Differentiation between meningeal fibrosis and chronic subdural hematoma after ventricular shunting: value of enhanced CT and MR scans

Unenhanced CT in four patients with long-standing ventricular shunts demonstrated bilateral low-density extraaxial collections that were indistinguishable from chronic subdural hematomas. After administration of contrast material, however, there was marked enhancement of the collections as well as prominent paratentorial and parafalcial enhancement. MR imaging, performed in three patients, demonstrated the extent and paradural location of the collections better than CT did, but, as with unenhanced CT, the collections could not be distinguished from chronic subdural hematomas. On follow-up CT and MR, there was no change in the size, enhancement, or intensity of the collections. Histologic examination of biopsies from two patients demonstrated fibrosis of the meninges characterized by granulation tissue and collagen deposition. Meningeal fibrosis is a rare postshunt phenomenon that may mimic chronic subdural hematoma on unenhanced CT and MR. Recognition of this entity is important, particularly if therapeutic intervention is being considered. Therefore, an enhanced CT or enhanced MR scan should be obtained in chronically shunted patients to differentiate between a drainable chronic subdural hematoma and meningeal fibrosis.     

Subdural and epidural empyemas: MR imaging

The MR images of six patients with extraaxial empyemas (five subdural and four epidural) were reviewed and compared with CT scans. MR demonstrated convexity and interhemispheric collections, which were mildly hyperintense relative to CSF and hypointense relative to white matter on short TR pulse sequences and hyperintense relative to CSF and white matter on long TR pulse sequences, allowing distinction from sterile effusions and most chronic hematomas. A hypointense rim, representing displaced dura, was depicted at the interface between the lesion and brain in epidural empyemas, a feature absent in subdural empyemas. Inflammation-induced parenchymal abnormalities, including edema, mass effect, and reversible cortical hyperintensity, were well depicted on MR imaging. MR was superior to CT in demonstrating the presence, nature, and extent of these lesions in all cases. Because early and accurate diagnosis will significantly improve the prognosis of these serious infections, MR is preferred to CT for patients in whom an acute intracranial infection is suspected.     

Coronal computed tomography: indications and accuracy.

The application of wide aperture scanners to neuroradiology permits improved anatomic definition and localization of intracranial and intraorbital lesions. Coronal scans are most useful in demonstrating lesions of the skull base and apex, distinguishing between infra- and supratentorial lesions, and in determining if a lesion is intra- or extraaxial. Limitations of coronal scans include discomfort in positioning, high spatial frequency artifacts, and additional radiation exposure.     

Diagnosis of extracerebral fluid collections by computed tomography.

The computed tomography scans of 90 patients with extracerebral fluid collections were reviewed. Epidural hematomas, acute, subacute, and chronic subdural hematomas, convexity subarachnoid hemorrhages, subdural hygromas, and one epidural empyema were seen. The CT findings were analyzed and correlated with the time elapsed since injury (when known) and the results of radionuclide scans (when available). The overall accuracy of CT in detecting extracerebral fluid was 90% with no acute hemorrhages missed. In subacute and chronic subdural collections, six CT scans were false negative in whole or in part. Three false positive interpretations were made and are discussed.     

Computed tomography in the evaluation of subdural hematomas.

Computed tomographic (CT) scans used in the diagnosis and management of subdural hematomas were analyzed with respect to their contribution to angiography and surgery. There has been a progressive increase in the use of CT in evaluating post-traumatic and postoperative subdural hematomas at the Mayo Clinic. At present, 40% of all patients undergo operation on the basis of the CT findings alone. False-positive diagnoses revealed at surgery have decreased to less than 4%. Erroneous negative interpretations have involved 10% of all patients whose diagnosis was subdural hematoma. Criteria for the interpretation of scans have been established.     

Prospective comparative study of intermediate-field MR and CT in the evaluation of closed head trauma

Forty patients with closed head trauma were evaluated prospectively with CT and intermediate-field-strength MR imaging to compare the diagnostic efficacies of the two techniques. Traumatic lesions were detected in 38 patients. The severity of injury, as determined by the Glascow Coma Scale, ranged from 3 to 14. The sensitivities of CT and MR were calculated for all subgroups of lesions: (1) hemorrhagic and nonhemorrhagic intraaxial lesions (diffuse axonal injury, cortical contusion, subcortical gray-matter injury, primary brainstem injury); (2) extraaxial hematomas (subdural, epidural); and (3) diffuse hemorrhage (subarachnoid, intraventricular). CT and MR (T1- and T2-weighted) studies were both highly and comparably sensitive in the detection of hemorrhagic intraaxial lesions. MR scans, however, were much more sensitive in detecting nonhemorrhagic lesions. cortical contusions and diffuse axonal injury constituted 91.9% of all intraaxial lesions. The sensitivities of the imaging techniques for this combined group of lesions were (1) nonhemorrhagic lesions (CT = 17.7%, T1-weighted MR = 67.6%, T2-weighted MR = 93.3%); (2) hemorrhagic lesions (CT = 89.8%, T1-weighted MR = 87.1%, T2-weighted MR = 92.5%). MR was also significantly better in detecting brainstem lesions (CT = 9.1%, T1-weighted MR = 81.8%, T2-weighted MR = 72.7%). The sensitivities of the diagnostic studies in the detection of extraaxial hematomas were CT = 73.2%, T1-weighted MR = 97.6%, T2-weighted MR = 90.5%). Intraventricular hemorrhage was consistently seen with all three imaging studies, but subarachnoid hemorrhage was detected much more frequently with CT. In summary, MR has clear advantages over CT in evaluating closed head trauma. Although its sensitivity in detecting hemorrhagic lesions is similar to that of CT, it is much better than CT in detecting nonhemorrhagic lesions, which are more prevalent. MR is more useful than CT in classifying primary and secondary forms of injury and directing treatment. CT's one advantage over MR is its ability to more rapidly assess unstable patients who may need surgery.     

Computed tomography of isoattenuating subdural hematomas.

CT scans of 87 patients with subdural hematoma were compared to those of 393 patients with midline shift caused by other intracranial lesions with regard to attenuation changes in the lesion and the character of the ventricular deformity. Isoattenuating was exhibited by 25% of the subdural hematomas and 5% of the other lesions. In 70 to 80% of the isoattenuating hematomas, the diagnosis could be made on the basis of the characteristic ventricular deformity. Other diagnostic procedures are not necessary in these cases.     

大脑镰硬膜下血肿的CT诊断

目的评价CT对大脑镰硬膜下血肿诊断的可行性。方法回顾性分析25例具有完整资料的外伤性大脑镰硬膜下血肿的CT表现。结果25例中,14例表现细绳索状高密度影,11例表现粗绳索状高密度影;粗绳索状影近中线侧平直,外侧呈浅波浪状,其对应脑回受压远离中线,脑沟及纵裂池模糊或消失。结论大脑镰硬膜下血肿是硬膜下血肿的一种少见类型,通过分析CT征象,能够作出正确诊断。     

Subtle pathology detection with multidetector row coronal and sagittal CT reformations in acute head trauma

We sought to analyze retrospectively the advantages of coronal and sagittal reformations obtained with multidetector row computed tomography (CT) in patients with acute head trauma. Multidetector 16-section CT was performed in 200 patients (110 male and 90 female; age range, 3–87 years; mean age, 45 years) with acute head trauma. Scans were performed sequentially, and axial 5-mm-thick slices were obtained from base of skull to vertex. The source data set was reformatted in coronal and sagittal planes, with 2-mm-thick sections at 2-mm intervals. Images were analyzed retrospectively by two independent, blinded readers. The final diagnosis was determined by clinical follow-up. CT imaging abnormalities were detected in 55 out of 200 patients who were scanned for head trauma. Acute traumatic intracranial abnormality was detected on axial scans in 45 patients. Subtle findings were confirmed on coronal and sagittal CT reformations in ten cases, and these were undetected initially on axial CT. Coronal and sagittal reformations confirmed subtle findings in 18.2% (10/55) of the cases (P = 0.001). Indeterminate neuroimaging findings confirmed by coronal and sagittal CT head reformations include tentorial and interhemispheric fissure subdural hemorrhage, subarachnoid hemorrhage, and inferior frontal and temporal lobe contusions. Coronal and sagittal CT head reformations improve the sensitivity and diagnostic confidence in the clinical setting of acute trauma. Overall, coronal and sagittal reformations improved diagnostic confidence and interobserver agreement over axial images alone for visualization of normal structures and in the diagnosis of acute abnormality.     

Statistical detection of nonvisible isodense subdural fluid collections.

An analytic method for detecting isodense subdural fluid collections from computed tomography (CT) scan pixel attenuation data is presented. Analysis of 44 CT scan levels from 8 patients with isodense subdural hematomas (ISDH) and 50 CT scan levels from 15 patients without ISDH indicates 6% false positive and 3% false negative errors if the analysis is restricted to noncontrast CT scans that demonstrate subcalvarial bilateral cortical attenuation symmetry in the pictorial display.     

Coronal computed tomography in orbital disease

Coronal computed tomography (CT) was applied to the diagnosis of orbital disease. With this technique, the size and extent of intraorbital tumors and their relationship to the eyeball, optic nerve, and extraocular muscles were demonstrated, often with information additional to that obtained by the standard axial transverse tomograms. In particular, inferior or superior displacement of the eyeball was clearly revealed. Coronal sections afforded easier comparison with other neuroradiologic examinations. In the evaluation of hyperthyroidism, the extraocular muscles were shown clearly in cross section and enlargement of the muscles was advantageously assessed by this technique. Coronal CT provides additional and complementary information to the conventional axial transverse tomography.     

Angiographic findings in subdural hematoma correlated with CT attenuation values

Twenty-eight subdural hematomas in 24 patients were examined by angiography and computed tomography (CT). The angiographic appearance of the hematomas was classified as either crescentic, lentiform, or transitional. The attenuation value of the hematomas was calculated from the CT scans. The mean attenuation of crescentic hematomas (13.8 EMI units--EU: 500 scale) was considerably lower than those of lentiform (21.7 EU) and transitional (19.8 EU) hematomas. The crescentic and transitional hematomas were either subacute or chronic, the chronic crescentic hematomas having an attenuation value at or around serum level. The lentiform hematomas were all more than 24 days old. The relatively high attenuation in chronic lentiform and transitional hematomas was probably caused by rebleeding, and the shape indicates enlargement of the hematomas after membrane formation has occurred. In the chronic, low attenuation crescentic hematomas, no recent bleed and no enlargement had occurred.     

Diagnosis of isodense subdural hematomas by computed tomography.

Subdural hematomas, whose absorption values approximate those of adjacent brain, are not visualized in routine computed tomography. Two clues indicating the presence of such "isodense" subdural hematomas are: (1) unilateral effacement of cerebral sulci on the convexities, and (2) midline shift or mass effect on the ventricles in the absence of abnormal areas of diminished or increased density in the brain. Nine cases were detected on pre- and postcontrast studies in 2,500 CT scans of the brain over a 10 month period. Delayed CT scanning 4-6 hr after intravenous contrast injection showed enhancement of the subdural hematoma in three of seven cases.     

Further experience with contrast-enhanced CT in head trauma

Summary Abnormal contrast enhancement was seen in 196 (39.8%) of 492 CT scans performed on patients for evaluation of head trauma. It proved most helpful in the diagnosis of isodense subdural hematomas and contusions. The advantages of contrast-enhanced CT scans in the evaluation of head trauma more than compensate for the additional time in performing the examination.     

Subdural hematomas in infants with benign enlargement of the subarachnoid spaces are not pathognomonic for child abuse

BACKGROUND AND PURPOSE: Patients who have benign enlargement of the subarachnoid spaces (BESS) have long been suspected of having an increased propensity for subdural hematomas either spontaneously or as a result of accidental injury. Subdural hematomas in infants are often equated with nonaccidental trauma (NAT). A better understanding of the clinical and imaging characteristics of subdural hematomas that occur either spontaneously or as a result of accidental trauma may help distinguish this group of patients from those who suffer subdural hematomas as a result of NAT. The purpose of this study is to describe the clinical and imaging characteristics of subdural hematomas that occur either spontaneously or as a result of accidental injury in infants with BESS. METHODS: We conducted a retrospective review of all patients with BESS complicated by subdural hematomas evaluated at a single institution from 1998 to 2004. Data concerning the patient's clinical presentation, physical findings, imaging, and management are described. RESULTS: During the study period, 7 patients with BESS complicated by subdural hematoma were identified. Their mean age at identification of the subdural hematoma was 7.4 months of age. In 5 cases, there was no recognized trauma before identification of the subdural hematoma. In 3 cases, baseline CT or MR imaging was available, showing prominent subarachnoid spaces without any evidence of subdural hemorrhage. CONCLUSION: Although suspicious for NAT, subdural hematomas can occur in children either spontaneously or as a result of accidental trauma. Caution must be exercised when investigating for NAT based on the sole presence of subdural hematomas, especially in children who are otherwise well and who have BESS.     

Acute subdural hematomas: atypical CT findings

Seventy-one patients with acute subdural hematomas were examined by CT within 72 hr of a documented head injury. Lesions often did not have the classical appearance of a homogeneous, high-density extracerebral collection of blood in a crescentic configuration. Specifically, 28 patients (39%) had mixed-density subdural hematomas (MDSDH) with various degrees of low-density blood within the subdural space. In 10 of these 28 patients, the hematoma had a relatively localized mass effect with a convex inner margin, occasionally mimicking the appearance of an epidural hematoma. The MDSDH group differed from the typical homogeneous high-density subdural hematomas in that they were larger (average maximal thickness was 18.1 mm versus 8.0 mm), had more midline shift, and had a higher mortality rate (50% versus 26%). Four patients with MDSDH demonstrated an unusual pattern of ventricular compression with trapping of cerebrospinal fluid in the body of the ipsilateral ventricle and compression of the body of the contralateral ventricle. This pattern has to our knowledge not been previously described. Possible causes of the low-density regions within the hematomas include unclotted blood in an early stage of hematoma development, serum extruded during the early phase of clot retraction, or cerebrospinal fluid within the subdural space due to an arachnoid tear.     

CT诊断特殊征象的蛛网膜下腔出血

目的:探讨蛛网膜下腔出血的特殊CT征象,提高对此病变的诊断率。方法:回顾性分析17例经证实的具有特殊CT表现的蛛网膜下腔出血病例,分析其形成机理,CT表现特征及与硬膜下血肿的鉴别要点。结果:所有病例均含有颅骨内板下新月形高密度影这种酷似硬膜下血肿的CT表现,但具有内缘不锐利,密度较低且不均匀的特征。结论:CT可以诊断具此特殊表现的蛛网膜下腔出血并与硬膜下血肿鉴别。     

CT of extraarachnoid metrizamide instillation

Because CT of spinal extraarachnoid metrizamide collections may be misleading, we reviewed the postmetrizamide CT scans of 425 patients in order to characterize the appearance of subdural or epidural metrizamide. Eight patients were found to have extraarachnoid metrizamide contrast collections. In all patients, both the subarachnoid space and the extraarachnoid collection were opacified with metrizamide. In seven patients, a subdural collection of metrizamide created a mass upon the opacified subarachnoid space. Three of these subdural collections were less dense than the opacified subarachnoid compartment and simulated soft-tissue disease, including tumor and an arteriovenous malformation. The hypodense collections are probably a result of leakage of metrizamide and cerebrospinal fluid through the spinal needle defect. CT clues for diagnosing these potentially misleading subdural collections include preservation of the normal dural and epidural interface, identification of small islands of metrizamide within a suspected soft-tissue "mass," the presence of concomitant epidural contrast material collections, and the absence of adjacent vertebral-body destruction.     

Petrosal bone: coronal reconstructions from axial spiral CT data obtained with 0.5-mm collimation can replace direct coronal sequential CT scans.

PURPOSE: To investigate whether coronal multiplanar reconstruction (MPR) images of the petrosal bone from axial spiral computed tomographic (CT) data obtained with 0.5-mm collimation can replace direct coronal sequential CT scans obtained with 0.5- or 1.0-mm collimation. MATERIALS AND METHODS: The differences in diagnostic quality between thin-section coronal sequential CT scans of 24 petrosal bones in 12 patients and matched MPR images were assessed by five observers. The matched MPR images were calculated with both trilinear and tricubic interpolation. Image resolution was determined by measuring the three-dimensional point spread function. RESULTS: All observers preferred tricubically interpolated MPR images over trilinearly interpolated images. Subjective differences in image quality between direct coronal scans and matched tricubically interpolated MPR images were small. Only the direct coronal scans with the highest image quality (0.5-mm collimation, 465 mAs) were judged to be slightly better than the matched MPR images. With regard to direct coronal scans obtained at 245 mAs and/or 1.0-mm collimation, either there was no preference or the MPR images were preferred. CONCLUSION: Coronal MPR images from axial spiral CT obtained with 0.5-mm collimation can replace direct coronal sequential CT scans.     

Some limitations of computed tomography in the diagnosis of neurological diseases.

Some of the limitations of CT in the diagnosis of neurologic disease are reported. Problem areas include small lesions; lesions obscured by adjoining structures; small vascular structures and detail of large vessels; cases in which the diagnosis is made but information is incomplete for treatment; cases of incorrect diagnosis; non-nenoplastic lesions mistaken for neoplasms; some subdural hematomas; occasional false negative findings; and misinterpretation due to technical errors. Knowledge and use of the clinical presentation, the performance of other complementary diagnostic procedures, repeat CT scans tailored to the region of interest, and repeat serial scans may assist in reaching the proper diagnosis and diminishing potential error.