Evaluation of 3D C-Arm Fluoroscopy versus Diagnostic CT for Deep Brain Stimulation Stereotactic Registration and Post-Operative Lead Localization.

INTRODUCTION: DBS efficacy depends on accuracy. CT-MRI fusion is established for both stereotactic registration and electrode placement verification. The desire to streamline DBS workflows, reduce operative time, and minimize patient transfers has increased interest in portable imaging modalities such as the Medtronic O-arm® and mobile CT. However, these remain expensive and bulky. 3D C-arm fluoroscopy (3DXT) units are a smaller and less costly alternative, albeit incompatible with traditional frame-based localization and without useful soft tissue resolution. We aimed to compare fusion of 3DXT and CT with pre-operative MRI to evaluate if 3DXT-MRI fusion alone is sufficient for accurate registration and reliable targeting verification. We further assess DBS targeting accuracy using a 3DXT workflow and compare radiation dosimetry between modalities. METHODS: Patients underwent robot-assisted DBS implantation using a workflow incorporating 3DXT which we describe. Two intra-operative 3DXT spins were performed for registration and accuracy verification followed by conventional CT post-operatively. Post-operative 3DXT and CT images were independently fused to the same pre-operative MRI sequence and co-ordinates generated for comparison. Registration accuracy was compared to 15 consecutive controls who underwent CT-based registration. Radial targeting accuracy was calculated and radiation dosimetry recorded. RESULTS: Data were obtained from 29 leads in 15 consecutive patients. 3DXT registration accuracy was significantly superior to CT with mean error 0.22 ± 0.03 mm (p < 0.0001). Mean Euclidean electrode tip position variation for CT to MRI versus 3DXT to MRI fusion was 0.62 ± 0.40 mm (range 0.0 mm-1.7 mm). In comparison, direct CT to 3DXT fusion showed electrode tip Euclidean variance of 0.23 ± 0.09 mm. Mean radial targeting accuracy assessed on 3DXT was 0.97 ± 0.54 mm versus 1.15 ± 0.55 mm on CT with differences insignificant (p = 0.30). Mean patient radiation doses were around 80% lower with 3DXT versus CT (p < 0.0001). DISCUSSION: Mobile 3D C-arm fluoroscopy can be safely incorporated into DBS workflows for both registration and lead verification. For registration, the limited field of view requires the use of frameless transient fiducials and is highly accurate. For lead position verification based on MRI co-registration, we estimate there is around a 0.4 mm discrepancy between lead position seen on 3DXT versus CT when corrected for brain shift. This is similar to that described in O-arm® or mobile CT series. For units where logistical or financial considerations preclude the acquisition of a cone beam CT or mobile CT scanner, our data support portable 3D C-arm fluoroscopy as an acceptable alternative with significantly lower radiation exposure.

Seeing Is Believing: Photon Counting Computed Tomography Clearly Images Directional Deep Brain Stimulation Lead Segments and Markers After Implantation.

BACKGROUND AND OBJECTIVES: Directional deep brain stimulation (DBS) electrodes are increasingly used, but conventional computed tomography (CT) is unable to directly image segmented contacts owing to physics-based resolution constraints. Postoperative electrode segment orientation assessment is necessary because of the possibility of significant deviation during or immediately after insertion. Photon-counting detector (PCD) CT is a relatively novel technology that enables high resolution imaging while addressing several limitations intrinsic to CT. We show how PCD CT can enable clear in vivo imaging of DBS electrodes, including segmented contacts and markers for all major lead manufacturers. MATERIALS AND METHODS: We describe postoperative imaging and reconstruction protocols we have developed to enable optimal lead visualization. PCD CT images were obtained of directional leads from the three major manufacturers and fused with preoperative 3T magnetic resonance imaging (MRI). Radiation dosimetry also was evaluated and compared with conventional imaging controls. Orientation estimates from directly imaged leads were compared with validated software-based reconstructions (derived from standard CT imaging artifact analysis) to quantify congruence in alignment and directional orientation. RESULTS: High-fidelity images were obtained for 15 patients, clearly indicating the segmented contacts and directional markers both on CT alone and when fused to MRI. Our routine imaging protocol is described. Ionizing radiation doses were significantly lower than with conventional CT. For most leads, the directly imaged lead orientations and depths corresponded closely to those predicted by CT artifact-based reconstructions. However, unlike direct imaging, the software reconstructions were susceptible to 180° error in orientation assessment. CONCLUSIONS: High-resolution photon-counting CT can very clearly image segmented DBS electrode contacts and directional markers and unambiguously determine lead orientation, with lower radiation than in conventional imaging. This obviates the need for further imaging and may facilitate anatomically tailored directional programming.

Multimodal mapping and monitoring is beneficial during awake craniotomy for intra-cranial tumours: results of a dual centre retrospective study.

BACKGROUND: The combination of awake craniotomy with multimodal neurophysiological mapping and monitoring in intra-axial tumour resection is not well described, but may have theoretical benefits which we sought to investigate. METHODS: All patients undergoing awake craniotomy for tumour resection with cortical and/or subcortical stimulation together with one or more of electrocorticography (ECoG/EEG), motor or somatosensory evoked potentials were identified from the operative records of two surgeons at two centres over a 5 year period. Patient, operative and outcome data were collated. Statistical analysis was performed to evaluate factors predictive of intra-operative seizures and surgical outcomes. RESULTS: 83 patients with a median age 50 years (18-80 years) were included. 80% had gliomas (37% low grade) and 13% metastases. Cortical mapping was negative in 35% (language areas) and 24% (motor areas). Complete or near total resection was achieved in 80% with 5% severe long-term neurological deficits. Negative cortical mapping was combined with positive subcortical mapping in 42% with no significant difference in extent of resection rates to patients undergoing positive cortical mapping (p = 0.95). Awake mapping could not be completed in 14%, but with no compromise to extent of resection (p = 0.55) or complication rates (p = 0.09). Intraoperative seizures occurred in 11% and were significantly associated with intra-operative EEG spikes (p = 0.003). CONCLUSIONS: Awake multi-modal monitoring is a safe and well tolerated technique. It provides preservation of extent of resection and clinical outcomes in cases of aborted awake craniotomy. Negative cortical mapping in combination with positive subcortical mapping was also shown to be safe, although not hitherto well described. Electrocorticography further enables the differentiation of seizure activity from true positive mapping, and the successful treatment of spikes prior to full clinical seizures occurring.

Safety and Utility of Spinal Magnetic Resonance Imaging in Patients with High-Frequency Spinal Cord Stimulators: A Prospective Single-Centre Study.

BACKGROUND: Implanted high-frequency spinal cord stimulators at 10 kHz (HF-SCS) have recently acquired conditional approval for magnetic resonance imaging (MRI), including retrospective application to previously implanted devices. Under certain conditions, there are greater specific absorption rate (SAR) scanning restrictions compared to some conventional alternatives. This poses technical challenges to obtain diagnostic quality imaging. OBJECTIVES: To describe our experience with 9 such scans, demonstrating that safe and diagnostically useful images can be obtained despite these restrictions. METHODS: We report a prospective single-centre series of 9 scans within a tertiary neuroscience centre, all obtained within the required SAR limit of ≤0.4 W/kg, and describe the scanning protocol we have developed. We further illustrate this with 2 representative patient cases. RESULTS: The imaging studies were well tolerated without complication. In all cases, the imaging quality was sufficient for the reporting neuroradiologist to answer the clinical question posed. CONCLUSION: Despite technical challenges, MRI is feasible, safe and diagnostically useful in HF-SCS-implanted patients. We would invite other centres that implant these devices to consider the development of their own scanning protocols to avoid the morbidity and inconvenience of explantation or computed tomography myelography. To our knowledge, this is the first reported study of MRI in HF-SCS-implanted patients achieving the requisite SAR limit of ≤0.4 W/kg.

Real-time ultrasound-guided external ventricular drain placement: technical note.

In the United Kingdom, ultrasound-guided external ventricular drain (EVD) insertion is becoming the standard of care to mitigate the morbidity associated with catheter malposition and multiple passes. Many neurosurgeons routinely use ultrasound to check the preinsertion trajectory, although real-time visualization of ventricular cannulation is preferable since minor deviations can be significant in patients with smaller ventricles, and live visualization further enables the catheter tip to be adjusted away from the choroid plexus. Such real-time ultrasound navigation has traditionally been limited by technical factors including the challenge of simultaneously manipulating the probe and inserting the catheter within the same image plane. The authors here describe a simple technique for precise EVD placement using a readily available bur hole ultrasound transducer attached to a 10-gauge needle guide channel (principally used for biopsy procedures) to accommodate a ventriculostomy catheter. The anticipated trajectory line is then projected onto the display and followed into the ipsilateral lateral ventricle. This is illustrated with a representative case and video demonstrating this rapid, user-friendly, and reliable technique. The authors invite others to consider this useful technique to minimize the risks of catheter misplacement or multiple cannulation attempts, which can be of particular benefit to junior neurosurgeons performing difficult cases under pressured conditions.

Spontaneous mesenteric hematoma complicating an exacerbation of Crohn's disease: report of a case.

CASE PRESENTATION: Spontaneous mesenteric haematoma is a rare condition that occurs due to localized bleeding in the mesenteric vascular tree of a bowel segment in the absence of an identifiable cause. Here we report a case of spontaneous mesenteric haematoma during an inflammatory exacerbation of Crohn's disease. The patient underwent surgical management for small bowel obstruction secondary to Crohn's disease, however the concurrent presence of a spontaneous mesenteric haematoma in the mid-jejunal mesentery was successfully managed conservatively. CONCLUSION: This case identifies the first association of spontaneous mesenteric haematoma with an exacerbation of Crohn's disease and highlights the need to consider rare differential diagnoses such as SMH when performing radiological assessment of unexplained symptoms in inflammatory bowel disease patients.

Bariatric Surgery or Non-surgical Weight Loss for Idiopathic Intracranial Hypertension? A Systematic Review and Comparison of Meta-analyses.

BACKGROUND: Idiopathic intracranial hypertension (IIH) is associated with obesity and weight loss by any means is considered beneficial in this condition. OBJECTIVES: This study aims to appraise bariatric surgery vs. non-surgical weight-loss (medical, behavioural and lifestyle) interventions in IIH management. METHODS: A systematic review and meta-analyses of surgical and non-surgical studies. RESULTS: Bariatric surgery achieved 100% papilloedema resolution and a reduction in headache symptoms in 90.2%. Non-surgical methods offered improvement in papilloedema in 66.7%, visual field defects in 75.4% and headache symptoms in 23.2%. Surgical BMI decrease was 17.5 vs. 4.2 for non-surgical methods. CONCLUSIONS: Whilst both bariatric surgery and non-surgical weight loss offer significant beneficial effects on IIH symptomatology, future studies should address the lack of prospective and randomised trials to establish the optimal role for these interventions.