Two cases of progressive multifocal leukoencephalopathy after allogeneic hematopoietic cell transplantation and a review of the literature.

Progressive multifocal leukoencephalopathy (PML) is a rare subacute demyelinating disorder of the central nervous system (CNS) caused by the DNA JC human polyomavirus. In immunocompromised hosts, PML is caused by reactivation of a latent infection rather than de novo primary exposure. PML in the setting of hematopoietic cell transplantation (HCT) is exceedingly rare. PML should be considered in the differential diagnosis of HCT recipients, autologous or allogeneic, presenting with worsening of neurological symptoms, especially associated with post-transplant neurodegenerative findings. Although DNA polymerase chain reaction (PCR) of the cerebrospinal fluid (CSF) has emerged as a promising tool for detecting JC virus, a negative result does not rule out PML. Brain biopsy remains the most reliable and accurate method for diagnosing JC virus-associated PML. Presently, there is no universally effective antiviral therapy against JC virus and outcome is fatal in the majority of cases. We hereby describe two cases of PML developing after allogeneic HCT and provide a comprehensive review of the literature.

Proliferating trichilemmal cysts of the scalp on CT.

Proliferating trichilemmal cysts, also known as pilar tumors, are slow-growing lobulated masses most commonly found on the scalp of elderly women. We present the case of a 69-year-old woman with a 25-year history of multiple enlarging scalp masses. The patient was evaluated for surgical consultation after the dominant mass presented with malignant degeneration. A CT of the head revealed multiple large, subcutaneous, cystic masses with calcifications.

Visualization of basilar invagination by computerized tomography.

Computerized tomography was used to visualize bony masses in the posterior fossa in a patient with basilar invagination associated with symptoms of vertebrobasilar insufficiency.

Brain magnetic resonance imaging in acute optic neuritis. Experience of the Optic Neuritis Study Group.

OBJECTIVE: Changes in the brain on magnetic resonance images are common in patients with optic neuritis even when there is no other clinical evidence of multiple sclerosis. The current study was designed to determine systematically the prevalence of brain abnormalities on magnetic resonance images in the patients entered into the Optic Neuritis Treatment Trial. DESIGN: Prospective multicenter clinical trial. SETTING: Referral centers. PATIENTS AND METHODS: Brain magnetic resonance images from 418 patients with acute optic neuritis (77% women; mean age, 32.0 years) were evaluated at a central reading center with the use of a standardized classification system (ranging from 0 for normal to IV for most extensive changes). RESULTS: Of the scans, 40.9% were classified as grade 0, 10.8% as grade I, 9.1% as grade II, 6.7% as grade III, and 32.5% as grade IV. For patients with isolated (monosymptomatic) optic neuritis, 26.7% had two or more lesions. CONCLUSIONS: We found a lower prevalence of brain magnetic resonance imaging abnormalities in isolated optic neuritis than previous studies have reported. This likely is due to our study having a higher degree of standardization of patient inclusion criteria, which limited patient selection bias.

Hemorrhagic necrosis and vascular injury in carbon monoxide poisoning: MR demonstration.

MR imaging of a patient 3-years status post-carbon monoxide (CO) poisoning revealed areas of abnormal signal bilaterally in the region of the globus pallidus that had shorter T1 characteristics and longer T2 characteristics than cerebrospinal fluid, probably representing methemoglobin, and that is surrounded by a rim of decreased signal on T2-weighted images, felt to represent hemosiderin. This case demonstrates characteristic findings on MR imaging of CO poisoning, as well as observations that suggest prior focal hemorrhage. Typical findings, neuropathology, and the role of vascular injury and prognosis are discussed.

Recognition of the aberrant right subclavian artery on cervical spine MR.

Neuroradiologists performing cervical spine MR scans are reminded that an aberrant right subclavian artery is detectable on sagittal cervical spine views. This review of 335 consecutive patients revealed two such anomalies for a prevalence of 0.6%, which compares favorably with the published range of occurrences in the literature (0.5 to 2%).

Cerebral aspergillosis: MR imaging and histopathologic correlation.

The authors report a case of intracranial aspergillosis secondary to immunosuppression. Signal intensity changes in the lesion on brain MR are compared with gross and histopathologic findings at autopsy. A peripheral ring of low signal intensity relates to a dense population of Aspergillus hyphal elements and small areas of hemorrhage. CT findings are included for comparison.

Prevalence and percutaneous drainage of cysts of the sacral nerve root sheath (Tarlov cysts).

PURPOSE: To describe a percutaneous CT-guided method for drainage of perineurial (Tarlov) cysts, which are a cause of sciatica and low back pain, and to report the prevalence of these cysts within the population as detected by MR. METHODS: Five hundred sequential lumbosacral spine MRs were evaluated for the presence of a perineurial cyst. Using CT-guided percutaneous drainage techniques, seven cysts were drained in five symptomatic patients. RESULTS: Of the 500 sequential lumbosacral spine MRs, examinations from 23 patients showed perineurial cysts, a prevalence of 4.6%. Five patients (1%) were symptomatic from the cysts. After CT-guided percutaneous drainage, instant pain relief lasted from 3 weeks to 6 months without the risk or cost of spine surgery. CONCLUSIONS: Lumbosacral perineurial cysts are common lesions that are usually asymptomatic but may cause pressure symptoms. Cyst puncture can alleviate the pain. Although the cysts repressurized and the patients' symptoms returned in most cases, this technique seems to be a quick and simple way of at least attaining a pain-free interval and possibly a complete cure as occurred in one patient in this study.

Postgadolinium enhancement of a compressive neuropathy of the optic nerve.

We report the MR and CT findings of a case of postgadolinium signal enhancement of the optic nerve secondary to an extrinsically compressive lesion in a 24-year-old woman with hypertrophy of the anterior clinoid.

Relationship of Schmorl's nodes to vertebral body endplate fractures and acute endplate disk extrusions.

BACKGROUND AND PURPOSE: Literature regarding clinical pain syndromes associated with acute, traumatic Schmorl's nodes (SNs) is limited. Our purpose was to determine whether an SN could be related to a previous traumatic event producing either acute SN or a vertebral endplate fracture. METHODS: Two neuroradiologists independently reviewed initial and follow-up MR examinations of 14 patients with a clinical diagnosis of acute, symptomatic thoracolumbar SNs or vertebral body endplate fractures that evolved into SNs to evaluate marrow edema, signal intensity, margin definition, presence of intravertebral extruded disk material, and pattern of contrast enhancement. RESULTS: Edema of the affected vertebral body, adjacent to an endplate without wedging or collapse, was observed on the initial MR images in all cases. The initial MR images of six (43%) of 14 patients exhibited only edema of the marrow immediately adjacent to the endplate without wedging or collapse. The MR images obtained at the time of follow-up showed subsequent formation of a chronic and eventually asymptomatic SN for all six patients. The initial MR images of eight (57%) of the 14 patients showed the typical appearance of acute SNs with marrow edema of the affected vertebra. The contrast-enhanced images of three patients manifested enhancement of the invaginated disk material in three (100%) of three cases and enhancement of the surrounding vertebral body in one case (33%). Six (43%) of 14 patients had acute typical compression fracture of a vertebral body of at least one additional level. CONCLUSION: Most (57%) of the SNs in this series could be traced to episodes of significant, sudden-onset, localized, nonradiating back pain and tenderness for which the MR images showed SNs surrounded by vertebral body marrow edema. The remaining SNs (43%) were not immediately apparent as SNs and manifested only as vertebral body edema representing endplate fracture but did evolve into classical chronic SNs that follow-up imaging revealed.

Measurement of the normal optic chiasm on coronal MR images.

PURPOSE: To develop an objective method for measuring the optic chiasm and to document its normal range in size. METHODS: Measurements of the height and area of the optic chiasm, made on coronal T1-weighted MR images with the use of commercially available region-of-interest software, were obtained in 114 healthy subjects who had a total of 123 MR studies. A normal range and standard deviation were calculated, and the information was broken down by age and sex. RESULTS: The mean area of the optic chiasm was 43.7 mm2, with a standard deviation of 5.21. The mean width was 14.0 mm, with a standard deviation of 1.68. CONCLUSION: The area and width of the optic chiasm can be measured with the use of commercially available software, which allows an objective estimate of the chiasm's size. Knowledge of the normal size range of the optic chiasm can be helpful in the early detection of some disorders.

Contrast-enhanced MR imaging of optic nerve lesions in patients with acute optic neuritis.

The purpose of this study was to determine if administration of gadopentetate dimeglumine aids in the MR detection of optic nerve lesions in patients with acute optic neuritis and to establish an efficient MR imaging protocol to effectively demonstrate such lesions. Patients with acutely decreased visual acuity were referred for MR imaging of the brain and orbits. Predominantly, T1-weighted images were obtained in axial and coronal planes with and without contrast administration. Enhancing lesions were observed in the optic nerve (7/14 patients) and optic chiasm (2/14), and associated white matter lesions were seen elsewhere in the brain (5/19). Our results indicate that administration of gadopentetate dimeglumine aids in the MR detection of lesions of the optic nerve and optic chiasm. Applicability of our MR imaging protocol was confirmed by the demonstration of these lesions and by the disseminated white matter lesions seen simultaneously elsewhere in the brain.

Pathognomonic MR imaging findings in Balo concentric sclerosis.

Irregular, concentric zones of increased signal on T2-weighted cranial MR imaging studies may strongly suggest Balo concentric sclerosis (BCS), a rare but recognized variant of multiple sclerosis. Differentiating BCS from multiple sclerosis or neoplasm can be difficult clinically, but MR imaging findings noted in this case may be pathognomonic.

Use of a clinical MR scanner for imaging the rat brain.

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy are established techniques that enable noninvasive anatomic and functional tissue characterization in vivo. These tools have been employed to probe experimental models of neoplasia, cerebrovascular disease, brain injury, and neurotransplantation in small animals. To date, these studies have been executed primarily on research-dedicated instruments of limited availability or resolution. Using relatively straightforward software and hardware modifications of a widely used clinical MRI unit, we were able to image numerous structures within the living rat brain including the neostriatum, hippocampus, periaqueductal gray, and the ventricular system. Illustrative applications of this imaging technique in two intracerebral infusion models involving rats are presented. Such adaptation of clinical MRI scanners has the potential to significantly expand the availability of high resolution in vivo imaging of small animals for a variety of experimental protocols.

Automatic tumor segmentation using knowledge-based techniques.

A system that automatically segments and labels glioblastoma-multiforme tumors in magnetic resonance images (MRI's) of the human brain is presented. The MRI's consist of T1-weighted, proton density, and T2-weighted feature images and are processed by a system which integrates knowledge-based (KB) techniques with multispectral analysis. Initial segmentation is performed by an unsupervised clustering algorithm. The segmented image, along with cluster centers for each class are provided to a rule-based expert system which extracts the intracranial region. Multispectral histogram analysis separates suspected tumor from the rest of the intracranial region, with region analysis used in performing the final tumor labeling. This system has been trained on three volume data sets and tested on thirteen unseen volume data sets acquired from a single MRI system. The KB tumor segmentation was compared with supervised, radiologist-labeled "ground truth" tumor volumes and supervised k-nearest neighbors tumor segmentations. The results of this system generally correspond well to ground truth, both on a per slice basis and more importantly in tracking total tumor volume during treatment over time.

Magnetic resonance imaging of syrinx associated with intramedullary metastases and leptomeningeal disease.

Intramedullary spinal cord metastasis with an associated syrinx diagnosed by magnetic resonance imaging (MR) is described. The patient had documented simultaneous leptomeningeal spread of malignant cells and intramedullary spinal cord metastasis with hyalinized blood vessels, venous dilatation, and cavitation detected by autopsy. Metastasis to the spinal cord is unusual, but well described. Syrinx associated with intramedullary spinal cord metastasis has been detected rarely. MRI of syrinx and intramedullary spinal cord metastasis, and the possible pathogenesis of these lesions are discussed.

Magnetic resonance imaging anatomy of the cranial nerves.

Correlation of findings on neurological examination of the cranial nerves with gross anatomy, neuroanatomy, and neuropathology provides the optimal diagnostic use of magnetic resonance imaging (MRI). Illustrations of the anatomy of each of the cranial nerves, with concise labeling of relevant anatomical relationships, are compared with brief neurological summaries and MRIs of patients.

Computed tomography and fluoroscopy guided anesthesia and steroid injection in facet syndrome.

One hundred patients with posterior compartment lumbar spinal axis pain syndromes and focal tenderness were injected with lidocaine and betamethasone in 194 sites. Lidocaine injection was diagnostic in 183 instances (94%) and steroid injection provided long-term relief (greater than 3 months) in 105 instances (54%). CT guidance proved helpful in directing the needle tip to the precise location for optimal delivery of medications to exact anatomical sites.

Computer tomographically guided discography as a determinant of normal disc level before fusion.

Computer tomographically guided discography was used as a reproducible and reliable method of determining the internal architecture and integrity of intervertebral discs before spinal fusion operation. One hundred disc levels were studied in 60 prospective patients with 54 (54%) of levels proving abnormal. Twenty-nine levels (29% of total levels) demonstrated complete anular tears, and 25 (25% of total) showed incomplete radial tears of the anulus, often multiple, indicative of degenerative change. In each of these cases, one level higher had to be studied and was subsequently found to be normal and would, therefore, support a fusion.