Atlantoaxial posterior screw fixation using intra-operative spinal navigation with three-dimensional isocentric C-arm fluoroscopy.

PURPOSE: Intra-operative image acquisition coupled with navigation aims to increase screw placement accuracy, and it is particularly helpful in complex spinal procedures. The aim of this study is to analyze the accuracy and reliability of posterior atlanto-axial fixation using spinal navigation combined with intra-operative 3D isocentric C-arm. METHODS: We retrospectively reviewed all patients presenting with C1-C2 instability and treated by posterior atlanto-axial fixation in our center between December 2016 and September 2018. Screw positioning was guided by intra-operative navigation, registered with surface matching procedure on a previously obtained CT scan and controlled by intra-operative 3D isocentric C-arm. Age, sex, pre- and post-operative neurological status, duration of surgery, presence/absence of vertebral artery injury, and screw placement were retrospectively collected from patients' records. All patients underwent clinical and radiological follow-up at three months after surgery. Radiological assessment of screw positioning was performed by an independent radiologist using the Gertzbein and Robbins grading. RESULTS: N = 11 (7F, 4 M) consecutive patients were included, with a mean age of 72 years (range from 51 to 85). N = 44 navigated screws were inserted and controlled with intra-operative 3D fluoroscopy at the end of the procedure. An acceptable screw positioning (Gertzbein-Robbins grade A and B) was obtained in all cases (100%). No vertebral artery injury was observed. Mean operating time was 123 minutes. At three months, no screw loosening or displacement was observed. CONCLUSION: In our experience, spinal navigation coupled with intra-operative 3D fluoroscopy proved to be reliable and safe for C1-C2 screw placement.

Acute Convexity Subarachnoid Hemorrhage Related to Cerebral Amyloid Angiopathy: Clinicoradiological Features and Outcome.

BACKGROUND: The specificities of acute convexity subarachnoid hemorrhage (cSAH) related to cerebral amyloid angiopathy (CAA) and its evolution are not well known. We aimed to describe the clinicoradiological pattern, the magnetic resonance imaging (MRI) evolution, and the risk of recurrent bleeding in such patients. METHODS: Among consecutive patients with an acute nontraumatic cSAH, subjects with available MRI who meet the modified Boston criteria for probable CAA were included. Review of medical records, MRI findings, and follow-up data was performed. RESULTS: Twenty-three patients (14 women; mean age ± standard deviation: 75.9 ± 7.3 years) were included. cSAH was revealed by transient focal neurological episodes (TFNEs) in 18 of 23 (78.3%) patients. In all patients, acute cSAH appeared as a sulcal fluid-attenuated inversion recovery hyperintensity and GRE T2 hypointensity. Cortical superficial siderosis and cortical microbleeds, respectively, were observed in 21 (91.3%) and 20 (86.9%) patients. Twenty patients (87%) had available follow-up data with a mean duration of 29.8 ± 20.2 months. Recurrent TFNEs occurred in 40% of patients. Acute cSAH evolved into cortical superficial siderosis in all patients. New subarachnoid bleedings defined by recurrent acute cSAH (n = 8) or extension of siderosis (n = 14) were detected in 83.3% of the patients. Lobar intracerebral hemorrhage (ICH) occurred in 7 patients (35%). CONCLUSION: CAA-related cSAH has a specific pattern defined by a high prevalence of TFNEs and cortical superficial siderosis, with a high risk of recurrent bleeding, either cSAH or lobar ICH. The systematic evolution from cSAH to focal cortical superficial siderosis reveals data on siderosis physiopathology.

State-of-the-art MRI techniques in neuroradiology: principles, pitfalls, and clinical applications.

This article reviews the most relevant state-of-the-art magnetic resonance (MR) techniques, which are clinically available to investigate brain diseases. MR acquisition techniques addressed include notably diffusion imaging (diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and diffusion kurtosis imaging (DKI)) as well as perfusion imaging (dynamic susceptibility contrast (DSC), arterial spin labeling (ASL), and dynamic contrast enhanced (DCE)). The underlying models used to process these images are described, as well as the theoretic underpinnings of quantitative diffusion and perfusion MR imaging-based methods. The technical requirements and how they may help to understand, classify, or follow-up neurological pathologies are briefly summarized. Techniques, principles, advantages but also intrinsic limitations, typical artifacts, and alternative solutions developed to overcome them are discussed. In this article, we also review routinely available three-dimensional (3D) techniques in neuro MRI, including state-of-the-art and emerging angiography sequences, and briefly introduce more recently proposed 3D quantitative neuro-anatomy sequences, and new technology, such as multi-slice and multi-transmit imaging.

3D fat-saturated T1 SPACE sequence for the diagnosis of cervical artery dissection.

INTRODUCTION: This study aims to demonstrate the added value of a 3D fat-saturated (FS) T1 sampling perfection with application-optimised contrast using different flip angle evolutions (SPACE) sequence compared to 2D FS T1 spin echo (SE) for the diagnosis of cervical artery dissection. METHODS: Thirty-one patients were prospectively evaluated on a 1.5-T MR system for a clinical suspicion of acute or subacute cervical artery dissection with 3D T1 SPACE sequence. In 23 cases, the axial 2D FS T1 SE sequence was also used; only these cases were subsequently analysed. Two neuroradiologists independently and blindly assessed the 2D and 3D T1 sequences. The presence of recent dissection (defined as a T1 hyperintensity in the vessel wall) and the quality of fat suppression were assessed. The final diagnosis was established in consensus, after reviewing all the imaging and clinical data. RESULTS: Overall sensitivity and specificity were 0.929 and 1 for axial T1 SE, and 0.965 and 0.945 for T1 SPACE (P > 0.05), respectively. The two readers had excellent agreement for both sequences (k = 1 and 0.8175 for T1 SE and T1 SPACE, respectively; P > 0.05). The quality of the fat saturation was similar. Very good fat saturation was obtained in the upper neck. Multiplanar reconstructions were very useful in tortuous regions, such as the atlas loop of the vertebral artery or the carotid petrous entry. 3D T1 SPACE sequence has a shorter acquisition time (3 min 25 s versus 5 min 32 s for one T1 SE sequence) and a larger coverage area. CONCLUSION: 3D T1 SPACE sequence offers similar information with its 2D counterpart, in a shorter acquisition time and larger coverage area.

Toxoplasmic encephalitis IRIS in HIV-infected patients: a case series and review of the literature.

BACKGROUND: Toxoplasmic encephalitis associated with immune reconstitution inflammatory syndrome (TE-IRIS) is rarely described. METHODS: To identify TE-IRIS cases, the authors performed a retrospective study of all HIV-infected patients diagnosed as having TE in our unit between January 2000 and June 2009, and a review of published cases. RESULTS: Three patients out of 65 toxoplasmic encephalitis (TE) cases, together with six from the literature, fulfilled the unmasking TE-IRIS definition. None fulfilled the paradoxical TE-IRIS definition. TE occurred within a median time of 48.5 days (IQ(25-75) 21-56) after starting antiretroviral therapy. Cases did not have distinctive clinical or neuroimaging features from TE occurring without immune reconstitution. However: (1) cases occurred at a median CD4 lymphocytes count of 222/µl (IQ(25-75) 160-280); (2) TE occurred in five patients who were supposed to take an effective chemoprophylaxis; (3) two patients had a brain biopsy showing an intense angiocentric inflammatory infiltrating with predominantly CD8 lymphocytes; (4) in one patient, the abnormal length of evolution under treatment might be due to the heightened immune response. CONCLUSION: Although rare, unmasking TE-IRIS exists and might occur despite effective prophylaxis and an unusually high CD4 lymphocyte count. Immune reconstitution inflammatory syndrome does not modify TE diagnosis and treatment but might extend its clinical course.

Patterns of convexal subarachnoid haemorrhage: clinical, radiological and outcome differences between cerebral amyloid angiopathy and other causes.

BACKGROUND: Cerebral amyloid angiopathy (CAA) is a common aetiology of convexal subarachnoid haemorrhage (cSAH) but little is known about its specific characteristics in comparison with cSAH from other causes. In this study we compared patients with CAA vs. non-CAA-related cSAH. METHODS: Retrospective review of baseline and follow-up data of consecutive patients admitted with a symptomatic acute cSAH. RESULTS: Sixty-two patients were included (mean age 66.2 ± 14.1 years), of whom 31 with probable CAA. CAA patients presented more frequently with transient symptoms (83.9 vs. 19.3%; p < 0.001) usually without headache (19.0 vs. 58.1%; p = 0.002). In CAA, these were essentially positive sensory disturbance that met the criteria of transient focal neurological episodes (TFNE). CAA was more often associated with cortical superficial siderosis (cSS) (80.6 vs. 0%; p < 0.001) and lobar cerebral microbleeds (83.4 vs. 9%; p < 0.001). During a mean of 22 months of follow-up, recurrent symptomatic cSAH occurred in 4/27 (12.9%) CAA patients and in 0/27 non-CAA patients. Among 40 patients with MRI follow-up, cSAH recurrences were observed in 44% of CAA patients vs. 13.3% of other cases (p = 0.08) and extension of cSS was detected only in CAA (60%) (p < 0.001). Acute cSAH evolved to cSS in 96 and 73.3% of CAA and non-CAA patients, respectively (p = 0.06). CONCLUSIONS: CAA differs from other cSAH in having TFNE as a frequent clinical presentation, a high prevalence of cSS and an increased risk of recurrent subarachnoid bleeding. However, evolution from acute cSAH to focal cSS may not be specific to CAA.

CO2BOLD assessment of moyamoya syndrome: Validation with single photon emission computed tomography and positron emission tomography imaging.

AIM: To compare the assessment of cerebrovascular reserve (CVR) using CO2BOLD magnetic resonance imaging (MRI) vs positron emission tomography (PET) and single photon emission computed tomography (SPECT) as reference standard. METHODS: Ten consecutive patients (8 women, mean age of 41 ± 26 years) with moyamoya syndrome underwent 14 pre-surgical evaluations for external-internal carotid artery bypass surgery. CVR was assessed using CO2BOLD and PET (4)/SPECT (11) with a maximum interval of 36 d, and evaluated by two experienced neuroradiologists. RESULTS: The inter-rater agreement was 0.81 for SPECT (excellent), 0.43 for PET (fair) and 0.7 for CO2BOLD (good). In 9/14 cases, there was a correspondence between CO2BOLD and PET/SPECT. In 4/14 cases, CVR was over-estimated in CO2BOLD, while in 1/14 case, CVR was underestimated in CO2BOLD. The sensitivity of CO2BOLD was 86% and a specificity of 43%. CONCLUSION: CO2BOLD can be used for pre-surgical assessment of CVR in patients with moyamoya syndrome and combines the advantages of absent irradiation, high availability of MRI and assessment of brain parenchyma, cerebral vessels and surrogate CVR in one stop.

Diagnosis of acute ischemia using dual energy CT after mechanical thrombectomy.

BACKGROUND AND PURPOSE: To assess the performance of dual energy unenhanced CT in the detection of acute ischemia after mechanical thrombectomy. METHODS: Retrospective study, approved by the local institutional review board, including all patients that underwent intra-arterial thrombectomy in our institution over a period of 2 years. The presence of acute ischemia and hemorrhage was evaluated by three readers. Sensitivity and specificity of the non-contrast CT weighted sum image (NCCT) and the virtual non-contrast reconstructed image (VNC) were estimated and compared using generalized estimating equations to account for the non-independence of regions in each patient. RESULTS: 58 patients (27 women and 31 men; mean age 70.4 years) were included in the study, yielding 580 regions of interest. Sensitivity and specificity in detecting acute ischemia were higher for all readers when using VNC, with a significant increase in sensitivity for two readers (p<0.001 and 0.01) and a significant increase in specificity in one reader (p<0.001). Specificity in detecting hemorrhage was excellent for all readers. CONCLUSIONS: Dual energy unenhanced CT VNC images were superior in the identification of acute ischemia in comparison with NCCT.

Arterial embolization with Onyx of head and neck paragangliomas.

OBJECT: To report the morbidity and long term results in the treatment of paragangliomas by transarterial embolization with ethylene vinyl alcohol (Onyx), either as preoperative or palliative treatment. METHODS: Between September 2005 and 2012, 18 jugulotympanic, 7 vagal, and 4 carotid body paragangliomas (CBPs) underwent Onyx embolization, accordingly to our head and neck multidisciplinary team's decision. CBPs were embolized preoperatively. Jugulotympanic and vagal paragangliomas underwent surgery when feasible, otherwise palliative embolization was carried out alone, or in combination with radiotherapy or tympanic surgery in the case of skull base or tympanic extension. Treatment results, and clinical and MRI follow-up data were recorded. RESULTS: In all cases, devascularization of at least 60% of the initial tumor blush was obtained; 6 patients underwent two embolizations. Post-embolization, 8 patients presented with cranial nerve palsy, with partial or complete regression at follow-up (mean 31 months, range 3-86 months), except for 2 vagal and 1 hypoglossal palsy. 10 patients were embolized preoperatively; 70% were cured after surgery and 30% showed residual tumor. 19 patients received palliative embolization, of whom 5 underwent radiotherapy and 3 received tympanic surgery post-embolization. Long term follow-up of palliative embolization resulted in tumor volume stability (75%) or extension in intracranial or tympanic compartments. Onyx embolization of CBPs resulted in more difficult surgical dissection in 2 of 4 cases. CONCLUSIONS: Onyx embolization is a valuable alternative to surgery in the treatment of jugulotympanic and vagal paragangliomas; tympanic surgery or radiosurgery of the skull base should be considered in selected cases. Preoperative Onyx embolization of CBPs is not recommended.

Safety and accuracy of robot-assisted versus fluoroscopy-guided pedicle screw insertion for degenerative diseases of the lumbar spine: a matched cohort comparison.

OBJECT: Recent years have been marked by efforts to improve the quality and safety of pedicle screw placement in spinal instrumentation. The aim of the present study is to compare the accuracy of the SpineAssist robot system with conventional fluoroscopy-guided pedicle screw placement. METHODS: Ninety-five patients suffering from degenerative disease and requiring elective lumbar instrumentation were included in the study. The robot cohort (Group I; 55 patients, 244 screws) consisted of an initial open robot-assisted subgroup (Subgroup IA; 17 patients, 83 screws) and a percutaneous cohort (Subgroup IB, 38 patients, 161 screws). In these groups, pedicle screws were placed under robotic guidance and lateral fluoroscopic control. In the fluoroscopy-guided cohort (Group II; 40 patients, 163 screws) screws were inserted using anatomical landmarks and lateral fluoroscopic guidance. The primary outcome measure was accuracy of screw placement on the Gertzbein-Robbins scale (Grade A to E and R [revised]). Secondary parameters were duration of surgery, blood loss, cumulative morphine, and length of stay. RESULTS: In the robot group (Group I), a perfect trajectory (A) was observed in 204 screws (83.6%). The remaining screws were graded B (n = 19 [7.8%]), C (n = 9 [3.7%]), D (n = 4 [1.6%]), E (n = 2 [0.8%]), and R (n = 6 [2.5%]). In the fluoroscopy-guided group (Group II), a completely intrapedicular course graded A was found in 79.8% (n = 130). The remaining screws were graded B (n = 12 [7.4%]), C (n = 10 [6.1%]), D (n = 6 [3.7%]), and E (n = 5 [3.1%]). The comparison of "clinically acceptable" (that is, A and B screws) was neither different between groups (I vs II [p = 0.19]) nor subgroups (Subgroup IA vs IB [p = 0.81]; Subgroup IA vs Group II [p = 0.53]; Subgroup IB vs Group II [p = 0.20]). Blood loss was lower in the robot-assisted group than in the fluoroscopy-guided group, while duration of surgery, length of stay, and cumulative morphine dose were not statistically different. CONCLUSIONS: Robot-guided pedicle screw placement is a safe and useful tool for assisting spine surgeons in degenerative spine cases. Nonetheless, technical difficulties remain and fluoroscopy backup is advocated.

Peripheral nerves, tumors, and hybrid PET-MRI.

The study of peripheral nerves (PN) is a challenge because of the orientation, size, and also because of the fact that these pathologies are not well known. The diagnosis of PN damage was based exclusively on clinical examination and electrophysiologic testing until few years ago. MRI is the examination of choice for studying peripheral nerves; recently, magnetic resonance neurography has been added as a part of clinical routine. However, the analysis of PN after surgical treatment remains difficult. This clinical case of a sarcoma of the right brachial plexus illustrates how hybrid PET-MRI in postsurgical evaluation will clearly improve the exact delimitation of residual metabolically active tumor after surgery.

Do brain T2/FLAIR white matter hyperintensities correspond to myelin loss in normal aging? A radiologic-neuropathologic correlation study.

BACKGROUND: White matter hyperintensities (WMH) lesions on T2/FLAIR brain MRI are frequently seen in healthy elderly people. Whether these radiological lesions correspond to irreversible histological changes is still a matter of debate. We report the radiologic-histopathologic concordance between T2/FLAIR WMHs and neuropathologically confirmed demyelination in the periventricular, perivascular and deep white matter (WM) areas. RESULTS: Inter-rater reliability was substantial-almost perfect between neuropathologists (kappa 0.71 - 0.79) and fair-moderate between radiologists (kappa 0.34 - 0.42). Discriminating low versus high lesion scores, radiologic compared to neuropathologic evaluation had sensitivity / specificity of 0.83 / 0.47 for periventricular and 0.44 / 0.88 for deep white matter lesions. T2/FLAIR WMHs overestimate neuropathologically confirmed demyelination in the periventricular (p < 0.001) areas but underestimates it in the deep WM (0 < 0.05). In a subset of 14 cases with prominent perivascular WMH, no corresponding demyelination was found in 12 cases. CONCLUSIONS: MRI T2/FLAIR overestimates periventricular and perivascular lesions compared to histopathologically confirmed demyelination. The relatively high concentration of interstitial water in the periventricular / perivascular regions due to increasing blood-brain-barrier permeability and plasma leakage in brain aging may evoke T2/FLAIR WMH despite relatively mild demyelination.

In situ evidence of JC virus control by CD8+ T cells in PML-IRIS during HIV infection.

OBJECTIVE: To determine the pathophysiologic features of progressive multifocal leukoencephalopathy (PML) associated with immune reconstitution inflammatory syndrome (PML-IRIS) in HIV-infected patients. METHODS: In a cross-sectional study, we retrospectively analyzed 11 HIV-infected patients with a firm diagnosis of PML-IRIS. Brain biopsies were collected from 5 patients and their histopathologic features were compared to those of 4 HIV-infected patients with classic PML. RESULTS: PML-IRIS developed soon after initiation of antiretroviral therapy in late-presenting HIV-infected patients. The lesions from the 5 biopsied PML-IRIS patients were characterized by a reduction in the density of JC virus (JCV)-infected cells when compared to the 4 patients with PML (11.1 ± 3.2/mm² vs 51.2 ± 4.3/mm², p = 0.01). Comparing the 5 patients with PML-IRIS vs the 4 patients with PML, this correlated with an increased accumulation of CD8+ T cells (818.2 ± 192.8/mm² vs 52.5 ± 10.6/mm², p = 0.01), CD20+ B cells (33.4 ± 13.5/mm² vs 0.5 ± 0.5/mm², p = 0.01), and CD138+ plasma cells (177 ± 84.1/mm² vs 0.25 ± 0.25/mm², p = 0.01), while the number of CD68+ macrophages/microglia did not differ. The ratio between CD8+ T cells and JCV-infected cells was 70 times higher in the 5 patients with PML-IRIS. These findings indicate a clear relationship between an enhanced recruitment of CD8+ T cells and the associated control of the JCV infection. CONCLUSIONS: Our data provide in situ evidence that PML-IRIS brain lesions are enriched in cytotoxic CD8+ T cells that engage JCV-infected oligodendrocytes. This leads to a better control of JCV dissemination, but at the cost of oligodendrocyte cell death and demyelination.

Magnetic resonance imaging of metabolic diseases of the cerebral white matter.

Metabolic diseases of the brain are a rare occurrence. They may be either occurring as inherited diseases causing a destruction of myelin, or they may be the result of toxicity. Neuroimaging, especially magnetic resonance imaging, plays an important role in the detection and classification of these rare diseases. Magnetic resonance spectroscopy is an important tool in the characterization and diagnosis of inherited metabolic diseases.