Digital subtraction angiography is the reference standard technique to evaluate intracranial vasc... more Digital subtraction angiography is the reference standard technique to evaluate intracranial vascular anatomy and used on the endovascular treatment of vascular diseases. A dedicated optical flow-based algorithm was applied to DSA to measure arterial flow. The first quantification results of internal carotid artery flow validated with Doppler sonography are reported.
Dear Editor, Spontaneous spinal epidural haematoma (SSEH) is a neurosurgical emergency and can oc... more Dear Editor, Spontaneous spinal epidural haematoma (SSEH) is a neurosurgical emergency and can occur due to spinal arteriovenous malformations, haemangiomas or rupture of epidural venous plexus favoured by coagulation disorders. The initial symptoms include back pain with radicular or pseudoradicular irradiation which can progress to neurological signs of complete spinal cord compression . Prognostic factors for recovery after surgical decompression include preoperative neurological deficits, extent of affected vertebral segments, radiological signs of spinal cord compression and the interval between symptom onset and surgery .
Flow-diverter stents modify intra-aneurysmal blood flow and induce the progressive thrombosis of ... more Flow-diverter stents modify intra-aneurysmal blood flow and induce the progressive thrombosis of intracranial aneurysms followed by stable vascular reconstruction. The aim of this study was to report a new method for the appraisal of intracranial blood flow from DSA performed during endovascular treatment procedures.
Background Multimodality treatment suites for patients with cerebral arteriovenous malformations ... more Background Multimodality treatment suites for patients with cerebral arteriovenous malformations (AVM) have recently become available. This study was designed to evaluate feasibility, safety and impact on treatment of a new intraoperative flat-panel (FP) based integrated surgical and imaging suite for combined endovascular and surgical treatment of cerebral AVM. Methods Twenty-five patients with AVMs to treat with combined endovascular and surgical interventions were prospectively enrolled in this consecutive case series. The hybrid suite allows combined endovascular and surgical approaches with intraoperative scanner-like imaging (XperCT®) and intraoperative 3D rotational angiography (3D-RA). The impact of intraoperative multimodal imaging on feasibility, workflow of combined interventions, surgery, and unexpected imaging findings were analyzed.
Interventional neuroradiology : journal of peritherapeutic neuroradiology, surgical procedures and related neurosciences, 2013
Ruptured cerebral arteriovenous malformations (AVMs) usually require treatment to avoid re-bleedi... more Ruptured cerebral arteriovenous malformations (AVMs) usually require treatment to avoid re-bleeding. Depending on the angioarchitecture and center strategy, the treatment can be surgical, endovascular, radiosurgical or combined methods. The classic endovascular approach is transarterial, but sometimes it is not always applicable. The transvenous approach has been described as an alternative for the endovascular treatment of small AVMs when arterial access or another therapeutic method is not possible. This approach can be considered when the nidus is small and if there is a single draining vein. We present a technical note on a transvenous approach for the treatment of a ruptured AVM in a young patient.
Cerebral aneurysms are an important cause of morbidity and mortality due to their causal effect i... more Cerebral aneurysms are an important cause of morbidity and mortality due to their causal effect in non-traumatic subarachnoid hemorrhage. Neurosurgical progress in the 20th century helped to improve patient outcomes greatly. In recent years, techniques such as intravascular treatment by coiling and/or stenting have found an additional place in the management of the disease. With the development of less and less invasive surgical and endovascular techniques, there has also been a continuous development in imaging techniques that have led to our current situation where we dispose of CT and MR techniques that can help improve treatment planning greatly. CT is able to detect and together with its adjunct techniques CT angiography and CT perfusion, it can allow us to provide the physicians in charge with a detailed image of the aneurysm, the feeding vessels as well as the status of blood flow to the brain. Angiography has evolved by becoming the standard tool for guidance during decision making for whatever therapy is being envisioned be it endovascular procedures and or surgery and has even progressed more recently due to the development of so-called flat panel technology that now allows to acquire CT-like images during and directly after an intervention. Thus nowadays, the diagnostic and interventional techniques and procedures have become so much entwined as to be considered a whole.
Background Aneurysmal subarachnoid haemorrhage (SAH) WFNS grade V is commonly known to be associa... more Background Aneurysmal subarachnoid haemorrhage (SAH) WFNS grade V is commonly known to be associated with high mortality and a very poor prognosis for survivors. Therefore, maximal invasive therapy is frequently delayed until any spontaneous improvement with or without an external ventricular drainage occurs. The aim of the study was to verify possible predictive factors and the probability of a favourable outcome in maximally treated patients. Methods One hundred and thirty-eight consecutive patients with WFNS grade V SAH were admitted between 03/2006 and 12/2010. Thirty-five patients died before aggressive therapy could proceed. One hundred and three patients received maximal treatment and were retrospectively evaluated. The outcome was assessed at discharge and in the follow-up with the Glasgow Outcome Scale. Univariate and multivariate linear regression models were performed to find predictors for an unfavourable outcome. Results Despite treatment, early mortality was 30 % (n=31). At discharge, the rate of both vegetative and severely disabled patients was 27 % (n=28). Favourable outcome at discharge was observed in 16 % (n=16) of cases, whereas in the followup it rose to 26 % (n=27). Multivariate full model regression identified intraventricular haematoma (IVH) and increasing age as independently predictive for poor outcome. Conclusions Despite treatment, initial mortality and severe disability remain high. Nevertheless, a favourable outcome was achieved in 26 % of aggressively treated patients, rendering the withdrawal of maximal therapy for WFNS grade V SAH patients unacceptable today. In cases of old patients with IVH, the indication for aggressive therapy should be put in place more carefully due to a very poor prognosis.
Background and purpose Accurate placement of an external ventricular drain (EVD) for the treatmen... more Background and purpose Accurate placement of an external ventricular drain (EVD) for the treatment of hydrocephalus is of paramount importance for its functionality and in order to minimize morbidity and complications. The aim of this study was to compare two different drain insertion assistance tools with the traditional free-hand anatomical landmark method, and to measure efficacy, safety and precision. Methods Ten cadaver heads were prepared by opening large bone windows centered on Kocher's points on both sides. Nineteen physicians, divided in two groups (trainees and board certified neurosurgeons) performed EVD insertions. The target for the ventricular drain tip was the ipsilateral foramen of Monro. Each participant inserted the external ventricular catheter in three different ways: 1) free-hand by anatomical landmarks, 2) neuronavigation-assisted (NN), and 3) XperCT-guided (XCT). The number of ventricular hits and dangerous trajectories; time to proceed; radiation exposure of patients and physicians; distance of the catheter tip to target and size of deviations projected in the orthogonal plans were measured and compared. Results Insertion using XCT increased the probability of ventricular puncture from 69.2 to 90.2 % (p=0.02). Non-assisted placements were significantly less precise (catheter tip to target distance 14.3± 7.4 mm versus 9.6± 7.2 mm, p=0.0003). The insertion time to proceed increased from 3.04±2.06 min. to 7.3±3.6 min. (p<0.001). The X-ray exposure for XCT was 32.23 mSv, but could be reduced to 13.9 mSv if patients were initially imaged in the hybridoperating suite. No supplementary radiation exposure is needed for NN if patients are imaged according to a navigation protocol initially. Conclusion This ex vivo study demonstrates a significantly improved accuracy and safety using either NN or XCTassisted methods. Therefore, efforts should be undertaken to implement these new technologies into daily clinical practice. However, the accuracy versus urgency of an EVD placement has to be balanced, as the image-guided insertion technique will implicate a longer preparation time due to a specific image acquisition and trajectory planning.
ABSTRACT The treatment of unruptured very small intracranial aneurysms (UVSIAs), defined as less ... more ABSTRACT The treatment of unruptured very small intracranial aneurysms (UVSIAs), defined as less than or equal to 3 mm, can be indicated in rare circumstances. Recent publications have examined the feasibility and outcomes of endovascular therapy for UVSIAs. However, the efficacy and complication rate related to surgical clipping of UVSIAs has not been well defined in any large series to date. Therefore, we conducted a multicenter study to examine surgical outcomes for UVSIAs.
Neuronavigation is widely considered as a valuable tool during skull base surgery. Advances in ne... more Neuronavigation is widely considered as a valuable tool during skull base surgery. Advances in neuronavigation technology, with the integration of augmented reality, present advantages over traditional point-based neuronavigation. However, this development has not yet made its way into routine surgical practice, possibly due to a lack of acquaintance with these systems. In this report, we illustrate the usefulness and easy application of augmented reality-based neuronavigation through a case example of a patient with a clivus chordoma. We also demonstrate how augmented reality can help throughout all phases of a skull base procedure, from the verification of neuronavigation accuracy to intraoperative image-guidance.
Digital subtraction angiography is the reference standard technique to evaluate intracranial vasc... more Digital subtraction angiography is the reference standard technique to evaluate intracranial vascular anatomy and used on the endovascular treatment of vascular diseases. A dedicated optical flow-based algorithm was applied to DSA to measure arterial flow. The first quantification results of internal carotid artery flow validated with Doppler sonography are reported.
Dear Editor, Spontaneous spinal epidural haematoma (SSEH) is a neurosurgical emergency and can oc... more Dear Editor, Spontaneous spinal epidural haematoma (SSEH) is a neurosurgical emergency and can occur due to spinal arteriovenous malformations, haemangiomas or rupture of epidural venous plexus favoured by coagulation disorders. The initial symptoms include back pain with radicular or pseudoradicular irradiation which can progress to neurological signs of complete spinal cord compression . Prognostic factors for recovery after surgical decompression include preoperative neurological deficits, extent of affected vertebral segments, radiological signs of spinal cord compression and the interval between symptom onset and surgery .
Flow-diverter stents modify intra-aneurysmal blood flow and induce the progressive thrombosis of ... more Flow-diverter stents modify intra-aneurysmal blood flow and induce the progressive thrombosis of intracranial aneurysms followed by stable vascular reconstruction. The aim of this study was to report a new method for the appraisal of intracranial blood flow from DSA performed during endovascular treatment procedures.
Background Multimodality treatment suites for patients with cerebral arteriovenous malformations ... more Background Multimodality treatment suites for patients with cerebral arteriovenous malformations (AVM) have recently become available. This study was designed to evaluate feasibility, safety and impact on treatment of a new intraoperative flat-panel (FP) based integrated surgical and imaging suite for combined endovascular and surgical treatment of cerebral AVM. Methods Twenty-five patients with AVMs to treat with combined endovascular and surgical interventions were prospectively enrolled in this consecutive case series. The hybrid suite allows combined endovascular and surgical approaches with intraoperative scanner-like imaging (XperCT®) and intraoperative 3D rotational angiography (3D-RA). The impact of intraoperative multimodal imaging on feasibility, workflow of combined interventions, surgery, and unexpected imaging findings were analyzed.
Interventional neuroradiology : journal of peritherapeutic neuroradiology, surgical procedures and related neurosciences, 2013
Ruptured cerebral arteriovenous malformations (AVMs) usually require treatment to avoid re-bleedi... more Ruptured cerebral arteriovenous malformations (AVMs) usually require treatment to avoid re-bleeding. Depending on the angioarchitecture and center strategy, the treatment can be surgical, endovascular, radiosurgical or combined methods. The classic endovascular approach is transarterial, but sometimes it is not always applicable. The transvenous approach has been described as an alternative for the endovascular treatment of small AVMs when arterial access or another therapeutic method is not possible. This approach can be considered when the nidus is small and if there is a single draining vein. We present a technical note on a transvenous approach for the treatment of a ruptured AVM in a young patient.
Cerebral aneurysms are an important cause of morbidity and mortality due to their causal effect i... more Cerebral aneurysms are an important cause of morbidity and mortality due to their causal effect in non-traumatic subarachnoid hemorrhage. Neurosurgical progress in the 20th century helped to improve patient outcomes greatly. In recent years, techniques such as intravascular treatment by coiling and/or stenting have found an additional place in the management of the disease. With the development of less and less invasive surgical and endovascular techniques, there has also been a continuous development in imaging techniques that have led to our current situation where we dispose of CT and MR techniques that can help improve treatment planning greatly. CT is able to detect and together with its adjunct techniques CT angiography and CT perfusion, it can allow us to provide the physicians in charge with a detailed image of the aneurysm, the feeding vessels as well as the status of blood flow to the brain. Angiography has evolved by becoming the standard tool for guidance during decision making for whatever therapy is being envisioned be it endovascular procedures and or surgery and has even progressed more recently due to the development of so-called flat panel technology that now allows to acquire CT-like images during and directly after an intervention. Thus nowadays, the diagnostic and interventional techniques and procedures have become so much entwined as to be considered a whole.
Background Aneurysmal subarachnoid haemorrhage (SAH) WFNS grade V is commonly known to be associa... more Background Aneurysmal subarachnoid haemorrhage (SAH) WFNS grade V is commonly known to be associated with high mortality and a very poor prognosis for survivors. Therefore, maximal invasive therapy is frequently delayed until any spontaneous improvement with or without an external ventricular drainage occurs. The aim of the study was to verify possible predictive factors and the probability of a favourable outcome in maximally treated patients. Methods One hundred and thirty-eight consecutive patients with WFNS grade V SAH were admitted between 03/2006 and 12/2010. Thirty-five patients died before aggressive therapy could proceed. One hundred and three patients received maximal treatment and were retrospectively evaluated. The outcome was assessed at discharge and in the follow-up with the Glasgow Outcome Scale. Univariate and multivariate linear regression models were performed to find predictors for an unfavourable outcome. Results Despite treatment, early mortality was 30 % (n=31). At discharge, the rate of both vegetative and severely disabled patients was 27 % (n=28). Favourable outcome at discharge was observed in 16 % (n=16) of cases, whereas in the followup it rose to 26 % (n=27). Multivariate full model regression identified intraventricular haematoma (IVH) and increasing age as independently predictive for poor outcome. Conclusions Despite treatment, initial mortality and severe disability remain high. Nevertheless, a favourable outcome was achieved in 26 % of aggressively treated patients, rendering the withdrawal of maximal therapy for WFNS grade V SAH patients unacceptable today. In cases of old patients with IVH, the indication for aggressive therapy should be put in place more carefully due to a very poor prognosis.
Background and purpose Accurate placement of an external ventricular drain (EVD) for the treatmen... more Background and purpose Accurate placement of an external ventricular drain (EVD) for the treatment of hydrocephalus is of paramount importance for its functionality and in order to minimize morbidity and complications. The aim of this study was to compare two different drain insertion assistance tools with the traditional free-hand anatomical landmark method, and to measure efficacy, safety and precision. Methods Ten cadaver heads were prepared by opening large bone windows centered on Kocher's points on both sides. Nineteen physicians, divided in two groups (trainees and board certified neurosurgeons) performed EVD insertions. The target for the ventricular drain tip was the ipsilateral foramen of Monro. Each participant inserted the external ventricular catheter in three different ways: 1) free-hand by anatomical landmarks, 2) neuronavigation-assisted (NN), and 3) XperCT-guided (XCT). The number of ventricular hits and dangerous trajectories; time to proceed; radiation exposure of patients and physicians; distance of the catheter tip to target and size of deviations projected in the orthogonal plans were measured and compared. Results Insertion using XCT increased the probability of ventricular puncture from 69.2 to 90.2 % (p=0.02). Non-assisted placements were significantly less precise (catheter tip to target distance 14.3± 7.4 mm versus 9.6± 7.2 mm, p=0.0003). The insertion time to proceed increased from 3.04±2.06 min. to 7.3±3.6 min. (p<0.001). The X-ray exposure for XCT was 32.23 mSv, but could be reduced to 13.9 mSv if patients were initially imaged in the hybridoperating suite. No supplementary radiation exposure is needed for NN if patients are imaged according to a navigation protocol initially. Conclusion This ex vivo study demonstrates a significantly improved accuracy and safety using either NN or XCTassisted methods. Therefore, efforts should be undertaken to implement these new technologies into daily clinical practice. However, the accuracy versus urgency of an EVD placement has to be balanced, as the image-guided insertion technique will implicate a longer preparation time due to a specific image acquisition and trajectory planning.
ABSTRACT The treatment of unruptured very small intracranial aneurysms (UVSIAs), defined as less ... more ABSTRACT The treatment of unruptured very small intracranial aneurysms (UVSIAs), defined as less than or equal to 3 mm, can be indicated in rare circumstances. Recent publications have examined the feasibility and outcomes of endovascular therapy for UVSIAs. However, the efficacy and complication rate related to surgical clipping of UVSIAs has not been well defined in any large series to date. Therefore, we conducted a multicenter study to examine surgical outcomes for UVSIAs.
Neuronavigation is widely considered as a valuable tool during skull base surgery. Advances in ne... more Neuronavigation is widely considered as a valuable tool during skull base surgery. Advances in neuronavigation technology, with the integration of augmented reality, present advantages over traditional point-based neuronavigation. However, this development has not yet made its way into routine surgical practice, possibly due to a lack of acquaintance with these systems. In this report, we illustrate the usefulness and easy application of augmented reality-based neuronavigation through a case example of a patient with a clivus chordoma. We also demonstrate how augmented reality can help throughout all phases of a skull base procedure, from the verification of neuronavigation accuracy to intraoperative image-guidance.
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Papers by Karl Schaller