Joshua P. Nickerson

Discrepancy Rates of On-Call Radiology Residents' Interpretations of CT Angiography Studies of the Neck and Circle of Willis

OBJECTIVEnThe purpose of our study was to determine the discrepancy rates of radiology residents interpretations of emergent CT angiography (CTA) studies of the neck and circle of Willis and to assess any adverse clinical outcomes.nnnMATERIALS AND METHODSnFive hundred thirty-eight CTA studies (287 circle of Willis and 251 neck) ordered emergently after hours and given preliminary readings by radiology residents from January 1, 2006, through December 31, 2007, were retrospectively reviewed. Discrepancies between the interpretations of radiology residents and the final reports of neuroradiology attending physicians were classified as either false-negatives (failure to recognize abnormalities) or false-positives (misinterpreting normal scans as abnormal). Discrepancies that could affect patient care or clinical care were considered major.nnnRESULTSnOverall, the discrepancy rate was 13.6% for circle of Willis CTA and 13.5% for neck CTA. The misinterpretation rate of first-year residents was 19.5%, which was statistically significant compared with more senior-level residents (p = 0.05). There were 57 false-negative interpretations. The most common misses were stenosis greater than 50% (n = 16) and aneurysm (n = 15), and the most common false-positive was overcalling a potential intracranial aneurysm (n = 7). No adverse clinical outcomes were detected.nnnCONCLUSIONnThe discrepancy rate between interpretations by on-call radiology residents and attending physicians of neuroradiology CTA studies was higher than expected at 13.6%, with a statistically significant greater miss rate among the most junior residents, which may be mitigated by recent changes with respect to the radiology residents overnight call. No adverse clinical outcome was detected.

Neuroimaging of Pediatric Intracranial Infection—Part 2: TORCH, Viral, Fungal, and Parasitic Infections

In the second half of this 2‐part review, the neuroimaging features of the most common viral, fungal, and parasitic infections of the pediatric central nervous system are discussed. Brief discussions of epidemiology and pathophysiology will be followed by a review of the imaging findings and potential differential considerations. J Neuroimaging 2012;22:e52–e63.

Potholes and Molehills: Bias in the Diagnostic Performance of Diffusion-Tensor Imaging in Concussion

PURPOSEnTo investigate the extent of bias in a clinical study involving pothole analysis of diffusion-tensor imaging (DTI) data used to quantify white matter lesion load in diseases with a heterogeneous spatial distribution of pathologic findings, such as mild traumatic brain injury (TBI), and create a mathematical model of the bias.nnnMATERIALS AND METHODSnUse of the same reference population to define normal findings and make comparisons with a patient group introduces bias, which potentially inflates reported diagnostic performance. In this institutional review board-approved prospective observational cohort study, DTI data were obtained in 20 patients admitted to the emergency department with mild TBI and in 16 control subjects. Potholes and molehills were defined as clusters of voxels with fractional anisotropy values more than 2 standard deviations below and above the mean of the corresponding voxels in the reference population, respectively. The number and volume of potholes and molehills in the two groups were compared by using a Mann-Whitney U test.nnnRESULTSnStandard analysis showed significantly more potholes in mild TBI than in the control group (102.5 ± 34.3 vs 50.6 ± 28.9, P < .001). Repeat analysis by using leave-one-out cross-validation decreased the apparent difference in potholes between groups (mild TBI group, 102.5 ± 34.3; control group, 93.4 ± 27.2; P = .369). It was demonstrated that even with 100 subjects, this bias can decrease the voxelwise false-positive rate by more than 30% in the control group.nnnCONCLUSIONnThe pothole approach to neuroimaging data may introduce bias, which can be minimized by independent training and test groups or cross-validation methods. This bias is sufficient to call into question the previously reported diagnostic performance of DTI for mild TBI.

Neuroimaging of Pediatric Intracranial Infection—Part 1: Techniques and Bacterial Infections

Conventional and advanced neuroimaging have become central to the diagnosis of infectious diseases of the pediatric central nervous system. Imaging modalities used by (pediatric) neuroradiologists include cranial ultrasound, computed tomography, and magnetic resonance imaging, including advanced techniques such as diffusion weighted or tensor imaging, perfusion weighted imaging, susceptibility weighted imaging, and 1H magnetic resonance spectroscopy. In this first of a two part review, imaging techniques in general and the imaging findings of bacterial infections of the intracranial compartment including epidural empyema, subdural empyema, meningitis, cerebritis, cerebral abscess, and pyogenic intraventricular empyema (ventriculitis) are discussed. J Neuroimaging 2012;22:e42–e51.

In Vivo Quantification of T1ρ in Lumbar Spine Disk Spaces at 3 T Using Parallel Transmission MRI

OBJECTIVEnT1ρ MRI is an emerging, quantitative imaging modality that has been shown to correlate with proteoglycan content of disk material in vitro at 1.5 T. The purpose of this study is to quantify T1ρ values at all lumbar spine disk space levels at 3 T with parallel-transmission MRI in healthy adult volunteers.nnnSUBJECTS AND METHODSnThirty-four subjects (15 men, ages 21-60 years [mean age, 38.4 years]; and 19 women, ages 20-56 years [mean age, 36.5 years]) with no history of back pain or surgery underwent T1ρ MRI of the lumbar spine at 3 T with parallel transmission and sagittal T2-weighted imaging. Mean T1ρ values of all lumbar spine disk space levels were quantified. Linear regression analysis and Spearman rank correlation were performed on age, sex, degenerative grade (Pfirrmann scores), and T1ρ with significance set at p < 0.05 and correlations considered strong for r > 0.7 and moderate for r = 0.5-0.7.nnnRESULTSnThere was a statistically significant moderate negative correlation between T1ρ and subject age at disk space levels L1-2 through L4-5 (inclusive) (p < 0.001) and L5-S1 (p < 0.01). There was a statistically significant difference in T1ρ between all age groups sampled (p < 0.01) and a significant difference between T1ρ and Pfirrmann grades 1-3 (p < 0.01).nnnCONCLUSIONnT1ρ MRI in the lumbar spine with parallel transmission shows signifi-cant negative correlations with age at all disk space levels, which lends support to a potential role for T1ρ as a quantitative, in vivo biomarker of disk degeneration.

Quantitative and morphologic change associated with breast cancer-related lymphedema. Comparison of 3.0T MRI to external measures.

UNLABELLEDnAbstract Introduction: Lymphedema is a chronic disease of increasing importance to cancer survivors. A tape measurement tool used for lymphedema relies on indirect volume calculations based on external circumference, which may not reflect the true extent of abnormal fluid accumulation accurately. Fluid-sensitive MRI sequences may be able to delineate the severity of this condition more precisely and thus also monitor response to therapy.nnnMETHODS AND RESULTSnEight patients being followed by physical therapy for clinically diagnosed breast cancer-related lymphedema were recruited to participate in this study. External measurements and upper extremity MRI were performed on all subjects. Arm circumference, arm volume, and lymphedema volumes were calculated for each method. MR imaging detected lymphedema in all study subjects. Correlation was found between external circumferential measurements and with the 3.0T MRI (r=0.9368). There was poor correlation between lymphedema volumes calculated from clinical measurements and MR imaging (r=0.5539).nnnCONCLUSIONSnExternal measurements were not found to be an accurate measure of lymphedema volume associated with breast cancer lymphedema. MRI is a reliable means to obtain upper extremity circumferential and volume measurements. MRI is able to evaluate morphologic change associated with breast cancer-related lymphedema. Lymphedema research requires integrated use of tools to further describe the disease process over time, quantitate the distribution of tissue changes, and improve the sensitivity and specificity of the measurements.

Onodi cell mucocele causing acute vision loss: Radiological and surgical correlation

In 1904 Onodi first described an anatomic variation in which a posterior ethmoid cell projected within the sphenoid bone [1]. Since that time the definition of the Onodi cell, as it has come to be known, has evolved to the most posterior eth-moid air cell that has pneumatized superior to the sphenoid sinus [2]. Among rhinology surgeons, the defining charac-teristic of an Onodi cell is that it contains the optic canal. Onodi cells have been reported to occur in approximately 7% of the general population in computed tomography (CT) studies, but in cadaveric studies they have been reported to be present in up to 60% of specimens [3]. The discrepancy may be due in part to the fact that older studies using thick section axial CT without isotropic resolution were less sen-sitive for detecting small air cells which are often flat in configuration within the plane of axial section [4]. Identifi-cation of an Onodi cell is of importance prior to sinonasal surgery due to the close anatomic relationship between this posterior air cell and the optic nerve ([5]; Fig. 1).Most often an incidental finding, the Onodi cell is rarely involved in pathologic processes. In essence any process which is typically associated with the paranasal sinuses may be found within an Onodi cell including infectious or inflammatory sinusitis, fungus ball, inverted papilloma, mucocele or sinonasal malignancy. Given the proximity of the adjacent optic nerve, lesions of the Onodi cell may pre-sent with vision changes as the process extends beyond the borders of the cell or expands the osseous margins [6].

IgG4-Related Neuromyopathy Associated With Recurrent Pleural Effusion.

Objective: Immunoglobulin G4-related disease (IgG4-RD) is an increasingly recognized idiopathic systemic disorder associated with elevated serum IgG4 level and tissue infiltration by IgG4-positive plasma cells. Multiple neurological manifestations, including peripheral neuropathy, have been described in IgG4-RD. Our objective is to discuss a case report and review of the literature, which would expand the spectrum of IgG4-RD. Methods: We describe the clinical features and biopsy findings in a patient with IgG4-RD who presented with features suggestive of neuromyopathy in the setting of recurrent pleural effusion and weight loss. Results: Electrodiagnostic findings were suggestive of an irritable myopathy and polyradiculoneuropathy with primary demyelination and secondary axonal degeneration. Pleural biopsy and laboratory studies confirmed the diagnosis. Improvement was sustained with steroid therapy. Conclusions: We describe the first case, to our knowledge, of IgG4-related neuromyopathy associated with recurrent pleural effusion. Our case expands the clinical spectrum of IgG4-RD. Neurologists should be aware of this treatable disorder and in the appropriate clinical context consider it in the differential diagnosis of neuromyopathy.

Dynamic changes in diffusion measures improve sensitivity in identifying patients with mild traumatic brain injury

The goal of this study was to investigate patterns of axonal injury in the first week after mild traumatic brain injury (mTBI). We performed a prospective cohort study of 20 patients presenting to the emergency department with mTBI, using 3.0T diffusion tensor MRI immediately after injury and again at 1 week post-injury. Corresponding data were acquired from 16 controls over a similar time interval. Fractional anisotropy (FA) and other diffusion measures were calculated from 11 a priori selected axon tracts at each time-point, and the change across time in each region was quantified for each subject. Clinical outcomes were determined by standardized neurocognitive assessment. We found that mTBI subjects were significantly more likely to have changes in FA in those 11 regions of interest across the one week time period, compared to control subjects whose FA measurements were stable across time. Longitudinal imaging was more sensitive to these subtle changes in white matter integrity than cross-sectional assessments at either of two time points, alone. Analyzing the sources of variance in our control population, we show that this increased sensitivity is likely due to the smaller within-subject variability obtained by longitudinal analysis with each subject as their own control. This is in contrast to the larger between-subject variability obtained by cross-sectional analysis of each individual subject to normalized data from a control group. We also demonstrated that inclusion of all a priori ROIs in an analytic model as opposed to measuring individual ROIs improves detection of white matter changes by overcoming issues of injury heterogeneity. Finally, we employed genetic programming (a bio-inspired computational method for model estimation) to demonstrate that longitudinal changes in FA have utility in predicting the symptomatology of patients with mTBI. We conclude concussive brain injury caused acute, measurable changes in the FA of white matter tracts consistent with evolving axonal injury and/or edema, which may contribute to post-concussive symptoms.