The Neuroimaging Spectrum of Septum Posticum Derangement and Associated Thoracic Myelopathy.

BACKGROUND: Arachnoid cysts and meningeal membranes are among the differential diagnostic considerations of extra-medullary causes of thoracic myelopathy. In this case series of 7 patients, we present compressive meningeal membranes mimicking dorsal arachnoid cyst. The propensity of the meningeal membranes for the dorsal aspect of upper thoracic spine may reflect derangements of the septum posticum. OBJECTIVE: To provide the spectrum of imaging appearances and clinical presentations of pathology of the septum posticum to improve imaging utilization and to better guide treatment planning. METHODS: Seven patients aged 40 to 75 with MRI findings of ventral displacement and dorsal cord compression in the upper thoracic spine were further evaluated with CT-myelograms. The primary indication was to exclude dorsal arachnoid cyst. Two patients with progressive symptoms and lower extremity weakness were operated for decompression. RESULTS: CT-myelogram excluded space occupying lesions and cord herniation in all cases. Intradural dorsal meningeal webs and membranes were inconsistently visualized. In the 2 operated cases, thick coalescing membranes and hyperdynamic turbulent CSF flow were severely compressing the thoracic cord. CONCLUSION: Derangements of septum posticum may present a spectrum of findings that should be considered in the differential of thoracic myelopathy. Flattening of the posterior cord margin is a reliable imaging clue for a dorsal extra-medullary compressive lesion. Cord compression results from combination of adhesive membranes and turbulent CSF flow. The clinical course may be difficult to predict. Periodic imaging follow up can be helpful to confirm stability of findings in expectantly managed cases.

Application of basic physics principles to clinical neuroradiology: differentiating artifacts from true pathology on MRI.

OBJECTIVE: This article outlines artifactual findings commonly encountered in neuroradiologic MRI studies and offers clues to differentiate them from true pathology on the basis of their physical properties. Basic MR physics concepts are used to shed light on the causes of these artifacts. CONCLUSION: MRI is one of the most commonly used techniques in neuroradiology. Unfortunately, MRI is prone to image distortion and artifacts that can be difficult to identify. Using the provided case illustrations, practical clues, and relevant physical applications, radiologists may devise algorithms to troubleshoot these artifacts.

Application of basic principles of physics to head and neck MR angiography: troubleshooting for artifacts.

Neurovascular imaging studies are routinely used for the assessment of headaches and changes in mental status, stroke workup, and evaluation of the arteriovenous structures of the head and neck. These imaging studies are being performed with greater frequency as the aging population continues to increase. Magnetic resonance (MR) angiographic imaging techniques are helpful in this setting. However, mastering these techniques requires an in-depth understanding of the basic principles of physics, complex flow patterns, and the correlation of MR angiographic findings with conventional MR imaging findings. More than one imaging technique may be used to solve difficult cases, with each technique contributing unique information. Unfortunately, incorporating findings obtained with multiple imaging modalities may add to the diagnostic challenge. To ensure diagnostic accuracy, it is essential that the radiologist carefully evaluate the details provided by these modalities in light of basic physics principles, the fundamentals of various imaging techniques, and common neurovascular imaging pitfalls.

T2 hyperintensity of medial lemniscus: higher threshold application to ROI measurements is more accurate in predicting small vessel disease.

BACKGROUND: Medial lemniscus T2 hyperintensity (MLH) has been recently demonstrated as potential imaging marker for small vessel disease (SVD). Our purpose in this study is to improve accuracy of regions of interest (ROI) analysis for this imaging finding. METHODS AND METHODS: Two neuroradiologists retrospectively reviewed 103 consecutive outpatient brain MRI. Medial lemniscus signal in dorsal pons was evaluated; visually on FLAIR and with ROI on T2. Original MRI interpretations were divided into three categories; SVD, multiple sclerosis (MS), and nonspecific WM changes (non). RESULTS: Thirty-seven patients had SVD, 14 patients had MS, 52 had Non. Visual MLH was seen exclusively with SVD and was generally bilateral. Patients with visual MLH belonged to advanced SVD by imaging and clinical parameters. Compared to visual data, ROI analyses of MLH has been known to be compounded by false positives and negatives at low threshold (20% of adjacent to normal brainstem signal). With application of higher ROI threshold (25%), false positives were eliminated but false negatives increased. ROI analyses of MLH by experienced neuroradiologist were more reliable. CONCLUSION: MLH seen on high threshold ROI analysis is a reliable radiologic marker in predicting SVD. ROI analysis of MLH should be performed by an experienced neuroradiologist.

Sterile brain abscess due to juvenile xanthogranuloma: DWI characteristics.

Juvenile xanthogranuloma (JXG) is a disorder of non-Langerhans cell histiocytosis that usually displays as a self-limiting course in children. Rare systemic involvement implies poor prognosis. Although conventional and spectroscopic magnetic resonance imaging (MRI) findings of JXG in CNS have been described, diffusion imaging of intracranial JXG has not been reported. Our case report is the first manuscript to describe diffusion restriction of a cerebral lesion seen in the setting of JXG. Since diffusion restriction has not been described in the setting of JXG but it is more commonly associated with infectious cerebral abscess, this finding has had significant impact in the management. Central nervous system (CNS) lesion of our patient has also had additional imaging features similar to typical infectious cerebral abscess. Extensive work-up has been unrevealing any infectious source. Patient has had biopsy proven peripheral sterile abscesses. After extensive discussion with the family, brain biopsy is deferred. Intravenous steroid therapy is initiated in intensive care setting. All of the lesions have gradually responded to steroid therapy. CNS lesion has taken the longest time to clear.

T2 hyperintensity of medial lemniscus is an indicator of small-vessel disease.

OBJECTIVE: Small-vessel disease is a common MRI finding that can be difficult to differentiate from other white matter (WM) diseases because of the lack of a specific pattern of brain involvement. The purpose of our study was to evaluate medial lemniscus hyperintensity seen on FLAIR images as an imaging marker for small-vessel disease. MATERIALS AND METHODS: Two blinded neuroradiologists retrospectively reviewed 103 consecutive outpatient brain MRI studies. Medial lemniscus signal in the dorsal pons was evaluated visually on FLAIR images and after placing regions of interest (ROIs) on T2-weighted images. On the basis of the original interpretations, scans were divided into three categories: small-vessel disease, multiple sclerosis (MS), and normal or nonspecific WM changes. Cardiovascular risk factors were recorded. Analysis of variance and Fisher exact tests were used to determine group differences, and kappa statistics was used to determine interrater agreement. RESULTS: Thirty-seven patients had small-vessel disease, 14 patients had MS, and 52 had nonspecific WM changes. Medial lemniscus hyperintensity was seen in about 20% of patients with small-vessel disease and was generally bilateral. Although ROI analyses identified a slightly higher number of patients with medial lemniscus signal > 20% of adjacent to normal-appearing brainstem, interrater reliability was moderate, and there were false-positive and false-negative cases in comparison with visual data. When small-vessel disease patients were further subdivided into mild or advanced subgroups, medial lemniscus hyperintensity was selectively seen in advanced small-vessel disease. Patients with medial lemniscus hyperintensity were older (p < 0.001) and had higher prevalence of diabetes (p = 0.03), hypertension (p = 0.009), and hypercholesterolemia (p = 0.03). CONCLUSION: Medial lemniscus hyperintensity seen on FLAIR images is a reliable radiologic marker of advanced small-vessel disease.

Prospective evaluation of the role of atherosclerosis on cerebral atrophy: pilot study.

PURPOSE: Our purpose was to study the association between atherosclerosis measured by arterial calcium on computed tomography (CT) and cerebral atrophy demonstrated by brain magnetic resonance imaging (MRI). MATERIALS AND METHODS: IRB approved this prospective study. Twenty-one consecutive patients with acute stroke-like symptoms who are scheduled to have brain MRI were recruited on a voluntary basis. electrocardiogram (ECG)-gated helical CT scans were used to determine the arterial calcium as a reliable index of underlying atherosclerosis. Extracranial arterial calcium content was measured quantitatively by special software available in our CT scanner. Intracranial calcium was graded qualitatively. Brain MRI was independently evaluated to identify cortical, central atrophy, and ischemic changes. Relationship between CT demonstrated atherosclerosis and cerebral ischemic changes, brain atrophy patterns were evaluated both without and with adjustment for age and hypertension. RESULTS: Out of 21 patients 20 were included in final study group. There was no correlation between atherosclerotic calcium measures and cortical atrophy, ischemic findings. Both intracranial and extracranial atherosclerosis had partial correlation with central atrophy (R= 0.43 and 0.52, respectively). After adjustment for age, only intracranial atherosclerosis maintained a partial correlation with central atrophy (R= 0.41). However, this correlation did not reach a statistically significant level (P= .10). CONCLUSIONS: Intracranial atherosclerosis demonstrated a possible correlation with central atrophy.

Unusual case of 2 renal cell carcinoma metastases ipsilateral to an occluded internal carotid artery.

Hemodynamic factors may play a role in the seeding and subsequent growth of cerebral metastasis. The authors present a case with 2 foci of cerebral metastasis in the same vascular territory ipsilateral to an occluded internal carotid artery. A 65-year-old man with chronic left frontal lobe infarct and left internal carotid artery occlusion was diagnosed with 2 large hemorrhagic metastases in the left middle cerebral artery territory. Diminished flow signals were seen in the trunk and branches of the left middle cerebral artery on magnetic resonance angiography. This case illustrates preferential seeding and growth of cerebral metastases in a region of the brain with diminished blood flow.

Nerve atrophy in severe trigeminal neuralgia: noninvasive confirmation at MR imaging--initial experience.

PURPOSE: To retrospectively evaluate the size of the trigeminal nerve on magnetic resonance (MR) images of patients with unilateral trigeminal neuralgia. MATERIALS AND METHODS: Institutional review board approval was obtained and informed consent was waived for this HIPAA-compliant study. The sizes of the trigeminal nerves in 31 patients (18 men and 13 women; mean age, 68 years; age range, 44-84 years) with clinically confirmed intractable unilateral trigeminal neuralgia were measured before treatment with gamma knife radiosurgery. Images were analyzed separately by two neuroradiologists who were blinded to the side of the face with symptoms. Coronal projection images were used to determine the diameter and cross-sectional area of the trigeminal nerves at 5 mm from the entry point of the nerve into the pons. Comparisons were made by using a paired t test. Interobserver variability was assessed by using the Pearson correlation coefficient. RESULTS: The mean diameter of the trigeminal nerve on the symptomatic side was significantly smaller than the mean diameter on the asymptomatic side in 30 of 31 patients (2.11 mm +/- 0.40 [standard deviation] and 2.62 mm +/- 0.56, P < .001, 95% confidence interval: -0.35, -0.67 mm). The mean cross-sectional area on the symptomatic side was significantly smaller than the area on the asymptomatic side in 27 of 31 patients (4.50 mm(2) +/- 1.75 and 6.28 mm(2) +/- 2.19, P < .001, 95% confidence interval: -2.41, -1.16 mm(2)). CONCLUSION: The results indicate that trigeminal nerve atrophy can be depicted noninvasively in patients with trigeminal neuralgia.

Association between neurovascular contact on MRI and response to gamma knife radiosurgery in trigeminal neuralgia.

Treatment with gamma knife radiosurgery (GKRS) provides adequate short-term pain control in about 70% of the patients with intractable trigeminal neuralgia (TN). The purpose of our study was to evaluate whether the presence of neurovascular contact (NVC) at the root entry zone of the trigeminal nerve on pre-gamma knife MR imaging predicts an increased likelihood of an adequate response to GKRS. We studied 40 consecutive patients who underwent GKRS for treatment of intractable TN. Two neuroradiologists blinded to the side of symptoms analyzed pre-treatment constructive interference in steady state (CISS) images to determine the presence of NVC by consensus. An adequate response was defined as freedom from pain with or without reduced need for medical therapy. Adequate short-term response to GKRS was seen in 29 (72.5%) of 40 patients. NVC was seen in 30 of the 40 patients. Twenty-five (83.3%) of 30 patients with NVC had adequate short-term response to GKRS. Only four (40%) of the 10 patients without NVC had adequate response to GKRS (X2=7.06; P<0.01). Patients with NVC were seven times more likely to have an adequate response to GKRS than those without NVC (odds ratio =7.5).The presence of NVC on pre-treatment MR imaging predicts an increased likelihood of an adequate response to GKRS.

Rapid development of optic glioma in a patient with hybrid phakomatosis: neurofibromatosis type 1 and tuberous sclerosis.

Increased propensity for tumor formation in neurofibromatosis and tuberous sclerosis exists because of defective tumor-suppressor genes. Although different tumor-suppressor genes may be involved in neurofibromatosis and tuberous sclerosis, at the cellular level these genes share rather common enzymatic pathways. We believe these genetic malfunctions have resulted in a cumulative or additive effect for rapid growth of optic glioma in the following unusual case that has hybrid phakomatosis.