Spine Surgery" and "Unilateral Biportal Endoscopic Spine Surgery" were used. The articles selected, were independently reviewed by 3 authors and 55 full text articles were reviewed. RESULTS: The FE and UBE Spine Surgery techniques were described. The FE technique is performed with a monoportal access under constant saline irrigation. The FE comprises the transforaminal and the interlaminar approaches, and the indication depends from the pathology to treat, and still remains controversial. UBE can approach also the spine from a posterior, postero lateral,and para spinal route. It uses two different ports addressed to a target with continuous irrigation. The process of establishing these two portals is called triangulation. CONCLUSION: FE and UBE spine surgery have demonstrated outcomes comparable to open surgery, minimizing complications and surgical footprint.

The Biomechanics of the Transpedicular Endoscopic Approach.

STUDY DESIGN: Biomechanical cadaveric study. OBJECTIVE: The goal of this study was to analyze the effects of an endoscopic transpedicular approach with different drill diameters (6 and 8 mm) to compare them with the intact native side. In addition, the influence of bone quality on the resistance of the pedicle was investigated. SUMMARY OF BACKGROUND DATA: Clinical studies have repeatedly highlighted the benefits of endoscopic transpedicular decompression for down-migrated lumbar disc herniations. However, the biomechanical effects on pedicle stability have not been studied up to now. METHODS: Twenty-four vertebras originating from four fresh-frozen cadavers were tested under uniaxial compression load in a ramp-to-failure test: (1) the tunneled pedicle on one side, and (2) the native pedicle on the other side. Twelve lumbar vertebrae were assigned to a drill diameter of 6 mm and the other 12 to a diameter of 8 mm. RESULTS: The median ratio of sustained force for the operated side compared to the intact contralateral side is equal to 74% (63-88) for both drill diameters combined. An 8 mm transpedicular approach recorded an axial resistance of 77% (60-88) compared to the intact contralateral side ( P =0.002). A 6 mm approach resulted in an axial resistance of 72% (66-84) compared to the intact opposite side ( P =0.01). No significant difference between the two different drill diameters was recorded ( P =1). For all 3 subgroups (intact, 8 mm, 6 mm) the HU-values and the absolute resistance force showed significant correlations (intact: ρ=0.859; P <0.001; 8 mm: ρ=0.902; P <0.001; 6 mm: ρ=0.835; P <0.001). CONCLUSION: Transpedicular approach significantly reduces the axial resistance force of the pedicle, which may lead to pedicle fracture. Bone quality correlated positively with the absolute resistance force of the pedicle, whereas the influence of the drill hole diameter plays only a limited role.

Combined endoscopic and microsurgical approach for the drainage of a multisegmental thoracolumbar epidural abscess: illustrative case.

BACKGROUND: Spinal epidural abscess is a rare but serious infectious disease that can rapidly develop into a life-threatening condition. Therefore, the appropriate treatment is indispensable. Although conservative treatment is justifiable in certain cases, surgical treatment needs to be considered as an alternative early on because of complications such as (progressive) neurological deficits or sepsis. However, traditional surgical techniques usually include destructive approaches up to (multilevel) laminectomies. Such excessive approaches do have biomechanical effects potentially affecting the long-term outcomes. Therefore, minimally invasive approaches have been described as alternative strategies, including endoscopic approaches. OBSERVATIONS: The authors describe a surgical technique involving a combination of two minimally invasive approaches (endoscopic and microsurgical) to drain a multisegmental (thoracolumbar) abscess using the physical phenomenon of continuous pressure difference to minimize collateral tissue damage. LESSONS: The combination of minimally invasive approaches, including the endoscopic technique, may be an alternative in draining selected epidural abscesses while achieving a similar amount of abscess removal and causing less collateral approach damage in comparison with more traditional techniques.

Durotomy- and Irrigation-Related Serious Adverse Events During Spinal Endoscopy: Illustrative Case Series and International Surgeon Survey.

BACKGROUND: Durotomy during endoscopic spine surgery can cause a patient's neurological or cardiovascular status to deteriorate unexpectedly intra- or postoperatively. There is currently limited literature regarding appropriate fluid management strategies, irrigation-related risk factors, and clinical consequences of incidental durotomy during spinal endoscopy, and no validated irrigation protocol exists for endoscopic spine surgery. Thus, the present article sought to (1) describe 3 cases of durotomy, (2) investigate standard epidural pressure measurements, and (3) survey endoscopic spine surgeons on the incidence of adverse effects believed to result from durotomy. MATERIALS AND METHODS: The authors first reviewed clinical outcomes and analyzed complications in 3 patients with intraoperatively recognized incidental durotomy. Second, the authors conducted a small case series with intraoperative epidural pressure measurements during gravity-assisted irrigated video endoscopy of the lumbar spine. Measurements were conducted on 12 patients with a transducer assembly that was introduced through the endoscopic working channel of the RIWOSpine Panoview Plus and Vertebris endoscope to the decompression site in the spine. Third, the authors conducted a retrospective, multiple-choice survey of endoscopic spine surgeons to better understand the frequency and seriousness of problems they attributed to irrigation fluid escaping from the surgical decompression site into the spinal canal and neural axis. Descriptive and correlative statistical analyses were performed on the surgeons' responses. RESULTS: In the first part of this study, durotomy-related complications during irrigated spinal endoscopy were observed in 3 patients. Postoperative head computed tomographic (CT) images revealed massive blood in the intracranial subarachnoid space, the basal cisterns, the III and IV ventricle, and the lateral ventricles characteristic of an arterial fisher grade IV subarachnoid hemorrhage, and hydrocephalus without evidence of aneurysms or angiomas. Two additional patients developed intraoperative seizures, cardiac arrhythmia, and hypotension. The head CT image in 1 of these 2 patients had intracranial air entrapment.In the second part, epidural pressure measurements in 12 patients who underwent uneventful routine lumbar interlaminar decompression for L4-L5 and L5-S1 disc herniation showed an average epidural pressure of 24.5 mm Hg.In the third part, the online survey was accessed by 766 spine surgeons worldwide and had a response rate of 43.6%. Irrigation-related problems were reported by 38% of responding surgeons. Only 11.8% used irrigation pumps, with 90% running the pump above 40 mm Hg. Headaches (4.5%) and neck pain (4.9%) were observed by nearly a 10th (9.4%) of surgeons. Seizures in combination with headaches, neck and abdominal pain, soft tissue edema, and nerve root injury were reported by another 5 surgeons. One surgeon reported a delirious patient. Another 14 surgeons thought that they had patients with neurological deficits ranging from nerve root injury to cauda equina syndrome related to irrigation fluid. Autonomic dysreflexia associated with hypertension was attributed by 19 of the 244 responding surgeons to the noxious stimulus of escaped irrigation fluid that migrated from the decompression site in the spinal canal. Two of these 19 surgeons reported 1 case associated with a recognized incidental durotomy and another with postoperative paralysis. CONCLUSIONS: Patients should be educated preoperatively about the risk of irrigated spinal endoscopy. Although rare, intracranial blood, hydrocephalus, headaches, neck pain, seizures, and more severe complications, including life-threatening autonomic dysreflexia with hypertension, may arise if irrigation fluid enters the spinal canal or the dural sac and migrates from the endoscopic site along the neural axis rostrally. Experienced endoscopic spine surgeons suspect a correlation between durotomy and irrigation-related extra- and intradural pressure equalization that could be problematic if associated with high volumes of irrigation fluid LEVEL OF EVIDENCE: 3.

Endoscopic Posterior Cervical Decompression for Ossified Posterior Longitudinal Ligament: A Technical Note.

BACKGROUND: Ossification of the posterior longitudinal ligament (OPLL) may cause cervical myelopathy. In its multilevel form, it may not be easy to manage. Minimally invasive endoscopic posterior cervical decompression may be an alternative to traditional laminectomy surgery. METHODS: Thirteen patients with multilevel OPLL and symptomatic cervical myelopathy were treated with endoscopic spine surgery from January 2019 to June 2020. In this consecutive observational cohort study, pre- and postoperative Japanese Orthopaedic Association (JOA) score and Neck Disability Index (NDI) were analyzed at a final follow-up of 2 years postoperatively. RESULTS: There were 13 patients consisting of 3 women and 10 men. The patient's average age was 51.15 years. At the final 2-year follow-up, the JOA score improved from a preoperative value of 10.85 ± 2.91 to 14.77 ± 2.13 postoperatively (P < 0.001). The corresponding NDI scores decreased from 26.61 ± 12.88 to 11.12 ± 10.85 (P < 0.001). There were no infections, wound complications, or reoperations. CONCLUSION: Direct posterior endoscopic decompression for multilevel OPLL is feasible in symptomatic patients when executed at a high skill level. While 2-year outcomes were encouraging and on par with historic data obtained with traditional laminectomy, future studies will need to show whether any long-term shortcomings exist.

Surgeon reported practice patterns related to full endoscopic cervical decompression procedures.

BACKGROUND: The microsurgical anterior approach to the cervical spine is commonplace. Fewer surgeons perform posterior cervical microsurgical procedures on a routine basis for lack of indication, more bleeding, persistent postoperative neck pain, and risk of progressive misalignment. In comparison, the endoscopic technique is preferentially performed through the posterior approach. Many spine surgeons and even surgeons versed in lumbar endoscopy are often reluctant to consider endoscopic procedures in the cervical spine. We report the results of a surgeon survey to find out why. METHODS: A questionnaire of 10 questions was sent to spine surgeons by email and chat groups in social media networks including Facebook, WeChat, WhatsApp, and LinkedIn to collect practice pattern data about microscopic and endoscopic spine surgery in the lumbar and cervical spine. The responses were cross-tabulated by surgeons' demographic data. Pearson Chi-Square measures, Kappa statistics, and linear regression analysis of agreement or disagreement were performed by analyzing the distribution of variances using the statistical package SPSS Version 27.0. RESULTS: The survey response rate was 39.7%, with 50 of the 126 surgeons who started the survey submitting a completed questionnaire. Of the 50 surgeons, 56.2% were orthopedic, and 42% neurological surgeons. Most surgeons worked in private practice (42%). Another 26% were university-employed, 18% were in private practice affiliated with a university, and the remaining 14% were hospital employed. The majority of surgeons (55.1%) were autodidacts. The largest responding surgeon groups were between 35-44 years (38%) and between 45-54 years of age (34%). Half of the responding surgeons were routinely performing endoscopic cervical spine surgery. The other half did not perform it for the main hurdle of fear of complications (50%). Lack of appropriate mentorship was listed as second most reason (25.4%). More concerns for not performing cervical endoscopic approaches were the perception of lack of technology (20.8%) and suitable surgical indication (12.5%). Only 4.2% considered cervical endoscopy too risky. Nearly a third (30.6%) of the spine surgeons treated over 80% of their cervical spine patients with endoscopic surgeries. Most commonly performed were posterior endoscopic cervical discectomy (PECD; 52%), posterior endoscopic cervical foraminotomy (PECF; 48%), anterior endoscopic cervical discectomy (AECD; 32%), cervical endoscopic unilateral laminotomy for bilateral decompression (CE-ULBD; 30%), respectively. CONCLUSION: Cervical endoscopic spine surgery is gaining traction among spine surgeons. However, by far most surgeons performing cervical endoscopic spine surgery work in private practice and are autodidacts. This lack of a teacher to shorten the learning curve as well as fear of complications are two of the major impediments to the successful implementation of cervical endoscopic procedures.

Full-Endoscopic Lumbar Discectomy Approach Selection: A Systematic Review and Proposed Algorithm.

STUDY DESIGN: A systematic review of the literature to develop an algorithm formulated by key opinion leaders. OBJECTIVE: This study aimed to analyze currently available data and propose a decision-making algorithm for full-endoscopic lumbar discectomy for treating lumbar disc herniation (LDH) to help surgeons choose the most appropriate approach [transforaminal endoscopic lumbar discectomy (TELD) or interlaminar endoscopic lumbar discectomy (IELD)] for patients. SUMMARY OF BACKGROUND DATA: Full-endoscopic discectomy has gained popularity in recent decades. To our knowledge, an algorithm for choosing the proper surgical approach has never been proposed. MATERIALS AND METHODS: A systematic review of the literature using PubMed and MeSH terms was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Patient samples included patients with LDH treated with full-endoscopic discectomy. The inclusion criteria were interventional research (randomized and nonrandomized trials) and observation research (cohort, case-control, case series). Exclusion criteria were case series and technical reports. The criteria used for selecting patients were grouped and analyzed. Then, an algorithm was generated based on these findings with support and reconfirmation from key expert opinions. Data on overall complications were collected. Outcome measures included zone of herniation, level of herniation, and approach (TELD or IELD). RESULTS: In total, 474 articles met the initial screening criteria. The detailed analysis identified the 80 best-matching articles; after applying the inclusion and exclusion criteria, 53 articles remained for this review. CONCLUSIONS: The proposed algorithm suggests a TELD for LDH located in the foraminal or extraforaminal zones at upper and lower levels and for central and subarticular discs at the upper levels considering the anatomic foraminal features and the craniocaudal pathology location. An IELD is preferred for LDH in the central or subarticular zones at L4/L5 and L5/S1, especially if a high iliac crest or high-grade migration is found.

Biomechanical limitations of partial pediculectomy in endoscopic spine surgery.

BACKGROUND CONTEXT: Transforaminal endoscopic decompression is an emerging minimally invasive surgical technique in spine surgery. The biomechanical effects and limitations of resections associated with this technique are scarce. PURPOSE: The objective of this study was to analyze the effects of three different extents of reduction at the craniomedial pedicle (10%, 25%, and 50%) and to compare them with the intact native side. In addition, the influence of bone quality on the resistance of the pedicle after reduction was investigated. STUDY DESIGN: Biomechanical cadaveric study. METHODS: Thirty lumbar vertebrae originating from six fresh frozen cadavers were tested under uniaxial compression load in a ramp-to-failure test: (1) the reduced pedicle on one side, and (2) the native pedicle on the other side. Of the 30 lumbar vertebrae, ten were assigned to each reduction group (10%, 25%, and 50%). RESULTS: On the intact side, the median axial compression force to failure was 593 N (442.4-785.8). A reduction of the pedicle by 10% of the cross-sectional area resulted in a decrease of the axial load resistance by 4% to 66% compared to the intact opposite side (p=.046). The median compression force to failure was 381.89 N (range: 336-662.1). A reduction by 25% resulted in a decrease of 7% to 71% (p=.001). The median compression force to failure was 333 N (265.1-397.3). A reduction by 50% resulted in a decrease of 39% to 90% (p<.001). The median compression force to failure was 200.9 N (192.3-283.9). At 10% pedicle reduction, the Hounsfield units (HU) value and the absolute force required to generate a pedicle fracture showed significant correlations (ρ=.872; p=.001). At 25%, a positive correlation between the two variables could still be identified (ρ=.603; p=.065). At 50%, no correlation was found (ρ=-.122; p=.738). CONCLUSION: Resection of the inner, upper part of the pedicle significantly reduces the axial resistance force of the pedicle until a fracture occurs. CLINICAL SIGNIFICANCE: The extent of pedicle reduction itself plays only a limited role: once the cortical bone in the pedicle region is compromised, significant loss of resistance to loading must be anticipated.

Biomechanics of Transforaminal Endoscopic Approaches.

STUDY DESIGN: Biomechanical cadaveric study. OBJECTIVE: The aim of this study was to compare the effect of transforaminal endoscopic approaches with open decompression procedures. SUMMARY OF BACKGROUND DATA: Clinical studies have repeatedly highlighted the benefits of endoscopic decompression, however, the biomechanical effects of endoscopic approaches (with and without injury to the disk) have not been studied up to now. MATERIALS AND METHODS: Twelve spinal segments originating from four fresh-frozen cadavers were biomechanically tested in a load-controlled endoscopic transforaminal approach study. Segmental range of motion (ROM) after endoscopic approach was compared with segmental ROM after (1) microsurgical decompression with unilateral laminotomy and (2) midline decompression with bilateral laminotomy. In the intact state and after decompression, the segments were loaded in flexion-extension (FE), lateral shear (LS), lateral bending (LB), anterior shear (AS), and axial rotation (AR). RESULTS: Vertebral segment ROM was comparable between the two endoscopic transforaminal approaches. However, there was a-statistically nonsignificant-trend for a larger ROM after accessing via the inside-out technique: FE: +3% versus +7%, P =0.484; LS: +1% versus +12%, P =0.18; LB: +0.6% versus +9%, P =0.18; AS: +2% versus +11%, P =0.31; AR: -4% versus +5%, P =0.18. No significant difference in vertebral segment ROM was seen between the transforaminal endoscopic approaches and open unilateral decompression. Vertebral segment ROM was significantly smaller with the transforaminal endoscopic approaches compared with midline decompression for almost all loading scenarios: FE: +4% versus +17%, P =0.005; AS: +6% versus 21%, P =0.007; AR: 0% versus +24%, P =0.002. CONCLUSION: The transforaminal endoscopic intracanal technique preserves the native ROM of lumbar vertebral segments and shows a trend toward relative biomechanical superiority over the inside-out technique and open decompression procedures.

Surgery for Glioblastoma: Impact of the Combined Use of 5-Aminolevulinic Acid and Intraoperative MRI on Extent of Resection and Survival.

BACKGROUND: There is rising evidence that in glioblastoma (GBM) surgery an increase of extent of resection (EoR) leads to an increase of patient's survival. Based on histopathological assessments tumor depiction of Gd-DTPA enhancement and 5-aminolevulinic-acid-fluorescence (5-ALA) might be synergistic for intraoperative resection control. OBJECTIVE: To assess impact of additional use of 5-ALA in intraoperative MRI (iMRI) assisted surgery of GBMs on extent of resection (EoR), progression free survival (PFS) and overall survival (OS). METHODS: We prospectively enrolled 33 patients with GBMs eligible for gross-total-resection(GTR) and performed a combined approach using 5-ALA and iMRI. As a control group, we performed a retrospective matched pair assessment, based on 144 patients with iMRI-assisted surgery. Matching criteria were, MGMT promotor methylation, recurrent surgery, eloquent location, tumor size and age. Only patients with an intended GTR and primary GBMs were included. We calculated Kaplan Mayer estimates to compare OS and PFS using the Log-Rank-Test. We used the T-test to compare volumetric results of EoR and the Chi-Square-Test to compare new permanent neurological deficits (nPND) and general complications between the two groups. RESULTS: Median follow up was 31 months. No significant differences between both groups were found concerning the matching criteria. GTR was achieved significantly more often (p <0.010) using 5-ALA&iMRI (100%) compared to iMRI alone (82%). Mean EoR was significantly (p<0.004) higher in 5-ALA&iMRI-group (99.7%) than in iMRI-alone-group (97.4%) Rate of complications did not differ significantly between groups (21% iMRI-group, 27%5-ALA&iMRI-group, p<0.518). nPND were found in 6% in both groups. Median PFS (6 mo resp.; p<0.309) and median OS (iMRI:17 mo; 5-ALA&iMRI-group: 18 mo; p<0.708)) were not significantly different between both groups. CONCLUSION: We found a significant increase of EoR when combining 5-ALA&iMRI compared to use of iMRI alone. Maximizing EoR did not lead to an increase of complications or neurological deficits if used with neurophysiological monitoring in eloquent lesions. No final conclusion can be drawn whether a further increase of EoR benefits patient's progression free survival and overall survival.

Cervical spondylodiscitis--a clinical analysis of surgically treated patients and review of the literature.

OBJECTIVE: The aim of this study was to analyze our clinical and neurological results of surgically treated patients suffering from cervical spondylodiscitis with focusing particularly on the surgical methods used and to review the literature. PATIENTS AND METHODS: We present a series of 21 patients operated with cervical spondylodiscitis between 1998 and 2011. Basic demographic data, comorbidities, the radiological segments involved, the surgical strategy with special consideration of the material used and the clinical outcome were evaluated retrospectively. RESULTS: The mean age of 6 female and 12 male patients was 65 years (range 28-89 years). The mean follow-up was 3.7 years ranging between 4 weeks and 9 years. The leading symptom was neurological deficits rather than pain. The segments C 5/6 (n=8) and C 6/7 (n=7) were most frequently involved. Different surgical methods depending on the location, anatomical and pathological condition and extension of the lesion were performed. CONCLUSION: In conclusion, cervical spondylodiscitis could effectively be treated in the presented patient cohort by surgical decompression, debridement and PMMA or bone graft implants followed by long term antibiotic therapy. The presented surgical reconstruction technique with PMMA might be a feasible alternative to the use of bone graft or cages. The promising clinical results warrant future prospective studies to further investigate this technique.

Occipital nerve stimulation for intractable chronic cluster headache or migraine: a critical analysis of direct treatment costs and complications.

BACKGROUND: Occipital nerve stimulation (ONS) has been shown to be effective for selected patients with intractable headache disorders. We performed a prospective critical evaluation of complications and direct treatment costs. METHODS: Twenty-seven patients with chronic cluster headache (CCH, N = 24) or chronic migraine (CM, N = 3) underwent a trial phase with bilateral ONS and subsequent implantation of a permanent generator (IPG), if responsive to treatment according to predefined criteria. Procedural and long-term complications as well as direct treatment costs of neuromodulation therapy of ONS were recorded over a mean follow-up period of 20 months (range 5-47 months). RESULTS: Twenty-five of 27 patients (93%) responded to treatment. Twenty-one complications in 14 patients were identified, necessitating reoperation in 13 cases. Overall treatment costs were €761,043, including hardware-related costs of €506,019, costs for primary hospital care of €210,496, and complications related to hospitalization costs of €44,528. This results in a per case-based cost of €9445 for hospitalization and €18,741 for hardware costs, totaling €28,186. CONCLUSION: ONS for treatment of refractory CCH and CM is a cost-intensive treatment option with a significant complication rate. Nevertheless, patients with refractory primary headache disorders may experience substantial relief of pain attacks, and headache days, respectively.

Stimulation of the greater occipital nerve: anatomical considerations and clinical implications.

BACKGROUND: Stimulation of the greater occipital nerve has been employed for various intractable headache conditions for more than a decade. Still, prospective studies that correlate stimulation of the greater occipital nerve with outcome of patients with respect to alleviation of headache are sparsely found in literature. OBJECTIVE: To identify anatomical landmarks for a reproducible stimulation of the greater occipital nerve. For the clinical implication, the individual response to therapy of patients with refractory chronic cluster headache undergoing occipital nerve stimulation was correlated with the postoperative localization of the electrodes and with the distribution of the stimulation field. STUDY DESIGN: Prospective observational study, approved by the local research ethics board (09-4143). SETTING: University hospital, departments of neurosurgery and neurology, institute of anatomy and radiology. METHODS: Ten formaldehyde fixed human cadavers were dissected to identify the passage of the greater occipital nerve through the trapezius muscle. The distance to the external occipital protuberance was triangulated measuring the distance of the nerve from the nuchal midline and the protuberance. Between December 2008 and December 2011, 21 consecutive patients suffering from chronic cluster headache underwent surgery in terms of bilateral occipital nerve stimulation, with electrodes placed horizontally at the level of C1. The postoperative x-rays were compared with the acquired landmarks from the anatomical study. The distribution of the stimulation field was correlated to the individual response of each patient to the therapy and prospectively analyzed with regard to reduction of daily cluster attacks and relief of pain intensity at 3 months and at last follow-up. RESULTS: The greater occipital nerve crosses the trapezius muscle at a mean distance of 31 mm below the occipital external protuberance and 14 mm lateral to the midline as found in the anatomical subjects. The electrodes were targeted at this level in all of our patients and stimulated the greater occipital nerve in all patients. Eighteen of the patients (85.7%) reported a significant reduction of the frequency of their cluster attacks and/or declined intensity of pain during the attacks. Yet, 3 of 21 patients (14.3%) did not benefit from the stimulation despite an adequate spread of the stimulation over the occiput. The spread of the stimulation-induced paraesthesias over the occiput was not correlated to a reduction of cluster attacks, to the intensity of attacks, or to the response to treatment at all. LIMITATIONS: Single center non-randomized non-blinded study. CONCLUSIONS: From our study we conclude that a reproducible stimulation of the greater occipital nerve can be achieved by placing the electrodes parallel to the atlas, at about 30 mm distance to the external occipital protuberance. The response to the stimulation is not correlated to the field width of the paraesthesia. We, therefore, consider stimulation of the main trunk of the greater occipital nerve to be more important than a large field of stimulation on the occiput. Still, an individual response to the occipital nerve stimulation cannot be predicted even by optimal electrode placement.

Intra-operative high frequency ultrasound improves surgery of intramedullary cavernous malformations.

Intra-operative ultrasound (ioUS) is a very useful tool in surgery of spinal lesions. Here we focus on modern ioUS to analyze its use for localisation, visualisation and resection control in intramedullary cavernous malformations (IMCM). A series of 35 consecutive intradural lesions were operated in our hospital in a time period of 24 months using modern ioUS with a high frequency 7-15 MHz transducer and a true real time 3D transducer (both Phillips iU 22 ultrasound system). Six of those cases were treated with the admitting diagnosis of a deep IMCM (two cervical, four thoracic lesions). IoUS images were performed before and after the IMCM resection. Pre-operative and early postoperative MRI images were performed in all patients. In all six IMCM cases a complete removal of the lesion was achieved microsurgically resulting in an improved neurological status of all patients. High frequency ioUS emerged to be a very useful tool during surgery for localization and visualization. Excellent resection control by ultrasound was possible in three cases. Minor resolution of true real time 3D ioUS decreases the actual advantage of simultaneous reconstruction in two planes. High frequency ioUS is the best choice for intra-operative imaging in deep IMCM to localize and to visualize the lesion and to plan the perfect surgical approach. Additionally, high frequency ioUS is suitable for intra-operative resection control of the lesion in selected IMCM cases.

Circulating extracellular proteasome in the cerebrospinal fluid: a study on concentration and proteolytic activity.

Alterations of the intracellular ubiquitin-proteasome pathway are found in neurodegenerative and inflammatory disorders of the central nervous system, as well as in its malignancies. Inhibitory substrates of the proteasomes represent promising approaches to control autoimmune inflammations and induction of apoptosis in cancer cells. Extracellular circulating proteasomes are positively correlated to outcome prognosis in hematogenic neoplasias and the outcome in critically ill patients. Previously, we reported raised levels of proteolytic active 20S proteasomes in the extracellular alveolar space in patients with acute respiratory distress syndrome (ARDS). For the cerebrospinal fluid, we assumed that extracellular circulating proteasomes with enzymatic activity can be found, too. Cerebrospinal fluid (CSF) samples of twenty-six patients (14 females, 12 males), who underwent diagnostic spinal myelography, were analyzed for leukocyte cell count, total protein content, lactate and interleukine-6 (Il-6) concentrations. CSF samples were analyzed for concentration and enzymatic activity of extracellular 20S proteasomes (fluorescenic substrate cleavage; femtokatal). Blood samples were analyzed with respect to concentration of extracellular circulating proteasomes. Choroidal plexus was harvested at autopsies and examined with immunoelectron microscopy (EM) for identification of possible transportation mechanisms. Statistical analysis was performed using SPSS (18.0.3). In all patients, extracellular proteasome was found in the CSF. The mean concentration was 24.6 ng/ml. Enzymatic activity of the 20S subunits of proteasomes was positively identified by the fluorescenic subtrate cleavage at a mean of 8.5 fkat/ml. Concentrations of extracellular proteasomes in the CSF, total protein content and Il-6 were uncorrelated. Immunoelectron microscopy revealed merging vesicles of proteasomes with the outer cell membrane suggestive of an exozytic transport mechanism. For the first time, extracellular circulating 20S proteasome in the CSF of healthy individuals is identified and its enzymatic activity detected. A possible exozytic vesicle-bond transportation mechanism is suggested by immunoelectron microscopy. The present study raises more questions on the function of extracellular proteasome in the CSF and encourages further studies on the role of extracellular protesomes in pathological conditions of the central nervous system (tumor lesions and inflammatory processes).