Upward movement of cerebrospinal fluid in obstructive hydrocephalus-revision of an old concept.

PURPOSE: The specific pathophysiological processes in many forms of obstructive hydrocephalus (HC) are still unclear. Current concepts of cerebrospinal fluid (CSF) dynamics presume a constant downward flow from the lateral ventricles towards subarachnoid spaces, which are in contrast to neurosurgical observations and findings of MRI flow studies. The aim of our study was to analyze CSF movements in patients with obstructive HC by neuroendoscopic video recordings, X-ray studies, and MRI. METHODS: One hundred seventeen pediatric patients with obstructive HC who underwent neuroendoscopy in our center were included. Video recordings were analyzed in 85 patients. Contrast-enhanced X-rays were conducted during surgery prior to intervention in 75 patients, and flow void signals on pre-operative MRI could be evaluated in 110 patients. RESULTS: In 83.5% of the video recordings, CSF moved upwards synchronous to inspiration superimposed by cardiac pulsation. Application of contrast medium revealed a flow delay in 52% of the X-ray studies prior to neurosurgery, indicating hindered CSF circulation. The appearances and shapes of flow void signals in 88.2% of the pre-operative MRI studies suggested valve-like mechanisms and entrapment of CSF. CONCLUSIONS: Neuroendoscopic observations in patients with obstructive HC revealed upward CSF movements and the corresponding MRI signs of trapped CSF in brain cavities. These observations are in contrast to the current pathophysiological concept of obstructive HC. However, recent real-time flow MRI studies demonstrated upward movement of CSF, hence support our clinical findings. The knowledge of cranial-directed CSF flow expands our understanding of pathophysiological mechanisms in HC and is the key to effective treatment.

Robot guidance for percutaneous minimally invasive placement of pedicle screws for pyogenic spondylodiscitis is associated with lower rates of wound breakdown compared to conventional fluoroscopy-guided instrumentation.

Postoperative wound healing can pose a problem in patients undergoing instrumented surgery for pyogenic spondylodiscitis. Robotic guidance allows the minimally invasive placement of pedicle screws in the thoracolumbar spine. We assessed whether using this technique to perform minimally invasive surgery had an impact on wound healing in patients with pyogenic spondylodiscitis when compared to conventional open fluoroscopy-guided surgery. We reviewed charts of 206 consecutive patients who underwent instrumentation for pyogenic spondylodiscitis. The need for wound revision was the primary outcome measure. Patient variables and comorbidities as well as surgical technique (robotic versus fluoroscopy-guided) were analyzed. We also compared fluoroscopy times between the two groups. Multivariate regression analysis was performed to identify predictors of wound breakdown. A total of 206 patients underwent surgery for spondylodiscitis. Robotic surgical assistance was used for percutaneous instrumentation in 47.6% of cases (n = 98). Wound healing problems requiring revision occurred in 30 out of 206 patients (14.6%). Univariate analysis revealed a potential association of wound breakdown with (1) robotic technique, (2) age > 70 years, and (3) the presence of methicillin-resistant Staphylococcus aureus. After multivariate correction however, only robotic technique retained significance with an odds ratio of 0.39 (CI 95% 0.16-0.94; p = 0.035). Wound revision was required in eight out of 98 patients (8.1%) in the robot group and 22/108 (20%) in the conventional surgery group. Fluoroscopy times were significantly lower in the robot group with a mean of 123 ± 86 s in comparison with a mean of 157 ± 99 s in the conventional group (p = 0.014). While initially designed to improve the accuracy of pedicle screw placement, robot-assisted minimally invasive technique had a tangible effect on both radiation exposure and the rate of wound breakdown in patients with pyogenic spondylodiscitis in our large single-center study.

Robotic versus fluoroscopy-guided pedicle screw insertion for metastatic spinal disease: a matched-cohort comparison.

OBJECTIVE Robot-guided pedicle screw placement is an established technique for the placement of pedicle screws. However, most studies have focused on degenerative disease. In this paper, the authors focus on metastatic spinal disease, which is associated with osteolysis. The associated lack of dense bone may potentially affect the automatic recognition accuracy of radiography-based surgical assistance systems. The aim of the present study is to compare the accuracy of the SpineAssist robot system with conventional fluoroscopy-guided pedicle screw placement for thoracolumbar metastatic spinal disease. METHODS Seventy patients with metastatic spinal disease who required instrumentation were included in this retrospective matched-cohort study. All 70 patients underwent surgery performed by the same team of experienced surgeons. The decision to use robot-assisted or fluoroscopy-guided pedicle screw placement was based the availability of the robot system. In patients who underwent surgery with robot guidance, pedicle screws were inserted after preoperative planning and intraoperative fluoroscopic matching. In the "conventional" group, anatomical landmarks and anteroposterior and lateral fluoroscopy guided placement of the pedicle screws. The primary outcome measure was the accuracy of screw placement on the Gertzbein-Robbins scale. Grades A and B (< 2-mm pedicle breach) were considered clinically acceptable, and all other grades indicated misplacement. Secondary outcome measures included an intergroup comparison of direction of screw misplacement, surgical site infection, and radiation exposure. RESULTS A total of 406 screws were placed at 206 levels. Sixty-one (29.6%) surgically treated levels were in the upper thoracic spine (T1-6), 74 (35.9%) were in the lower thoracic spine, and the remaining 71 (34.4%) were in the lumbosacral region. In the robot-assisted group (Group I; n = 35, 192 screws), trajectories were Grade A or B in 162 (84.4%) of screws. The misplacement rate was 15.6% (30 of 192 screws). In the conventional group (Group II; n = 35, 214 screws), 83.6% (179 of 214) of screw trajectories were acceptable, with a misplacement rate of 16.4% (35 of 214). There was no difference in screw accuracy between the groups (chi-square, 2-tailed Fisher's exact, p = 0.89). One screw misplacement in the fluoroscopy group required a second surgery (0.5%), but no revisions were required in the robot group. There was no difference in surgical site infections between the 2 groups (Group I, 5 patients [14.3%]; Group II, 8 patients [22.9%]) or in the duration of surgery between the 2 groups (Group I, 226.1 ± 78.8 minutes; Group II, 264.1 ± 124.3 minutes; p = 0.13). There was also no difference in radiation time between the groups (Group I, 138.2 ± 73.0 seconds; Group II, 126.5 ± 95.6 seconds; p = 0.61), but the radiation intensity was higher in the robot group (Group I, 2.8 ± 0.2 mAs; Group II, 2.0 ± 0.6 mAs; p < 0.01). CONCLUSIONS Pedicle screw placement for metastatic disease in the thoracolumbar spine can be performed effectively and safely using robot-guided assistance. Based on this retrospective analysis, accuracy, radiation time, and postoperative infection rates are comparable to those of the conventional technique.

Accuracy of robot-guided versus freehand fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery.

OBJECTIVE The quest to improve the safety and accuracy and decrease the invasiveness of pedicle screw placement in spine surgery has led to a markedly increased interest in robotic technology. The SpineAssist from Mazor is one of the most widely distributed robotic systems. The aim of this study was to compare the accuracy of robot-guided and conventional freehand fluoroscopy-guided pedicle screw placement in thoracolumbar surgery. METHODS This study is a retrospective series of 169 patients (83 women [49%]) who underwent placement of pedicle screw instrumentation from 2007 to 2015 in 2 reference centers. Pathological entities included degenerative disorders, tumors, and traumatic cases. In the robot-assisted cohort (98 patients, 439 screws), pedicle screws were inserted with robotic assistance. In the freehand fluoroscopy-guided cohort (71 patients, 441 screws), screws were inserted using anatomical landmarks and lateral fluoroscopic guidance. Patients treated before 2009 were included in the fluoroscopy cohort, whereas those treated since mid-2009 (when the robot was acquired) were included in the robot cohort. Since then, the decision to operate using robotic assistance or conventional freehand technique has been based on surgeon preference and logistics. The accuracy of screw placement was assessed based on the Gertzbein-Robbins scale by a neuroradiologist blinded to treatment group. The radiological slice with the largest visible deviation from the pedicle was chosen for grading. A pedicle breach of 2 mm or less was deemed acceptable (Grades A and B) while deviations greater than 2 mm (Grades C, D, and E) were classified as misplacements. RESULTS In the robot-assisted cohort, a perfect trajectory (Grade A) was observed for 366 screws (83.4%). The remaining screws were Grades B (n = 44 [10%]), C (n = 15 [3.4%]), D (n = 8 [1.8%]), and E (n = 6 [1.4%]). In the fluoroscopy-guided group, a completely intrapedicular course graded as A was found in 76% (n = 335). The remaining screws were Grades B (n = 57 [12.9%]), C (n = 29 [6.6%]), D (n = 12 [2.7%]), and E (n = 8 [1.8%]). The proportion of non-misplaced screws (corresponding to Gertzbein-Robbins Grades A and B) was higher in the robot-assisted group (93.4%) than the freehand fluoroscopy group (88.9%) (p = 0.005). CONCLUSIONS The authors' retrospective case review found that robot-guided pedicle screw placement is a safe, useful, and potentially more accurate alternative to the conventional freehand technique for the placement of thoracolumbar spinal instrumentation.

Unskilled unawareness and the learning curve in robotic spine surgery.

BACKGROUND: Robotic assistance for the placement of pedicle screws has been established as a safe technique. Nonetheless rare instances of screw misplacement have been reported.The aim of the present retrospective study is to assess whether experience and time affect the accuracy of screws placed with the help of the SpineAssist™ robot system. METHODS: Postoperative computed tomography (CT) scans of 258 patients requiring thoracolumbar pedicle screw instrumentation from 2008 to 2013 were reviewed. Overall, 13 surgeons performed the surgeries. A pedicle breach of >3 mm was graded as a misplacement. Surgeons were dichotomised into an early and experienced period in increments of five surgeries. RESULTS: In 258 surgeries, 1,265 pedicle screws were placed with the aid of the robot system. Overall, 1,217 screws (96.2 %) were graded as acceptable. When displayed by surgeon, the development of percent misplacement rates peaked between 5 and 25 surgeries in 12 of 13 surgeons. The overall misplacement rate in the first five surgeries was 2.4 % (6/245). The misplacement rate rose to 6.3 % between 11 and 15 surgeries (10/158; p = 0.20), and reached a significant peak between 16 and 20 surgeries with a rate of 7.1 % (8/112; p = 0.03). Afterwards, misplacement rates declined. CONCLUSIONS: A major peak in screw inaccuracies occurred between cases 10 and 20, and a second, smaller one at about 40 surgeries. One potential explanation could be a transition from decreased supervision (unskilled but aware) to increased confidence of a surgeon (unskilled but unaware) who adopts this new technique prior to mastering it (skilled). We therefore advocate ensuring competent supervision for new surgeons at least during the first 25 procedures of robotic spine surgery to optimise the accuracy of robot-assisted pedicle screws.

Intermittent visual field defects caused by a dilated Virchow-Robin space close to the optic radiation: Therapeutic and pathomechanical considerations.

OBJECTIVE: Virchow-Robin spaces (VRSs) are extensions of subarachnoid spaces that accompany vessels entering the brain. T2-weighted magnetic resonance imaging detects VRS in about 95 percent of patients in a recent study. VRSs are considered a normal variant with benign prognosis. Occasionally, VRS might become symptomatic causing neurological deficits depending on their location. CASE DESCRIPTION: We report the case of a 55-year-old female patient with dilated VRS presenting with visual field disturbances and cognitive deficits. The patient underwent endoscopic fenestration of a large periventricular VRS located next to the visual radiation into the posterior horn of the right lateral ventricle. During the postoperative course, visual field disturbances were resolved but cognitive deficits remained unchanged. CONCLUSION: Dilated VRSs can cause a variety of neurological deficits depending on their size and location. Therefore, patients harboring dilated VRS should undergo early close inspection and in case of progressive neurological deficits, an operative therapy should be done; as valve mechanisms can cause a reduction of size when brain scans are conducted and later lead to occurrence of severe neurological deficits during phase of dilation.

Misdirection of regenerating motor axons after nerve injury and repair in the rat sciatic nerve model.

Misdirection of regenerating axons is one of the factors that can explain the poor results often found after nerve injury and repair. In this study, we quantified the degree of misdirection and the effect on recovery of function after different types of nerve injury and repair in the rat sciatic nerve model; crush injury, direct coaptation, and autograft repair. Sequential tracing with retrograde labeling of the peroneal nerve before and 8 weeks after nerve injury and repair was performed to quantify the accuracy of motor axon regeneration. Digital video analysis of ankle motion was used to investigate the recovery of function. In addition, serial compound action potential recordings and nerve and muscle morphometry were performed. In our study, accuracy of motor axon regeneration was found to be limited; only 71% (+/-4.9%) of the peroneal motoneurons were correctly directed 2 months after sciatic crush injury, 42% (+/-4.2%) after direct coaptation, and 25% (+/-6.6%) after autograft repair. Recovery of ankle motion was incomplete after all types of nerve injury and repair and demonstrated a disturbed balance of ankle plantar and dorsiflexion. The number of motoneurons from which axons had regenerated was not significantly different from normal. The number of myelinated axons was significantly increased distal to the site of injury. Misdirection of regenerating motor axons is a major factor in the poor recovery of nerves that innervate different muscles. The results of this study can be used as basis for developing new nerve repair techniques that may improve the accuracy of regeneration.

Two-dimensional digital video ankle motion analysis for assessment of function in the rat sciatic nerve model.

Ankle motion analysis may provide a better method to assess function in the rat sciatic nerve model than the standard method, the sciatic functional index (SFI), but it is not widely used in experiments on nerve regeneration possibly because of complicated analysis. In this study, we investigated the practical use of a two-dimensional (2D) digital video motion analysis system. Reproducibility was investigated in normal rats. Recovery of ankle motion was analyzed after sciatic, tibial, and peroneal nerve crush injury. Results were compared with scores for the SFI. Results were not significantly different from animal-to-animal and day-to-day. Interobserver variability also was small. In the analysis of recovery after separate nerve crush injuries, subtle differences in ankle plantar flexion and dorsiflexion could be detected. The method was also more sensitive than the SFI: whereas scores for the SFI had returned to normal 4 weeks after sciatic nerve crush injury, the ankle angle at mid-stance was still significantly different from that in sham-operated animals 6 weeks after the injury. 2D digital video ankle motion analysis is a practical and sensitive method to assess function in the rat sciatic nerve model.