Denial or unawareness of cognitive deficit associated with multiple sclerosis? A case report.

A nondemented, 55-year-old woman with a 20-year history of relapsing-remitting multiple sclerosis (MS) recently began having significant difficulties performing her job after several years of successful employment. While the patient acknowledged that others considered her job performance as being below standards, she did not subjectively experience any change in her cognitive functioning that would negatively impact job performance. She had no explanation as to why her job performance was now considered unsatisfactory. She also appeared to be in no distress over her situation. Was the patient's unawareness a form of anosognosia or psychological denial of her clinical condition? We provide neuropsychological, neuroimaging, and behavioral descriptions of the patient that suggest that the underlying disturbance appeared to be a neuropsychologically based, impaired self-awareness (ISA). Clinical suggestions are provided for distinguishing between ISA and denial of disability (DD) in MS patients.

Reevaluating the imaging definition of tumor progression: perfusion MRI quantifies recurrent glioblastoma tumor fraction, pseudoprogression, and radiation necrosis to predict survival.

INTRODUCTION: Contrast-enhanced MRI (CE-MRI) represents the current mainstay for monitoring treatment response in glioblastoma multiforme (GBM), based on the premise that enlarging lesions reflect increasing tumor burden, treatment failure, and poor prognosis. Unfortunately, irradiating such tumors can induce changes in CE-MRI that mimic tumor recurrence, so called post treatment radiation effect (PTRE), and in fact, both PTRE and tumor re-growth can occur together. Because PTRE represents treatment success, the relative histologic fraction of tumor growth versus PTRE affects survival. Studies suggest that Perfusion MRI (pMRI)-based measures of relative cerebral blood volume (rCBV) can noninvasively estimate histologic tumor fraction to predict clinical outcome. There are several proposed pMRI-based analytic methods, although none have been correlated with overall survival (OS). This study compares how well histologic tumor fraction and OS correlate with several pMRI-based metrics. METHODS: We recruited previously treated patients with GBM undergoing surgical re-resection for suspected tumor recurrence and calculated preoperative pMRI-based metrics within CE-MRI enhancing lesions: rCBV mean, mode, maximum, width, and a new thresholding metric called pMRI-fractional tumor burden (pMRI-FTB). We correlated all pMRI-based metrics with histologic tumor fraction and OS. RESULTS: Among 25 recurrent patients with GBM, histologic tumor fraction correlated most strongly with pMRI-FTB (r = 0.82; P < .0001), which was the only imaging metric that correlated with OS (P<.02). CONCLUSION: The pMRI-FTB metric reliably estimates histologic tumor fraction (i.e., tumor burden) and correlates with OS in the context of recurrent GBM. This technique may offer a promising biomarker of tumor progression and clinical outcome for future clinical trials.

Anosognosia for hemiplegia with preserved awareness of complete cortical blindness following intracranial hemorrhage.

A 51-year-old woman presented with anosognosia for hemiplegia (AHP), neglect, and a complete loss of vision, for which she was almost immediately aware. Neuroimaging studies revealed intracranial hemorrhages in the medial temporal lobes bilaterally, extending back to the occipital cortex, but sparing the calcarine cortex. A large right frontal-parietal hemorrhage which extended to the posterior body of the corpus callosum was also observed. The patient's vision slowly improved, and by 11 months post onset, formal visual fields revealed improvement primarily in the left upper quadrants only. In contrast, resolution of her AHP occurred between the 26th and 31st day post onset. Awareness of motor impairment was correlated with her ability to initiate finger tapping in her left hemiplegic/paretic hand. During the time she was unaware of her motor deficits but aware of her visual impairments, her dreams did not reflect concerns over visual or motor limitations. The findings support a "modular" theory of anosognosia.

Perioperative ischemic complications of the brain after carotid endarterectomy.

BACKGROUND: The potential morbidity of cerebral ischemia after carotid endarterectomy (CEA) has been recognized, but its reported incidence varies widely. OBJECTIVE: To prospectively evaluate the development of cerebral ischemic complications in patients treated by CEA at a high-volume cerebrovascular center. METHODS: Fifty patients with moderate or severe carotid stenosis awaiting CEA were studied with perioperative diffusion-weighted imaging of the brain and standardized neurological evaluations. Microsurgical CEA was performed by 1 of 2 vascular neurosurgeons. Radiological studies were evaluated by faculty neuroradiologists who were blinded to the details of the clinical situation. RESULTS: Preoperative diffusion-weighted imaging studies were performed within 24 hours of surgery. A second study was obtained within 24 (92% of patients), 48 (4% of patients), or 72 (4% of patients) hours after surgery. Intraluminal shunting was used in 1 patient (2%), and patch angioplasty was used in 2 patients (4%). No patient had diffusion-weighted imaging evidence of procedure-related cerebral ischemia. Nonischemic complications consisted of postoperative confusion in an 87-year-old man with a urinary tract infection and a marginal mandibular nerve paresis in another patient. Radiological studies were normal in both patients. CONCLUSION: CEA is a relatively safe procedure that may be performed with an acceptable risk of cerebral ischemia in select patients. The low rate of ischemic complications associated with CEA sets a standard to which other carotid revascularization techniques should be held. The current results are presented with a discussion of the senior author's preferred surgical technique and a brief review of the literature.

Anatomical and biomechanical analyses of the unique and consistent locations of sacral insufficiency fractures.

STUDY DESIGN: Correlation of locations of sacral insufficiency fractures is made to regions of stress depicted by finite element analysis derived from biomechanical models of patient activities. OBJECTIVE: Sacral insufficiency fractures occur at consistent locations. It was postulated that sacral anatomy and sites of stress within the sacrum with routine activities in the setting of osteoporosis are foundations for determining patterns for the majority of sacral insufficiency fractures. SUMMARY OF BACKGROUND DATA: The predominant vertical components of sacral insufficiency fractures most frequently occur bilaterally through the alar regions of the sacrum, which are the thickest and most robust appearing portions of the sacrum instead of subjacent to the central sacrum, which bears the downward force of the spine. METHODS: First, the exact locations of 108 cases of sacral insufficiency fractures were catalogued and compared to sacral anatomy. Second, different routine activities were simulated by pelvic models from CT scans of the pelvis and finite element analysis. Analyses were done to correlate sites of stress with activities within the sacrum and pelvis compared to patterns of sacral insufficiency fractures from 108 cases. RESULTS: The sites of stress depicted by the finite element analysis walking model strongly correlated with identical locations for most sacral and pelvic insufficiency fractures. Consistent patterns of sacral insufficiency fractures emerged from the 108 cases and a biomechanical classification system is introduced. Additionally, alteration of walking mechanics and asymmetric sacral stress may alter the pattern of sacral insufficiency fractures noted with hip pathology (P = 0.002). CONCLUSION: Locations of sacral insufficiency fractures are nearly congruous with stress depicted by walking biomechanical models. Knowledge of stress locations with activities, cortical bone transmission of stress, usual fracture patterns, intensity of sacral stress with different activities, and modifiers of walking mechanics may aid medical management, interventional, or surgical efforts.

Occipitocervical vertical distraction injuries: anatomical biomechanical, and 3-tesla magnetic resonance imaging investigation.

STUDY DESIGN: Biomechanical load-to-failure findings correlated with anatomic dissection measurements and intact (prefailure) 3-Tesla (3-T) magnetic resonance images (MRI). OBJECTIVE: To better understand why the same distractive force to the head can result in occipitoatlantal dislocation (OAD) in some individuals and atlantoaxial dislocation (AAD) in others. SUMMARY OF BACKGROUND DATA: Distraction injuries to the cranio-vertebral junction have been studied biomechanically but have not been studied relative to ligamentous anatomic variations. We theorized that morphologic variations in the ligaments should influence the injury pattern during axial distraction. METHODS: After obtaining 3-T MRI scans, 10 occiput-C2 specimens were loaded to failure under axial tension. Direct anatomic measurements were also obtained from the distracted and injured specimens. RESULTS: AAD was observed in 7 specimens (mean force +/- standard deviation 1229 +/- 181 N) at a significantly higher magnitude than OAD, which was observed in 3 specimens (823 +/- 127 N; P = 0.009, nonpaired t test). In OAD specimens, the superior cruciate ligament (SCL), which was smaller than the inferior cruciate ligament (ICL), failed. The apical ligament was unidentifiable in these 3 specimens. In 5 of the 7 AAD specimens, the ICL ruptured and was smaller than the SCL. In the remaining 2 specimens, both SCL and ICL ruptured. The apical ligament, which ruptured, was identifiable in all 7 specimens. CONCLUSION: Axial distraction across the cranio-vertebral junction can produce either OAD or AAD. The SCL and ICL dimensions, alar ligament orientations, and apical ligament presence may affect the injury site. Visualization with 3-T MRI allows better understanding of the injury mechanism and location, which is important clinically in selecting single- or multilevel fixation.

Magnetic resonance imaging of the craniocervical junction at 3-T: observation of the accessory atlantoaxial ligaments.

OBJECTIVE: Instability of the craniocervical junction can cause neurological sequelae or pain. Stability of this region depends on extensive ligamentous support structures, most of which are well studied by magnetic resonance imaging (MRI) scanning. Although the contribution of the accessory atlantoaxial ligament to rotational stability has been described, this ligament has not been identified by imaging. Therefore, we investigated the imaging characteristics of this ligament and its relationship to the ligamentous complex of the craniocervical junction using the high resolution offered by 3-T MRI scans. METHODS: Ten healthy volunteers underwent MRI scanning at 3-T to determine the normal anatomy of this ligament. RESULTS: The atlantoaxial (C1-C2) segment of the ligament was identified in all 10 subjects bilaterally and symmetrically. Its mean dimensions were 2.8 x 1.8 mm. In four out of 10 subjects, the occipitoatlantal (C0-C1) segment was observed. At this level, the mean dimensions of the ligament were 1.6 x 1.2 mm on the right and 1.8 x 1.4 mm on the left. Its size varied between the right and left sides. CONCLUSION: The accessory atlantoaxial ligament can be visualized using high-resolution MRI scans at 3-T. The ligament was most consistent and robust at C1-C2. The ligament may, therefore, contribute to rotational stability at this level. Future studies will determine the biomechanical importance of this ligament, especially in the setting of trauma.

Measurement error of percent diameter carotid stenosis determined by conventional angiography: implications for noninvasive evaluation.

BACKGROUND AND PURPOSE: Our aim was to quantitate the range of error in measurement of percent diameter carotid stenosis using conventional angiography in order to estimate the misclassification rate in selecting patients for carotid endarterectomy. METHODS: A secondary or meta-analysis of published data regarding carotid stenosis measurement error associated with angiography yielded a narrow range of standard deviation across several studies using different measurement protocols. A simulation of the measurement process was developed to model this error and allow estimation of misclassification rates compared with true values for stenosis. RESULTS: A standard deviation of 8% describes the average error observed at 60% diameter stenosis across a number of studies. Using the measurement model, for a population with 30% prevalence of 60% stenosis, this finding implies a misclassification rate of approximately 4% overall for conventional angiography. CONCLUSION: Like all diagnostic tests, angiography is associated with measurement error. This does not affect the results of carotid stenosis therapy trials using angiography but does need to be taken into account when evaluating noninvasive alternative tests for carotid stenosis.

Brain imaging in the unsedated pediatric patient: comparison of periodically rotated overlapping parallel lines with enhanced reconstruction and single-shot fast spin-echo sequences.

BACKGROUND AND PURPOSE: Periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER or PROP) is an effective means of compensating for head motion during MR imaging in adults. The aim of this study was to assess the value of this novel technique in unsedated children. METHODS: PROP T2-weighted fast spin-echo (FSE) imaging (TR/TE/NEX, 4000/83/2; 50 seconds) and T2-weighted single-shot FSE (SS-FSE) imaging (19,929/92/0.5; imaging time, 25 seconds) were performed in 35 unsedated children (mean age, 4.7 years +/- 4.2) who were undergoing brain MR imaging. Two observers assessed unlabelled images for motion artifact, other artifacts, visibility of pathology, and the preferred image overall. Sequences were compared by using the chi(2) test and concordant data from both observers. RESULTS: Both PROP and the SS-FSE imaging offered equal degrees of motion correction. Metallic artifacts were worse on PROP imaging, likely because of a higher receiver bandwidth (P <.001, chi(2) test). Pathology was present in 28 subjects and equally well seen on PROP and SS-FSE images. Overall, PROP was preferred, largely because of its improvements in image contrast (P <.001, chi(2) test). CONCLUSION: SS-FSE imaging and PROP provide equal motion correction, although PROP enables better assessment of the brain parenchyma.

Effects of zero-filled interpolation on cervical magnetic resonance angiographic measurement.

BACKGROUND AND PURPOSE: The aim of this study was to assess the effect of zero-filled interpolation (ZIP) on measurements of the cervical arteries because its benefits on the accuracy and precision of measurements in medium-sized arteries remains unknown. METHODS: Three observers measured 36 computer-simulated vessels (2-6.8 mm) and 130 normal cervical vessels (assessed with two-dimensional time-of-flight MR angiography) from 512-, 256-, and 256-ZIP matrix source images. The accuracy and precision of measurement was assessed for each matrix by using the Student t test and F test of variance, respectively. The effect of vessel size and matrix placement on measurement error was determined by means of linear regression and the Student t test, respectively. RESULTS: No significant difference was observed between simulated measurements obtained on the 512 matrix and their true value. The 256 matrix caused overestimation of vessel diameter compared with 512 matrix (mean bias, 0.3 mm for computer-simulated vessels and 0.1 mm for normal vessels). This effect was reduced with ZIP, by a mean of 0.1 mm for both groups (P <.03). Precision was not affected by the matrix size or ZIP, and vessel size and matrix placement did not alter the measurement error. CONCLUSION: Vessel diameter is overestimated on 256-matrix MR angiographic source images. ZIP reduces this overestimation; however, the effect is small and unlikely to be clinically important.

Improved image quality and detection of acute cerebral infarction with PROPELLER diffusion-weighted MR imaging.

PURPOSE: To compare periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) multishot fast spin-echo diffusion-weighted magnetic resonance (MR) imaging with single-shot echo-planar diffusion-weighted MR imaging for image quality and visualization of acute cerebral infarction. MATERIALS AND METHODS: Seventy subjects (35 men, 35 women; mean age, 55 years +/- 24 [SD]) who were suspected of having acute cerebral infarction (symptom duration, 2.8 days +/- 2.7) underwent PROPELLER and echo-planar MR imaging (b = 1,000 sec/mm(2)). Two neuroradiologists compared unlabeled images for presence of artifacts, visualization of infarction, and their preference of images. Interobserver agreement and image comparison were assessed by using the kappa statistic and the chi(2) test, respectively. RESULTS: PROPELLER MR imaging reduced susceptibility artifacts (n = 70 subjects), which limited visualization of temporal (echo-planar, n = 64; PROPELLER, n = 0; P <.01, chi(2) test), frontal (echo-planar, n = 58; PROPELLER, n = 1; P <.01), and parietal lobes (echo-planar, n = 5; PROPELLER, n = 0; P <.05) and cerebellum (echo-planar, n = 36; PROPELLER, n = 0; P <.01) and brainstem (echo-planar, n = 23; PROPELLER, n = 0; P <.01). Acute infarction (n = 31 subjects) was better demonstrated at PROPELLER MR imaging (PROPELLER better, n = 18; echo-planar better, n = 1; PROPELLER and echo-planar equal, n = 12; P <.01, chi(2) test). PROPELLER MR imaging was preferred in all (n = 70) but one case in which the lesion lay within the intersection gap (PROPELLER preferred, n = 69; echo-planar preferred, n = 1; P <.01, chi(2) test). CONCLUSION: With a short increase in imaging time, PROPELLER MR imaging offers better image quality and detection of acute cerebral infarction than does echo-planar MR imaging.

Neural correlates of self-reflection.

The capacity to reflect on one's sense of self is an important component of self-awareness. In this paper, we investigate some of the neurocognitive processes underlying reflection on the self using functional MRI. Eleven healthy volunteers were scanned with echoplanar imaging using the blood oxygen level-dependent contrast method. The task consisted of aurally delivered statements requiring a yes-no decision. In the experimental condition, participants responded to a variety of statements requiring knowledge of and reflection on their own abilities, traits and attitudes (e.g. 'I forget important things', 'I'm a good friend', 'I have a quick temper'). In the control condition, participants responded to statements requiring a basic level of semantic knowledge (e.g. 'Ten seconds is more than a minute', 'You need water to live'). The latter condition was intended to control for auditory comprehension, attentional demands, decision-making, the motoric response, and any common retrieval processes. Individual analyses revealed consistent anterior medial prefrontal and posterior cingulate activation for all participants. The overall activity for the group, using a random-effects model, occurred in anterior medial prefrontal cortex (t = 13.0, corrected P = 0.05; x, y, z, 0, 54, 8, respectively) and the posterior cingulate (t = 14.7, P = 0.02; x, y, z, -2, -62, 32, respectively; 967 voxel extent). These data are consistent with lesion studies of impaired awareness, and suggest that the medial prefrontal and posterior cingulate cortex are part of a neural system subserving self-reflective thought.