Michael Stoffel

Accuracy of robot-assisted placement of lumbar and sacral pedicle screws: a prospective randomized comparison to conventional freehand screw implantation.

Study Design. Single-center prospective randomized controlled study. Objective. To evaluate the accuracy of robot-assisted (RO) implantation of lumbar/sacral pedicle screws in comparison with the freehand (FH) conventional technique. Summary of Background Data. SpineAssist is a miniature robot for the implantation of thoracic, lumbar, and sacral pedicle screws. The system, studied in cadaver and cohort studies, revealed a high accuracy, so far. A direct comparison of the robot assistance with the FH technique is missing. Methods. Patients requiring mono- or bisegmental lumbar or lumbosacral stabilization were randomized in a 1:1 ratio to FH or RO pedicle screw implantation. Instrumentation was performed using fluoroscopic guidance (FH) or robot assistance. The primary end point screw position was assessed by a postoperative computed tomography, and screw position was classified (A: no cortical violation; B: cortical breach <2 mm; C: ≥2 mm to <4 mm; D: ≥4 mm to <6 mm; E: ≥6 mm). Secondary end points as radiation exposure, duration of surgery/planning, and hospital stay were assessed. Results. A total of 298 pedicle screws were implanted in 60 patients (FH, 152; RO, 146). Ninety-three percent had good positions (A or B) in FH, and 85% in RO. Preparation time in the operating room (OR), overall OR time, and intraoperative radiation time were not different for both groups. Surgical time for screw placement was significantly shorter for FH (84 minutes) than for RO (95 minutes). Ten RO screws required an intraoperative conversion to the FH. One FH screw needed a secondary revision. Conclusion. In this study, the accuracy of the conventional FH technique was superior to the RO technique. Most malpositioned screws of the RO group showed a lateral deviation. Attachment of the robot to the spine seems a vulnerable aspect potentially leading to screw malposition as well as slipping of the implantation cannula at the screw entrance point.

The use of dynamic O-(2-18F-fluoroethyl)-l-tyrosine PET in the diagnosis of patients with progressive and recurrent glioma

BACKGROUND We evaluated the diagnostic value of static and dynamic O-(2-[(18)F]fluoroethyl)-L-tyrosine ((18)F-FET) PET parameters in patients with progressive or recurrent glioma. METHODS We retrospectively analyzed 132 dynamic (18)F-FET PET and conventional MRI scans of 124 glioma patients (primary World Health Organization grade II, n = 55; grade III, n = 19; grade IV, n = 50; mean age, 52 ± 14 y). Patients had been referred for PET assessment with clinical signs and/or MRI findings suggestive of tumor progression or recurrence based on Response Assessment in Neuro-Oncology criteria. Maximum and mean tumor/brain ratios of (18)F-FET uptake were determined (20-40 min post-injection) as well as tracer uptake kinetics (ie, time to peak and patterns of the time-activity curves). Diagnoses were confirmed histologically (95%) or by clinical follow-up (5%). Diagnostic accuracies of PET and MR parameters for the detection of tumor progression or recurrence were evaluated by receiver operating characteristic analyses/chi-square test. RESULTS Tumor progression or recurrence could be diagnosed in 121 of 132 cases (92%). MRI and (18)F-FET PET findings were concordant in 84% and discordant in 16%. Compared with the diagnostic accuracy of conventional MRI to diagnose tumor progression or recurrence (85%), a higher accuracy (93%) was achieved by (18)F-FET PET when a mean tumor/brain ratio ≥2.0 or time to peak <45 min was present (sensitivity, 93%; specificity, 100%; accuracy, 93%; positive predictive value, 100%; P < .001). CONCLUSION Static and dynamic (18)F-FET PET parameters differentiate progressive or recurrent glioma from treatment-related nonneoplastic changes with higher accuracy than conventional MRI.

Endoscopic transnasal resection of the odontoid: case series and clinical course

The transoral route is the gold standard for odontoid resection. Results are satisfying though surgery can be challenging for patients and surgeons due to its invasiveness. A less invasive transnasal approach could provide a sufficient extent of resection with less collateral damage. The technique of transnasal endoscopic odontoid resection is demonstrated by a case series of three patients. A fully endoscopic transnasal odontoid resection was conducted by use of CT-based neuronavigation. A complete odontoid resection succeeded in all patients. Symptoms such as dysarthria, swallowing disturbance, salivary retention, myelopathic gait disturbances, neck pain, and tetraparesis improved in all patients markedly. Transnasal endoscopic odontoid resection is a feasible alternative to the transoral technique. It leaves the oropharynx intact, which could result in lower approach related complications especially in patients with bulbar symptoms.

Utility of diffusion tensor-imaged (DTI) motor fiber tracking for the resection of intracranial tumors near the corticospinal tract

PurposeTreatment of intracranial tumors near the corticospinal tract remains a surgical challenge. Several technical tools to map and monitor the motor tract have been implemented. The present study aimed to assess the utility of diffusion tensor imaging (DTI) fiber tracking in the surgical treatment of motor eloquent tumors at our institution.MethodsPatients operated for intracranial tumors close to the motor tract with the use of intraoperative image guidance including DTI fiber tracking of the corticospinal tract and intraoperative motor evoked potential (MEP) monitoring were analyzed. The intraoperative utility of fiber tracking data was analyzed. Furthermore, preoperative MRI scans with and without motor fiber tracking were reevaluated post hoc for tumor relation to the motor tract, estimated resectability, and best approach. Thereby, the utility of fiber tracking in surgical planning was assessed.ResultsNineteen patients were analyzed. The estimation of tumor localization in relation to the motor tract and of resectability was not influenced by fiber tracking in any of the cases. Only in one single case did evaluating surgeons change their surgical approach after the addition of the fiber tracking data. In all cases, fiber tracking included in image guidance did not change the intraoperative strategy, while MEP monitoring did.ConclusionsDTI fiber tracking did not influence the surgical planning or the intraoperative course. However, it is still used at our institution due to its ease in acquisition and its potential impact in a larger series. Furthermore, more experience with this technique is required to lead to a technical improvement.

Minimally invasive decompression of chronic subdural haematomas using hollow screws: efficacy and safety in a consecutive series of 320 cases.

Dear Editor, We thank Kolias et al. for their thoughtful comments on our publication. We actually concur with almost all points, especially that there is a need to generate level I evidence for this very common neurosurgical disorder. A randomised controlled trial will answer a lot of the questions raised in their comment. For the time being most things remain speculative and there are many options to treat chronic subdural haematomas. The one described by us is just one of them, which we prefer as first line treatment, primarily for its ease. We think we have shown approximately equivalent safety and efficacy in comparison to other methods. This was our goal. No less, no more.

Prospective Study on Salivary Evening Melatonin and Sleep before and after Pinealectomy in Humans.

Melatonin is secreted systemically from the pineal gland maximally at night but is also produced locally in many tissues. Its chronobiological function is mainly exerted by pineal melatonin. It is a feedback regulator of the main circadian pacemaker in the hypothalamic suprachiasmatic nuclei and of many peripheral oscillators. Although exogenous melatonin is approved for circadian rhythm sleep disorders and old-age insomnia, research on endogenous melatonin in humans is hindered by the great interindividual variability of its amount and circadian rhythm. Single case studies on pinealectomized patients report on disrupted but also hypersomnic sleep. This is the first systematic prospective report on sleep with respect to pinealectomy due to pinealocytoma World Health Organization grade I without chemo- or radiotherapy. Before and after pinealectomy, 8 patients completed questionnaires on sleep quality and circadian rhythm (Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, and Morningness-Eveningness Questionnaire), 2 nights of polysomnography, salivary evening melatonin profiles, and qualitative assessment of 2 weeks of actigraphy and sleep logs. Six patients were assessed retrospectively up to 4 years after pinealectomy. Before pinealectomy, all but 1 patient showed an evening melatonin rise typical for indifferent chronotypes. After pinealectomy, evening saliva melatonin was markedly diminished, mostly below the detection limit of the assay (0.09 pg/mL). No systematic change in subjective sleep quality or standard measures of polysomnography was found. Mean pre- and postoperative sleep efficiency was 94% and 95%, and mean sleep-onset latency was 21 and 17 min, respectively. Sleep-wake rhythm during normal daily life did not change. Retrospective patients had a reduced sleep efficiency (90%) and more stage changes, although this was not significantly different from prospective patients. In conclusion, melatonin does seem to have a modulatory, not a regulatory, effect on standard measures of sleep. Study output is limited by small sample size and because only evening melatonin profiles were assessed.

Experience with a gravitational valve in the management of symptomatic overdrainage in children with shunts

OBJECT Symptomatic overdrainage in children with shunt-treated hydrocephalus represents one of the more difficult shunt-related diseases and may require repeated surgery. Gravity-assisted valve design has become a standard device to avoid overdrainage in many European pediatric hydrocephalus centers. However, the use of a gravitational valve for relieving symptoms associated with overdrainage has not yet been addressed. The goal of this study was to evaluate the effectiveness of a gravitational valve in the treatment of symptomatic overdrainage in children with shunts. METHODS Seventeen children with an adjustable shunt system and symptomatic overdrainage were treated by insertion of a gravitational valve. Clinical and radiological outcome were monitored for a minimum of 12 months after surgery. RESULTS Implantation of a gravitational valve resulted in either resolution (n = 12) or improvement (n = 5) of the symptoms. In 1 patient, symptoms remained almost unchanged and the gravitational valve had to be upgraded, resulting in resolution of the symptoms. During follow-up, the pressure setting of the adjustable differential pressure valve had to be changed in 7 patients. CONCLUSIONS The gravitational valve was effective in improving symptomatic overdrainage in the majority of patients in the present study. Because the ideal pressure setting for a given patient is hard to determine a priori, adjustable valve systems appear to be beneficial.

Sleep disturbance after pinealectomy in patients with pineocytoma WHO°I

BackgroundBecause the pineal gland produces melatonin, it is suggested to be involved in the regulation of sleep and circadian rhythm, though there is scant proof of this. Tumors of the pineal gland are rare and various in terms of histological and biological malignancy. We evaluated the occurrence of subjective sleep disturbances in nine patients who underwent a pinealectomy due to pineocytoma WHO°I without additional therapy.MethodsPatients with intracranial low-grade lesions and patients without a craniotomy who underwent a microscopic lumbar discectomy were matched to our study group by gender, age, and date of surgery. We used standardized sleep questionnaires on sleepiness during the daytime, sleep disturbances, and general pathologic sleep patterns.ResultsPatients who underwent a craniotomy either without a pinealectomy (7.2 ± 2.0 points) or with a pinealectomy experienced increased sleep disturbances (6.6 ± 1.3 points) compared to patients who had a lumbar discectomy (2.8 ± 0.4 points), according to the Pittsburgh Sleep Quality Index (PSQI) (p < 0.05). Moreover, sleep disturbances as measured by the insomnia severity index (ISI) were most pronounced in patients who underwent a craniotomy without a pinealectomy (10.4 ± 3.1 points) compared to patients who underwent a pinealectomy or discectomy (5.9 ± 1.9 and 3.3 ± 1.3 points).ConclusionsPinealectomy itself did not cause specific sleep impairment, but craniotomy in general did. This interesting and clinically relevant finding needs further investigation.

Debridement and fusion with polyetheretherketone implants in purulent spondylodiscitis: a clinical experience with nine patients

Dear Editor, Spinal infections occur with increasing incidence. Conservative, nonoperative treatment, including external immobilisation with bed rest or orthesis and long-term antibiotic therapy, is still considered the first tier therapy by some authors, but should, in our view, be reserved for beginning slight spondylodiscitis, patients suffering from catecholaminedependent sepsis until improvement of general health, and patients with significant co-morbidities, which exclude surgery, e.g. vital indications for anticoagulation. Long bedrest implies complications like muscle atrophy, pneumonia, lung embolism and acceleration of osteoporosis. Above that, it leads to a “clinical success” in only 75% of patients. In cases of neurological deficits and/or segmental instability, surgical treatment, including decompression and stabilisation, is required. There is no significant evidence for the benefit of postoperative bracing in spondylodiscitis. In case of sparse bone damage, there is no significance for an additional external immobilisation after the surgery to be beneficial for the recovery. As yet, there is plenty of experience with autologous bone or titanium implants, but only scarce experience with the use of polyetheretherketone (PEEK) implants in the surgical treatment of spinal infections. Both Mondorf et al. [1] and Walter et al. [3] described their clinical experience with single-step surgery using PEEK implants for the cervical spine in five patients suffering from spondylodiscitis with good outcome and complete recovery from the infection in all cases [1, 3]. Pee at al. [2] described the use of PEEK implants in the surgical treatment of ten patients presenting with lumbar spondylodiscitis with comparable satisfactory findings. We present a consecutive retrospective series of nine patients [three cervical (monosegmental) and six lumbar (three monosegmental and three bisegmental spondylodiscitis)] treated in our institution between January 2006 and May 2010 consisting of clinical evaluation, standardised questionnaires [EQ-5D, SF-36 and oswestry disability index (ODI)], magnetic resonance imaging (MRI) and computerized tomography (CT) scans for assessment of instability, as well as C-reactive protein (CRP) levels collected during the perioperative period and the outpatient follow-ups (mean: 13 months). This series represents currently our complete experience with PEEK in this disease. The mean age was 61.7 years (min–max 47–81) for cervical spondylodiscitis and 65.8 years (min–max 60– 82) for lumbar spondylodiscitis. All patients had significant neck/back pain, one patient complained of brachialgia. Two cervical and two lumbar spondylodiscitis patients suffered from infection with significant epidural mass and sensorimotor deficits, one of the cervical patients even with tetraplegia and bowel/bladder dysfunction. Two lumbar patients presented a septic disease with significantly increased infection parameters, especially the CRP. One cervical and three lumbar patients had additional further A. Brase (*) : F. Ringel :C. Stuer : B. Meyer :M. Stoffel Department of Neurosurgery, Klinikum rechts der Isar, University of Technology Munich, Ismaninger Strasse 22, 81675 Munich, Germany e-mail: agnes.podlewski@lrz.tum.de

Norepinephrine and cerebral blood flow regulation in patients with arteriovenous malformations

OBJECTIVE To test the hypothesis that the sympathetic nervous system plays a role in cerebral blood flow regulation in patients with arteriovenous malformations (AVM). METHODS Cortical interstitial norepinephrine was measured by means of microdialysis, regional cerebral blood flow was measured by a thermal diffusion technique, and regional oxygen saturation (SO2) was measured by microspectrophotometry in 12 patients harboring cerebral AVMs (AVM group) and in 15 patients with deep-seated nonvascular lesions (control group) before and after resection. Measurements were compared according to groups and times of measurements. All values are given as means +/- standard deviation. RESULTS Cortical regional SO2 increased significantly (P < 0.05) in both groups after surgery (AVM group: presurgery 52.4 +/- 12.5% SO2, postsurgery 71.4 +/- 7.4% SO2; control group: presurgery 57.1 +/- 8.4% SO2, postsurgery 69.9 +/- 8.7% SO2), whereas regional cerebral blood flow increased only in the AVM group (AVM group: presurgery 18.9 +/- 6.6 ml/100 g/min, postsurgery 26.2 +/- 6.9 ml/100 g/min; control group: presurgery 20.1 +/- 7.6 ml/100 g/min, postsurgery 19.4 +/- 7.8 ml/100 g/min). Norepinephrine concentrations were significantly lower in the AVM group as compared with the control group before surgery. Although there was no significant difference between pre- and postsurgery conditions in the AVM group, the norepinephrine level of the control group was significantly lower after surgery (AVM group: presurgery 3.3 +/- 1.2 nmol/L, postsurgery 2.9 +/- 1.7 nmol/L; control group: presurgery 5.4 +/- 1.4 nmol/L, postsurgery 4.2 +/- 1.1 nmol/L). CONCLUSION Chronically lowered perfusion pressure seems to induce the hypothesized adaptive down-regulation of sympathetic nervous system activity, yet protective up-regulation after a sudden elevation of cerebral perfusion pressure after AVM excision could not be shown in this study.