Major Radiologic and Clinical Outcomes of Total Spine MRI Performed in the Emergency Department at a Major Academic Medical Center.

BACKGROUND AND PURPOSE: Total spine MRIs are requested by the emergency department when focused imaging can not be ordered on the basis of history or clinical findings. However, their efficacy is not known. We assessed the following: 1) major radiologic and clinical outcomes of total spine MR imaging performed by the emergency department, and 2) whether the presence of a high-risk clinical profile and/or neurologic findings impacts the clinical outcomes. MATERIALS AND METHODS: Total spine MRIs requested by the emergency department during a 28-month period were evaluated for major radiologic (cord compression, cauda equina compression, and other significant findings) and major clinical outcomes (hospital admission during the visit followed by an operation, radiation therapy, or intravenous antibiotics or steroids). Associations between a high-risk clinical profile (cancer, infection, coagulopathy) and/or the presence of neurologic findings and outcomes were assessed. RESULTS: After we excluded trauma or nondiagnostic studies, 321/2047 (15.7%) MRIs ordered during study period were total spine MR imaging; 117/321 (36.4%) had major radiologic and 60/321 (18.6%) had major clinical outcomes (34/60 in <24 hours); and 58/117(49.6%) with major radiologic outcome were treated compared with 2/205 (1.0%) without (OR = 99, P < .001). The presence of both a high-risk clinical profile and neurologic findings concurrently in a patient (142/321) increased the likelihood of major clinical outcomes during the same visit (OR = 3.1, P < .001) and in <24-hours (OR = 2.6, P = .01) compared with those with either a high-risk clinical profile or neurologic findings alone (179/321). CONCLUSIONS: Total spine MR imaging ordered by our emergency department has a high radiologic and significant clinical yield. When a high-risk clinical profile and neurologic findings are both present in a patient, they should be prioritized for emergent total spine MR imaging, given the increased likelihood of clinical impact.

Low-power inversion recovery MRI preserves brain tissue contrast for patients with Parkinson disease with deep brain stimulators.

BACKGROUND AND PURPOSE: Fast spin-echo short τ inversion recovery sequences have been very useful for MR imaging-guided deep brain stimulation procedures in Parkinson disease. However, high-quality fast spin-echo imaging deposits significant heat, exceeding FDA-approved limits when patients already have undergone deep brain stimulation and need a second one or a routine brain MR imaging for neurologic indications. We have developed a STIR sequence with an ultra-low specific absorption rate that meets hardware limitations and produces adequate tissue contrast in cortical and subcortical brain tissues for deep brain stimulation recipients. MATERIALS AND METHODS: Thirteen patients with medically refractory Parkinson disease who qualified for deep brain stimulation were imaged at 1.5T with a fast spin-echo short τ inversion recovery sequence modified to meet conditional MR imaging hardware and specific absorption rate restrictions. Tissue contrast-to-noise ratios and implant localization were objectively and subjectively compared by 2 neuroradiologists, and image quality for surgical planning was assessed by a neurosurgeon for high and low specific absorption rate images. RESULTS: The mean contrast-to-noise ratio for cerebral tissues without including the contrast-to-noise ratio for ventricular fluid was 35 and 31 for high and low specific absorption rate images. Subjective ratings for low specific absorption rate tissue contrast in 77% of patients were identical to (and in a few cases higher than) those of high specific absorption rate contrast, while the neurosurgical coordinates for fusing the stereotactic atlas with low specific absorption rate MR imaging were equivalent to those of the high specific absorption rate for 69% of patients. CONCLUSIONS: Patients with Parkinson disease who have already had a deep brain stimulation face a risk of neural injury if routine, high specific absorption rate MR imaging is performed. Our modified fast spin-echo short τ inversion recovery sequence conforms to very conservative radiofrequency safety limits, while it maintains high tissue contrast for presurgical planning, postsurgical assessment, and radiologic evaluations with greater confidence for radiofrequency safety.

A 3T MR imaging investigation of the topography of whole spinal cord atrophy in multiple sclerosis.

BACKGROUND AND PURPOSE: Spinal cord atrophy is a common feature of MS. However, it is unknown which cord levels are most susceptible to atrophy. We performed whole cord imaging to identify the levels most susceptible to atrophy in patients with MS versus controls and also tested for differences among MS clinical phenotypes. MATERIALS AND METHODS: Thirty-five patients with MS (2 with CIS, 27 with RRMS, 2 with SPMS, and 4 with PPMS phenotypes) and 27 healthy controls underwent whole cord 3T MR imaging. The spinal cord contour was segmented and assigned to bins representing each C1 to T12 vertebral level. Volumes were normalized, and group comparisons were age-adjusted. RESULTS: There was a trend toward decreased spinal cord volume at the upper cervical levels in PPMS/SPMS versus controls. A trend toward increased spinal cord volume throughout the cervical and thoracic cord in RRMS/CIS versus controls reached statistical significance at the T10 vertebral level. A statistically significant decrease was found in spinal cord volume at the upper cervical levels in PPMS/SPMS versus RRMS/CIS. CONCLUSIONS: Opposing pathologic factors impact spinal cord volume measures in MS. Patients with PPMS demonstrated a trend toward upper cervical cord atrophy. However patients with RRMS showed a trend toward increased volume at the cervical and thoracic levels, which most likely reflects inflammation or edema-related cord expansion. With the disease causing both expansion and contraction of the cord, the specificity of spinal cord volume measures for neuroprotective therapeutic effect may be limited.

Reading impairment in the neuronal migration disorder of periventricular nodular heterotopia.

OBJECTIVE: To define the behavioral profile of periventricular nodular heterotopia (PNH), a malformation of cortical development that is associated with seizures but reportedly normal intelligence, and to correlate the results with anatomic and clinical features of this disorder. METHODS: Ten consecutive subjects with PNH, all with epilepsy and at least two periventricular nodules, were studied with structural MRI and neuropsychological testing. Behavioral results were statistically analyzed for correlation with other features of PNH. RESULTS: Eight of 10 subjects had deficits in reading skills despite normal intelligence. Processing speed and executive function were also impaired in some subjects. More marked reading difficulties were seen in subjects with more widely distributed heterotopia. There was no correlation between reading skills and epilepsy severity or antiepileptic medication use. CONCLUSION: The neuronal migration disorder of periventricular nodular heterotopia is associated with an impairment in reading skills despite the presence of normal intelligence.

Characterization of experimental spinal cord injury with magnetization transfer ratio histograms.

This study was designed to characterize the severity of tissue damage in experimental spinal cord injury using magnetization transfer (MT) histogram analysis. Seven Sprague-Dawley rats were subjected to laminectomy and standard weight-drop injury to the spinal cord (four rats at 15 cm drop-height and three rats at 2.5 cm). Three control animals underwent laminectomy without weight-drop. After sacrifice, the animals were scanned at 1.9 T with a pulsed off-resonance MT technique. Following magnetic resonance (MR) imaging, the cords were embedded in paraffin and sectioned into 5-microm sections for semiquantitative histopathological analysis. Composite histograms were generated using data spanning an axial distance of 3 cm centered on the injury site. MT histogram parameters, such as the amount of tissue with statistical correspondence to normal white matter, were highly predictive of histopathological results, including myelination state and neurofilament damage. Less correlation with edema was observed, suggesting that the technique was most sensitive to true tissue alteration.

Diffusional anisotropy in cranial nerves with maturation: quantitative evaluation with diffusion MR imaging in rats.

PURPOSE: To investigate the correlation between diffusional anisotropy and developmental changes in anatomy, which include myelination, in central and peripheral nerves in an animal model by using quantitative diffusion magnetic resonance (MR) imaging and electron microscopy. MATERIALS AND METHODS: In vivo transverse and longitudinal apparent diffusion coefficients (ADCs) of the optic and trigeminal nerves in 2-10-week-old rats were measured with MR imaging. Then the animals were sacrificed at each time point, and transverse and longitudinal sections of optic and trigeminal nerves were studied with electron microscopy. RESULTS: In the optic nerve, the ADC parallel to the neurofibers increased with development and increased contemporaneously with myelination, while the ADC perpendicular to the nerve did not change. This resulted in a significant increase in diffusional anisotropy. There were no significant changes in ADCs in either direction in the trigeminal nerve. Longitudinal sections of optic nerve showed a marked change in the orientation of each fiber. As development proceeded, the axons, which initially followed tortuous courses, assumed straighter and more parallel orientations. Trigeminal nerves displayed straight parallel courses at 2 weeks that did not change over the study period. CONCLUSION: Changes in fiber anatomy in maturation from tortuous to straighter and more parallel orientation can account for changes in longitudinal ADC and in diffusional anisotropy.

Transient MRI enhancement in a patient with seizures and previously resected glioma: use of MRS.

A 35-year-old man presented with partial seizures 10 years after resection of a left-sided glioblastoma multiforme. At the old operative site MRI demonstrated extensive cortical and white matter gadolinium enhancement, and PET showed hypermetabolism. Biopsy of the area was postponed when MRS showed a normal biochemical spectrum. MRI and PET abnormalities resolved after control of the seizures. MRS is noninvasive and can provide essential information in the management of patients with seizures and previously treated cerebral neoplasms.

Dependence of apparent diffusion coefficients on axonal spacing, membrane permeability, and diffusion time in spinal cord white matter.

We used a numerical simulation of water self-diffusion among permeable cylinders to predict the dependence of MR-based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion-sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 microsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 microm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2-microm and 11-microm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white-matter disease.

Catamenial mononeuropathy and radiculopathy: a treatable neuropathic disorder.

OBJECT: The aim of this study was to investigate the indications and treatment options in patients with lower-extremity neuropathies and radiculopathies caused by endometriosis. METHODS: The authors identified five patients whose symptoms included catamenial pain, weakness, and sensory loss involving the sciatic and femoral nerves and multiple lumbosacral nerve roots. Radiographic studies supported the diagnosis of catamenial neuropathy or radiculopathy, but definitive diagnosis depended on surgical and pathological examination. Treatment of symptoms, including physical therapy and a course of antiinflammatory or analgesic medication, was not helpful. Patients responded favorably to hormonal therapy. Laparoscopy or open exploration for extrapelvic lesions was performed for diagnosis or for treatment when hormone therapy failed. Pain and sensory symptoms responded well to therapy. Weakness improved, but never recovered completely. CONCLUSIONS: Catamenial neuropathy or radiculopathy should be considered when evaluating reproductive-age women with recurring focal neuropathic leg pain, weakness, and sensory loss.

Numerical model for calculation of apparent diffusion coefficients (ADC) in permeable cylinders--comparison with measured ADC in spinal cord white matter.

We have implemented a numerical method for calculation of the apparent diffusion coefficient (ADC) in spinal cord injury, which takes into account the distribution of axon diameters and permeability found in spinal cord white matter, as well as relative axonal volume. We propose a procedure for determining the status of axonal integrity from measured ADC values. These methods have been applied to a well characterized rat spinal cord injury model, affording a prediction of the increase in axonal permeability which is presumed to be closely related to functional deficit. ADC values are compared to those calculated from analytical formulas in the literature, and possible factors underlying the ADC behavior are explored. Calculated results indicate both axonal swelling and cell membrane permeability to be important factors contributing to ADC in traumatic spinal cord injury.