Cerebellar herniation and infarction as a complication of an occult postoperative lumbar dural defect.

A patient who underwent lumbar spine surgery sustained an occult dural injury. After unrecognized suction drainage of cerebrospinal fluid through a surgical drain, caudal herniation of the cerebellum with superior cerebellar infarction developed. This mechanism should be considered in patients in whom acute mental status changes develop after spinal surgery.

Aneurysmal bone cyst of the thoracic spine: evolution after particulate embolization.

A case of aneurysmal bone cyst of the thoracic spine treated with serial particulate embolization responded with involution of soft-tissue and cystic components and diffuse ossification of the mass. Reappearance of foci of bony rarefaction or cystic change at 4-year follow-up indicates the need for continued surveillance.

Venous sinus occlusive disease: MR findings.

PURPOSE: To study MR patterns of venous sinus occlusive disease and to relate them to the underlying pathophysiology by comparing the appearance and pathophysiologic features of venous sinus occlusive disease with those of arterial ischemic disease. METHODS: The clinical data and MR examinations of 26 patients with venous sinus occlusive disease were retrospectively reviewed with special attention to mass effect, hemorrhage, and T2-weighted image abnormalities as well as to abnormal parenchymal, venous, or arterial enhancement after intravenous gadopentetate dimeglumine administration. Follow-up studies when available were evaluated for atrophy, infarction, chronic mass effect, and hemorrhage. RESULTS: Mass effect was present in 25 of 26 patients. Eleven of the 26 had mass effect without abnormal signal on T2-weighted images. Fifteen patients had abnormal signal on T2-weighted images, but this was much less extensive than the degree of brain swelling in all cases. No patient showed abnormal parenchymal or arterial enhancement. Abnormal venous enhancement was seen in 10 of 13 patients who had contrast-enhanced studies. Intraparenchymal hemorrhage was seen in nine patients with high signal on T2-weighted images predominantly peripheral to the hematoma in eight. Three overall MR patterns were observed in acute sinus thrombosis: 1) mass effect without associated abnormal signal on T2-weighted images, 2) mass effect with associated abnormal signal on T2-weighted images and/or ventricular dilatation that may be reversible, and 3) intraparenchymal hematoma with surrounding edema. CONCLUSION: MR findings of venous sinus occlusive disease are different from those of arterial ischemia and may reflect different underlying pathophysiology. In venous sinus occlusive disease, the breakdown of the blood-brain barrier (vasogenic edema and abnormal parenchymal enhancement) does not always occur, and brain swelling can persist up to 2 years with or without abnormal signal on T2-weighted images. Abnormal signal on T2-weighted images may be reversible and does not always indicate infarction.

Cystic acoustic schwannomas: MR characteristics.

PURPOSE: To evaluate the spectrum of MR characteristics of cystic acoustic schwannoma and to investigate its incidence. METHODS: We retrospectively reviewed the MR findings and clinical records of 16 patients with cystic acoustic schwannomas. In addition, the MR examinations of 411 consecutive patients referred for clinical suspicion of acoustic schwannomas were reviewed retrospectively to assess the incidence of acoustic schwannomas with cystic lesions arising from the internal auditory canal. RESULTS: Of the 16 acoustic schwannomas with MR evidence of intramural cysts, 11 tumors had single small cysts, and five had multiple intramural cysts of variable size. Intramural cysts in 11 of the 16 tumors exhibited higher signal intensity than that of cerebrospinal fluid; the remainder were isointense to cerebrospinal fluid on both T1- and T2-weighted images. All intramural cysts showed circumferential enhancement after contrast administration. Nine of the 16 cystic acoustic schwannomas also had MR evidence of extramural/arachnoid cysts. Six of the extramural/arachnoid cysts had epicenters away from the dural interface, and the other three cysts were broadly based against the dura. The incidence of cystic acoustic schwannomas was 11.3% and association with extramural/arachnoid cysts 7.5%. CONCLUSION: Our series suggests that cystic changes in acoustic schwannomas and the association with extramural/arachnoid cysts are not as rare as previously reported by other diagnostic methods. The high signal intensity of intramural cysts is probably related to necrotic material, blood, or colloid-rich fluid. The difference in the MR characteristics of extramural/arachnoid cysts associated with acoustic schwannomas and those of typical arachnoid cysts not associated with neoplasia may be related to higher protein and/or colloid contents secreted by the tumor. Most extramural/arachnoid cysts had epicenters between the tumor and brain, suggesting that the most likely mechanism of formation is peritumoral adhesions. It creates a pseudo-duplication caused by the trapping of fluid between the leptomeninges and the mass, resulting in an acquired type of arachnoid cyst.

Adult cerebellar medulloblastoma: imaging features with emphasis on MR findings.

PURPOSE: To describe the MR imaging features of cerebellar medulloblastoma in the adult. MATERIALS AND METHODS: The neuroimages and records of 15 adults with proved cerebellar medulloblastoma were retrospectively evaluated. In 12 patients, preoperative MR scans were reviewed; nine had Gd-DTPA-enhanced scans. RESULTS: Of the 12 tumors evaluated preoperatively, eight were hemispheric, two hemispheric-vermian, and two vermian. Tumor margins were well demarcated, except in three cases, two of which had large infiltrative tumors. In 10 cases, tumor extended to the brain surface, and in five of these, contiguity with the tentorium or cerebellopontine angle cistern was such than an extraaxial tumor was considered. The tumors were typically hypointense on T1 but a spectrum was seen on T2-weighted images. Enhancement ranged from minimal and patchy to marked. One tumor became isointense after Gd-DTPA. Other features included cystic changes, hemorrhage, exophytic invasion at the cerebellopontine angle, spinal cerebrospinal fluid seeding, intraventricular seeding, and bone metastasis. CONCLUSION: Although there is no pathognomonic MR appearance of adult cerebellar medulloblastoma, the finding of a well-demarcated, mild to moderately enhancing hemispheric mass involving the brain surface in a young adult is suggestive of medulloblastoma. Awareness that this tumor may resemble meningioma may avoid misdiagnosis and aid surgical planning.

Peripheral angiography: optimal technique and current status in vascular imaging.

Angiography is the standard with which new methods of vascular imaging are compared. In this article, selected recent developments affecting the practice of angiography will be discussed. First, a brief review and update of contrast media for intravascular use will be presented. Second, principles and current methods of optimizing the diagnostic arteriogram will be covered with emphasis on the extremities and aorto-femoral angiography. Finally, some of the advantages, limitations, and the role of modern angiography will be discussed.

Pituitary metastases: MR findings.

Tumors metastatic to the pituitary gland are uncommon, and they are difficult to differentiate radiologically from pituitary adenomas. We retrospectively reviewed the MR examinations and clinical records of nine patients with radiographic and/or clinical evidence of pituitary metastases. The most common clinical symptoms included cranial nerve deficits (67%) and/or pituitary dysfunction (30%). Both occurred acutely and progressed rapidly over 1-4 weeks in all patients. Cranial nerve involvement was predominantly multiple (83%), a reflection of involvement of the adjacent cavernous sinus. In contrast to previous reports indicating a predilection for symptoms related to posterior lobe involvement (71%), our study shows that symptoms related to the anterior lobe are as common as posterior lobe symptoms. Useful MR findings included a relatively small, enhancing pituitary lesion (< or = 1.5 cm in 56%) that was relatively isointense to brain on both T1- and T2-weighted images (78%) and involvement of the hypothalamus/pituitary infundibulum (44%) or cavernous sinus (56%).

Metastatic lesions involving the cerebellopontine angle.

PURPOSE: To evaluate the clinical and MR findings of metastatic lesions involving the cerebellopontine angle (CPA), which may be useful in differentiating them from the more commonly occurring benign CPA lesions. METHODS: Clinical and MR findings of 14 patients with clinical/radiologic (seven) or pathologic (seven) diagnoses of CPA metastasis were retrospectively reviewed. RESULTS: Useful clinical findings included acute onset and rapid progression of cranial nerve symptoms, especially 7th and/or 8th cranial nerve deficits (92.9%). Cranial nerve symptoms could be unilateral (50%) and frequently involved multiple cranial nerves (64.3%). MR findings showed significantly more extensive disease than suggested by clinical presentation, with 100% of patients having multiple cranial nerve involvement and 85.7% bilateral. Useful MR findings included small and/or bilateral CPA-enhancing lesions with relative isointensity to brain parenchyma on precontrast MR, with associated findings of multiple and/or bilateral cranial nerve and/or leptomeningeal lesions. CONCLUSIONS: These associated findings suggest that cerebrospinal fluid dissemination and/or leptomeningeal extension may be an important pathway for metastatic spread to the CPA. Because the CPA metastasis may be the initial or only site of metastasis, and may occur many years after the initial diagnosis of malignancy, MR findings with clinical correlation are not only useful for the detection of CPA metastases, but also for their differentiation from the more common benign CPA tumors.

MR imaging of spinal cord and vertebral body infarction.

PURPOSE: To study the usefulness of MR in the evaluation of spinal cord infarctions and associated findings. MATERIALS AND METHODS: MR examinations of 12 patients (10 men and two women) were reviewed retrospectively. Onset of symptoms of spinal cord ischemia was abrupt in all patients; MR was performed 8 hr to 4 months after onset. Contrast-enhanced MR was performed in four of the patients. RESULTS: Abnormal MR findings of the spinal cord included abnormal cord signal (11 of 12), best demonstrated on T2-weighted images, and morphologic changes (cord enlargement during the acute phase in nine patients and cord atrophy during the chronic phase in two), best demonstrated on T1-weighted images. Vascular abnormalities (aortic) were detected by MR in four of the 12 patients. Three of these four patients also had abnormal bone marrow signal, predominantly in the anterior half (one) or in multiple areas near the endplate and/or deep medullary portion of the vertebral body involving several vertebrae (two). T1-weighted images were not sensitive in detecting signal changes in either the bone marrow (two of three) or spinal cord (nine of 12). Enhanced MR imaging was performed in four patients (two in the acute phase and two in the chronic phase) and showed diffuse enhancement of the spinal cord proximal to a relatively unenhancing distal conus in one of the two patients imaged during the acute phase. No abnormal enhancement was noted in the other three patients. CONCLUSION: MR is a useful means of detecting spinal cord infarction and associated vascular and bony changes. The patterns of bone marrow abnormalities reflect the underlying pathophysiology of the blood supply to the spinal cord and bone. The associated vascular and bone marrow abnormalities serve as additional information for the diagnosis of spinal cord infarction.

Evaluation of women with possible appendicitis using technetium-99m leukocyte scan.

The authors evaluated the use of technetium-99m albumin colloid white blood cell (TAC-WBC) scan in women with possible appendicitis. One hundred and nine women underwent 110 TAC-WBC scans. One woman had a second scan on a separate admission and was considered two individual patients in the analysis. Twenty-six women had appendicitis, 10 of whom had a perforated appendix at surgery. The TAC-WBC scan was indeterminate (abnormal but nondiagnostic for appendicitis) in 52 women (47%), nine of whom had appendicitis. Fifty-eight scans were read as positive or negative for appendiceal pathology. There were 16 true positives, 5 false positives, 36 true negatives, and 1 false negative. The predictive value of a positive scan was 76%, and the predictive value of a negative scan was 97%. The TAC-WBC scan was positive in 62% of patients with appendicitis and negative in 43% of the patients without appendicitis resulting in an overall accuracy of 47% in the 109 women. The main value of TAC-WBC scan in women with possible appendicitis is its high negative predictive value and the main problem with the TAC-WBC scan is its high indeterminate rate.

Perirenal hemangioendothelioma in a newborn: sonograph and MR findings.

This is a case report of perirenal hemangioendothelioma in a newborn and discussion of lesions in the perirenal space in newborns. The findings in this case, high echogenicity on sonographic images and high signal intensity on T2-weighted spin echo magnetic resonance images, mimic those described for hemangiomas in other locations.