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Biomedical subjects

K A Thuomas

Publications and source records attributed to K A Thuomas.

At least 37 records · Page 2Linked to original sources
PubMed1996

Proton MR spectroscopy and MR imaging in acute and chronic multiple sclerosis--ringlike appearances in acute plaques.

PURPOSE: We wanted to compare the metabolite status of brain lesions in different clinical subtypes of multiple sclerosis (MS). Two acute MS lesions with ringlike appearances were also investigated. MATERIAL AND METHODS: Twenty-three clinically stable MS patients, 2 patients with acute relapses, and 15 healthy individuals were examined by MR imaging and localized proton MRS. RESULTS: No metabolite differences were seen in plaques of different subtypes. Decreased NAA/Cr and NAA/choline ratios as well as increased inositol/Cr ratios were observed in the plaques of the clinically stable or chronic active MS patients as compared with controls. The ring plaques had hyperintense cores with surrounding halos, separated from the cores by rings with low signal intensity in T2-weighted images. The core exhibited a prolonged T2 relaxation time. Proton spectra initially contained lactate. CONCLUSION: No differences between the metabolite status of nonacute plaques in different clinical subtypes could be detected. The ring plaques contained lactate signals indicating oedema, inflammation, and macrophage invasion, and may be transition forms between acute oedematous lesions and chronic demyelinated plaques.

Adult↗
PubMed1996

Degenerative changes following anterior cervical discectomy and fusion evaluated by fast spin-echo MR imaging.

PURPOSE: To review pre- and postoperative fast spin-echo (FSE) MR images of disc herniation and spondylosis in patients after spinal cervical surgery. MATERIAL AND METHODS: Data were reviewed of 68 patients after anterior discectomy and fusion (ADF) operations using the Cloward technique with solid single level (C5-C6 or C6-C7) or 2-level fusions (C5-C7). The average interval from surgery to review was 37 months. Age- and sex-matched controls without neck problems were examined. RESULTS: Preoperatively, the fusion groups had a higher incidence of protruded disc, and anterior and posterior osteophytes at the levels to be fused than the controls. Post-operatively, there was a significantly higher incidence of posterior osteophytes at the fused levels compared with the controls. Furthermore, the disc herniations and anterior osteophytes at the levels above and below the operated segments were more frequent in the fusion group. CONCLUSION: ADF causes acceleration of the degenerative changes at the fused level and at the levels below and above the fused segments.

Case-Control Studies↗
PubMed1995

Neurological Wilson's disease studied with magnetic resonance imaging and with positron emission tomography using dopaminergic markers.

Four patients with neurological Wilson's disease were investigated using magnetic resonance imaging (MRI) and positron emission tomography (PET). All patients had dystonia as their major clinical manifestation but also had dysarthria and at the presentation of the disease had choreoathetoid movements in at least one limb. A multitracer approach with PET was used to visualize various aspects of dopaminergic function; [11C]-(+)-nomifensine (NMF), [11C]raclopride (RAC) and [11C]-L-DOPA (one patient). Correlation analysis of RAC and NMF binding as well as putamen/caudate uptake ratios showed corresponding reductions. The patient investigated with [11C]-L-DOPA had a normal striatal uptake. Generally, structural changes as shown by MRI corresponded to reductions both in NMF and RAC binding. There was no evident correspondence between PET findings and the severity of clinical symptoms seen in the individual patient. In two patients with discrete neurological impairment at the time of investigation, PET showed serious presynaptic dopaminergic lesions in the putamen. Our data suggest that the striatal degeneration seen in Wilson's disease comprises a complex pathology involving both afferent and efferent projections. The discrete neurological impairment seen in some patients with gross striatal pathology might be due to concomitant lesions in functionally counteracting basal ganglia circuits.

Adult↗
PubMed1995

Biplane transoesophageal echocardiography, transthoracic Doppler, and magnetic resonance imaging in the assessment of coarctation of the aorta.

This study compared flow-sensitive magnetic resonance imaging with biplane transoesophageal echocardiography in combination with continuous wave Doppler from the suprasternal notch in patients with native coarctation or after surgical repair. Twenty patients (mean age 33 years, range 17-60) were investigated, of whom 15 had undergone surgery at mean age 13 years, range 5-43. Peak and mean flow in the ascending and descending aorta as well as coarctation peak velocity were determined with the magnetic resonance imaging phase contrast technique. Coarctation peak velocity was also measured by Doppler from the jugulum. Magnetic resonance imaging axial sections as well as biplane transoesophageal echocardiography were used to measure the smallest diameter of the constricted segment. Sixteen healthy volunteers, mean age 36 years, range 22-63, provided reference values for magnetic resonance imaging determined volume of flow in the aorta. Peak flow in the descending aorta was 9.2 +/- 3.7 l. min-1 (reference 13.0 +/- 2.5, P < 0.01) and mean flow 3.1 +/- 0.9 l. min-1 (reference 3.4 +/- 0.8, P > 0.05). The ratio of descending-to-ascending peak flow was 0.54 +/- 0.17 (reference 0.69 +/- 0.10, P < 0.01) and mean flow 0.68 +/- 0.15 (reference 0.69 +/- 0.08, P > 0.05). The coarctation velocity was slightly higher with Doppler than with magnetic resonance imaging (+0.24 +/- 0.44 m. s-1, 95% confidence interval +0.45 to +0.02 m. s-1, P = 0.05). The coarctation diameter was slightly larger with magnetic resonance imaging than with transoesophageal echocardiography (1.4 +/- 3.5 mm, 95% confidence interval +3.1 to -0.3 mm, P = 0.11). Both methods are suitable for the assessment and follow-up of coarctation of the aorta. Flow assessment with magnetic resonance imaging provides a hitherto unavailable measure with which to assess the severity of obstruction.

Adolescent↗
PubMed1995

Neurological dysfunction above cele level in children with spina bifida cystica: a prospective study to three years.

The aim of this study was to characterize the neurological dysfunction above the cele level in children with spina bifida cystica. 22 neonates were investigated prospectively to a median age of three years. Before primary closure of the spinal malformation and at three and 18 months of age, MRI and inspection of vocal cord function were performed. The children were also assessed by a physical therapist at 12 and 24 months, 19 children had a Chiari malformation, 18 children developed neurological dysfunction above the cele level. Children with signs of isolated motor impairment stabilized or improved during the second year. Six children developed severe functional impairment of respiration, feeding and motor performance within the first three months of life. Severe neurological signs/symptoms were associated with myeloschisis, clinical signs of a tethered cord and recurrent periods of shunt dysfunction.

Child, Preschool↗
PubMed1995

M-mode magnetic resonance imaging: a new modality for assessing cardiac function.

Magnetic resonance imaging (MRI) studies of the heart have been used for some years, but there are few tools available to quantify cardiac motion. A method has been developed that creates an M-mode MRI image, analogous to the one used in echocardiography, to display motion along a line as a function of time. The M-mode image is created from MRI images acquired with an ordinary gradient echo cine sequence. In a cinematographic display of the images, a cursor line can be positioned in order to determine the orientation of the measurement. A resampling algorithm then calculates the appearance of the M-mode image along the cursor line. The MRI method has been compared to echocardiographic M-mode in a phantom study and by measuring mitral and tricuspid annulus motion in 20 normal subjects. The phantom study showed no significant differences between MRI and echocardiographic M-mode measurements (difference < 1 mm). The annulus motion exhibits a similar pattern using both methods and the measured amplitudes are in close agreement. M-mode MRI provides similar information to echocardiography, but the cursor line can be placed arbitrarily within the image plane and the method is thus not limited to certain acoustic windows. This makes M-mode MRI a promising technique for assessing cardiac motion.

Adult↗
PubMed1995

Macrovascular causes underlying otoneurological disturbances.

In the diagnostic procedure for patients with symptoms and signs indicating VIIIth nerve or brain stem disturbances, the possible presence of tumors, infarcts, bleedings or microvascular loops are taken into account. Ten patients with vertigo, balance disorders, tinnitus or unilateral hearing loss proved to have a similar cause underlying the disturbances. They ranged in age from 51 to 80 years and had a duration of their symptoms of 1-10 years. In the test battery audiology, electronystagmography, broad-frequency rotatory testing and dynamic posturography were used. No uniform pattern was present. The results showed VIIIth nerve as well as CNS signs. Trigeminal neuralgia and hemifacial spasm were observed. CT, NMR or angiography were performed. The common finding for these patients were ectatic vertebral and/or basilar arteries. The size and position of the vessels indicated that compression of the VIIIth nerve or brainstem was the cause underlying their disturbances. To exclude that macrovessels appear in patients without neurotological symptoms and signs 300 consecutive NMR investigations in patients referred for other than neurotogic indications were scrutinized. In these patients no macrovessels were found. The findings indicate that ectatic vessels may cause disturbances mimicking a pontine angle tumor, Meniere's disease and other peripheral or central conditions with inner ear symptoms, vertigo and balance disorders. Arterial loops in the pontine angle may give indications for microvascular surgery, but the big ectatic vertebral and basilar arteries may offer surgical decompression possibilities, though with large risks.

Aged↗
PubMed1995

Gd-DPTA enhanced MRI in Bell's palsy and herpes zoster oticus: an overview and implications for future studies.

Magnetic resonance imaging (MRI) is a new and important tool for use in diagnosing and investigating diseases affecting the facial nerve. In recent gadolinium-DTPA enhanced MRI (Gd-MRI) studies it has unequivocally been demonstrated that ipsilateral facial nerve contrast enhancement, predominantly in the meatal portion, is present in both Bell's palsy and herpes zoster oticus. In this overview, the results of MRI studies performed on patients with acute peripheral facial palsy, especially Bell's palsy and herpes zoster oticus, are discussed. The Gd-MRI pattern in Bell's palsy is very similar to that seen in herpes zoster oticus, and the findings reported so far support the theory that an inflammation may be the cause of the nerve injury in both cases. So far, however, Gd-MRI has not been helpful in evaluating the severity and/or prognosis of the facial palsy. Further studies employing improved techniques, including three-dimensional fast (or turbo) spin echo (3DFSE) MRI with heavily T2-weighted sections and high resolution three-dimensional Fourier transform (3DFT) MRI, need to be conducted in order to determine whether it is possible to follow the course of the disease and whether MRI and/or Gd-MRI are useful prognostic tools in the early stages of palsy.

Contrast Media↗
PubMed1995

Pituitary microadenoma. MR appearance and correlation with CT.

Twenty surgically proven pituitary microadenomas were examined with MR imaging and CT. MR demonstrated 20 of 20 microadenomas: 90% of the tumors were hypointense on T1-weighted images before Gd-DTPA administration and in 45% the tumors were more clearly delineated postcontrast. CT demonstrated 19 of 20 diagnosed microadenomas: showing low attenuation in 85% of the tumors precontrast. Iohexol facilitated delineation of the tumors in 45%. Focal enlargement of the gland and diaphragma sellae convexity were more useful than infundibular tilting and sellar-floor erosion as ancillary findings supporting the diagnosis. In general, CT and MR agreed regarding the microadenomas size and location, measurement of enlarged intrasellar contents, detection of the diaphragma sellae bulge, and demonstration of infundibulum abnormality. CT was more sensitive than MR in identifying sellar-floor erosion. We suggest that CT be the first method for demonstration of microadenomas.

Adenoma↗
PubMed1995

MR imaging of 495 consecutive cases with sensorineural hearing loss.

PURPOSE: To examine patients with sensorineural hearing loss (SNHL) with MR. MATERIAL AND METHODS: 495 consecutive patients with SNHL and 120 age-matched healthy controls were examined. Spin-echo (SE) and fast spin-echo (FSE) images were used with 1.5 T equipment. RESULTS: An intracranial abnormality was found in 211 (42.6%) of the patients with 95 (19.2%) along the acoustic pathway. Eleven of the 95 patients had sensory hearing loss while 84 had neural hearing loss with the retrocochlear auditory pathway affected by lesions. In 62 of the 84 patients, the internal acoustic canal and cerebellopontine angle were involved. Twenty-two patients had intra-axial lesions. The controls had no pathologic changes along the auditory pathway. CONCLUSION: MR imaging in a patient with SNHL must cover the entire acoustic pathway from the cochlea to the superior temporal gyrus, and all the components of the auditory pathway should be scrutinized. The FSE-technique can be used to detect the lesions causing SNHL. FSE-sequences can replace SE-sequences.

Adolescent↗
PubMed1993

Facial nerve enhancement in Bell's palsy demonstrated by different gadolinium-enhanced magnetic resonance imaging techniques.

Twenty-one patients with an acute complete peripheral facial palsy, Bell's palsy, were examined by medium- and high-Tesla magnetic resonance imaging. Three contrast techniques were used: intravenous gadolinium; oral carbohydrate and intravenous gadolinium; and gadolinium, carbohydrate, and readministration of gadolinium. Three to 22 days after the onset of palsy, 12 of the 21 patients demonstrated ipsilateral facial nerve enhancement, most consistently in the meatal region, which is indicative of an inflammatory reaction. Two to 4.5 months after the onset, the enhancement had disappeared in 10 of the 12 patients. For the individual patient, contrast-enhanced magnetic resonance imaging gave little or no help in predicting the outcome of palsy. It is speculated that the intake of carbohydrate and readministration of gadolinium may improve the sensitivity of medium-high-Tesla magnetic resonance imaging in some cases.

Administration, Oral↗
PubMed1993

Magnetic resonance imaging of the brain in Wilson's disease.

Fifteen patients with Wilson's disease were examined, using spin-echo (SE) and gradient-echo (GE) sequences with 0.5 T and 1.5 T magnetic resonance (MR) imagers. They fell into three groups: groups 1 and 2 were examined retrospectively after 3-18 years of treatment, while group 3 was examined prospectively from the start of treatment, after recommencement of treatment, or inadequate treatment. MRI was sensitive to changes in the basal ganglia at sites typical of Wilson's disease and was useful for documenting the effects of treatment. It was found necessary to estimate the relaxation times T1 and T2, to better assess improvement or transient worsening of the disease in the prospective group. Residual cavitation and gliosis could be distinguished in the retrospective group using a subtraction technique.

Adult↗
PubMed1993

Inflammatory paranasal sinus disease in Bell's palsy demonstrated by magnetic resonance imaging.

The paranasal sinuses of 20 consecutive young adult patients with a complete Bell's palsy were investigated by magnetic resonance imaging (MRI) to obtain more information on the etiology of the disease. A high signal intensity on T2-weighted MRI was demonstrated in the paranasal sinuses, mainly the maxillary sinuses, in 12 of 20 (60%) patients in the early stage of Bell's palsy. Eleven of the 12 patients with positive MRI were followed up after 2 to 8 months (median 3 months), and in six of these, the bright signal intensity had disappeared, in two patients there was a regress, and in three patients the signal changes were persistent. The MRI findings indicate that transient inflammatory paranasal sinus disease, which may be caused by a viral and/or bacterial infection, infrequently may be associated with Bell's palsy. However, the relationship to the pathophysiologic process in Bell's palsy is still uncertain.

Adult↗
PubMed1993

Changes in intracranial morphology, regional cerebral water content and vital physiological variables during epidural bleeding. An experimental MR study in dogs.

Epidural bleeding was produced in 8 anaesthetised and heparinised dogs by an artificial system. Changes in vital physiological variables were related to intracranial shifts and tissue water content assessed with MR imaging. Six animals survived while 2 succumbed. In the surviving animals intracranial shifts and compressions remained unchanged from an early stage. The cerebral perfusion pressure was reduced from between 80 and 110 mm Hg to between 40 and 60 mm Hg. Some increase in supratentorial white matter tissue water was observed. In the lethal experiments cerebral perfusion pressure fell to less than 40 mm Hg. Moreover, secondary delayed anatomical changes were seen including hydrocephalus. Increase in cerebral tissue water was more intense and widespread than in the survivors. These findings indicate that the outcome of epidural bleeding is related to cerebral perfusion pressure with secondary deterioration resulting from additional volume loading from increased tissue water and hydrocephalus.

Animals↗
PubMed1993

Progressive brain compression. Changes in vital physiological variables, correlated with brain tissue water content and brain tissue displacement. Experimental MR imaging in dogs.

Continuous recording of vital physiological variables and sequential MR imaging were performed simultaneously during continuous expansion of an epidural rubber balloon over the left hemisphere in anaesthetised dogs. Balloon expansion led to a progressive and slightly nonlinear rise in intracranial CSF pressures and a fall in local perfusion pressures. Changes in systemic arterial pressure, pulse rate, and respiration rate usually appeared at a balloon volume of 4% to 5% of the intracranial volume (reaction volume), together with a marked transtentorial pressure gradient and MR imaging changes consistent with tentorial herniation. Respiratory arrest occurred at a balloon volume of approximately 10% of the intracranial volume (apnoea volume), which was associated with occlusion of the cisterna magna, consistent with some degree of foramen magnum herniation. Increase in tissue water was observed beginning at approximately the reaction volume, presumably due to ischaemic oedema, due to the fall in perfusion pressures.

Animals↗