Multiple sclerosis of the spinal cord: diagnosis and follow-up with contrast-enhanced MR and correlation with clinical activity.

PURPOSE: Although MR findings in multiple sclerosis (MS) are well known, the relationship between MR-detected lesions and clinical activity has not been studied in the spinal cord. The purpose of this study was to determine whether serial MR imaging provides evidence of disease activity unsuspected on clinical examination and to determine whether it is useful in monitoring patients with MS primarily affecting the spinal cord. METHODS: Twenty-five consecutive patients with MS and with signs and symptoms of myelopathy underwent a full neurologic examination and contrast-enhanced MR imaging of the spinal cord at intervals of 0, 2, 6, and 12 months. Disability was rated according to Kurtzke's functional systems and the expanded disability status scale (EDSS). Clinical status of myelopathy (improved, deteriorated, or stable) was also assessed. Hyperintense lesions were counted on T2-weighted images and a weighted lesion load was calculated for each patient. The number of enhancing lesions was also determined. RESULTS: We found a moderate correlation between lesion load and sensory function and EDSS. Seventy percent of patients with new clinical manifestations of myelopathy had one or more enhancing lesions. Agreement between MR findings and clinical examination in evincing disease activity was found in 60% of follow-up examinations. MR images showed lesion progression in seven (44%) of 16 occurrences of clinical deterioration and in 21 (35%) of 60 occurrences of clinical improvement or stability. CONCLUSION: Serial MR imaging provides evidence of disease activity unsuspected on clinical examination and could be useful in monitoring patients with MS primarily affecting the spinal cord.

Spinal metastases as a first presentation of malignant astrocytoma.

A 46-year-old man presented with low dorsal pain and paresthesia. Computed tomography showed an osteolytic lesion involving most of the vertebral body and the left pedicle of the 12th thoracic vertebra (T12). Contrast-enhanced magnetic resonance imaging (MRI) of the spine showed an enhancing soft-tissue mass that involved the T11 and T12 vertebral bodies, as well as that of the first lumbar vertebra; the mass caused cord compression. Another lesion was identified at T9. The findings of percutaneous needle aspiration biopsy of the lesion were consistent with metastatic astrocytoma, a diagnosis confirmed at surgery. MRI of the brain showed an asymptomatic lesion of the left temporal lobe; histologic confirmation of malignant astrocytoma was obtained by stereotactic biopsy. This report shows that metastatic bone disease secondary to malignant astrocytoma may manifest itself before the primary lesion becomes symptomatic. This presentation of astrocytoma was unusual because there were no symptoms of the intracranial tumour and because metastatic disease to the bones is less common than to the chest and the lymph nodes.

Long term survivors of childhood brain stem gliomas treated with hyperfractionated radiotherapy. Clinical characteristics and treatment related toxicities. The Pediatric Oncology Group.

BACKGROUND: Over the past decade, the principal focus of research in pediatric brain stem gliomas has been on the use of hyperfractionated radiotherapy (HRT). The purpose of this study was to evaluate the clinical characteristics and treatment related toxicities of long term survivors of HRT treatment. METHODS: Of the 130 children with brain stem tumors treated with escalating doses of HRT on Pediatric Oncology Group (POG) #8495, there are only 9 long term survivors. Prospectively collected data, including flow sheets and all pretreatment and follow-up radiologic studies, were reviewed for these patients. Additional information was requested from the treating institutions with regard to sequelae of treatment. RESULTS: Clinical characteristics (including age, sex, duration of symptoms, and presenting signs) for the nine surviving patients were not different from the total population of patients treated on POG #8495. Pretreatment imaging, however, revealed that only four of the nine patients had typical diffuse intrinsic pontine lesions and, conversely, that at least three of the nine patients had lesions that would now be considered relatively favorable. Complete information regarding treatment related toxicity was available for eight patients, only one of whom is without sequelae. Seven have schooling difficulties, two have a seizure disorder, five have hearing loss, and two have required growth hormone replacement. Follow-up imaging findings were striking in four of the eight patients because of white matter changes consistent with leukoencephalopathy (two patients), diffuse microhemorrhages (one patient), and dystrophic calcification (one patient) in the radiation field. CONCLUSIONS: The high frequency of treatment related sequelae in long term survivors of HRT suggests a need for caution in the use of HRT, particularly in patients who have brain stem tumors with a more favorable prognosis.

Subcortical white matter lesions in osmotic demyelination syndrome.

We describe a case of histologically proved osmotic demyelination syndrome. In addition to abnormal T2 signal within the pons and thalami, MR showed linear enhancing lesions at the cortical medullary junction.

Herpes zoster vasculitis: demonstration by MR angiography.

A patient presented with multiple cerebral infarcts in various vascular territories after having been treated for herpes zoster ophthalmicus. Magnetic resonance angiography demonstrated multiple focal stenoses involving the proximal intracranial vessels which corresponded to endarteritis at autopsy.

Chest "gestalt" and detectability of lung lesions.

Image perception in chest radiography is thought to occur on two levels, (a) a fast global response based on learned templates ("gestalt") and, (b) a slower systematic scan process. The relative importance of "gestalt" on the detection of nodular lung cancers was studied by disturbing the "gestalt" through rotation of the radiograph but not actually diminishing the image content available for viewing. Sixty chest radiographs (20 normals, 21 with subtle lung cancers, 19 with obvious lung cancers) were presented to three readers in normal and abnormal (rotated randomly in 90 degree increments) orientation for varying durations (0.25 s, 1 s, 4 s and unlimited viewing time). The results indicate that the detectability of obvious and subtle lung lesions was degraded by the disturbed "gestalt" for both short and long viewing times. The readers did not significantly increase their unlimited viewing time when faced with rotated images (4.4 +/- 3.4 s) as opposed to non-rotated images (4.0 +/- 3.2 s). We conclude that the detection of lung lesions relies heavily on the chest "gestalt" and that systematic scanning cannot fully compensate for an impaired global response due to a disturbed "gestalt."

CT and MR imaging findings in adults with cerebellar medulloblastoma: comparison with findings in children.

The goal of this study was to determine if certain imaging features suggest the diagnosis of cerebellar medulloblastoma in adults and to determine how often the classic CT appearance seen in children is present in adults. The study included 28 adult patients with proved cerebellar medulloblastoma. The tumor was located in the cerebellar vermis in 14 patients and in a cerebellar hemisphere in 14 patients. Thirteen patients had unenhanced CT of the brain, all patients had contrast-enhanced CT, and eight patients had unenhanced MR imaging. The imaging features in adults were compared with those in children, as described in the literature. In our adult patients, all tumors were hyperdense compared with gray matter on unenhanced CT and showed a slight to moderate increase in density after injection of contrast medium. Thirteen lesions had well-defined margins, and 15 had poorly defined margins. Low-density areas consistent with cystic and necrotic degeneration were detected in 23 (82%) of the 28 tumors. By comparison, in children, medulloblastoma usually originates in the vermis. As in adults, the mass is hyperdense on unenhanced CT, but enhances markedly and homogeneously after injection of contrast medium. Usually no evidence of cyst formation or necrosis is seen, and the tumor margins are well defined. This classic CT appearance of medulloblastoma in children was identified in only three (11%) of the 28 adult patients. Medulloblastoma has a variable MR appearance in both children and adults. On T2-weighted images, lesions are hypo-, iso-, or hyperintense compared with normal gray matter. The CT findings of medulloblastoma in adults usually differ from those of medulloblastoma in children. The tumor has a variable and nonspecific appearance in adults and should always be considered in the differential diagnosis of a mass in the posterior fossa.

Low-grade myxoid chondrosarcoma of the base of the skull: CT, MR, and histopathology.

A retrospective CT, MR, and histopathologic study was performed in five patients with histologically verified low-grade myxoid chondrosarcoma of the base of the skull. In four patients, the tumor originated off the midline and was associated with bone destruction at the petrous apex near the petrooccipital fissure. Tumor extent included the cerebellopontine angle in three patients and the parasellar area in two patients. The fifth tumor originated on the midline and was associated with destruction at the dorsum sellae. Three tumors contained calcifications, whereas two lesions were mostly isodense with brain on CT scan. All tumors were hypointense on T1-weighted MR images and very intense on T2-weighted images except for areas of signal void consistent with calcifications. Light microscopy revealed islands of mature hyaline cartilage in an abundant myxoid ground substance. Histology and immunocytochemical analysis were consistent with a low-grade myxoid chondrosarcoma. The CT and MR features of low-grade myxoid chondrosarcoma are comparable with those of chordoma. Chordoma usually arises from the midline, but cases with origin from the lateral portion of the clivus or the petrous apex have been described. Low-grade myxoid chondrosarcoma has distinct histologic and immunocytochemical features and includes lesions formerly called "chondroid chordomas."

Bronchogenic carcinoma: analysis of staging in the mediastinum with CT by correlative lymph node mapping and sampling.

One hundred forty-three patients with bronchogenic carcinoma were studied prospectively with computed tomography (CT) to determine the accuracy of CT in the evaluation of mediastinal nodal metastases. Mediastinal lymph nodes were localized according to the lymph node mapping scheme of the American Thoracic Society and were considered abnormal if they exceeded 1 cm in short-axis diameter. All patients underwent surgical staging, which consisted of either mediastinoscopy alone or mediastinoscopy and thoracotomy. At the time of surgical staging, all accessible nodes were either removed or sampled. The sensitivity of CT for mediastinal nodes on a per-patient basis was 64%, with a specificity of 62%. The sensitivity of CT for individual nodal stations involved with tumor was only 44%. The presence of obstructive pneumonitis did not appreciably alter the sensitivity of CT, but the specificity was lower (43%). The likelihood of metastases increased with lymph node size; however, seven of 19 (37%) lymph nodes that measured 2-4 cm in short-axis diameter were hyperplastic and did not contain metastases. The relative insensitivity of CT makes formal nodal sampling at the time of mediastinoscopy or thoracotomy essential to detect lymph node metastases.

Hydrocephalus and prominence of the choroid plexus: an unusual computed tomographic presentation of cerebral toxoplasmosis in AIDS.

Toxoplasmosis is a frequent cause of infection of the central nervous system (CNS) in patients with acquired immunodeficiency syndrome. Computed tomography (CT) usually shows solitary or multiple parenchymal lesions, which are most often located in the cortex, the juxtacortical white matter and the basal ganglia. The authors describe a 30-year-old immunocompromised Haitian woman with pathologically proven CNS toxoplasmosis who presented with hydrocephalus and prominence of the choroid plexus; there was no evidence of focal parenchymal lesions in contrast-enhanced CT scans. An autopsy revealed diffuse destruction of the ependyma of the lateral, the third and the fourth ventricles. Necrosis was evident, and the periventricular tissues and the choroid plexus were infiltrated with neutrophils and macrophages. Pseudocysts of Toxoplasma were identified near the ventricular surface.

Multiple occult vascular malformations of the brain and spinal cord: MRI diagnosis.

We report a patient with multiple angiographically occult vascular malformations in the brain and spine. Magnetic resonance imaging showed multiple lesions in brain and spine with hypointense areas on both T1 and T2-weighted images. These hypointense areas are usually secondary to hemosiderin deposits consistent with remote bleeding in the lesions. We conclude that when magnetic resonance reveals an intraspinal lesion with signal intensity characteristics consistent with a vascular malformation, an examination of the brain should be performed to rule out associated intracranial lesions. The finding of multiple lesions in the brain with identical signal intensity characteristics reinforces the diagnosis of vascular malformation.

Differentiation of bronchogenic carcinoma from postobstructive pneumonitis by magnetic resonance imaging: histopathologic correlation.

Obstructive pneumonitis frequently occurs distal to hilar bronchogenic carcinomas or in lung adjacent to peripheral tumors. The article evaluates the role of MRI in the differentiation of tumor from pneumonitis. Twelve patients underwent MRI of the thorax before surgery. T1-weighted (SE 310/20) and T2-weighted (SE 2000/60-120) images were obtained through the tumor and presumed areas of pneumonitis. Five histologic types of pneumonitis were identified on pathologic examination of the 12 specimens. Cholesterol pneumonitis, found in 7 patients, was the most common type. Organizing pneumonitis, bronchiectasis with mucus plugs, atelectasis, and abscess were found in 3, 4, 2, and 1 patients, respectively. MRI was able to differentiate tumor from pneumonitis in 5 of 6 patients with a hilar mass and in 5 of 6 patients with a peripheral tumor. This was achieved by a visual difference in signal intensity on heavily T2-weighted (SE 2000/120) images. Cholesterol pneumonitis and bronchiectasis with mucus plugs were always hyperintense relative to tumor, and organizing pneumonitis and atelectasis were isointense and indistinguishable from tumor. MRI can differentiate tumor from pneumonitis provided that pneumonitis is of the cholesterol type or if there are mucus plugs in the collapsed lung.

Impact of postprocessing on the detection of simulated pulmonary nodules with digital radiography.

The authors compared the impact of five postprocessing algorithms on diagnostic performance in the detection of simulated pulmonary nodules on storage phosphor-based digital chest radiographs. Tissue equivalent paraffin nodules (0.5-2.5 cm diameter) were randomly positioned over the chest of a normal volunteer. Receiver operating characteristics (ROC) analysis of a total of 2500 observations by five readers indicated that the default unenhanced image having the appearance of a conventional chest radiograph (ROC area = 0.87 +/- 0.05) was as good as an image with moderate enhancement of medium frequencies (ROC area = 0.85 +/- 0.03), an image with reversed gray scale polarity (ROC area = 0.84 +/- 0.02), an image with reversed gray scale and moderate enhancement of medium frequencies (ROC area = 0.87 +/- 0.03), and an image with a linear rather than a sigmoid gradation curve and incorporating moderate enhancement of medium frequencies (ROC area = 0.87 +/- 0.03). The authors conclude that the specific algorithms they tested had no effect on the detection of pulmonary nodules.

Plexiform neurofibromatosis of the mediastinum: CT appearance.

We studied the CT findings in four patients with pathologically proved thoracic plexiform neurofibromatosis. In all four patients, CT showed an infiltrative process and masses that involved the mediastinum along the distribution of the sympathetic chains, phrenic, and vagus nerves. The lesions had lower attenuation values than did chest-wall muscle. In one patient, CT revealed calcifications and peripheral enhancement of nodular components after IV infusion of contrast material. In the appropriate clinical setting, CT detection of lesions in the distribution of the mediastinal nerves strongly favors the diagnosis of plexiform neurofibromatosis.

Subtle lung cancers: impact of edge enhancement and gray scale reversal on detection with digitized chest radiographs.

The authors studied the impact of edge enhancement and gray scale polarity reversal on the detection of subtle lung cancers. Three experienced readers reviewed 46 biopsy-proved subtle lung cancers and 46 normal controls on chest radiographs that had been digitized into a 1,024 X 1,536-pixel matrix 8 bits deep. Receiver-operating characteristics (ROC) analysis of 1,656 pooled observations indicated that performance was best with the unmodified images (ROC area = 0.83), degraded by moderate enhancement of medium frequencies (ROC area = 0.80), and markedly impaired by severe enhancement of low frequencies (ROC area = 0.69). Gray scale polarity reversal further degraded performance (unenhanced ROC area = 0.74; moderately enhanced ROC area = 0.76; severely enhanced ROC area = 0.76). The authors conclude that edge enhancement and gray scale polarity reversal can impair the detectability of subtle lung cancers on digitized radiographs of medium resolution.

Lung lesions: correlation between viewing time and detection.

The influence of viewing time on the detectability of subtle and obvious lung cancers was studied. Frontal chest radiographs of 40 patients with subtle cancers, 40 patients with obvious cancers, and 40 healthy control subjects were shown to four observers for four different viewing times (0.25 second, 1 second, 4 seconds, and unlimited time). Receiver operating characteristic analysis was used to compare the detectability of lesions. Performance was degraded as viewing time decreased. The true-positive fractions for subtle and obvious cancers were 30% and 70% at 0.25 second and 74% and 98% at unlimited viewing time, respectively, for a given false-positive fraction of 20%. Thus, even with unlimited viewing time, the false-negative fraction for subtle cancers was 26%. The difference in detectability between subtle and obvious lung cancers was exaggerated at 1.0 second compared with 4 seconds and unlimited viewing time. The following conclusions were reached: (a) a substantial proportion of subtle lung lesions are missed, even with unlimited viewing time; (b) a large proportion of obvious lung cancers are detected with flash viewing; (c) the detectability of lesions decreases considerably as viewing time becomes less than 4 seconds; and (d) differences in detectability are exaggerated by short viewing times.

Transthoracic needle aspiration biopsy: evaluation of the blood patch technique.

A study was undertaken to evaluate the effectiveness of the blood patch technique in the prevention of pneumothorax after transthoracic needle aspiration biopsy. A total of 140 needle biopsies were performed with a coaxial system. Two groups of patients were defined according to whether or not autologous blood was injected into the introducing needle as it was withdrawn after needle aspiration biopsy. Fifty-two biopsies were performed with the blood patch technique (group A), while 88 biopsies were performed without the blood patch technique (group B). The frequency of postbiopsy pneumothorax was 28.8% (15 of 52 patients) in group A and 34.1% (30 of 88 patients) in group B. Chest tube insertion was required in 7.7% (four of 52 patients) in group A and in 9.1% (eight of 88 patients) in group B. There was no statistically significant difference in pneumothorax rate and chest-tube insertion rate between the two groups (P greater than .05). In this series of 140 biopsies, the blood patch technique failed to affect the rate of pneumothorax after transthoracic needle aspiration biopsy.