Magnetic resonance imaging of cystic meningiomas and its surgical implications

Our purpose was to document the incidence and imaging features of cystic meningiomas, to correlate the imaging features of cystic meningiomas with the histopathological findings, and to analyze the surgical implications of the imaging features of cystic meningiomas. The imaging studies, clinical histories, operative findings, and histopathological findings of a total of 128 patients with meningiomas were reviewed retrospectively. The 15 cystic meningiomas in our series could be morphologically divided into three major types: cystic areas contained wholly within the tumor (6 meningiomas), cystic areas at the periphery of, but wholly within, the margins of the tumor (5 meningiomas), and cystic areas peripheral to the tumor, lying on the adjacent brain (4 meningiomas). A majority of cystic meningiomas were histopathologically diagnosed to be meningothelial (8 of 15 meningiomas). Cellular atypia was seen in many patients. Meningiomas may simulate astrocytomas or metastatic lesions on imaging studies. Magnetic resonance imaging had a diagnostic accuracy of 80% (12 of 15 patients), which was significantly better than the computed tomography diagnostic accuracy of 50% or less. Magnetic resonance imaging with contrast enhancement could distinguish Type 2 (cyst wall containing tumor cells) and Type 3 (cyst wall containing gliotic tissue without tumor invasion) cystic meningiomas. Cyst wall enhancement was seen in Type 2, but not in Type 3, cystic meningiomas. Cystic meningiomas represented approximately 10% of all meningiomas in our series. Histiologically, they were usually relatively aggressive, which probably partly explains why cystic changes may be secondary to tumor necrosis or hemorrhage. Recognition of the diagnostic features of cystic meningiomas is important, because they may mimic metastatic neoplasms or primary gliomas.(ABSTRACT TRUNCATED AT 250 WORDS)

Subdural empyema of the cervical spine: clinicopathological correlates and magnetic resonance imaging. Report of three cases

A paucity of formally described information is available in the scientific literature regarding spinal subdural empyema. Patients presenting with neurological deterioration associated with subdural empyema are rarely identified, and treatment is often based upon anecdotal cases. The authors contribute three cases of primary cervical spinal subdural empyema and review the seven found in the literature. All patients had clinical evidence of neurological compromise, cervical tenderness, cervical pain, and leukocytosis upon admission. Cervical involvement ranged from C-2 to C-7. All patients underwent laminectomy with durotomy and drainage. The authors recommend prompt surgical decompressive laminectomy, copious irrigation, and drainage, followed with appropriate adjunctive antibiotic therapy for treatment of these patients.

MRI of intraventricular cysticercosis: surgical implications

OBJECTIVE

Our goal was to evaluate the role of Gd-enhanced MR in the diagnosis and surgical planning of intraventricular cysticercosis cysts.

MATERIALS AND METHODS

Thirty-three patients with intraventricular cysticercosis were evaluated with Gd-enhanced MRI including follow-up studies ranging over time periods from 6 months to 8 years. The patient age ranged from 17 to 65 years. All had lived in Mexico or Central America.

RESULTS

Twenty patients had surgical removal of the cysts. The majority of patients (18 of 20) who had surgical removal of the cyst showed improvement with resolution of hydrocephalus. Two of 20 patients required additional shunting to alleviate hydrocephalus. In these two patients, Gd-enhanced MR showed cyst wall enhancement. Ependymitis with adhesion was found at surgery in these two patients. Nine patients had shunt placement; one of nine patients showed cyst enlargement 2.5 years later that required surgical removal. Of the remaining eight patients, four showed irregular, thick, ring-like enhancement mimicking a neoplasm on follow-up imaging studies. Four patients with cysts in the lateral ventricle did not require treatment. Two of the four patients showed irregular, thick, ring-like enhancement on follow-up imaging studies.

CONCLUSION

Gadolinium-enhanced MR is more sensitive than contrast-enhanced CT for detecting ependymitis, which is essential in deciding whether surgical removal of the cyst or shunt placement is indicated. A degenerating intraventricular cysticercosis cyst may present as an irregular, thick, ring-like enhancing lesion or a nodular enhancing lesion with varying degrees of surrounding edema, mimicking a neoplasm.

Spinal tuberculosis: atypical observations at MR imaging

PURPOSE

To evaluate atypical magnetic resonance (MR) imaging features of spinal tuberculosis.

MATERIALS AND METHODS

Between 1990 and 1993, five of 11 consecutive patients with spinal tuberculosis (two men and three women, aged 30-57 years) had MR findings more suggestive of neoplasm than infection. One patient, a European immigrant, had acquired immunodeficiency syndrome (AIDS).

RESULTS

Areas involved with tuberculosis were hypointense on T1-weighted images and hyperintense on T2-weighted images, and became enhanced with gadopentetate dimeglumine. In two patients, tuberculosis affected only a single vertebral body without paraspinal abscesses or involvement of the end plates and disk spaces. In two other patients, only a single spinous process was replaced with tuberculous abscess. In the remaining patient, the sacrum and multiple lower lumbar vertebrae were affected, but the intervertebral disk spaces were not affected. More typical findings of spinal tuberculosis include destruction of two adjacent vertebral bodies and opposing end plates, destruction of intervening disk space, and/or occurrence of paravertebral abscesses.

CONCLUSION

Neither clinical examination nor MR findings may be reliable in helping differentiate spinal infections from one another or from neoplasm. Adequate biopsy is essential for early diagnosis and prompt treatment.

Magnetic resonance imaging and pathological correlates of meningiomas

We examined the relationships between specific magnetic resonance imaging features and certain gross and microscopic characteristics of meningiomas, including vascularity, gross texture (consistency), and venous sinus involvement. Magnetic resonance imaging scans, surgery reports, and the histopathological findings of tumors were examined retrospectively in 54 patients. Sinus involvement was accurately predicted on T1-weighted images in 9 of 10 cases (P = 0.001) and tumors with cystic changes in 3 of 3 cases. T1-weighted images were not useful for predicting vascularity unless actual flow voids could be visualized (five of six cases). There was no correlation between T1 signal intensity, tumor consistency, or histological findings. In tumors without detectable vascularity on T1-weighted images, hyperintensity relative to gray matter on T2-weighted images was correlated with increased vascularity (P = 0.004). Tumors with soft consistency (P = 0.007), cellular atypia, invasion, angioblastic, or melanocytic components were also hyperintense, compared with gray matter on T2-weighted images (P = 0.0266). Aggressive meningiomas were found to be more vascular (P = 0.045). No correlation was found between the degree of surrounding edema or contrast enhancement with histopathological findings, vascularity, or consistency.

The role of magnetic resonance imaging in acute transverse myelitis

Eighteen adult patients presenting with acute transverse myelitis (ATM) were evaluated using magnetic resonance imaging. Only 7 had abnormal scans showing an area of increased signal intensity within the cord solely on T2 weighted images; T1 weighted images were normal. The MRI abnormality did not correlate with the cause of the transverse myelitis, the extent of maximum neurological deficit, or the prognosis. A scan performed more than 5 days after the onset of disease was most likely to be positive. Even though the prognostic value of MRI in ATM may be limited, it remains a valuable technique for ruling out other causes of noncompressive spinal cord lesions, such as hemorrhage, vascular malformation, or tumor.

Meningeal melanocytoma: diagnostic criteria for a rare lesion

A case of meningeal melanocytoma, the 14th in the literature, is presented. Neurodiagnostic imaging, with both computed tomographic scan and magnetic resonance imaging, is included. Pathological examination of the tumor consisted of light microscopy, electron microscopy, and immunohistochemistry. The literature is reviewed and pathological criteria are presented to distinguish meningeal melanocytoma from meningiomas containing melanin pigment and from malignant melanoma.

Radionecrosis secondary to interstitial brachytherapy: correlation of magnetic resonance imaging and histopathology

Radiation-induced tissue damage in the central nervous system is a well-known complication of interstitial brachytherapy for brain tumors, yet imaging correlates have historically been based upon computed tomographic scans. We now present magnetic resonance imaging (MRI) to correlate radiation changes after interstitial brachytherapy with the histopathology. The central nervous system of a 38-year-old man with a left frontal cerebral glioma diagnosed by stereotactic biopsy was treated with interstitial brachytherapy (iridium-192, 47 Gy), followed by limited-field irradiation (45 Gy). With progressive deterioration, a second biopsy demonstrated radiation changes. Despite aggressive medical management, the patient died 9 months after completion of radiation therapy. Postmortem evaluation compared MRI scans of the intact, fixed brain with the histopathology. Axial sections (10 mm) obtained by MRI scan and autopsy brain slices were cut in the identical plane. Neuroimaging and histopathological findings of the lesion correlated within 2 to 3 mm resolution. In the peripheral white matter, MRI scan did not indicate the extent of radiation effect histologically. We suggest that MRI has limited utility in assessing the extent of impact of radiation on surrounding brain.

Diseases of the lumbar spine: findings on fat-suppression MR imaging

Fat-suppression MR techniques have been useful in imaging both the head and neck and the orbit. The lumbar spine is not as complex as the head and neck and does not contain as much fat as the orbit. Nevertheless, high signal from epidural and marrow fat in the lumbar spine can make it difficult to detect and define pathologic processes. In addition, the administration of gadopentetate dimeglumine can cause some infectious and neoplastic lesions of the spine to become isointense with fat on T1-weighted images. Compared with conventional MR imaging without fat suppression, contrast-enhanced fat-suppression MR imaging can better differentiate these enhancing lesions from surrounding fat. In this essay, we illustrate the findings of fat-suppression MR imaging in a variety of diseases of the lumbar spine.

Magnetic resonance imaging of meningiomas

MRI with gadolinium enhancement is the imaging modality of choice in the diagnosis of meningiomas. Various MRI features are described. MRI signal intensity characteristics in meningiomas contain information that could be correlated with the histopathology of the tumor. Hyperintensity on T2-weighted images indicates soft tumor consistency and microhypervascularity and is more often seen in aggressive, angioblastic, or meningothelial meningiomas. MRI is useful in demonstrating dural sinus involvement. Meningiomas in unusual locations and their mimics are also presented.

SPIR MRI in spinal diseases

We report on our experience with the fat suppression technique of spectral presaturation with inversion recovery MR in imaging certain spinal disorders. This technique may assist in demonstrating or excluding the presence of fat within a lesion (such as lipoma, dermoid, teratoma) or within a normal structure (i.e., vertebral body or epidural space). The method can also be used to suppress normal fat (such as marrow or epidural fat) thus increasing the conspicuity of adjacent high signal intensity lesions seen on T1-weighted images (such as blood and contrast-enhancing tumors or inflammatory lesions).

Cystic fluid in craniopharyngiomas: MR imaging and quantitative analysis

A prospective study of cystic fluid in craniopharyngiomas in 10 patients was performed to correlate signal intensity on T1-weighted magnetic resonance (MR) images and biochemical analysis. Within 2 days before surgery, each patient underwent MR imaging before and after administration of gadopentetate dimeglumine. Five patients had cystic fluid lower in signal intensity than white matter, with protein levels less than 9,000 mg/dL (90.00 g/L) and no free methemoglobin. One of the five patients had the highest triglyceride concentration (84 mg/dL [0.95 mmol/L]) of all 10 patients; another of these five had the highest cholesterol concentration of all (270 mg/dL [6.98 mmol/L]). It is concluded that the increased signal intensity of cystic fluid in craniopharyngiomas on T1-weighted MR images can be caused by a protein concentration greater than or equal to 9,000 mg/dL (90.00 g/L), the presence of free methemoglobin, or both. In the ranges of concentrations measured in this study, cholesterol and triglyceride did not increase signal intensity.

MR imaging in rhinocerebral and intracranial mucormycosis with CT and pathologic correlation

Three cases of mucormycosis, two in diabetics and one in an intravenous drug abuse patient, are presented. Magnetic resonance imaging proved to be useful in all cases, as was computed tomography. In one case, extremely low signal was detected from the fungal mass. It is surmised that this appearance was a result of high concentrations of iron and manganese. The low-signal area simulated air in paranasal sinuses; however, CT displayed a mildly enhancing soft tissue mass and allowed the correct diagnosis to be made. In another patient, pontine infarction was demonstrated by MR. In the third case the MR findings of mucormycosis involving the basal ganglia are shown and correlated with CT. Subsequent imaging studies demonstrated reduction of the mass, corresponding to clinical improvement.

Lhermitte-Duclos disease: CT and MR findings

The typical CT findings of Lhermitte-Duclos disease (dysplastic gangliocytoma of the cerebellum) are a hypodense nonenhancing unilateral posterior fossa mass, with or without adjacent occipital thinning, hydrocephalus, and calcification. Magnetic resonance (MR) has been found to be very helpful, and superior to CT, in delineating the margins of the lesion for determining the extent of surgical resection. Since recurrence is known, MR is important in the follow-up of these patients. To our knowledge this is the first reported case that included MR examination with administration of gadolinium. There was no enhancement of the lesion, consistent with previous reports of no contrast enhancement on CT.

Recurrent intraparenchymal hemorrhages from angiographically occult vascular malformations

Thirteen patients with recurrent hemorrhages from angiographically occult vascular malformations are presented. Recurrent hemorrhages were indicated by the exacerbation of neurological deficits, the appearance of a new neurological deficit, or the onset of acute severe headache confirmed by evidence of recent hemorrhage on either computerized tomography or magnetic resonance imaging. Persistent neurological deficits correlated with an increased number of recurrent hemorrhages and their location. The median time from initial hemorrhage to the first recurrent hemorrhage was 12 months and the second rebleed generally occurred much earlier, with a median time of 2 months after the first. Eight patients underwent surgery with total excision and favorable results. One patient with a large pontine lesion underwent partial excision and has had a progressing neurological deficit from recurrent hemorrhages. Histopathological review confirmed the excised lesions to be cavernous angiomas. The authors conclude that angiographically occult vascular malformations are not the benign entity they were previously thought to be, and that they are prone to cause recurrent hemorrhages and persistent neurological deficits. Surgery can be effective and relatively safe in removing these lesions even in eloquent areas of the brain, but the necessity of occasional incomplete removal must be recognized in order to avoid creating an unacceptable neurological outcome.

Evolution of central necrosis in a meningioma: CT and MR features

A 44-year-old patient underwent CT and magnetic resonance (MR) imaging and was found to have a typical appearing meningioma. The meningioma was of increased density relative to brain and enhanced homogeneously on CT. It was slightly hypointense on T1-weighted MR images and isointense on T2-weighted MR images relative to cortex. Thirty days later, repeat CT and MR scans showed change of the tumor consistent with central necrosis. An area of central low density developed on the CT scans, and a central high signal developed on the T2-weighted MR images. Pathological sectioning confirmed central necrosis of a syncytial meningioma.

MRI evaluation of AIDS-related encephalopathy: toxoplasmosis vs. lymphoma

The spectrum of cranial MRI findings was evaluated in 113 patients with the acquired immunodeficiency syndrome, assessing lesion number, size, location, and configuration in association with the autopsy and/or biopsy results. Correlation of cranial MRI and CT was performed in 32 patients. MRI was shown to be superior in sensitivity of lesion detection demonstrating more lesions than CT in 14 studies (44%) and equivalent information in 18 studies (56%). In no case did CT demonstrate lesions not detected on MRI. We conclude that MRI should be the study of choice in evaluating AIDS-related encephalopathy. Multiple lesions that involve both deep gray matter and white matter suggest the possibility of CNS lymphoma. The "target" appearance on MRI is not helpful in distinguishing toxoplasmosis from lymphoma.

Magnetic resonance imaging features in melanoma

T1 and T2 relaxation time shortening secondary to paramagnetic compounds has been described in melanoma. The purpose of this paper is to evaluate the signal behavior of melanoma involved in various body areas using short TR, TE and long TR, TE sequences. Twenty-seven sites of melanoma were evaluated with MR using T1 weighted and T2-weighted techniques. Using fat and muscle signal intensities as references tissues, lesions were graded into high, low or intermediate intensity categories for each of the sequences. Four signal patterns emerged. The typical pattern characterized by high signal on T1-weighted images and low signal on T2-weighted images reflected T1 and T2 shortening. The other pattern categories comprised of lesions demonstrating low signal T1-weighted images and high signal on T2-weighted images, high signal on both T1- and T2-weighted images and lesions showing intermediate signal on either T1- or T2-weighted images. We observed a tendency away from the typical signal pattern in extraocular melanoma cases with only one of 14 demonstrating this pattern. Moreover, only seven of thirteen ocular melanomas exhibited such behavior. Possible explanations for this findings as well as the existence of a variety of MR appearances to melanoma are offered. We conclude that while signal patterns showing T1 and T2 shortening are typical of melanoma, the absence of these does not exclude the diagnosis.

MRI of the skull

Thirty-four patients with a wide variety of benign and malignant incidental skull findings on routine magnetic resonance (MR) imaging of the brain were reviewed. In most instances detection of the lesions was not difficult. However, recognition of various patterns of skull involvement in different disease processes is important. This is particularly true in differentiating benign from malignant lesions, which may be a critical factor in patient management.

Magnetic resonance imaging of pediatric spinal dysraphism

Thirty pediatric patients with spinal dysraphism were studied with magnetic resonance imaging. A variety of dysraphic anomalies were visualized, including syringohydromyelia, tethered cord, widened spinal canal, meningomyelocele, lipomyelomeningocele, lipomeningocele, intraspinal lipoma, congenital dermal sinus tract, and scoliosis. In 29 of 30 cases, MRI diagnostically visualized spinal cord and dysraphic anatomy. A combination of T1-weighted sagittal and axial imaging planes provided the most complete visualization. In specific cases, T2-weighted examinations were useful in demonstrating likely regions of inflammation bordering infected sinus tracts. MRI demonstrates a wide variety of dysraphic spinal anomalies and effectively screens children for occult spinal dysraphism.

MR imaging of neurocysticercosis

Magnetic resonance (MR) was performed in 50 patients with neurocysticercosis. Comparison was made with other neuroradiological imaging modalities including CT, myelography, CT ventriculography, and CT myelocisternography. Eighteen patients were found to have intraventricular cysts. In several patients, these were multiple and 22 intraventricular cysts were discovered. Although 4 of the 22 ventricular cysts were missed by MR, T1-weighted images can play a significant role in the early detection of intraventricular cysticercosis cysts, showing the cyst wall (9 of 22), a high intensity mural nodule (6 of 22), and increased signal intensity of the cyst fluid (5 of 22). Cisternal cysts (14 cysts in 10 patients) could be identified; they appear similar to intraventricular cysts, but mural nodules are infrequently seen (1 of 14). Twenty-nine patients had 69 parenchymal cysts. An attempt was made to assess the viability of these parenchymal lesions by matching the CT and MR findings with the Escobar pathologic staging system. Neuroimaging findings seemed compatible with early parenchymal lesions in the vesicular stage in 11 instances. Findings in cases with later stage cysts tend to support the concept that a dying larva provokes pronounced inflammatory reaction in the adjacent brain. Computed tomography remains the superior modality for depicting parenchymal calcifications within dead larvae. A case of a spinal cysticercosis cyst demonstrated with MR (in a patient with extensive intracranial cisternal cysts and a fourth ventricular cyst) is described.

The motion artifact suppression technique (MAST) in magnetic resonance imaging: clinical results

The Motion Artifact Suppression Technique (MAST) is a method which uses a series of gradient echos that are computed to cancel velocity, acceleration and pulsatility components of involuntary motion in MR imaging. A total of 916 patient studies were performed over a nine month period using MAST sequences with a TE 40, 60, 80, 100, 120, and 26/112. There was considerable improvement in long TR, long TE images. Cerebrospinal fluid flow artifacts were reduced. Body and spine images had reduced flow and respiratory artifacts. Spin rephasing in blood vessels caused increase intraluminal signal. This might be useful for cardiovascular imaging.

Computed imaging stereotaxy: experience and perspective related to 500 procedures applied to brain masses

The evolution of more sophisticated imaging techniques has initiated a renewed interest in stereotactic devices, methods, and applications. The Brown-Roberts-Wells instrument was available to us early in its prototype stage, and this report reviews the first 500 cases using the system at the University of Southern California Medical Center Hospitals. Procedures were undertaken after recognition of apparent structural alterations on imaging studies, with objectives being both diagnostic and therapeutic. Target locations were predominantly within the cerebral centrum-basal ganglia (284 cases) and diencephalic-mesencephalic regions (129 cases). Operative objectives included: histological and microbiological assay, cyst and abscess aspiration, installation of temporary or permanent drainage conduits, point source and colloid base brachytherapy, cerebroscopy and ventriculoscopy with biopsy, aspiration, and excision, and intraoperative vascular localization. Using multiple instrumentation at the target point (741 point placements), we realized procedural objectives in 95.6% of the cases. The mortality was 0.2% and the morbidity was 1%: hematoma, 2 cases; infection, 1 case; increased deficit, 1 case; intraprocedural seizure, 1 case. A specific diagnosis was not obtained in 4.4% (necrosis, 10 cases; inflammatory response, 9 cases; granuloma, 1 case; gliosis, 1 case; diagnostic error, 1 case). Individual guidelines for case selection, technique, institutional requirements, and applications of the method are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)