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L M Ramos

Publications and source records attributed to L M Ramos.

At least 37 records · Page 2Linked to original sources
PubMed1998

Changes in the disc space after fractures of the thoracolumbar spine.

We have studied the intervertebral discs adjacent to fractured vertebral bodies using MRI in 63 patients at a minimum of 18 months after injury. There were 75 thoracolumbar fractures of which 26 were treated conservatively and 37 by posterior reduction and fusion with an AO internal fixator. We identified six different types of disc using criteria based on the morphology and the intensity of the MRI signal. The inter- and intraobserver variability of this system was good. Most of the discs showed predominantly morphological changes with no variation in signal intensity. Some disc types were associated with progressive kyphosis in patients treated conservatively. In those managed by operation, recurrent kyphosis appeared to result from creeping of the disc in the central depression of the bony endplate rather than from disc degeneration. Changes in the disc space after posterior fixation should not be seen as a form of chronic instability but as a redistribution of the disc tissue in the changed morphology of the space after fractures of the endplate.

Adolescent↗
PubMed1998

High-flow bypass using nonocclusive excimer laser-assisted end-to-side anastomosis of the external carotid artery to the P1 segment of the posterior cerebral artery via the sylvian route. Technical note.

In a patient with a giant aneurysm of the basilar artery trunk, a vein graft was interposed between the external carotid artery in the neck and the P1 segment of the posterior cerebral artery. Balloon occlusion of both vertebral arteries was performed 3 days later. The sylvian route was used for the grafting procedure and the connection to the posterior cerebral artery was made by using the excimer laser-assisted nonocclusive anastomosis technique.

Adult↗
PubMed1997

Radiation-induced brachial plexopathy: MR imaging.

OBJECTIVE: To describe the MR imaging appearance of radiation-induced brachial plexopathy. DESIGN: MR imaging was performed in two patients with the clinical diagnosis of radiation-induced brachial plexopathy and in one with surgically proven radiation fibrosis of the brachial plexus. PATIENTS: Three patients who had had radiation therapy to the axilla and supraclavicular region (two with breast carcinoma and one with Hodgkin's lymphoma) presented with symptoms in the arm and hand. To exclude metastases or tumor recurrence MR imaging was performed. RESULTS AND CONCLUSION: In one patient, fibrosis showing low signal intensity was found, while in two patients high signal intensity fibrosis surrounding the brachial plexus was found on the T2-weighted images. In one case gadolinium enhancement of the fibrosis was seen 21 years after radiation therapy. It is concluded that radiation-induced brachial plexopathy can have different MR imaging appearances. We found that radiation fibrosis can have both low or high signal intensities on T2-weighted images, and that fibrosis can enhance even 21 years after radiation therapy.

Adult↗
PubMed1997

Assessment of the preferred plane and sequence in the depiction of mesial temporal sclerosis using magnetic resonance imaging.

RATIONALE AND OBJECTIVES: Definition of optimal magnetic resonance (MR) scanning plane and conventional MR sequence for the detection of mesial temporal sclerosis (MTS). METHODS: Coronal and axial T2-weighted images and axial T2-weighted images parallel to the long axis of the hippocampus (APLAH) and coronal inversion recovery (IR) images were obtained in patients with medically intractable temporal lobe epilepsy in their phase 1 preoperative evaluation. Thirty-three consecutive MR scans were reviewed by a panel of three radiologists. Twenty-three patients had MR abnormalities consistent with MTS, and ten scans were normal. To assess the best single scanning technique, another group of three radiologists, who were masked to all patient data, individually assessed the different planes and sequences of the 33 studies presented separately in a random fashion. For each plane and sequence, the likelihood (L) ratio for the correct diagnosis was determined separately. RESULTS: For all planes considered separately, a likelihood ratio of 4.4 was optimal for the coronal T2-weighted images. The likelihood ratio of APLAH T2 was 2.2; of axial T2, 3.9; of coronal IR, indefinite because of 100% specificity. CONCLUSIONS: For the assessment of MTS, coronal T2-weighted images were considered the best single scanning technique.

Adolescent↗
PubMed1997

Magnetic resonance imaging of the brachial plexus in patients with multifocal motor neuropathy.

We studied whether magnetic resonance (MR) imaging of the brachial plexus is useful to distinguish multifocal motor neuropathy (MMN) from lower motor neuron disease (LMND) and whether abnormalities resemble those of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We compared MR images of the brachial plexus of nine patients with MMN with scans from five patients with CIDP, eight patients with LMND, and 174 controls. In two patients with MMN, and in three patients with CIDP, the MR images showed an increased signal intensity on the T2-weighted images of the brachial plexus. Two other patients with MMN demonstrated a more focal, increased signal intensity on the T2-weighted images, occurring in one patient only in the axilla, and in the other patient in the axilla and in the ventral rami of the roots. MR images of the brachial plexus of eight patients with LMND were normal. The distribution of the MR imaging abnormalities corresponded with the distribution of symptoms of the patients: asymmetrical in MMN and symmetrical in CIDP. These findings demonstrate that MR imaging abnormalities of the brachial plexus in patients with MMN resemble those seen in CIDP and may be useful to distinguish MMN from LMND.

Adult↗
PubMed1996

Cerebral metabolic differences between the severe and critical hypoperfused brain.

Occlusion or severe stenosis, with a reduction in the diameter of the extracranial arteries of more than 70%, may lead to hypoperfusion of the brain with an increased risk of cerebral infarction. The aim of this study was to investigate whether a decrease in metabolism in noninfarcted hypoperfused cerebral areas is correlated with the level of hypoperfusion. Fifty-one patients without infarcts, with borderzone infarcts, with territory infarcts, and fourteen healthy control subjects were investigated with MRI and MR spectroscopic imaging. The NAA/choline ratio in the symptomatic hermisphere was significantly decreased in patients with borderzone infarcts compared with patients without infarcts, with patients with territory infarcts, and with control subjects. Furthermore, patients with borderzone infarcts had a relatively high frequency of cerebral lactate. These results indicate that there might be a lower limit of hypoperfusion that can be measured indirectly with MR spectroscopic imaging, below which irreversible cerebral damage occurs.

Analysis of Variance↗
PubMed1995

Familial subarachnoid hemorrhage: distinctive features and patterns of inheritance.

To delineate the distinctive features of familial subarachnoid hemorrhage, we compared gender and age at the time of subarachnoid hemorrhage, as well as site and number of aneurysms, in patients with familial subarachnoid hemorrhage (at least 1 first-degree relative with subarachnoid hemorrhage) and patients with sporadic subarachnoid hemorrhage (no subarachnoid hemorrhage in first- or second-degree relatives), in a prospective, hospital-based series of patients. In addition we studied the pattern of inheritance in 17 families with familial subarachnoid hemorrhage. Mean age at the time of hemorrhage in patients with the familial form was 6.8 years lower than that in those with the sporadic form, and middle cerebral artery aneurysms occurred more often in patients with familial disease. Sex distribution and number of aneurysms were similar in the two groups. Inheritance was compatible with autosomal dominant transmission in some families, and with autosomal recessive or multifactorial transmission in others. In our 5 families as well as in all 18 previously reported families with two affected generations, the age at the time of subarachnoid hemorrhage was invariably lower in later generations, which is suggestive of anticipation. We conclude that familial subarachnoid hemorrhage is a separate entity with occurrence at a young age, predilection for aneurysms of the middle cerebral artery, and variable modes of inheritance, including autosomal dominant inheritance with possible anticipation.

Adult↗
PubMed1994

Retinoblastoma: CT and MRI.

To evaluate the effectiveness of CT and MRI at 0.5 T in the diagnosis and staging of retinoblastoma, we studied 11 patients in whom retinoblastoma was clinically suspected. Nine of the eleven had surgically proven retinoblastoma; in the other two a diagnosis of Coats' disease was made. MRI was not as specific as CT for diagnosing retinoblastoma, due to its lack of sensitivity in detecting calcification; it did, however, have superior contrast resolution. On MRI, Coats' disease was reliably diagnosed and easily differentiated from retinoblastoma. Moreover, the greater ability of MRI to differentiate subretinal fluid from tumour also confers high accuracy in measuring tumour size. CT is still the study of choice in the diagnosis of retinoblastoma, but when MRI is available, it should be performed for better differentiation from lesions such as Coats' disease.

Child↗
PubMed1994

Segmental fasciculations as a late sequel of spinal cord injury.

In two patients with a history of spinal cord injury many years ago fasciculations developed in muscles belonging to previously damaged segments. In both patients MRI of the cervical spine showed an area of abnormal signal intensity representing a cavity, near the level of the neurological abnormalities and the cord injury. During a 4-year follow-up period no new neurological or MRI abnormalities were detected. A hypothesis for the genesis of fasciculations following spinal cord injury is presented.

Adult↗
PubMed1994

Simulation of susceptibility artifacts in 2D and 3D Fourier transform spin-echo and gradient-echo magnetic resonance imaging.

A method is presented for simulating susceptibility artifacts in 2D and 3D spin-echo and gradient-echo imaging of arbitrary susceptibility distributions. The method incorporates object induced field perturbations in the time domain (k-space) and is demonstrated for spherical nonuniformities in susceptibility. Both simulations and experimental results for multi-slice 2D and 3D imaging of phantoms and human subjects are provided.

Artifacts↗
PubMed1994

Visually induced central pain and arm withdrawal after right parietal lobe infarction.

A 46 year old man with ischaemic infarction of the right parietal cortex had left hemianaesthesia when his eyes were closed. With eyes open, visual stimuli induced withdrawal of the arm and a burning pain in the numb side of the body. Visually induced central pain is a new clinical finding and may be related to damage of cells with anticipatory inhibitory function in the parietal association cortex.

Arm↗
PubMed1994

Impact of microembolism and hemodynamic changes in the brain during carotid endarterectomy.

BACKGROUND AND PURPOSE: Monitoring of carotid endarterectomy with electroencephalography and transcranial Doppler ultrasonography provides instantaneous information about hemodynamic changes and embolic signals. However, a relation between these findings and intraoperative infarcts has not yet been demonstrated. METHODS: In this study we compared preoperative and post-operative computed tomographic scans (58 patients) or magnetic resonance imaging (40 patients) of the brain, assessed by two independent observers, to detect intraoperative infarcts, and we related any such new lesions to the findings of intraoperative monitoring. RESULTS: In the computed tomography series one intraoperative infarct occurred, with corresponding clinical deficits. In the magnetic resonance group four patients developed new lesions that occurred intraoperatively, all of which were clinically silent. There was a significant relation between the number of embolic signals during the surgical dissection of the carotid artery and the occurrence of intraoperative infarcts (P < .005). Three of the four infarcts were of the lacunar type; the fourth patient had a border-zone infarct, associated not only with many embolic signals but also with low flow during cross-clamping. There were no demonstrable ultrasound side effects on brain tissue. CONCLUSIONS: Embolic signals detected by transcranial Doppler monitoring in the dissection phase of carotid endarterectomy show a significant relation to new ischemic lesions and therefore are potentially harmful. The phenomenon should alert the vascular surgeon.

Adult↗
PubMed1994

Temporal lobe epilepsy: the various MR appearances of histologically proven mesial temporal sclerosis.

PURPOSE: To determine the frequency of appearance of various MR signs in mesial temporal sclerosis, to determine the optimal scanning planes for their visualization, and to propose a histologic explanation for the diminished demarcation between gray and white matter in the temporal lobe, a frequent MR finding in patients with mesial temporal sclerosis. METHODS: MR scans of 14 surgically treated patients with epilepsy and histologically proven mesial temporal sclerosis were assessed for the presence of six features: feature 1, high signal intensity in the hippocampus; 2, reduced hippocampal size; 3, ipsilateral atrophy of the hippocampal collateral white matter; 4, enlarged temporal horn; 5, reduced gray-white matter demarcation in the temporal lobe; and 6, decreased temporal lobe size. RESULTS: Feature 1 was present in 14 patients and was best appreciated on the T2-weighted images in planes parallel to the long axes of the hippocampi. Feature 2, present in 12 patients, and feature 6, present in 9 patients, were optimally seen in the coronal planes and on the inversion-recovery sequences in particular. Feature 3, present in 12 patients, was optimally seen on the coronal T2-weighted images. Feature 4, seen in 11 patients, was equally well seen in all planes (transverse, coronal, and parallel to the long axes of the hippocampi). Feature 5, seen in 10 patients, was best appreciated on the T2-weighted images in the planes of the long axes of the hippocampi. Histologic investigation of the temporal lobe white matter in the 10 patients with feature 5 demonstrated on the MR scan showed abnormalities in 7 cases. Oligodendroglia cell clusters were found in 6, with concomitant corpora amylacea in 1 case and perivascular macrophages with pigment a sole finding in another case. CONCLUSION: Of the six features found in cases of mesial temporal sclerosis on MR, increased hippocampal signal intensity is the most consistent. A decreased gray-white matter demarcation in the temporal lobe parenchyma is also a frequent feature of this disease. A combination of multiple scanning planes results in an optimal demonstration of lesions.

Adolescent↗
PubMed1993

Carotid bifurcation imaging: magnetic resonance angiography compared to conventional angiography and Doppler ultrasound.

PURPOSE: to evaluate the clinical usefulness of the two dimensional "Time of Flight" (2D TOF) Magnetic Resonance Angiography technique (MRA) in imaging the carotid bifurcation as compared to conventional angiography and pulsed and colour Doppler ultrasound. METHODS: in 19 patients with possible cerebrovascular disease and eight volunteers, contrast angiography was compared with MRA in 21 carotid bifurcations and with Doppler ultrasound in 23 bifurcations by two independent observers. In 19 bifurcations, all three techniques were available for comparison. Internal carotid arteries were graded normal/minimal disease, mild, moderate or severe stenosis, or occluded. RESULTS: overall agreement between contrast angiography and MRA existed in 62% for one observer and 76% for the other. When MRA and Doppler agreed, agreement between these two investigations and contrast angiography existed in 77-81%. The major problem with MRA was overestimation of moderately stenosed vessels; 50% of the vessels with a moderate stenosis on contrast angiography were judged severely stenosed on MRA. An occlusion was never mistaken for a stenosis by MRA. Evaluating the separate slices, acquired in the 2D TOF MRA investigation, appeared to be essential to avoid this mistake. CONCLUSION: at present 2D TOF MRA is not clinically useful for diagnosing the degree of carotid artery stenosis. MRA has a clear tendency to overestimate the degree of stenosis especially moderately severe stenoses. To date, there are no objective methods to correct for this mistake. Technical improvements may make MRA a better diagnostic tool in the future.

Adolescent↗