Are Dynamic Arterial Spin-Labeling MRA and Time-Resolved Contrast-Enhanced MRA Suited for Confirmation of Obliteration following Gamma Knife Radiosurgery of Brain Arteriovenous Malformations?

BACKGROUND AND PURPOSE: Intra-arterial DSA has been traditionally used for confirmation of cure following gamma knife radiosurgery for AVMs. Our aim was to evaluate whether 4D arterial spin-labeling MRA and contrast-enhanced time-resolved MRA in combination can be an alternative to DSA for confirmation of AVM obliteration following gamma knife radiosurgery. MATERIALS AND METHODS: In this prospective study, 30 patients undergoing DSA for confirmation of obliteration following gamma knife radiosurgery for AVMs (criterion standard) also underwent MRA, including arterial spin-labeling MRA and contrast-enhanced time-resolved MRA. One dataset was technically unsatisfactory, and the case was excluded. The DSA and MRA datasets of 29 patients were independently and blindly evaluated by 2 observers regarding the presence/absence of residual AVMs. RESULTS: The mean time between gamma knife radiosurgery and follow-up DSA/MRA was 53 months (95% CI, 42-64 months; range, 22-168 months). MRA total scanning time was 9 minutes and 17 seconds. Residual AVMs were detected on DSA in 9 subjects (obliteration rate = 69%). All residual AVMs were detected on at least 1 MRA sequence. Arterial spin-labeling MRA and contrast-enhanced time-resolved MRA showed excellent specificity and positive predictive values individually (100%). However, their sensitivity and negative predictive values were suboptimal due to 1 false-negative with arterial spin-labeling MRA and 2 with contrast-enhanced time-resolved MRA (sensitivity = 88% and 77%, negative predictive values = 95% and 90%, respectively). Both sensitivity and negative predictive values increased to 100% if a composite assessment of both MRA sequences was performed. Diagnostic accuracy (receiver operating characteristic) and agreement (κ) are maximized using arterial spin-labeling MRA and contrast-enhanced time-resolved MRA in combination (area under receiver operating characteristic curve = 1, P < .001; κ = 1, P < .001, respectively). CONCLUSIONS: Combining arterial spin-labeling MRA with contrast-enhanced time-resolved MRA holds promise as an alternative to DSA for confirmation of obliteration following gamma knife radiosurgery for brain AVMs, having provided 100% sensitivity and specificity in the study. Their combined use also enables reliable characterization of residual lesions.

Heteronuclear local field NMR spectroscopy under fast magic-angle sample spinning conditions

The acquisition of bidimensional heteronuclear nuclear magnetic resonance local field spectra under moderately fast magic-angle spinning (MAS) conditions is discussed. It is shown both experimentally and with the aid of numerical simulations on multispin systems that when sufficiently fast MAS rates are employed, quantitative dipolar sideband patterns from directly bonded spin pairs can be acquired in the absence of (1)H-(1)H multiple-pulse homonuclear decoupling even for "real" organic solids. The MAS speeds involved are well within the range of commercially available systems (10-14 kHz) and provide sidebands with sufficient intensity to enable a reliable quantification of heteronuclear dipolar couplings from methine groups. Simulations and experiments show that useful information can be extracted in this manner even from more tightly coupled -CH(2)- moieties, although the agreement with the patterns simulated solely on the basis of heteronuclear interactions is not in this case as satisfactory as for methines. Preliminary applications of this simple approach to the analysis of molecular motions in solids are presented; characteristics and potential extensions of the method are also discussed. Copyright 2000 Academic Press.

Assessment of visual impairment in patients with Alzheimer's disease.

We examined five patients with Alzheimer's disease who complained of poor vision. Two patients had mild Alzheimer's disease; they complained of problems with reading and of "bumping into things," yet both had normal visual acuities. One patient with moderate Alzheimer's disease had abnormal eye movements, visual-evoked potentials, and contrast sensitivity. The other two patients had severe Alzheimer's disease. Despite difficulties in performing the examination, we were able to see moderate impairments in visual acuity and visual fields, as well as marked dyschromatopsia, severe deficits in contrast sensitivity, and markedly abnormal eye movements and visual-evoked potentials.

Optic neuropathy in ethambutol-treated renal tuberculosis.

Ethambutol is frequently used in the treatment of tuberculosis, and, although optic neuropathies have been reported with the use of ethambutol, this adverse side effect has been considered to be rare and generally reversible with discontinuation of the medication. However, we recently saw two patients with renal tuberculosis treated with ethambutol in whom visual loss from toxic optic neuropathies was severe and irreversible despite careful ophthalmological monitoring and prompt discontinuation of the agent at the first sign of impaired visual function. While ethambutol treatment is most commonly instituted for pulmonary tuberculosis, it is interesting to note that both of these patients had renal tuberculosis. Since ethambutol is actively excreted via the renal system, compromise of renal function such as due to renal tuberculosis may lead to serum concentration elevations of ethambutol sufficient to produce optic neuropathy.

Breast carcinoma metastatic to the orbit.

Breast carcinoma metastatic to the orbit presented in four patients as a diffuse mass lesion. Clinical findings included restricted ocular motility, palpable mass, enophthalmos, and ptosis. The delay in diagnosis in three cases was due to subtle early findings, the long time interval from the primary breast lesion, lack of other metastases, and, in each of the four cases, the patient's reluctance to disclose any history of breast disease. Pathologic examination of the orbital breast metastases revealed two types: an adenocarcinomatous pattern with nests of pleomorphic malignant appearing cells and a histiocytoid variant with bland, large cells similar to histiocytes.