Journal Scan – This Month in Other Journals, April 2017

Zurawski J, Lassmann H, Bakshi R. Use of Magnetic Resonance Imaging to Visualize Leptomeningeal Inflammation in Patients With Multiple Sclerosis. JAMA Neurol. 2017;74(1):100. doi:10.1001/jamaneurol.2016.4237.

You are well aware that MS is a chronic demyelinating disease traditionally characterized by an initial relapsing-remitting clinical course and focal inflammatory lesions that have a predilection for the periventricular white matter.  However, histopathologic and imaging studies have illustrated a more complex pathologic substrate involving cortical demyelination, gray matter atrophy, and meningeal inflammation.  The authors evaluate the status and prospects regarding the emerging role of MR to visualize leptomeningeal enhancement (LME) in patients with MS and place these findings in the proper pathobiologic and clinical context.

Absinta et al (Absinta M, Vuolo L, Rao A, et al. Gadolinium-based MRI characterization of leptomeningeal inflammation in multiple sclerosis. Neurology. 2015;85(1):18-28.) found that LME was significantly more common than had been initially reported, and its presence was associated with patient age, disease severity, and clinical type of MS. The authors used high-resolution 3T 3-dimensional T2 FLAIR MRI with a voxel size of 1.0 × 1.0 × 1.0mm and postcontrast images obtained 10 minutes after gadolinium injection. They demonstrated LME in 74 of 299 patients with MS (24.7%) compared with only 1 of 37 (2.7%) age-matched controls with out MS. Perhaps of particular importance, LME was twice as frequent (33%) in patients with progressive forms of MS (present in 44 patients with secondary progressive MS) (SPMS) and 74 patients with primary progressive MS (PPMS) compared with those with relapsing-remitting (RR) disease (19%). Disease duration, and Expanded Disability Status Scale scores were associated with LME. Whole-brain and cortical atrophy were also associated with LME. There was no association between LME and WM lesion enhancement or WM lesion volume. Leptomeningeal enhancement topography abutted the pial surface on the cerebral convexity (19% of lesions), within a sulcus (56%), along a dural fissure (17%), or involved more than 1 of these areas (7%).

Zivadinov et al (Zivadinov R, Ramasamy DP, VaneckovaM, et al. Leptomeningeal contrast enhancement is associated with progression of cortical atrophy in MS: a retrospective, pilot, observational longitudinal study [published online November 3, 2016]. Mult Scler. doi:10.1177/1352458516678083) evaluated 50 patients (27 with RRMS and 23 with SPMS) by 3T 3-dimensional high resolution post contrast T2 FLAIR MRI. Half of the patients showed LME, of whom most (56.0%) had SPMS. In addition, the SPMS group was significantly more likely to have multiple foci of LME compared with those with RRMS.  An MRI based group analysis showed that patients with LME had statistically significantly larger percent decreases in global cerebral GM volume and global cortical GM volume in the previous 5 years compared with patients without LME.

The authors conclude that a growing body of evidence suggests that gray matter demyelination, cortical atrophy, and leptomeningeal inflammation may be important components of MS pathology, in particular in progressive stages of the disease. The way in which these processes are interconnected remains an area of active investigation. Evaluation with MRI of focal LME may prove a useful surrogate marker for meningeal inflammation and cortical demyelination.

5 Figures

I was slightly more enthusiastic about this until I saw the images…the areas of LE shown are quite small, and a single sulcus seems to be involved. I have not seen images of more extensive LE. On the other hand, the small foci do seem real, so I will be interested to see where it goes.

Patel N V., Mian M, Stafford RJ, et al. Laser Interstitial Thermal Therapy Technology, Physics of Magnetic Resonance Imaging Thermometry, and Technical Considerations for Proper Catheter Placement During Magnetic Resonance Imaging–Guided Laser Interstitial Thermal Therapy. Neurosurgery. 2016;79(6):S8-S16. doi:10.1227/NEU.0000000000001440.

In this review, the authors describe the basic physics of magnetic resonance–guided laser-induced thermal therapy and describe several common techniques for accurate Visualase laser catheter placement in a stepwise fashion.

Two major commercially available laser products are in use: the Visualase (Medtronic, Minneapolis, Minnesota) and Monteris Systems (Monteris Medical, Plymouth, Minnesota). The general steps for laser catheter placement involve stereotactic registration with burr hole creation, catheter placement, laser ablation, and post-procedure care. There is the potential for great variation in laser catheter placement techniques, as multiple registration and guidance systems are available, each with different software and hardware. Although traditional frame-based techniques were initially and continue to be used, the various other available approaches have been reported, including frameless, trajectory guides/platforms, and stereotactic robots.

Frameless systems theoretically allow for greater flexibility in trajectories, reduce the physical bulk of the procedure, and eliminate the risk of frame displacement, but introduce the risk of loss of registration from the shift of the reference fiducials relative to the head. Use of anatomic landmarks, pattern tracing, gadolinium stick-on fiducials, and skull-implanted fiducials has been reported in the literature. The most common software systems used with these techniques have been StealthStation (Medtronic) and Brainlab (Brainlab AG, Feldkirchen, Germany).

Use of the Leksell (Elekta Inc, Norcross, Georgia) or Cosman-Roberts-Wells (CRW Frame; Integra Inc, Plainsboro, New Jersey) has shown success for accurate laser placement. It is historically considered the most accurate method to reach a deep target in the brain accurately when using preoperative imaging. Typically, the process occurs in a fashion similar to stereotactic biopsy planning. After placement of the stereotactic frame, an MR volumetric image set (typically with contrast) is obtained, or a CT scan is performed and merged with preoperative MRI. The patient is then transferred back to the operating room.  The intended target coordinates are defined and translated into frame coordinates using the software on most neuronavigation systems.

5 Figures

There is much, much more to this review than I can summarize here, including specific nuances for specific systems, so check it out if you are interested.

Cancienne JM, Werner BC, Puvanesarajah V, et al. Does the Timing of Preoperative Epidural Steroid Injection Affect Infection Risk After ACDF or Posterior Cervical Fusion? Spine (Phila Pa 1976). 2017;42(2):71-77. doi:10.1097/BRS.0000000000001661.

ESIs continue to be the most commonly performed procedures in pain clinics throughout the United States, with approximately 2.3 million procedures performed yearly among Medicare patients alone. Furthermore, rates of cervical and thoracic transforaminal epidural injections have increased 142% from 2000 to 2011. The authors utilized a national insurance database to compare postoperative infection rates within 90 days in patients who received a CESI before ACDF or posterior cervical fusion (PCF). Three cohorts were created for each procedure: PCF (n=402) or ACDF (n=4354) within 3 months, PCF (n=586) or ACDF (n=5183) between 3 and 6 months, and PCF (n=629) or ACDF (n=3648) between 6 and 12 months following a CESI. These cohorts were compared with control cohorts who underwent PCF (n=61,253) or ACDF (n=241,678) without prior CESI. Postoperative infection rates within 90 days were assessed using ICD-9 and CPT codes. Patients who underwent CESI within 3 months and within 3 to 6 months before PCF had significantly increased odds of developing a postoperative infection. Patients who underwent CESI within 3 months before ACDF had significantly increased odds of developing a postoperative infection.  The association of ESI to infection was not noted when cervical ESI was performed more than 6 months before posterior cervical fusion or more than 3 months before ACDF.

Noriega DC, Hernández-Ramajo R, Rodríguez-Monsalve Milano F, et al. Risk-benefit analysis of navigation techniques for vertebral transpedicular instrumentation: a prospective study. Spine J. 2017;17(1):70-75. doi:10.1016/j.spinee.2016.08.004.

Background: Screw position in this article is defined by the Heary grade. Heary Grade I pedicle screw position is denoted by a well-placed screw entirely contained within the pedicle and VB; Grade II screw violates the lateral pedicle wall but is still contained within the pedicle–rib complex, and the tip of the screw is entirely contained within the VB; Grade III shows a screw tip penetrating the anterior or lateral VB; Grade IV screws breach the medial or inferior pedicle borders; and Grade V positioning is reserved for screws that endanger the spinal cord, nerve root, or great vessels by violating the VB or pedicle cortices (Heary RF et al, J Neurosurg 2004; 100 (4 suppl spine): 325-31).

This prospective, randomized observational study in 114 patients (level II evidence) compared the malposition rate between intraoperative CT assisted-navigation and free-hand fluoroscopy-guided techniques for placement of pedicle screw instrumentation. Forty-four out of 625 implanted screws were malpositioned: 11 (3.6%) in the navigated surgery group and 33 (10.3%) in the free-hand group. Screw position according to the Heary scale was Grade II (4 navigated surgery, 6 fluoroscopy guided), Grade III (3 navigated surgery, 11 fluoroscopy guided), Grade IV (4 navigated surgery, 16 fluoroscopy guided), and Grade V (1 fluoroscopy guided). There was only one symptomatic case in the conventional surgery group. The results show the statistically significant superiority of transpedicular screw placement using CT-assisted surgery. This technique of pedicle screw placement not only has the best accuracy rate for placement but also minimizes the severity of malpositioning.

Harston GWJ, Okell TW, Sheerin F, et al. Quantification of Serial Cerebral Blood Flow in Acute Stroke Using Arterial Spin Labeling. Stroke. 2017;48(1):123-130. doi:10.1161/STROKEAHA.116.014707.

The aim of the study was to explore the relationship between dynamic CBF and tissue outcome in the month after acute stroke onset in 40 patients by performing repeated MRI with ASL. Imaging was performed at presentation, 2 hours, 1 day, 1 week, and 1 month. Imaging included vessel encoded pseudocontinuous arterial spin labeling using multiple postlabeling delays to quantify CBF in gray matter regions of interest. ROC curves were used to predict tissue outcome using CBF. Repeatability was assessed in 6 healthy volunteers. DWI and T2-weighted FLAIR were used to define tissue outcome.

The study found variability and overlap of CBF at several levels. Contralateral normal brain showed a weighted mean CBF of 52 (plus or minus 42) mL/100g/min. Between patients, there was marked overlap in presenting and serial CBF values. ROC curve analysis of CBF generated an area under the curve (AUC) of 0.71 for predicting final infarct using all patients scanned within 6 hours.  They saw marked heterogeneity in the patterns of perfusion within identically defined ROIs between patients. Both sustained ischemia and reperfusion to varying degrees were seen in the ischemic core and early and late infarct growth ROIs. The only uniform pattern was seen in periinfarct ROIs, which by definition survived, where all patients demonstrated a CBF value of >20 mL/100 g/min by 24 hours. They concluded that a single CBF measurement to predict tissue outcome at presentation in an individual is not sufficient, even with knowledge of final perfusion status. The predominant source of variability in the measurement of CBF was the variation seen between individuals (as opposed to temporal variation within individuals and other factors including noise). This individual variation may reflect differences in age, hypertension, and the burden of preexisting cerebrovascular disease.

The authors conclude that without exogenous contrast, CBF values were derived that were consistent with more invasive techniques. The ability to acquire serial data highlighted the heterogeneity of perfusion characteristics between individuals and the need for other information, including tissue susceptibility and metabolism, to fully understand tissue fate in acute stroke.

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Williamson PR, Jarvis JN, Panackal AA, et al. Cryptococcal meningitis: epidemiology, immunology, diagnosis and therapy. Nat Reviews Neurology. 2016;13(1):13-24. doi:10.1038/nrneurol.2016.167.

This is an in-depth review of the epidemiology and clinical features of cryptococcal meningitis (CM). CM is the most common cause of adult meningitis in large parts of the world with high rates of HIV infection.  It also occurs in an increasing number of patients with other forms of natural and iatrogenic immunosuppression, and in the apparently immunocompetent, particularly in the Far East.  A recent analysis  estimates CM to cause 140,000 deaths per year, of which 102,000 are in Africa, and suggests that CM accounts for 17% of AIDS-related mortality. In Europe and North America, the numbers of cryptococcal cases fell dramatically after introduction of effective antiretroviral therapy (ART), with hospitalizations falling by half. However, there is no evidence of a decrease in cases in many high-incidence African countries despite increased access to ART. Cryptococcal meningitis is a significant problem in transplant recipients and other patients with defects in cell-mediated immunity, with high rates of death despite therapy. In a US series of over 300 HIV-negative patients with cryptococcal infection, half had CNS involvement and of these, 25% had received steroid therapy, 24% had chronic liver, kidney or lung disease, 16% had a malignancy, and 15% had received solid organ transplants.

Immune reconstitution inflammatory syndrome (IRIS) is a common and life theatening complication of CM. In the context of HIV, there are two forms of IRIS: “paradoxical” IRIS (in patients who respond to antifungal therapy for CM before starting ART and then have a relapse of CM symptoms after starting ART) and “unmasking” IRIS in individuals who present with CM for the first time after ART is started. In the HIV-negative host, paradoxical immune reactions are an important cause of poor outcome in CM. In patients who have previously been immunosuppressed prior to bone marrow transplantation or given chemotherapy for hematological malignancies, reductions in immunosuppressive medications to boost the immune response frequently result in an IRIS-like reconstitution syndrome.

5 Figures and 1 Table

Sorenson T, Brinjikji W, Rabinstein AA, Lanzino G. Advances in the Treatment of Acute Ischemic Stroke : A Primer for Neurosurgeons. Contemp Neurosurg. 2017;39(1):0-5.

This is a review of the history and current status of endovascular therapy for acute stroke, and provides a nice summary of the recent randomized controlled clinical trials (MR CLEAN, EXTEND-Ia, SWIFT PRIME and ESCAPE). These trials have provided convincing evidence that endovascular therapy, alone or in combination with IV pharmacologic thrombolysis is the optimal approach for many patients evaluated within the first several hours after acute ischemic stroke.  Degree of disability at 90 days, as measured by modified Rankin Score (mRS), is nearly twofold lower in patients undergoing IA therapy as compared with patients receiving only IV therapy. Early recanalization rates for IA treatment are double those achieved with IV t-PA. On the down side, the studies have reported widely disparate absolute proportions of patients who achieved good outcomes, with MR CLEAN reporting 33% and EXTEND-IA reaching closer to 70%. These variances likely reflect patient selection criteria, emphasizing that proper candidate selection is the key to success.

The complexity of imaging used in patient selection varied considerably amongst the trials. MR CLEAN only required a noncontrast CT scan and evidence of large-vessel occlusion on imaging for inclusion. They reported good neurologic outcome rates of 33% for endovascular and 19% for medical treatment arms. ESCAPE required noncontrast CT and multiphase CT angiography (CTA) to document occlusion and collateral status and they reported good neurologic outcome rates of 53% endovascular and 29% medical. EXTEND-IA required noncontrast CT and CT perfusion to document the presence of a large penumbra and reported good neurologic outcome rates of 71% endovascular and 40% medical. Since benefit was observed even in the absence of advanced imaging (i.e., MR CLEAN study), advanced imaging benefits do not supersede the benefits of timely intervention.

4 Figures

Gao M, Sun J, Jiang Z, et al. Comparison of Tuberculous and Brucellar Spondylitis on Magnetic Resonance Images. Spine (Phila Pa 1976). 2017;42(2):113-121. doi:10.1097/BRS.0000000000001697.

This is a retrospective case series evaluating the imaging characteristics of brucellar spondylitis (BS)(n=26) and tuberculous spondylitis (TS)(n=18). They found statistically different changes between TS and BS including:

  1. Increased subligamentous spread to 3 or more vertebral levels in TS (54% vs 8%);
  2. thoracic spine involvement in TS (50% vs 4%; and lumbar spine involvement in BS (77% vs 22%);
  3. abnormal signal from the vertebral disc on T2-weighted images in BS (85% vs 33%);
  4. focal or fan-shaped hyperintense signals on sagittal fat-suppressed T2-weighted images in BS (50% vs 14%)—usually arising from the vertebral corners.

They consider the most distinctive findings for TS to be 1) a clear predominance of dorsal involvement; 2) relative disc preservation and a relatively normal signal from the disc on T2-weighted images; 3) a pattern of mainly bone destruction; 4) typical psoas abscesses and more extensive subligamentous spread; 5) diffuse, abnormal signal from the whole involved body on sagittal views.

8 Figures

Worth looking at this article for the images alone.

Journal Scan – This Month in Other Journals, April 2017
jross
Jeffrey Ross • Mayo Clinic, Phoenix

Dr. Jeffrey S. Ross is a Professor of Radiology at the Mayo Clinic College of Medicine, and practices neuroradiology at the Mayo Clinic in Phoenix, Arizona. His publications include over 100 peer-reviewed articles, nearly 60 non-refereed articles, 33 book chapters, and 10 books. He was an AJNR Senior Editor from 2006-2015, is a member of the editorial board for 3 other journals, and a manuscript reviewer for 10 journals. He became Editor-in-Chief of the AJNR in July 2015. He received the Gold Medal Award from the ASSR in 2013.

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