Faculty Bibliography

PURPOSE: To compare neoplastic and nonneoplastic disease in the anterior extradural space (AES) with regard to the contour of the disease and the tethering of the central septum, as seen on axial magnetic resonance (MR) images. MATERIALS AND METHODS: In this institutional review board-approved HIPAA-compliant study, the data of patients who had AES disease determined at MR imaging and underwent diagnostic biopsy were studied. Two blinded observers reviewed the MR images and assigned the patients to one of two groups on the basis of the contour of AES disease: those with a centrally convex disease contour posteriorly and those whose disease contour was tethered in the midline to the posterior aspect of the vertebral body. Biopsy results served as the standard of reference. The two-tailed Fisher exact test, the Breslow-Day test, and kappa statistics were used to compare groups. The sensitivity, specificity, and accuracy of the midline tethered contour of AES disease for the detection of neoplasm were calculated. RESULTS: The data of 32 patients (16 men, 16 women; mean age, 68 years) were studied. Seventeen patients had malignant epidural disease. Fifteen patients had nonneoplastic epidural disease: Six patients had hematomas, and nine had abscesses. A greater proportion of AES neoplasms (13 [76%] and 14 [82%] of 17 lesions for observers 1 and 2, respectively) than nonneoplastic AES lesions (four [27%] and three [20%] of 15 lesions for observers 1 and 2, respectively) demonstrated midline tethering of the central septum. For observers 1 and 2, a unilobed or bilobed appearance of AES disease had sensitivities of 76% (13 of 17 lesions) and 82% (14 of 17 lesions), respectively; specificities of 73% (11 of 15 lesions) and 80% (12 of 15 lesions), respectively; and accuracies of 75% (24 of 32 lesions) and 81% (26 of 32 lesions), respectively, for the detection of neoplasm. The mean kappa value for interobserver variability was 0.62 (95% confidence interval: 0.35, 0.90). CONCLUSION: AES disease preserving the midline tethering of the central septum is more common with neoplastic disease than with infections or hematomas.

OBJECTIVE: Dural metastases and meningiomas are extraaxial lesions that may be difficult to distinguish using conventional imaging methods. This distinction, however, is clinically important. Perfusion MRI may play a role in preoperative assessment. The aim of this study was to evaluate the utility of perfusion parameters in differentiating between these two entities. In particular, we evaluated two new metrics that reflect the first-pass wash-in characteristics of perfusion. MATERIALS AND METHODS: Patients with intracranial extraaxial masses who underwent perfusion MRI were included. Region-of-interest analysis was performed and several perfusion metrics were calculated including relative cerebral blood volume (rCBV), mean transit time and time to peak (TTP) enhancement from initial bolus enhancement (T0), calculated as TTP-T(0). Two new metrics characterizing first pass wash-in enhancement were also measured: relative wash-in time and wash-in slope. Lesions were divided into two groups: meningioma and metastasis. Comparisons between the two groups were made using Wilcoxon rank sum and Fisher exact tests. RESULTS: Twenty lesions were studied (12 meningioma and 8 metastases). Compared with meningiomas, relative wash-in time was statistically lower in metastases (p < 0.05). No other statistically significant differences were observed. Specifically, there was no difference between the two study groups in rCBV. CONCLUSION: First-pass wash-in characteristics of dural lesions may be useful for evaluating and characterizing lesions. In particular, a metric describing the wash-in phase of perfusion-that is, relative wash-in time-was found to be lower in metastases compared with meningiomas. Contrary to a prior report, we found rCBV to be limited in the evaluation of extraaxial lesions.

A case of Whipple's disease with development of antibiotic resistance is reported. The patient's symptomatology correlated with evolution of diffusion abnormality rather than with lesion enhancement. The lesion demonstrated no hyperperfusion, moderately elevated choline, and decreased N-acetylaspartate. Conventional magnetic resonance (MR) imaging findings of central nervous system Whipple's disease are nonspecific and may mimic neoplasm. MR perfusion and spectroscopy findings are reported, which may assist in diagnosis. Change in diffusion restriction appears to be a potential imaging indicator of clinical progression and response to therapy

OBJECTIVE: Diffusion tensor imaging (DTI) allows in vivo delineation of brainstem white matter tracts. The purpose of this study was to determine whether or not abnormalities of DTI metrics and fiber tractography correlate with neurological deficits and clinical status in patients with primary posterior fossa tumors. METHODS: A review of patients with primary posterior fossa tumors who underwent magnetic resonance imaging with DTI was performed. Patients were stratified by tumor type (well-circumscribed or infiltrating lesions). Fractional anisotropy (FA) color maps were used to localize the corticospinal tracts within the brainstem. FA, mean diffusivity, and eigenvalues were measured. Tractography was performed. Correlations between DTI metrics and clinical status and between DTI metrics and neurological examination findings were assessed within each patient group using Bonferroni correction for multiple comparisons. Comparisons of DTI metrics were also made between patient groups (infiltrating lesions versus well-circumscribed lesions). RESULTS: Thirty patients were studied (mean age, 14.1 yr; 16 male, 14 female). Eighteen patients had infiltrating lesions and 12 had well-circumscribed lesions. Twelve patients (four well-circumscribed and eight infiltrating) demonstrated motor weakness on physical examination (four right, three left, five bilateral). Patients with well-circumscribed lesions and weakness had higher mean diffusivity and lower FA in the contralateral corticospinal tract (P < 0.05). No such association was seen in patients with infiltrating tumors. In 102 total patient-years of follow-up (average follow-up period, 4.2 yr), 17 patients (six well-circumscribed and 11 infiltrating lesions) demonstrated complete response or stable disease and six patients (three well-circumscribed and three infiltrating lesions) demonstrated progressive disease or death. No differences were seen in terms of DTI metrics between patients with infiltrating lesions and those with well-circumscribed lesions. Patients with well-circumscribed tumors and a bad outcome had significantly lower transverse eigenvalue measures in the corticospinal tracts compared with those with a more favorable clinical status (P < 0.05). CONCLUSION: In patients with well-circumscribed primary posterior fossa masses, higher mean diffusivity and lower FA in the brainstem corticospinal tract are associated with contralateral motor deficits; lower transverse eigenvalue may be observed with an unfavorable clinical outcome

Revesz syndrome is a variant of dyskeratosis congenita characterized by aplastic anemia, retinopathy, and central nervous system abnormalities. We describe a 3-year-old boy in whom the spectrum of neuroimaging findings, including intracranial calcifications, cerebellar hypoplasia and unusual brain lesions were found by biopsy to be gliosis despite their enhancement and progression. In patients with dyskeratosis-related syndromes, non-neoplastic parenchymal brain lesions occur and gliosis should be considered in the differential diagnosis for progressive enhancing brain lesions. Should this finding be confirmed consistently in additional cases, brain biopsy could potentially be avoided.

OBJECTIVE AND IMPORTANCE/OBJECTIVE:Locked-in syndrome is a state of preserved consciousness in the setting of quadriplegia, anarthria, and usually also includes lateral gaze palsy. It is most commonly associated with upper brainstem infarction variably sparing the third cranial nerve nucleus. There are likely many etiologies that contribute to this clinical syndrome. These are incompletely understood, and the syndrome remains a rare but devastating complication that can occur after neurosurgical and neurovascular interventions. Advanced magnetic resonance imaging techniques such as perfusion and diffusion tensor imaging may help to elucidate the mechanism behind locked-in syndrome. To the authors' knowledge, there are no reports in the literature of perfusion and diffusion tensor findings in patients with this syndrome. A postprocedural case of locked-in syndrome is described with abnormalities on perfusion and diffusion tensor imaging in the absence of any changes in conventional magnetic resonance imaging. CLINICAL PRESENTATION/METHODS:A 57-year-old man who presented with acute onset headache, ataxia, and other nonspecific symptoms was found on imaging to have a giant fusiform basilar artery aneurysm. INTERVENTION/METHODS:A saphenous vein graft bypass between the proximal right external carotid artery and P2 segment of the right posterior cerebral artery followed immediately by endovascular embolization of the aneurysm sac and distal left vertebral artery was performed. CONCLUSION/CONCLUSIONS:Postprocedural angiography demonstrated patency of the bypass graft, and diffusion weighted imaging showed no evidence for acute brainstem infarction. Nevertheless, despite technically successful procedures and the absence of abnormalities on conventional magnetic resonance imaging, the patient developed quadriplegia and anarthria and remained in a locked-in state until he expired. Abnormalities were, however, seen on both perfusion and diffusion tensor imaging, where hypoperfusion, increased mean diffusivity, and decreased fractional anisotropy were observed in the ventral brainstem. The findings suggested a disruption of pontine white matter tracts. Advanced imaging techniques may allow us to image important microstructural changes that were previously not discernable and assist in the evaluation of patients with complex neurological sequelae such as locked-in syndrome.

BACKGROUND AND PURPOSE: Patients with nonlesional temporal lobe epilepsy have long been known to have abnormalities of memory. Recently, these patients have been shown to have increased diffusivity in the hippocampus. We hypothesized that in these patients, a negative correlation would exist between diffusivity measures of the mesial temporal lobe and performance on neuropsychological tests. METHODS: Twenty presurgical patients with temporal lobe epilepsy and 20 age- and sex-matched healthy controls underwent MR imaging of the brain. Apparent diffusion coefficient region of interest measures were taken in both hippocampi and parahippocampal gyri by 2 independent observers. Mean whole brain diffusivity was calculated. All patients completed neuropsychological testing. Electroencephalogram and pathology results were collected. Patients and controls were compared with respect to each apparent diffusion coefficient measure. In patients, apparent diffusion coefficients ipsilateral and contralateral to the seizure focus were compared. Associations were assessed between diffusivity measures and neuropsychological scores. RESULTS: Eleven patients had right-sided seizure foci and 9 had left-sided seizure foci. Patients demonstrated higher apparent diffusion coefficient values than controls over the whole brain, in the hippocampi, and in the parahippocampal gyri (P < .05). Patients demonstrated higher apparent diffusion coefficient within the ipsilateral hippocampus (1.19 +/- 0.22 x 10(-3) s/mm2) and parahippocampal gyrus (1.02 +/- 0.12 x 10(-3) s/mm2) compared with the contralateral side (1.02 +/- 0.16 x 10(-3) s/mm2 and 0.96 +/- 0.09 x 10(-3) s/mm2, respectively) (P < .05). Negative correlations were seen between hippocampal apparent diffusion coefficients and multiple memory tests (P < .05). CONCLUSION: Quantitative diffusion measurements in the hippocampus correlate with memory dysfunction in patients with temporal lobe epilepsy

OBJECTIVE: Our purpose was to determine the clinical significance of polyps missed on CT colonography using histologic analysis and the natural history of colorectal polyps and to propose guidelines for follow-up colon surveillance based on CT colonographic findings. SUBJECTS AND METHODS. One hundred eighty-six men (age range, 40-87 years; mean, 62.3 years) underwent CT colonography immediately before conventional colonoscopy. All polyps detected on CT colonography were measured and imaged, and their segmental location was documented. All polyps detected on colonoscopy were measured, photographed, biopsied, and histologically analyzed. Results of CT colonography and conventional colonoscopy were compared with the final pathology reports. Conventional colonoscopy was used as the gold standard unless CT colonography showed a lesion measuring 10 mm or more that was not detected on conventional colonoscopy and had characteristics of a polyp. In these cases, follow-up conventional colonoscopy was offered. RESULTS: One hundred ninety-one polyps were detected on conventional colonoscopy. CT colonography prospectively detected 53 polyps. Histologic analysis of the polyps not detected on CT colonography showed that of those 5 mm or smaller, 58.1% were not adenomas, and of those measuring 6-9 mm, 42.8% were not adenomas. Both missed polyps at CT colonography of 10 mm or more were adenomas. Of the 22 polyps measuring 10 mm or more, three were not detected on conventional colonoscopy. Of these three, CT colonography showed a lesion having characteristics of a polyp, follow-up endoscopy confirmed the presence of the lesion, and histologic analysis showed a villous adenoma, a tubulovillous adenoma, and a tubular adenoma. CONCLUSION: If CT colonography shows no abnormality, follow-up screening in 5 years is recommended. If CT colonography detects a lesion smaller than 5 mm, follow-up imaging in 3-5 years is recommended. If CT colonography detects a lesion measuring 6 mm or more, endoscopy and polypectomy should be offered unless contraindicated

PURPOSE: To compare thin-section multi-detector row computed tomographic (CT) colonography with conventional colonoscopy in the evaluation of colorectal polyps and cancer in asymptomatic average-risk patients. MATERIALS AND METHODS: Sixty-eight asymptomatic men (age > 50 years) scheduled to undergo screening colonoscopy were enrolled in this study. CT colonography was followed by conventional colonoscopy, performed on the same day. Supine and prone CT colonography were performed after colonic insufflation with room air. A gastroenterologist measured all polyps, which were categorized as 1-5, 6-9, or over 10 mm. Biopsy and histologic evaluation were performed of all polyps. CT colonography and colonoscopy results were compared for location, size, and morphology of detected lesions. Point estimates and 95% CIs were provided for specificity and sensitivity of CT by using results at conventional colonoscopy as the reference standard. RESULTS: At colonoscopy, 98 polyps were identified in 39 patients; 21 (21.4%) of 98 were detected at CT colonography. Sensitivity was 11.5% (nine of 78) for polyps 1-5 mm, 52.9% (nine of 17) for polyps 6-9 mm, and 100% (three of three) for polyps over 10 mm. Results at colonoscopy were normal in 29 (42.6%) of 68 patients; at CT colonography, results were correctly identified as normal in 26 of these 29 patients. In one of these patients, a lesion larger than 10 mm was detected at CT colonography. The per-patient specificity of CT was 89.7% (26 of 29; 95% CI: 72.7%, 97.8%). The mean time for CT image interpretation was 9 minutes. CONCLUSION: In patients at average risk for colorectal cancer, CT colonography is a sensitive and specific screening test for detecting polyps 10 mm or larger; the sensitivity for detecting smaller polyps is decreased. Examination findings can be interpreted in a clinically feasible amount of time