Computed diffusion-weighted imaging in patients with transient neurovascular symptoms with and without ischemic infarction.

PURPOSE: Detection of ischemic lesions in patients with transient neurovascular symptoms is relevant for the estimation of the risk of a subsequent stroke and etiological classification. To improve detection rates, different technical approaches have been used, such as diffusion-weighted imaging (DWI) with high b-values or higher magnetic field strength. Here, we sought to investigate the value of computed DWI (cDWI) with high b-values in these patients. METHODS: From an MRI report database we identified patients with transient neurovascular symptoms who underwent repeated MRI including DWI. cDWI was calculated with a monoexponential model with high b-values (2000, 3000, and 4000 s/mm2) and compared to the routinely used standard DWI with regard to presence of ischemic lesions and lesion detectability. RESULT: Overall 33 patients with transient neurovascular symptoms (71 [IQR 57-83.5] years; 21 [63.6%] male) were included. On DWI, acute ischemic lesions were observed in 22 (78.6%). Acute ischemic lesions were observed in 17 (51.5%) patients on initial DWI, and in 26 (78.8%) patients on follow-up DWI. Lesion detectability was rated significantly better on cDWI at 2000s/mm2 compared to standard DWI. In 2 (9.1%) patients, cDWI at 2000s/mm2 revealed an acute ischemic lesion proven on follow-up standard DWI which was not detected with certainty on the initial standard DWI. CONCLUSION: cDWI might be a valuable addition to routinely acquired standard DWI in patients with transient neurovascular symptoms since its use might result in improved ischemic lesion detection. A b-value of 2000s/mm2 seems most promising for clinical practice.

GLOS and HARM in patients with transient neurovascular symptoms with and without ischemic infarction.

BACKGROUND AND PURPOSE: Gadolinium leakage in ocular structures (GLOS) on fluid attenuated inversion recovery images (FLAIR) is a novel imaging marker in acute ischemic stroke and other neurological disorders. METHODS: In patients with transient neurovascular symptoms who underwent repeated MRI with intravenous contrast agent administration, the presence of acute ischemic lesions on diffusion-weighted images (DWI) as well as the frequency and pattern of blood-brain barrier and blood-retina barrier impairment as demonstrated by the hyperintense acute reperfusion marker (HARM) and GLOS respectively on postcontrast FLAIR were evaluated. RESULTS: Overall 28 patients with transient neurovascular symptoms (median age 70.5 years; 18 (64.3%) male) were included. Follow-up MRI was performed within 35 (IQR 21-47) hours after the initial MRI. On DWI, acute ischemic lesions were observed in 22 (78.6%). On contrast-enhanced FLAIR, GLOS was observed in 12 (42.9%) patients: in 1 (3.6%) only in the anterior chamber, and in 11 (39.3%) in the anterior chamber and vitreous body. HARM was observed in 3 (10.7%) patients. In one patient without ischemic lesion on DWI or HARM on FLAIR, GLOS was observed in the anterior chamber and vitreous body. Presence of GLOS was associated with higher age (p = 0.04) and detection of HARM (p = 0.03). CONCLUSIONS: In patients with transient neurovascular symptoms, GLOS is a frequent finding and associated with HARM on contrast-enhanced FLAIR. As GLOS was observed in one patient without an ischemic lesion or HARM, it might be useful as an additional imaging marker.

Asymmetrical Gadolinium Leakage in Ocular Structures in Stroke Due to Internal Carotid Artery Stenosis or Occlusion.

PURPOSE: Gadolinium leakage in ocular structures (GLOS) on fluid-attenuated inversion recovery images (FLAIR) is a novel imaging marker in acute ischemic stroke. The present study sought to investigate the frequency and pattern of blood-retina barrier impairment in acute ischemic stroke due to internal carotid artery (ICA) stenosis or occlusion as demonstrated by GLOS. METHODS: From a magnetic resonance imaging (MRI) report database patients were identified with acute ischemic stroke due to ICA stenosis/occlusion who underwent repeated MRI with intravenous contrast agent administration and FLAIR and MR angiography (MRA). On FLAIR the presence of GLOS was noted in the vitreous body. RESULTS: Overall 51 patients with a median age of 70 years (interquartile range, IQR 63-77 years) were included. Of these, 22 (43.1%) patients had an ICA stenosis and 29 (56.9%) an ICA occlusion. On contrast-enhanced FLAIR, GLOS was observed in 29 (56.9%) patients: in 7 (13.7%) unilateral, in 15 (68.2%) bilateral asymmetrical and in 7 (31.8%) bilateral symmetrical. In unilateral asymmetrical GLOS, more pronounced enhancement was always found ipsilateral to ICA stenosis/occlusion. In 4 (5.9%) patients with asymmetrical GLOS a pre-existing signal increase in the vitreous body was found on native FLAIR. The presence of GLOS was associated with an impaired collateralization through the circle of Willis (p < 0.001) and external carotid artery branches (p = 0.03). CONCLUSION: In patients with ischemic stroke due to ICA stenosis/occlusion, GLOS is frequent, commonly unilateral or bilateral asymmetrical, and in some patients associated with pre-existing ocular signal abnormalities. An insufficient collateralization may contribute to the development of unilateral/asymmetrical GLOS.

Gadolinium leakage in ocular structures: A novel MRI finding in transient global amnesia.

BACKGROUND AND PURPOSE: We investigated the frequency and pattern of blood-brain barrier as well as blood-retina barrier impairment in transient global amnesia (TGA) as demonstrated by hyperintense acute reperfusion marker (HARM) and gadolinium leakage in ocular structures (GLOS) respectively on fluid attenuated inversion recovery images (FLAIR). METHODS: Patients with TGA who underwent repeated MRI after intravenous contrast agent administration were identified and the presence of GLOS in the anterior chamber and vitreous body and HARM noted on FLAIR. RESULTS: Overall 10 patients (IQR 64.25-71.75 years; 4 (40%) patients were male) were included. On contrast-enhanced FLAIR, GLOS was observed in 3 (30%) patients; in all of these in the anterior chamber and vitreous body as well as bilateral and symmetrical. HARM was observed in none of the patients. Frequency of hippocampal DWI lesions, as well as extent of age related white matter lesions did not differ significantly between patients with and without GLOS. CONCLUSIONS: In contrast to HARM, GLOS is a relatively common finding in TGA patients. As GLOS is thought to share its pathophysiology at least to some extent with HARM and is associated with HARM in ischemic stroke, it might be used as surrogate marker for blood-brain barrier impairment in TGA.

Deoxysphingolipid precursors indicate abnormal sphingolipid metabolism in individuals with primary and secondary disturbances of serine availability.

Patients with primary serine biosynthetic defects manifest with intellectual disability, microcephaly, ichthyosis, seizures and peripheral neuropathy. The underlying pathogenesis of peripheral neuropathy in these patients has not been elucidated, but could be related to a decrease in the availability of certain classical sphingolipids, or to an increase in atypical sphingolipids. Here, we show that patients with primary serine deficiency have a statistically significant elevation in specific atypical sphingolipids, namely deoxydihydroceramides of 18-22 carbons in acyl length. We also show that patients with aberrant plasma serine and alanine levels secondary to mitochondrial disorders also display peripheral neuropathy along with similar elevations of atypical sphingolipids. We hypothesize that the etiology of peripheral neuropathy in patients with primary mitochondrial disorders is related to this elevation of deoxysphingolipids, in turn caused by increased availability of alanine and decreased availability of serine. These findings could have important therapeutic implications for the management of these patients.

Hippocampal infarction: Identification of three new types.

BACKGROUND AND PURPOSE: Hippocampal infarction (HI) is common but yet still not comprehensively studied. In the present study, we aimed to identify novel HI patterns and to describe additional ischemic lesions outside the hippocampus to draw conclusions regarding the underlying vessel occlusion. METHODS: In 222 patients (mean age 69.9 (±13.6) years; 129 (58.1%) male, 93 (41.9%) female) with HI, diffusion-weighted images were analyzed with emphasis on HI patterns and associated ischemic lesions outside the hippocampus. HI were classified as type 1 (complete), 2 (lateral), 3 (dorsal), and 4 (circumscribed). Further possible HI patterns were defined and classified as type 5 (ventral), 6 (ventrolateral), and 7 (dorsolateral). RESULTS: Unilateral HI was found in 218 (98.2%) patients. In these, type 5 and 6 were identified in 5 (2.3%) patients, and type 7 in 8 (3.7%) patients respectively. Type 1 was found in 62 (28.4%), 2 in 53 (24.3%), 3 in 57 (26.1%), and 4 in 28 (12.8%) patients. Further ischemic lesions were found in the territory of the anterior cerebral artery (3.6%), middle cerebral artery (14.9%), anterior choroidal artery (AChA) (7.2%), posterior cerebral artery (89.6%), and in the brainstem (6.3%) and cerebellum (20.3%). Type 5 and 6 were significantly associated with acute ischemic lesions in the AChA territory (6/10 (60%) vs. 11/200 (5.5%), P<0.001). CONCLUSIONS: We identified three novel HI types. Probably, type 5 and 6 can be attributed to occlusion of the AChA. Overall, these HI types are rare, possibly due to a better collateralization in the case of AChA occlusion.

Isolated punctuate hippocampal infarction and transient global amnesia are indistinguishable by means of MRI.

Background Small punctuate lesions in the hippocampus on diffusion-weighted images are a typical finding in transient global amnesia. Consequently, it has been suggested that diffusion-weighted images findings might corroborate the diagnosis of transient global amnesia. However, isolated punctuate hippocampal infarction might be a differential diagnosis of transient global amnesia. Aim Evaluation of isolated punctuate hippocampal infarction frequency and comparison of its clinical presentation and MRI findings to transient global amnesia. Methods From an MRI database, we identified 10 patients with isolated punctuate hippocampal infarction and compared these to 12 patients with transient global amnesia with diffusion-weighted images lesion with regard to clinical symptoms and MRI findings. Results Disorientation and memory deficits were more common in transient global amnesia patients, whereas dysphasia/aphasia and vertigo were more common in hippocampal infarction patients. MRI findings in isolated punctuate hippocampal infarction and transient global amnesia did not differ significantly, neither regarding the affected hemisphere, lesion distribution, size, nor relative ADC values. Conclusions Differentiation of isolated punctuate hippocampal infarction and transient global amnesia based on neuroimaging findings is not possible. Thus, in the case of isolated punctuate hippocampal diffusion-weighted images lesions the final diagnosis of hippocampal infarction or transient global amnesia should be based on the clinical presentation.

Pharmacokinetic Modeling of Intra-arterial Nimodipine Therapy for Subarachnoid Hemorrhage-Related Cerebral Vasospasm.

PURPOSE: Intra-arterial (IA) administration of nimodipine has been shown to be an effective treatment for subarachnoid hemorrhage-related cerebral vasospasm. The concentrations achieved in cerebral arteries during this procedure, though, are unknown. Therefore, there are no clinical studies investigating dose-dependent effects of nimodipine. We aimed at providing a pharmacokinetic model for IA nimodipine therapy for this purpose. METHODS: A two-compartment pharmacokinetic model for intravenous nimodipine therapy was modified and used to assess cerebral arterial nimodipine concentration during IA nimodipine infusion into the internal carotid artery (ICA). RESULTS: According to our simulations, continuous IA nimodipine infusion at 2 mg/h and 1 mg/h resulted in steady-state cerebral arterial concentrations of about 200 ng/ml and 100 ng/ml assuming an ICA blood flow of 200 ml/min and a clearance of 70 l/h. About 85 % of the maximal concentration is achieved within the first minute of IA infusion independent on the infusion dose. Within the range of physiological and pharmacokinetic data available in the literature, ICA blood flow has more impact on cerebral arterial concentration than nimodipine clearance. CONCLUSION: The presented pharmacokinetic model is suitable for estimations of cerebral arterial nimodipine concentration during IA infusion. It may, for instance, assist in dose-dependent analyses of angiographic results.

[Not Available]. / IQWiG Arbeitspapier GA15-02: "Stents zur Behandlung intrakranieller Stenosen: VISSIT Studie und Akutbehandlung in Deutschland". Kommentar des Berufsverbandes der Neuroradiologen (BDNR), der Deutschen Gesellschaft für Neuroradiologie (DGNR), der Deutschen Gesellschaft für Neurologie (DGN) und der Deutschen Schlaganfall-Gesellschaft (DSG).

There is an ongoing discussion about reimbursement of stent-angioplasty for the treatment of intracranial stenoses in Germany. The discussion was initiated by the statutory health insurance companies after publication of the SAMMPRIS study results, which were in favor for medical management compared to stent-angioplasty with the Wingspan® stent system. A report (Rapid report N14-01) mainly based on SAMMPRIS was written by the German Institute for Quality and Efficiency in Health Care (IQWiG) and serves as a basis for the decision-making process. This report was previously commented by the medical societies involved. Limitations of the SAMMPRIS trial and vital indications for intracranial stenting were outlined in this comment (acute vessel occlusion, hemodynamic impairment, recurrent symptoms under medical treatment). Currently also emergency stent procedures are a matter of debate. In this context a second IQWiG report was commissioned (GA 15 - 02) addressing the results of the VISSIT trial, the transferability of the results of the first report to emergency treatments and the practice of emergency intracranial stent treatment in Germany. Regarding transferability of results the main conclusion was that there was no evidence that the results of the studies analyzed for the first report (mainly SAMMPRIS) could not be transferred to emergency treatments. From a medical professional and scientific standpoint it is inacceptable to compare outcomes of a secondary prophylactic treatment with emergency procedures. The analysis of emergency treatments in Germany based on retrospective case series with a cumulative number of 31 patients. Since most emergency procedures are performed in a clinical context and are not necessarily subject to scientific evaluation, this does not reflect current practice in Germany. The first part of this statement briefly outlines the design of SAMMPRIS and VISSIT and the interpretation of the trial results from a professional perspective. The current state of discussion regarding reimbursement of intracranial stenting is summarized. The second section contains a detailed comment on the current IQWiG report GA15-02 "Stents for the treatment of intracranial artery stenosis: VISSIT study and acute treatment in Germany".

IQWiG Arbeitspapier GA15-02: "Stents zur Behandlung intrakranieller Stenosen: VISSIT Studie und Akutbehandlung in Deutschland" : Kommentar des Berufsverbandes der Neuroradiologen (BDNR), der Deutschen Gesellschaft für Neuroradiologie (DGNR), der Deutschen Gesellschaft für Neurologie (DGN) und der Deutschen Schlaganfall-Gesellschaft (DSG).

There is an ongoing discussion about reimbursement of stent-angioplasty for the treatment of intracranial stenoses in Germany. The discussion was initiated by the statutory health insurance companies after publication of the SAMMPRIS study results, which were in favor for medical management compared to stent-angioplasty with the Wingspan® stent system. A report (Rapid report N14-01) mainly based on SAMMPRIS was written by the German Institute for Quality and Efficiency in Health Care (IQWiG) and serves as a basis for the decision-making process. This report was previously commented by the medical societies involved. Limitations of the SAMMPRIS trial and vital indications for intracranial stenting were outlined in this comment (acute vessel occlusion, hemodynamic impairment, recurrent symptoms under medical treatment).Currently also emergency stent procedures are a matter of debate. In this context a second IQWiG report was commissioned (GA 15 - 02) addressing the results of the VISSIT trial, the transferability of the results of the first report to emergency treatments and the practice of emergency intracranial stent treatment in Germany6. Regarding transferability of results the main conclusion was that there was no evidence that the results of the studies analyzed for the first report (mainly SAMMPRIS) could not be transferred to emergency treatments. From a medical professional and scientific standpoint it is inacceptable to compare outcomes of a secondary prophylactic treatment with emergency procedures. The analysis of emergency treatments in Germany based on retrospective case series with a cumulative number of 31 patients. Since most emergency procedures are performed in a clinical context and are not necessarily subject to scientific evaluation, this does not reflect current practice in Germany.The first part of this statement briefly outlines the design of SAMMPRIS and VISSIT and the interpretation of the trial results from a professional perspective. The current state of discussion regarding reimbursement of intracranial stenting is summarized. The second section contains a detailed comment on the current IQWiG report GA15-02 "Stents for the treatment of intracranial artery stenosis: VISSIT study and acute treatment in Germany".

The pre-interventional psychiatric history - an underestimated confounder in benign intracranial lesions studies.

OBJECTIVES: The current study was designed to analyze the influence of a positive pre-interventional psychiatric history on the quality of life (QOL) after successful treatment of benign intracranial extra-cerebral lesions. METHODS: Patients treated due to meningioma WHO I or unruptured intracranial aneurysms in two German neurosurgical centers between 2007 and 2013 were screened for exclusion criteria including malignant/chronic diseases, recurrence of the tumor/aneurysm and neurological deficits among others. 131 patients who met the criteria of an objectively unaffected health status were included. The pre-interventional psychiatric histories and the rates of post-interventional headaches, sleeping disorders, symptoms of chronic fatigue syndrome (CFS), post-traumatic stress disorder (PTSD) and QOL were determined by questionnaires which were mailed to the patients. RESULTS: 103 patients returned the questionnaires. Despite the objectively unaffected health status, the patients with a positive pre-interventional psychiatric history demonstrated a post-interventionally significantly lower QOL (p=0.002), a significantly higher Pittsburgh Sleep Quality Index sum score (p=0.009), as well as significantly higher rates of symptoms of a chronic fatigue syndrome (p=0.003) and PTSD (p=0.024), compared to the patient collective with a negative pre-interventional psychiatric status. CONCLUSION: The results of the current study demonstrate the importance of taking the pre-interventional psychiatric history as a significant and independent confounder into consideration when evaluating the outcome after treatment of benign intracranial extra-cerebral lesions. A pre-interventional psychiatric screening and an early psychological intervention might help to improve the overall outcome after successful treatment of such lesions.

Patient characteristics support unfavorable psychiatric outcome after treatment of unruptured intracranial aneurysms.

INTRODUCTION: Previous studies demonstrated an unfavorable psychological outcome after treatment of unruptured intracranial aneurysms despite an objectively favorable clinical and radiological outcome. The current study was therefore designed to analyze the psychiatric vulnerability of this specific patient collective. MATERIALS AND METHODS: Patients treated for a WHO grade I meningioma and incidental intracranial aneurysms in two German neurosurgical centers between 2007 and 2013 were screened for exclusion criteria including malignant/chronic diseases, recurrence of the tumor/aneurysm after more than 12 months and focal neurological deficits, among others. Seventy-five meningioma patients (M) and 56 incidental aneurysm patients (iA) met the inclusion criteria. The past medical psychiatric history, post-morbid personality characters and coping strategies were determined by questionnaires mailed to the patients in a printed version (Brief COPE, Big Five Personality Test). RESULTS: Fifty-eight M and 45 iA patients returned the questionnaires. Patients with iA demonstrated significantly higher pre-interventional rates of depressive episodes (p = 0.002) and psychological supervision (p = 0.038). These findings were especially aggravated in iA patients who received their cranial imaging for unspecific symptoms such as dizziness, headaches or tinnitus (n = 33, history of depressions: 39.4%; previous psychological supervision: 33.3%). Furthermore, the analysis of the Big Five personality traits revealed remarkably elevated neuroticism scores in the iA collective. CONCLUSION: The current study demonstrates an increased rate of positive pre-interventional psychiatric histories in the iA collective. Although those patients represent only a small subgroup, they still may play an important role concerning the overall outcome after iA treatment. Early detection and psychological support in this subgroup might help to improve the overall outcome. Further studies are needed to evaluate the influence of this new aspect on the multifactorial etiology of unfavorable psychiatric outcome after treatment of iA.

A comparison of CT/CT angiography and MRI/MR angiography for imaging of vertebrobasilar dolichoectasia.

PURPOSE: Vertebrobasilar dolichoectasia (VBD) is a rare dilatative arteriopathy predominantly affecting the basilar artery (BA) and vertebral arteries. Until today, the value of computed tomography (CT)/CT angiography (CTA) compared with magnetic resonance imaging (MRI)/time-of-flight MR angiography (TOF-MRA) has not been studied systematically. METHODS: We (1) compare CTA and TOF-MRA according to the established criteria (diameter at the mid-pons level, height, and lateral position), (2) explore the value of further CTA- and TOF-MRA-derived measures (maximum transverse diameter and length), as well as (3) explore the value of further non-contrast-enhanced MRI sequences such as T1, fluid-attenuated inversion recovery, and T2* for a detailed characterization of VBD in a series of 18 patients. RESULTS: Comparison of CTA and TOF-MRA revealed very good consistency of the measured diameter (Pearson's r = 0.994, p = 0.01) and the noted height of the BA (Kendall's tau = 1.0, p = 0.001). The same held true for the maximum transverse diameter (Pearson's r = 0.988, p = 0.01) and length of the BA (Pearson's r = 0.986, p = 0.01). In contrast to this, there was a lower agreement concerning the lateral position (Kendall's tau = 0.866, p = 0.01). In comparison with the diameter at the mid-pons level, the maximum transverse diameter was significantly larger (p = 0.002). Luminal thrombus was detected equally well by CTA and TOF-MRA. CT was useful to detect small circumscribed calcifications, whereas MRI was advantageous to demonstrate perifocal brainstem edema. CONCLUSIONS: We could demonstrate a substantial comparability of CT/CTA and MRI/TOF-MRA in the diagnosis of VBD. The maximum transverse diameter and length may be useful when an endovascular treatment is considered. Taking into account the different informative value of both techniques, it may be worth to perform both imaging procedures.

Value of diffusion-weighted imaging in central pontine and extrapontine myelinolysis.

INTRODUCTION: Central pontine myelinolysis (CPM) and extrapontine myelinolysis (EPM) are rare neurological disorders characterized by demyelination in and/or outside the pons. Whether diffusion-weighted imaging (DWI) might facilitate an earlier diagnosis has not yet been studied systematically. METHODS: We describe demographics, clinical presentation, and early magnetic resonance imaging (MRI) findings with special emphasis on the relevance for diagnosis of CPM and/or EPM in eight patients. RESULTS: Of the analysed eight patients (aged 37-70 years; two men, six women), CPM was diagnosed in three, EPM in one, and a combination of CPM and EPM in four patients. Aetiology was rapid correction of sodium in two patients; a combination of hyponatremia, alcoholism and alcohol withdrawal in five patients and unclear in one patient. Seven patients suffered from chronic alcoholism and four from malnutrition. Demyelinating lesions were found in the pons, thalamus, caudate nucleus, putamen and midbrain. While the lesions could be clearly delineated on T2- and T1-weighted images, DWI demonstrated a strong signal in only six patients. Furthermore, DWI demonstrated lesions only to some extent in two patients and was completely negative in two patients on initial MRI. In none of the patients did the demonstration of hyperintense lesions on DWI precede detection on conventional MRI sequences. Apparent diffusion coefficient (ADC) values were heterogenous with a decrease in two cases and an increase in the remainder. CONCLUSIONS: We conclude that early DWI changes are a common finding in CPM/EPM but do not regularly precede tissue changes detectable on conventional MRI sequences. Heterogenous ADC values possibly represent different stages of disease.

In vivo X-ray digital subtraction and CT angiography of the murine cerebrovasculature using an intra-arterial route of contrast injection.

BACKGROUND AND PURPOSE: Investigation of the anatomy, patency, and blood flow of arterial and venous vessels in small animal models of cerebral ischemia, venous thrombosis, or vasospasm is of major interest. However, due to their small caliber, in vivo examination of these vessels is technically challenging. Using micro-CT, we compared the feasibility of in vivo DSA and CTA of the murine cerebrovasculature using an intra-arterial route of contrast administration. MATERIALS AND METHODS: The ECA was catheterized in 5 C57BL/6J mice. During intra-arterial injection of an iodized contrast agent (30 µL/1 sec), DSA of the intra- and extracranial vessels was performed in mice breathing room air and repeated in hypoxic/hypercapnic mice. Micro-CTA was performed within 20 seconds of intra-arterial contrast injection (220 µL/20 sec). Image quality of both methods was compared. Radiation dose measurements were performed with thermoluminescence dosimeters. RESULTS: Both methods provided high-resolution images of the murine cerebrovasculature, with the smallest identifiable vessel calibers of ≤ 50 µm. Due to its high temporal resolution of 30 fps, DSA allowed identification of anastomoses between the ICA and ECA by detection of retrograde flow within the superficial temporal artery. Micro-CTA during intra-arterial contrast injection resulted in a reduced injection volume and a higher contrast-to-noise ratio (19.0 ± 1.0) compared with DSA (10.0 ± 1.8) or micro-CTA when using an intravenous injection route (1.3 ± 0.4). CONCLUSIONS: DSA of the murine cerebrovasculature is feasible using micro-CT and allows precise and repeated measurements of the vessel caliber, and changes of the vessel caliber, while providing relevant information on blood flow in vivo.

Visualisation of the zona incerta for deep brain stimulation at 3.0 Tesla.

PURPOSE: Deep-brain stimulation (DBS) of the zona incerta (ZI) has shown promising results for medication-refractory neurological disorders including Parkinson's disease (PD) and essential tremor (ET). The success of the intervention is indispensably dependent on the reliable visualisation of the ZI. The aim of the study was to evaluate different promising new magnetic resonance imaging (MRI) methods at 3.0 Tesla for pre-stereotactic visualisation of the ZI using a standard installation the protocol. METHODS: MRI of nine healthy volunteers was acquired (T1-MPRAGE, T2-FLAIR, T2*-FLASH2D, T2-SPACE and susceptibility-weighted imaging (SWI). Image quality and visualisation of the ZI for each sequence were analysed independently by two neuroradiologists using a 6-point scale. For T2*-FLASH2D the axial, coronal and sagittal planes were compared. The delineation of the ZI versus the internal capsule, the subthalamic nucleus and the pallidofugal fibres was evaluated in all sequences and compared to T2-FLAIR using a paired t-test. Inter-rater reliability, contrast-to-noise ratios (CNR), and signal-to-noise ratios (SNR) for the ZI were computed. For illustration, coronal T2*-FLASH2D images were co-registered with the corresponding section schema of the Schaltenbrand-Wahren stereotactic atlas. RESULTS: Only the rostral part of the ZI (rZI) could be identified. The rZI was best and reliably visualised in T2*-FLASH2D (particularly coronal orientation; p < 0.05). No major artifacts in the rZI were observed in any of the sequences. SWI, T2-SPACE, and T2*-FLASH imaging offered significant higher CNR values for the rZI compared to T2-FLAIR imaging using standard parameters. The co-registration of the coronal T2*-FLASH2D images projected the ZI clearly into the boundaries of the anatomical sections. CONCLUSIONS: The delineation of the rZI is best possible in T2*-FLASH2D (particularly coronal view) using a standard installation protocol at 3.0 T. The caudal ZI could not be discerned in any of the sequences.

Endovascular repositioning of a pipeline embolization device dislocated from the vertebral into the basilar artery using a stent-in-stent technique. Practical and technical considerations.

PURPOSE: Stent dislocation is a rarely encountered problem in interventional neuroradiology. This article describes the repositioning of a pipeline embolization device (PED) dislocated from the vertebral artery (VA) into the basilar artery (BA) using a stent-in-stent technique. Based on this case additional in vitro measurements were performed. METHODS: In a patient, a larger PED (4.0 × 20 mm) was partially opened in a PED (3.0 × 20 mm) floating freely within the distal BA. The microcatheter with the partially opened stent was pulled back hereby pulling back the stent-in-stent construct into the VA. In vitro the maximum tensile force that could be applied to a 3.5 mm and a 4.5 mm PED before dislodgement out of a 3.0 mm PED was determined. Videomorphometric analyses of the stent-in-stent construct were performed while applying traction to the construct. RESULTS: Repositioning of a dislocated PED is feasible using a stent-in-stent technique. Higher dislodgement forces can be applied using a larger PED (4.5 mm, 0.36 N) whereas dislodgement occurred faster using a smaller PED (3.5 mm, 0.26 N). Before dislodgement occurs, elongation and tapering of both stents can be seen. Finally, it was found that incidental extraction of the 4.5 mm PED out of the delivering microcatheter during traction is possible. CONCLUSIONS: Repositioning of a lost PED is feasible using a stent-in-stent technique. Principally, dislodgement force is higher using a larger PED, while in this case care has to be taken to avoid incidental extraction of the second PED out of the microcatheter.

Decomposing the Hounsfield unit: probabilistic segmentation of brain tissue in computed tomography.

PURPOSE: The aim of this study was to present and evaluate a standardized technique for brain segmentation of cranial computed tomography (CT) using probabilistic partial volume tissue maps based on a database of high resolution T1 magnetic resonance images (MRI). METHODS: Probabilistic tissue maps of white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF) were derived from 600 normal brain MRIs (3.0 Tesla, T1-3D-turbo-field-echo) of 2 large community-based population studies (BiDirect and SEARCH Health studies). After partial tissue segmentation (FAST 4.0), MR images were linearly registered to MNI-152 standard space (FLIRT 5.5) with non-linear refinement (FNIRT 1.0) to obtain non-binary probabilistic volume images for each tissue class which were subsequently used for CT segmentation. From 150 normal cerebral CT scans a customized reference image in standard space was constructed with iterative non-linear registration to MNI-152 space. The inverse warp of tissue-specific probability maps to CT space (MNI-152 to individual CT) was used to decompose a CT image into tissue specific components (GM, WM, CSF). RESULTS: Potential benefits and utility of this novel approach with regard to unsupervised quantification of CT images and possible visual enhancement are addressed. Illustrative examples of tissue segmentation in different pathological cases including perfusion CT are presented. CONCLUSION: Automated tissue segmentation of cranial CT images using highly refined tissue probability maps derived from high resolution MR images is feasible. Potential applications include automated quantification of WM in leukoaraiosis, CSF in hydrocephalic patients, GM in neurodegeneration and ischemia and perfusion maps with separate assessment of GM and WM.

Arterial spin labeling at 3.0 Tesla in subacute ischemia: comparison to dynamic susceptibility perfusion.

PURPOSE: Arterial spin labeling (ASL) is a promising but clinically not established non-invasive method to assess cerebral perfusion. The purpose of this study was to compare perfusion imaging with pulsed ASL (pASL) to conventional dynamic susceptibility contrast (DSC) perfusion-weighted imaging (PWL) using commercially available equipment and postprocessing (3.0 Tesla, 32-channel head coil) in patients with subacute ischemia. METHODS: The pASL and DSC-PWI techniques were compared in 15 patients with subacute ischemia (age 49-88 years, 6 females and 9 males, time from onset to scan 4-161 h). Image inhomogeneity was assessed with the non-uniformity index. Image quality, delineation of hypoperfusion and degree of hypoperfusion were rated by two readers using a 5-scale grading system. The volume of hypoperfusion was quantified planimetrically. RESULTS: Image quality and image inhomogeneity were superior in DSC time-to-peak (TTP) compared to pASL cerebral brain flow (CBF; both p < 0.05). The delineation of hypoperfusion was better in DSC-TTP (p < 0.05) and the hypoperfusion was graded as more severe in DSC-TTP (p < 0.05). The volume of hypoperfusion did not differ between pASL-CBF and DSC-TTP, however, in pASL-CBF five cases with small infarctions (lacunar and pontine) were false negative compared to DSC-relative CBF. The mismatch frequency was lower in pASL (13%) than in DSC-rCBF (20%) and DSC-TTP (47%). CONCLUSIONS: Using a commercially available sequence and a 32-channel head coil at 3.0 Tesla pASL-CBF is feasible but limited compared to DSC-PWI in the assessment of ischemic stroke. In its present form pASL has a reserve role in clinical practice for situations when gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) is contraindicated.

Acetylsalicylic acid does not prevent digital subtraction angiography-related high signal intensity lesions in diffusion-weighted imaging in cerebrovascular patients. A retrospective analysis.

PURPOSE: Assuming thromboembolic events to be the origin of silent strokes during cerebral digital subtraction angiography (DSA), antiplatelet therapy with acetylsalicylic acid (ASA) should significantly reduce the risk for DSA-related silent stroke. The aim of this retrospective analysis was to assess whether ASA does prevent DSA-related silent stroke in terms of high signal intensity lesions in diffusion-weighted magnetic resonance imaging (DW-MRI). METHODS: All patients underwent a baseline DW-MRI 24 h before DSA and a follow-up DW-MRI 3-24 h after DSA. Patients were considered to have an acute (silent) infarction caused by DSA if there was at least one hyperintense lesion of at least 1 mm in diameter and no neurological deficits. RESULTS: Out of 52 patients in the ASA group 11 (21.2%) had high signal lesions on DW-MRI and 20 out of 123 (16.3%) in the non-ASA group. No significant relationship between the ASA and non-ASA group and the post-angiographic appearance of high signal intensity lesions in DW-MRI could be found (Wilcoxon 2-sample test: p-value 0.9). CONCLUSIONS: The use of oral antiplatelet therapy by ASA (100 mg/day) in cerebrovascular patients did not prevent DSA-related high signal intensity lesions in DW-MRI in this study. Despite a potential bias of this retrospective analysis the findings challenge the current theory of thromboembolisms being the predominant origin of silent stroke. The findings therefore support alternative hypotheseses of the etiology of silent strokes, such as air embolism and mobilized embolic material by the catheter at the vessel wall.