Transcranial color Doppler sonography in the emergency diagnosis of middle cerebral artery occlusion in a patient after head injury.

The purpose of this report is to highlight the utility of transcranial color Doppler sonography (TCCDS) in the emergency diagnosis of an ischemic stroke in a 64-year-old patient after head injury. An emergency CT identified a subdural hematoma, subarachnoid hemorrhage, a brain contusion and edema. The patient's status deteriorated after admission, and a second CT revealed an intracerebral hematoma and marked mass effect. Transcranial color sonography revealed no flow in the ipsilateral middle and anterior cerebral arteries, which was consistent with ischemic stroke. This case demonstrates that transcranial color Doppler sonography performed early after head injury may be useful in detecting associated occlusion of cerebral vessels.

Cervical spondylosis: contrast-enhanced magnetization transfer prepulsed 3D turbo field echo MR imaging.

Magnetic resonance (MR) imaging of the cervical spine with axial, low flip angle three-dimensional (3D) gradient-echo sequences is limited by long acquisition times and also by increased sensitivity to extrinsic and intrinsic magnetic field inhomogeneity, magnetic susceptibility differences, chemical shifts, and cerebrospinal fluid pulsatility. We attempted to assess the performance of gadolinium-enhanced, magnetization transfer (MT) prepulsed 3D fast gradient-echo sequences in demonstrating spondylotic changes of the cervical spine. Twenty patients with known cervical spine spondylosis were prospectively imaged in the axial plane using two gradient-echo-based MR techniques: 3D fast field echo (FFE) and gadolinium-enhanced, MT prepulsed, segmented turbo field echo (TFE). An average of 58 neural foramina on the 3D FFE images and 47 neural foramina on the contrast-enhanced TFE images were judged to be narrowed. The degree of neural foraminal narrowing was significantly less on the contrast-enhanced TFE images compared with the FFE images (P <0.001). Contrast-enhanced, MT prepulsed, segmented 3D TFE MR imaging has potential for ameliorating some of the limitations encountered in the more widely used gradient-echo techniques.

Transcranial colour Doppler sonography in emergency management of intracerebral haemorrhage caused by an arteriovenous malformation: case report.

We present a case which demonstrates the use of transcranial colour Doppler (TCCD) sonography in screening for an underlying arteriovenous malformation (AVM) in a middle-aged hypertensive patient with a spontaneous thalamic haematoma. The AVM was not detected on emergency CT but its presence, site and shape were demonstrated by TCCD, in the presence of a massive cerebral haemorrhage and acute intracranial hypertension.

Polyarteritis nodosa presenting as temporal arteritis in a 9-year-old child.

A 9-year-old Haitian girl presented initially with monocular blindness and an isolated temporal arteritis, confirmed by angiographic studies and temporal artery biopsy findings. CT and MR studies of the intracranial circulation showed only an enlarged, dense superficial temporal artery. Systemic workup revealed a mildly elevated erythrocyte sedimentation rate, mild changes in white and red blood cells, and a remote history of sensorineural hearing loss. Pathologic examination of the biopsy specimen narrowed the differential diagnosis to giant cell temporal arteritis and polyarteritis nodosa. Treatment with corticosteroids alone failed, and the child returned 1 month later with severe systemic illness and encephalopathy. MR studies showed multiple cortical and subcortical foci of increased T2 signal, and gyriform enhancement on T1-weighted images. Renal and mesenteric arteriograms showed innumerable tiny aneurysms at branch points in small and medium-sized vessels, typical of polyarteritis nodosa. We found no previous reports of this initial presentation in the pediatric population for either polyarteritis nodosa or giant cell temporal arteritis.

MR imaging of the hippocampus: measurement of T2 with four dual-echo techniques.

PURPOSE: To assess the effect of cerebrospinal fluid (CSF) signal nulling and different magnetic resonance (MR) imaging read-out implementations on the precision of T2 measurements in the hippocampus. MATERIALS AND METHODS: Oblique coronal MR imaging was performed in 12 healthy volunteers by using four dual-echo MR sequences: conventional spin-echo (SE), fast SE, gradient-echo and SE (GRASE), and fast fluid-attenuated inversion-recovery (FLAIR) imaging. T2 measurements were obtained from T2 maps derived from regions of interest within the head of both hippocampi. T2 measurements obtained with the four MR sequences were compared, as were differences in T2 between right and left hippocampi. Interrater and test-retest consistency were determined. RESULTS: Fast FLAIR imaging provided the smallest normal range and SD of T2 measurements. Fast FLAIR and fast SE imaging provided the smallest coefficients of variation. GRASE imaging provided a lower coefficient of variation than that of conventional SE. The mean difference between left and right hippocampi was smallest at fast FLAIR imaging. CONCLUSION: Use of a CSF-nulling inversion prepulse, fast SE read-out, or GRASE read-out MR sequence helps improve the precision of the hippocampal T2 measurements in comparison with use of conventional SE imaging. T2 measurements obtained at dual-echo fast FLAIR imaging may help detect subtle hippocampal abnormalities.

Usefulness of optimized gadolinium-enhanced fast fluid-attenuated inversion recovery MR imaging in revealing lesions of the brain.

OBJECTIVE: The purpose of this study was to compare the contrast enhancement of lesions of the brain revealed by gadolinium-enhanced optimized fast fluid-attenuated inversion recovery (FLAIR) MR imaging with that of lesions on gadolinium-enhanced optimized T1-weighted spin-echo MR imaging. SUBJECTS AND METHODS: Using computer simulations, we optimized the fast FLAIR parameters (TR, TEeff, and inversion time) and the T1-weighted spin-echo parameters (TR and TE) to provide maximum difference in signal intensity between enhancing lesions of the brain and white matter. Seventy-six consecutive patients referred for single-dose gadolinium-enhanced MR imaging of the brain underwent both optimized techniques, which were matched for spatial resolution, bandwidth, and number of excitations. The gadolinium-enhanced fast FLAIR and T -weighted spin-echo MR images were evaluated independently by two observers for number and size of enhancing lesions and for the degree of gray-white matter differentiation. Contrast-to-noise ratios were measured for enhancing lesions 1.0 cm or larger in diameter using 8 x 8 pixel regions of interest in the enhancing lesions and normal white matter. RESULTS: The most revealing parameters for fast FLAIR MR imaging proved to be a TR of 1500 msec, an inversion time of 683 msec, and a TEeff of 16 msec. For T1-weighted spin-echo MR imaging, the optimized parameters were a TR of 550 msec and a TE of 16 msec. In 28 patients, we saw enhancing lesions of the brain with at least one MR imaging technique. More lesions were seen on the T1-weighted spin-echo sequence (n = 141) than on the fast FLAIR sequence (n = 94) (p < .03). Gray-white matter differentiation was significantly better on the fast FLAIR sequence (p < .001). Contrast-to-noise ratios of enhancing lesions were greater on the T1-weighted spin-echo sequence (p < .001). CONCLUSION: In this study, optimized gadolinium-enhanced conventional T1-weighted spin-echo MR imaging proved superior to gadolinium-enhanced fast FLAIR MR imaging in revealing lesions of the brain.

Cyclic GMP contact points within the 63-kDa subunit and a 240-kDa associated protein of retinal rod cGMP-activated channels.

Ion channels from retinal rods and a variety of other cells are directly gated by cyclic nucleotides. The rod channel is known to contain a 63-kDa subunit, and there is molecular genetic evidence for the existence, in human retina, of a second subunit with a deduced molecular mass of about 100 kDa. When purified from bovine rods, the channel consists of the 63-kDa subunit and a 240-kDa associated protein that has been shown recently to contain a version of the cloned second subunit as part of a larger complex. We had previously shown that a photoaffinity analog of cGMP, 8-(p-azidophenacylthio)-[32P]cGMP, specifically labels both the 63- and 240-kDa proteins. Here the analog was used to identify cGMP-binding regions and amino acid contact points within these proteins. The specific labeling of the 63-kDa subunit was localized to a 66 amino acid fragment (Tyr-515-Met-580) that is contained entirely within a 110 amino acid region proposed to be the cGMP-binding site on the basis of homology with other cyclic nucleotide-binding proteins. Within this fragment, amino acid residues Val-524, Val-525, and Ala-526 were found to contain label. These residues are part of a larger hydrophobic cluster that appears to line the binding pocket. The results also indicate that the 240-kDa protein contains a similar cGMP-binding site. Sequencing of a specifically labeled 8-kDa fragment through 16 amino acid residues indicated that the fragment was derived from the portion of the 240-kDa complex that contains the second subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of retinal rod cGMP-gated channels: what makes for an effective 8-substituted derivative of cGMP?

Analogs of cGMP bearing diverse substituents at the C8 position of the guanine ring system have been shown to activate the cGMP-activated channel of retinal rods at concentrations lower than cGMP itself. In an effort to understand this behavior, we synthesized eight novel C8-substituted derivatives and tested their ability to activate channels in excised patches from salamander rod outer segments. We express the effectiveness of each analog as a ratio (in brackets) of the concentration required to open half of the channels in a patch to that required of 8-Br-cGMP, previously shown to be about 10 times more effective than cGMP. Five of the derivatives contained a thio substitution at C8: n-propylthio-cGMP [0.61], sulfoethylthio-cGMP [0.90], carboxyethylthio-cGMP [0.97], aminoethylthio-cGMP [2.8], and (trimethylamino)ethylthio-cGMP [8.5]. Three of the derivatives contained an amino substitution at C8: carboxyethylamino-cGMP [22], n-propylamino-cGMP [25], and aminoethylamino-cGMP [230]. The results indicate that thio-substitution at C8 produces more effective analogs than does amino-substitution, regardless of the chemical nature of the terminal functional group. Derivatives containing neutral and apolar tails opened channels at much lower concentrations than their positively-charged counterparts with the same C8 substituent. Analogs having negatively-charged tails were also more effective than those with positive charge but not quite as effective as those with neutral tails.(ABSTRACT TRUNCATED AT 250 WORDS)