Although similar findings were found in some lesions, the large histologic variability of NF hampers the definition of a prototype of NF on MRI. However, the MRI appearance of the myxoid subtype is rather characteristic. Histologic findings reflect the different SI characteristics and enhancement pattern on MRI.

Spinal tumors are uncommon lesions but may cause significant morbidity in terms of limb dysfunction. In establishing the differential diagnosis for a spinal lesion, location is the most important feature, but the clinical presentation and the patient's age and gender are also important. Magnetic resonance (MR) imaging plays a central role in the imaging of spinal tumors, easily allowing tumors to be classified as extradural, intradural-extramedullary or intramedullary, which is very useful in tumor characterization. In the evaluation of lesions of the osseous spine both computed tomography (CT) and MR are important. We describe the most common spinal tumors in detail. In general, extradural lesions are the most common with metastasis being the most frequent. Intradural tumors are rare, and the majority is extramedullary, with meningiomas and nerve sheath tumors being the most frequent. Intramedullary tumors are uncommon spinal tumors. Astrocytomas and ependymomas comprise the majority of the intramedullary tumors. The most important tumors are documented with appropriate high quality CT or MR images and the characteristics of these tumors are also summarized in a comprehensive table. Finally we illustrate the use of the new World Health Organization (WHO) classification of neoplasms affecting the central nervous system.

The purpose of this study was to determine the prevalence, extension and signal characteristics of fluid-fluid levels in a large series of 700 bone and 700 soft tissue tumors. Out of a multi-institutional database, MRI of 700 consecutive patients with a bone tumor and MRI of 700 consecutive patients with a soft tissue neoplasm were retrospectively reviewed for the presence of fluid-fluid levels. Extension (single, multiple and proportion of the lesion occupied by fluid-fluid levels) and signal characteristics on magnetic resonance imaging of fluid-fluid levels were determined. In all patients, pathologic correlation was available. Of 700 patients with a bone tumor, 19 (10 male and 9 female; mean age, 29 years) presented with a fluid-fluid level (prevalence 2.7%). Multiple fluid-fluid levels occupying at least one half of the total volume of the lesion were found in the majority of patients. Diagnoses included aneurysmal bone cyst (ten cases), fibrous dysplasia (two cases), osteoblastoma (one case), simple bone cyst (one case), telangiectatic osteosarcoma (one case), "brown tumor" (one case), chondroblastoma (one case) and giant cell tumor (two cases). Of 700 patients with a soft tissue tumor, 20 (9 males and 11 females; mean age, 34 years) presented with a fluid-fluid level (prevalence 2.9%). Multiple fluid-fluid levels occupying at least one half of the total volume of the lesion were found in the majority of patients. Diagnoses included cavernous hemangioma (12 cases), synovial sarcoma (3 cases), angiosarcoma (1 case), aneurysmal bone cyst of soft tissue (1 case), myxofibrosarcoma (1 case) and high-grade sarcoma "not otherwise specified" (2 cases). In our series, the largest reported in the literature to the best of our knowledge, the presence of fluid-fluid levels is a rare finding with a prevalence of 2.7 and 2.9% in bone and soft tissue tumors, respectively. Fluid-fluid levels remain a non-specific finding and can occur in a wide range of bone and soft tissue tumors, both benign and malignant. Therefore, they cannot be considered diagnostic of any particular type of tumor, and the diagnosis should be made on the basis of other radiological and clinical findings.

A 28-year-old man presented with a swelling at the right thoracic wall. Computed tomography showed an aggressive process involving the cortex of the rib with concomitant soft tissue mass. However, a needle biopsy specimen revealed an enchondroma and consequently the physician decided to apply a "wait-and-see" strategy. After 3 years of careful follow-up by MR imaging, the patient complained of subtle enlargement of the lesion, which was later confirmed on repeated CT scan. Despite an aggressive appearance on control MR imaging, histopathological examination after incisional biopsy could not differentiate between enchondroma and low-grade chondrosarcoma. Wide excision including previous biopsy trajectory was performed. Diagnosis of a low-grade (grade I) chondrosarcoma was made on findings of the excisional specimen and seeding of cartilage tissue along the previous incisional biopsy trajectory was found.

No abstract

Our aim was to establish the normal range of MRI findings after successful lumbar discectomy. We prospectively examined 34 consecutive patients with an excellent clinical outcome by MRI 6 weeks and 6 months after surgery. All examinations included sagittal and axial spin-echo (SE) T1-weighted images before and after intravenous gadolinium-DTPA and fast SE T2-weighted images. Contrast enhancement along the surgical tract was seen in all patients 6 weeks and 6 months after surgery. After 6 months minimal or no mass effect on the dural sac by epidural scar was seen. In 20% of patients there was recurrent disc herniation, with mass effect. Enhancing nerve roots were seen in 20% of patients 6 weeks postoperatively, and half of these were associated with recurrent disc herniation at the same side. None of these patients still showed nerve root enhancement 6 months after surgery. Postoperative MRI studies must be interpreted with great care since the features described in the failed back surgery syndrome are also found, to some extent, in asymptomatic postoperative patients.

We evaluated the role of MRI in the diagnosis of postoperative spondylodiscitis. Spondylodiscitis is a serious complication of surgery, and the diagnosis frequently depends on a combination of clinical, laboratory and imaging findings. We compared the MRI findings in six patients with biopsy- or surgery-proven spondylodiscitis with those in 38 asymptomatic postoperative patients. Contrast enhancement and signal changes in the intervertebral disc or the vertebral endplates are not specific for spondylodiscitis, being also seen in the asymptomatic patients. However, absence of Modic type 1 changes, of contrast enhancement of the disc or of enhancing paravertebral soft tissues suggests that the patient does not have spondylodiscitis. MRI appears more useful for exclusion than for confirmation of postoperative spondylodiscitis.

The clinical relevance of subtle changes on magnetic resonance imaging (MRI) for evaluating haemophilia treatment is unknown. To determine the relationship of findings on MRI with joint function and bleeding in joints with apparently very mild arthropathy, a prospective study was performed. Knees and ankles of 26 patients, 13-26 years, were scanned. Two blinded radiologists scored the MRI (IPSG consensus score) and the radiography [Pettersson score (PS)]. Clinical function (HJHS) was scored by one physiotherapist. Life-time number of bleeds was collected from patient files. Of 104 joints scanned, three were excluded because of previous arthrodesis or trauma. Remaining 101 MRI scores correlated weakly with clinical function (r = 0.27, P = 0.01) and less with lifetime number of bleeds (r = 0.16, P = 0.14). MRI scores were 0 in 58 joints, including 27 with major bleeds. In three joints of patients playing intensive sports MRI showed minor changes (MRI score = 1) in the absence of bleeds. Agreement was reasonable between PS and MRI score (r = 0.41, P < 0.01). In 30% of joints, MRI detected abnormalities in soft-tissue and cartilage, while PS was 0 points. No evidence of occult haemorrhages was found. Instead, we found no abnormalities on MRI in 43 joints with a history of repeated joint bleeding. Haemosiderin seemed associated with the time between assessment and last bleed; joints that had suffered a bleed long before MRI had hardly haemosiderin, while those with a recent bleed showed haemosiderin, suggesting joint damage may be reversible. Abnormalities detected by MRI, but not by PS were minor and their clinical implications are not yet clear.