MR imaging of the postoperative knee: a pictorial essay.

Magnetic resonance (MR) imaging of the postoperative knee has become more common because more arthroscopic repair procedures are being performed. The most common procedures include partial meniscectomy and meniscal repair, anterior cruciate ligament (ACL) reconstruction, and cartilage repair procedures. Specific findings of a retorn meniscus following meniscal repair or partial meniscectomy are increased signal intensity extending through the site of repair on T2-weighted images, displaced meniscal fragments, and abnormal signal intensity at a site distant from the repair. Findings of ACL graft disruption on T2-weighted MR images include absence of intact graft fibers and increased signal intensity similar to that of fluid within the expected region of the graft. Partial tears of the graft appear as areas of increased signal intensity affecting a portion of the graft with some intact fibers still present. An impinged ACL graft may appear to be draped over the anterior inferior edge of the intercondylar roof or be posteriorly bowed. Localized anterior arthrofibrosis appears on T1-weighted MR images as a focal nodular lesion of low signal intensity that is anterior to the ACL graft in the intercondylar notch and is indistinguishable from adjacent joint fluid. On T2-weighted images, the nodule is well differentiated from high-signal-intensity joint fluid. Finally, MR imaging has been shown to be accurate in the evaluation of cartilage repair tissue. Knowledge of the normal MR imaging appearance of the knee after the more common repair procedures will allow radiologists to recognize complications associated with such procedures.     

Magnetic resonance imaging evaluation of the ascending aorta after graft-inclusion surgery: Comparison between an ultrafast contrast-enhanced MR sequence and conventional cine-MRI

The aim of this study was to compare the value of two magnitude-based MR sequences, a contrast-enhanced ultrafast MR sequence and a cine MR sequence, for the detection of flow around the graft in the postoperative ascending thoracic aorta. Thirteen patients who underwent ascending aortic surgery for dissection (n = 11) and aneurysm (n = 2) were enrolled. They were referred to MRI for mediastinum enlargement on the chest x-ray or mediastinal symptoms. All patients had replacement of the diseased ascending aorta using a graft-inclusion technique (with wrapping of the native aorta over the graft). Delays between surgery and MRI ranged from 15 days to 8 years (mean: 10 months). All patients were examined using a T1-weighted spin-echo sequence, a magnitude-based cine gradient-echo sequence, and an ultrafast contrast-enhanced MR sequence. MR images of the cine and the contrast-enhanced sequences were retrospectively and independently analyzed by two qualified radiologists for evidence of flow or thrombus around the graft, including perigraft structure and aneurysmal formations. Evidence of flow was detected by both methods in all aneurysmal formations of the ascending aorta located at suture level (n = 6). Evidence of flow in the perigraft structure was found in seven cases by contrast-enhanced MR sequence and in only four cases by cine MR sequence. Contrast-enhanced ultrafast MR sequence could be proposed as a minimally invasive and fast modality for assessing the perigraft structure, in graft-in-clusion surgical procedures of the ascending aorta, when noncontrast enhanced MR sequences do not exclude the possibility of flowing blood in this structure.     

Small hepatocellular carcinoma treated with percutaneous ethanol injection: MR imaging findings.

Fifty-seven magnetic resonance (MR) imaging examinations were obtained at 0.5 T in 19 patients before and after percutaneous ethanol injection (PEI) for 23 hepatocellular carcinoma (HCC) lesions less than 3.5 cm in diameter. Seventeen patients also underwent MR imaging 6 months after completion of therapy. In 11 patients, computed tomography was performed before and after treatment. After PEI, fine-needle biopsy specimens were obtained in all cases. Before treatment, HCC lesions had low signal intensity on T1-weighted images in 13 cases, had the same signal intensity as normal liver parenchyma in six, and had high signal intensity in four; all 23 tumors had high signal intensity on T2-weighted images. After treatment and at 6-month follow-up, all 21 lesions that contained no malignant cells at fine-needle biopsy had high signal intensity on T1-weighted images and had low signal intensity on T2-weighted images. The remaining two HCC lesions in which tumor necrosis was not achieved with PEI displayed a different MR pattern, since the residual neoplastic tissue showed no change in signal intensity on either T1- or T2-weighted images. The authors conclude that MR imaging may be useful for evaluating the effectiveness of PEI in achieving tumor regression.     

Composite graft replacement of the ascending aorta: leakage detection with gadolinium-enhanced MR imaging.

PURPOSE: To assess the value of magnetic resonance (MR) imaging in the detection of postoperative complications after composite valve graft replacement. MATERIALS AND METHODS: Spin-echo and gradient-echo MR imaging was performed in 52 patients 1/2 to 200 months after composite graft replacement of the ascending aorta (22 for dissection, 30 for aneurysm). The prosthetic aortic segment, distal and proximal anastomoses, general morphologic characteristics, and diameter of the reimplanted coronary arteries were evaluated. In patients with abnormal perigraft thickening, additional spin-echo imaging was performed after injection of gadopentetate dimeglumine. RESULTS: Normal postoperative perigraft thickening (< or = 10 mm) was observed in 42 patients. Ten patients had abnormal periprosthetic thickening of 15-52 mm. Gadolinium-enhanced MR imaging demonstrated leakage in five of those 10 patients. The lack of enhancement excluded the presence of bleeding in the remaining five patients (three with chronic hematomas, one with infection, and one with granulation tissue). These findings were confirmed at surgery or with subsequent follow-up MR examinations. CONCLUSION: MR imaging was an optimal imaging modality for evaluating the morphologic characteristics of composite grafts and reimplanted coronary arteries. Gadolinium-enhanced MR imaging is a simple, accurate, and noninvasive method for detecting a leak, which necessitates urgent repeat surgery.     

Brachytherapy for prostate cancer: endorectal MR imaging of local treatment-related changes

PURPOSE: To determine the local treatment-related endorectal magnetic resonance (MR) imaging findings after brachytherapy for prostate cancer. MATERIALS AND METHODS: Endorectal MR imaging was performed in 35 consecutive patients at a mean interval of 12 months (range, 1-31 months) after brachytherapy for prostate cancer. Transverse T1-weighted and high-spatial-resolution transverse and coronal T2-weighted images were acquired. Two readers reviewed MR image quality and findings, with discrepancies resolved by consensus. Posttreatment urinary symptoms in patients (n = 24) were documented by using chart review. RESULTS: All studies were of diagnostic quality. On T2-weighted images, prostatic findings consisted of diffuse low signal intensity (n = 35) and indistinct zonal anatomy (n = 34). Intra- and extraprostatic seed locations could be distinguished. The most common extraprostatic site of seed implantation was the neurovascular bundles (n = 35, bilateral in 32). The most common extraprostatic tissue finding was increased signal intensity on T2-weighted images in the levator ani muscle (n = 34) and the genitourinary diaphragm (n = 28). Postbrachytherapy urinary symptoms showed no demonstrable correlation with periurethral or genitourinary diaphragm seed implantation or with signal intensity change in the genitourinary diaphragm. CONCLUSION: Endorectal MR imaging can be used to evaluate seed distribution and to demonstrate treatment-related changes after brachytherapy for prostate cancer.     

Transient osteoporosis of the hip: MR imaging

Three patients with transient osteoporosis of the hip underwent magnetic resonance (MR) imaging. MR images showed decreased signal intensity of bone marrow in the femur on T1-weighted images and increased signal intensity relative to the intensity of normal bone marrow on T2-weighted images. Joint effusions were seen on MR images of all patients on T2-weighted images. The findings on MR images concurred with histologic findings, such as increased bone turnover and mild inflammatory reaction, in one patient. The clinical symptoms and abnormalities on MR images regressed completely within 6-10 months. Familiarity with the distinct features of transient osteoporosis on MR images may be important in the differential diagnosis of adults with hip pain.     

MR of denervated tongue: temporal changes after radical neck dissection.

PURPOSEThe purpose of this study was to evaluate the temporal changes of MR imaging in the denervated tongue after a radical neck dissection.METHODSOne hundred seventy-four consecutive MR studies in 116 patients with radical neck dissections for malignant tumors of the head and neck were evaluated retrospectively. Patients with tumors involving the tongue or hypoglossal nerve were not included in this study.RESULTSAbnormal signal intensity and/or hemiatrophy on the side of the tongue operated on was seen in 22 patients who had hypoglossal paralysis after radical neck dissection. The denervated side of the tongue appeared hypointense to hyperintense relative to the normal side on T1-weighted images and hyperintense on T2-weighted images. Signal intensity ratios of the abnormal to normal muscles were 0.9-1.6 on T1-weighted images and 1.3-2.8 on T2-weighted images. High signal intensity on T1-weighted images appeared 5 months or more after the dissection, whereas on T2-weighted images, the most prominent increases in signal intensity appeared in the first several months after denervation. Hemiatrophy of the tongue was observed on MR images obtained more than 6 months after surgery.CONCLUSIONMR findings in the denervated tongue are compatible with histologic changes and are characterized by an enlarged extracellular fluid space or fatty infiltration. The pattern of signal intensity and the degree of hemiatrophy suggest the duration of denervation.     

MR imaging findings of Rathke's cleft cysts: significance of intracystic nodules

BACKGROUND AND PURPOSE: Rathke's cleft cysts often may be difficult to differentiate from other intrasellar or suprasellar masses on radiologic studies. The purpose of this study was to describe the significance of intracystic nodules, a diagnostic characteristic found in Rathke's cleft cysts, on MR images. METHODS: A retrospective review of MR studies was conducted for 13 patients who, after pathologic analysis, were diagnosed as having Rathke's cleft cyst. These patients underwent unenhanced and contrast-enhanced T1- and T2-weighted axial and coronal spin-echo sequential imaging. The signal intensity and incidence of the intracystic nodules on T1- and T2-weighted images were analyzed. The signal intensity of the nodule was compared with that of white matter and surrounding cyst fluid. The signal intensity of cyst fluid was compared with the intraoperative appearance of the cyst fluid. Biochemical and pathologic analyses of the intracystic nodules were conducted in two cases. RESULTS: An intracystic nodule having high signal intensity on T1-weighted images and low signal intensity on T2-weighted images was observed in 10 (77%) of the cases. At surgery, intracystic nodules were yellow, waxy, solid masses. Pathologic analysis showed this nodule to be a mucin clump. Biochemical analysis of the intracystic nodules showed cholesterol and proteins as the main constituents. In the Rathke's cleft cyst with intracystic nodules, cyst fluid revealed low signal intensity to isointensity relative to the intensity of the nodules on T1-weighted images, and isointensity to high signal intensity on T2-weighted images. Intracystic nodules were clearly visible on T2-weighted images. CONCLUSION: Because cyst fluid of Rathke's cleft cysts shows variable intensities on MR images, the specific diagnosis is often difficult when based on MR signal intensity values alone. The presence of an intracystic nodule with characteristic signal intensities on MR images may be indicative of the diagnosis of Rathke's cleft cyst.     

Mediastinal lymphoma: quantitative changes in gadolinium enhancement at MR imaging after treatment

PURPOSE: To compare changes in gadolinium enhancement at magnetic resonance (MR) imaging with outcome in mediastinal lymphoma after treatment. MATERIALS AND METHODS: Thirty-one patients with bulky mediastinal lymphoma (17 with Hodgkin disease, 14 with non-Hodgkin lymphoma) underwent serial MR imaging before and up to 50 months after treatment, with routine follow-up (including computed tomography). Signal intensity ratios between masses and muscle were calculated on T1-weighted, T2-weighted, and contrast material-enhanced T1-weighted spin-echo MR images. The percentage enhancement and signal intensity ratios of mediastinal masses on T2-weighted MR images were calculated at diagnosis and during and after treatment. RESULTS: Twenty-one patients with persistent complete remission had a mean percentage enhancement of residual masses (4%; range, -26% to 40%) that was significantly lower than that of initial masses (78%; range, 41%-124%). Although the mean signal intensity ratio of residual masses on T2-weighted images was significantly lower than that of initial masses, an increase in this ratio was observed in four patients after treatment. In seven patients with relapse, the percentage enhancement value of the residual mass was as high as that of the initial mass. CONCLUSION: Gadolinium enhancement of lymphomatous masses of the mediastinum decreased markedly after treatment in patients in continuous complete remission but not in patients with relapse.     

Preliminary results of MR imaging with superparamagnetic iron oxide in pancreatic and retroperitoneal disorders

The authors conducted a preliminary evaluation of the potential of superparamagnetic iron oxide as contrast material for delineation of the bowel. Ten patients with various pancreatic diseases and 18 patients with suspected retroperitoneal disease underwent T1- and T2-weighted MR imaging before and after contrast material was administered. Two radiologists reviewed randomized images and scored them for depiction of anatomic structures and abnormalities. In most patients, postcontrast T1-weighted images showed improved delineation of the retroperitoneal small bowel (duodenum), stomach, and pancreas. Postcontrast T2-weighted images showed improved delineation of retroperitoneal small bowel, para-aortic region, peripancreatic fat, and renal veins. There was no improvement in delineation of retroperitoneal diseases, except for lymphadenopathy, which was better seen on both T1- and T2-weighted postcontrast images. Preliminary results suggest that superparamagnetic iron oxide is a useful contrast agent for delineating some normal retroperitoneal structures, lymphadenopathy, and pancreatic disease and that it is less useful in evaluating other retroperitoneal masses.     

MR imaging of the posterior cruciate ligament graft: initial experience in 15 patients with clinical correlation

PURPOSE: To describe the magnetic resonance (MR) appearance of the posterior cruciate ligament (PCL) graft in the 1st postoperative year and to correlate the MR findings with clinical examination findings. MATERIALS AND METHODS: Nineteen MR examinations were performed in 15 patients (with 15 grafts) 1-33 months after PCL reconstruction. Results of clinical follow-up were available in 14 patients. Graft shape and thickness were recorded, and intrasubstance signal intensity at T2-weighted imaging was graded. The MR findings were correlated with the time between surgery and clinical examination. RESULTS: At MR imaging, 13 grafts appeared intact, one could not be assessed owing to hardware artifact, and one initially appeared disrupted. Graft thickness was 7-19 mm. There was no significant difference between graft thickness versus time since surgery and signal intensity versus time since surgery (P =.14). In two of three patients who underwent sequential MR examinations, graft thickness and intrasubstance signal intensity decreased as the time between reconstruction and MR imaging increased. Two of 14 patients who underwent physical examination had a posterior drawer, and one also had an anterior cruciate ligament graft tear. Both patients with knee instability demonstrated intact PCL graft fibers at MR imaging. There was no correlation between knee stability and graft thickness, signal intensity, or shape. CONCLUSION: After PCL reconstruction, MR imaging in the 1st year depicts a thickened graft with increased signal intensity. There does not appear to be a relationship between clinical stability and findings at MR imaging.     

Granulomatous spinal infections: MR imaging

The value of magnetic resonance (MR) imaging in evaluating granulomatous spinal infection was retrospectively assessed in 81 patients with proved disease; 27 were reexamined after administration of gadolinium diethylenetriaminepentaacetic acid, and 25 underwent follow-up studies. Blinded interpretations were correlated with clinical, microbiologic, and surgical findings. MR imaging enabled prediction of the presence of neurologic complications in 93% of patients and diagnosis of the type of infection in 94%, and correlated well with surgical findings in 24 of 27 patients. Vertebral intraosseous abscesses, meningeal involvement, subligamentous spread, and paraspinal abscess location were best identified on contrast-enhanced studies and were seen most frequently in tuberculous spondylitis. High signal intensity on T1-weighted images of previously affected vertebrae suggested healing and correlated well with symptoms. The authors conclude that MR imaging may be useful as the method of first choice for the initial assessment and posttherapy follow-up of patients with granulomatous spinal infection.     

Occult intraosseous fracture: detection with MR imaging

Magnetic resonance (MR) images were retrospectively evaluated in eight patients who had recent, symptomatic knee injuries and in whom plain radiographs showed no fractures. T2-weighted images revealed irregular, intraosseous areas of high signal intensity; T1-weighted and proton density images revealed speckled or linear regions of low signal intensity in corresponding areas. In the seven patients whose injuries did not result from direct contusion, abnormalities occurred in subchondral locations. Two patients underwent bone scintigraphy, which showed increased activity in locations corresponding to areas of abnormality noted on MR images. Two patients underwent follow-up MR imaging at 6 weeks and 3 months, which showed complete resolution of the abnormalities. The authors speculate that the MR imaging findings represent microscopic compression fracture of trabecular bone and discuss the related entity, stress fracture.     

Ewing sarcoma: MR imaging of chemotherapy-induced changes with histologic correlation.

In a study group of 18 consecutive patients with Ewing sarcoma proved by means of biopsy, the signal intensity characteristics of tumor on magnetic resonance (MR) images were assessed before and after chemotherapy. Sixteen patients underwent MR imaging at 1.5 T before chemotherapy; all 18 patients underwent MR imaging at 1.5 T within 10 days after chemotherapy. Standard spin-echo sequences were used with T1 and T2 weighting in all patients. The primary tumor was visualized in all 16 patients who underwent MR imaging before chemotherapy. Histologic correlation, obtained in 14 patients, showed that areas of high T2-weighted signal intensity on MR images obtained after chemotherapy may represent tumor necrosis, cystic hemorrhagic areas, and fibroblastic repair tissue. In 10 patients (71%), microscopic clusters of viable tumor cells were depicted in areas of both low and high signal intensity after treatment. It is concluded that MR imaging is unreliable for exclusion of active disease, although a pattern of change in signal intensity is qualitative evidence of chemotherapeutic effect.     

Amyloid arthropathy of the hip joint: MR demonstration of presumed amyloid lesions in 152 patients with long-term hemodialysis

The aim of this study was to determine the spectrum of MR findings of presumed amyloid arthropathy of the hip joints in patients on long-term hemodialysis. We prospectively performed T1- and T2-weighted spin-echo imaging on 152 consecutive patients on hemodialysis. The duration of hemodialysis ranged from 5 months to 24 years, 2 months (mean: 8 years, 8 months). The frequency, location, and signal intensity of bone lesions were assessed. In 12 cases with contrast-enhanced MR examination, enhancement pattern of bone lesions, synovial lesions, and intra-articular lesions were characterized. Bone lesions presumed to be amyloid deposits were identified in 60 patients (39 %). Magnetic resonance imaging revealed that amyloid lesions were more extensive than anticipated by plain radiographs. All bone lesions showed decreased signal intensity on T1-weighted images. On T2-weighted images, bone lesions showed increased signal intensity in 32 patients (54 %), decreased signal intensity in 11 patients (18 %), and both increased and decreased signal intensity in 17 patients (28 %). Following intravenous injection of gadolinium-based contrast, all bone lesions showed moderate enhancement. Synovial thickening could not be identified on T1- and T2-weighted images. However, contrast-enhanced images showed thickened synovial membrane, which could be differentiated from joint fluid. Intra-articular nodules showed decreased or intermediate signal intensity on T1-weighted images and decreased signal intensity on T2-weighted images; the intra-articular nodules were contiguous with subchondral bone lesions. Magnetic resonance imaging is useful for evaluating the distribution and extent of amyloidosis of the hip joints in patients undergoing long-term hemodialysis. Received 5 August 1997; Revision received 22 October 1997; Accepted 11 February 1998     

Nipah virus encephalitis: serial MR study of an emerging disease.

PURPOSE: To report the serial magnetic resonance (MR) imaging findings of the Nipah virus. MATERIALS AND METHODS: Twelve patients underwent serial MR imaging. Eight patients were examined at the outbreak; 11, at 1 month; and seven, at 6 months. Contrast material-enhanced MR images, diffusion-weighted images, and single-voxel proton MR spectroscopic images were reviewed. Clinical and neurologic assessment, as well as analysis of the size, location, and appearance of brain lesions on MR images, were performed. RESULTS: During the outbreak, all eight patients had multiple small foci of high signal intensity within the white matter on T2-weighted images. In six patients, cortical and brain stem lesions were also detected, and five patients had diffusion-weighted MR imaging-depicted hyperintensities. One month after the outbreak, five patients had widespread tiny foci of high signal intensity on T1-weighted images, particularly in the cerebral cortex. Diffusion-weighted images showed decreased prominence or disappearance of lesions over time. There was no evidence of progression or relapse of the lesions at 6-month follow-up. MR spectroscopy depicted reduction in N-acetylaspartate-to-creatine ratio and elevation of choline-to-creatine ratios. CONCLUSION: The Nipah virus has findings unlike other viral encephalitides: small lesions that are primarily within the white matter, with transient punctate cortical hyperintensities on T1-weighted images.     

Lumbar spine: postoperative assessment with surface-coil MR imaging

A prospective study of 15 patients who were scheduled to undergo various types of lumbar spine surgery was undertaken to assess the postoperative changes observable with magnetic resonance (MR) imaging. Patients underwent imaging preoperatively, immediately postoperatively (1-10 days), and late postoperatively (2-6 months). A retrospective review of MR images obtained in 62 patients who had undergone lumbar surgery but still had low back pain was also conducted. Epidural soft-tissue change and mass effect mimicking preoperative findings were present in nine of 13 patients who underwent laminectomy and diskectomy. Mass effect improved in appearance by the late postoperative period in eight of nine patients. T2-weighted sagittal images were best in demonstrating the site of anulus disruption immediately after diskectomy, which was seen in 11 of 13 patients, and the rent resolved on the late images in eight of ten cases. Sites of foraminotomy were seen as a loss of the normal foraminal fat signal. Extensive soft-tissue changes present in the immediate postoperative period severely limit the usefulness of MR imaging in that period for evaluating persistent symptoms. The exception may be hemorrhage, as its distinctive signal on T1-weighted images makes its identification possible.     

Uterine fibroleiomyoma: MR imaging appearances before and after embolization of uterine arteries

PURPOSE: To evaluate the magnetic resonance (MR) imaging appearances of uterine fibroleiomyoma before and after embolization and to determine whether there are preembolization MR imaging characteristics that are predictive of a successful outcome. MATERIALS AND METHODS: MR imaging was performed in 18 patients (32 fibroleiomyomas) before and at 2 and 6 months after embolization of the uterine arteries. On each occasion, fibroleiomyoma signal intensity and gadolinium enhancement characteristics were assessed in comparison with those of myometrium on T1-weighted and gadolinium-enhanced images or with those of skeletal muscle on T2-weighted images. Fibroleiomyoma volume was measured by using the ellipsoid formula. RESULTS: The mean fibroleiomyoma volume before embolization was 340 cm3 (range, 15-1,383 cm3). The mean reduction in fibroleiomyoma volume was 43% at 2 months and 59% at 6 months. Before embolization, high signal intensity on T1-weighted images was predictive of a poor response (P = .008), and high signal intensity on T2-weighted images was predictive of a good response (P = .007). The degree of gadolinium enhancement was not correlated with fibroleiomyoma volume reduction (P = .46). CONCLUSION: MR imaging was useful for evaluation of changes in fibroleiomyoma volume after uterine arterial embolization. MR imaging characteristics of fibroleiomyomas before embolization can help predict subsequent response to treatment.     

Interdigital (Morton) neuroma: high-resolution MR imaging with a solenoid coil

Fifteen patients (17 feet) with symptoms suggestive of plantar interdigital neuroma underwent magnetic resonance (MR) imaging at 1.5 T with a solenoid forefoot coil with an 8-cm field of view. Surgery was subsequently performed on six feet. Fifteen interdigital masses were identified with MR imaging. Five of these, in feet that underwent surgery, were pathologically confirmed neuromas. In the remaining foot that underwent surgery, flexor tendon injury with probable inflammatory reaction was demonstrated with MR imaging but was interpreted as indeterminate for neuroma. No neuronal was identified at surgery, which otherwise confirmed the MR imaging findings. Neuromas were most conspicuous on T1-weighted images as foci of decreased signal intensity well demarcated from adjacent fat tissue. The lesions were poorly seen on T2-weighted images, where they appeared isointense or slightly hypointense to fat tissue in all cases. Prominent regions of increased signal intensity, presumably representing fluid in intermetatarsal bursae, were seen proximal to 10 of the 15 masses found with MR imaging.     

Osteogenic sarcoma: MR signal abnormalities of the brain in asymptomatic patients treated with high-dose methotrexate

The advent of lesions with high signal intensity in periventricular white matter was incidentally observed on T2-weighted images in one patient who underwent magnetic resonance (MR) imaging of the brain after administration of high-dose methotrexate (HDMTX) for osteogenic sarcoma. Twenty-one additional symptom-free patients who had been treated with the same regimen and 10 patients who had undergone cisplatin-based chemotherapy for testicular cancer also underwent examination. Fourteen of the patients with osteosarcoma showed high-signal-intensity lesions in white matter on T2-weighted images. The interval between the last course of chemotherapy and MR imaging was a factor in this finding, as 12 of 14 patients who underwent examination within 2 years after chemotherapy had a positive finding, as opposed to two of eight patients who underwent examination later. The patients with testicular cancer had normal MR images. The occurrence of MR imaging abnormalities in asymptomatic patients treated with HDMTX for osteogenic sarcoma may be subclinical evidence of treatment-related central nervous system toxicity.