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K C Seelos

Publications and source records attributed to K C Seelos.

At least 19 recordsLinked to original sources
PubMed2001

Identification and anatomic description of the anterior choroidal artery by use of 3D-TOF source and 3D-CISS MR imaging.

BACKGROUND AND PURPOSE: The importance of the anterior choroidal artery (AChA) is related to its supply of crucial anatomic structures, such as the internal capsule. Angiographically, the AChA can be detected in 71% to 98% of patients, but as yet, its visibility on MR images has not been evaluated. Our goal was to assess the sensitivity of MR imaging in the identification of the AChA and its anatomic characteristics. METHODS: Twenty volunteers underwent MR imaging with a 3D time-of-flight (3D-TOF) sequence, 10 of them additionally with a 3D Fourier transformation constructive interference in steady state (3D-CISS) sequence. The MR angiographic source images and the 3D-CISS images were analyzed independently by two neuroradiologists, who evaluated the ability to identify the different segments of the AChA and the posterior communicating artery (PComA) according to a previously defined scoring system (0 = not identified, 1 = most probably identified, 2 = identified with certainty). Additionally, three patients were examined who had an arteriovenous malformation (AVM) supplied by the AChA. RESULTS: In the volunteers, the PComA was identified with certainty in 87.5% on 3D-TOF sequences and in 95% on 3D-CISS sequences; the AChA was identified with certainty in 92.5% on 3D-TOF sequences and in 90% on 3D-CISS sequences. 3D-CISS images showed additional anatomic information in six of 20 vessels. In the three patients, the enlarged AChA was identified with certainty on both imaging sequences. CONCLUSION: The AChA can be reliably identified using both 3D-CISS sequences and the source images of the 3D-TOF sequence. MR imaging can be used to assess and follow-up AChA-related disorders, especially AVMs.

Adult↗
PubMed2001

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: decrease in regional cerebral blood volume in hyperintense subcortical lesions inversely correlates with disability and cognitive performance.

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathic syndrome related to a genetic defect on chromosome 19. Characteristic changes in CADASIL can be observed onT2-weighted MR images in the subcortical white matter. The purpose of this study was to measure changes of regional cerebral blood volume (rCBV) with dynamic contrast-enhanced MR imaging and to correlate the changes to disability and cognitive performance. METHODS: We obtained rCBV measurements of 24 individuals with proven CADASIL on a 1.5-T MR imaging unit. A susceptibility-weighted MR imaging sequence was used for bolus tracking. Principles of the indicator dilution theory were applied to estimate values of absolute rCBV (mL/100 g). Disability was determined by using the Rankin scale, and overall cognitive performance was assessed by using the Mini-Mental State Examination. RESULTS: The mean rCBV in the subcortical white matter that was hyperintense on the T2-weighted images (2.7 +/- 0.8 mL/100 g) was significantly lower than the rCBV in the white matter that appeared normal on the T2-weighted images (4.4 +/- 1.3 mL/100 g) (P <.05). The mean rCBV in the gray matter was within the normal range (8.3 +/- 1.7 mL/100 g). Both cognitive impairment and disability negatively correlated with rCBV in the subcortical white matter that was hyperintense (P <.05) but not with rCBV in the normal appearing white matter. rCBV did not correlate with age. CONCLUSION: rCBV measured in the hyperintense subcortical white matter in individuals with CADASIL was decreased and inversely correlated with disability and cognitive impairment.

Adult↗
PubMed2000

Cerebellar activation during optokinetic stimulation and saccades.

OBJECTIVE: To investigate the activation pattern of cerebellar structures during small-field optokinetic stimulation (OKN) by functional MRI (fMRI) and compare it with that obtained during voluntary saccades and fixation suppression of OKN. METHODS: Functional images were acquired from oblique transverse slices of eight healthy, right-handed volunteers using a radio frequency-spoiled, single-slice, fast low-angle shot (FLASH) pulse sequence with high-spatial resolution. RESULTS: Horizontal OKN and saccades were associated with bilateral activity in the cerebellar hemispheres (superior semilunar lobule, simple lobule, quadrangular lobule, inferior semilunar lobule), the middle cerebellar peduncle, the dentate nucleus, and medially in the culmen and uvula of cerebellar nuclei. The pattern and extent of activation were independent of the stimulus direction for OKN and saccades. During fixation suppression, the extent of activation was significantly diminished (hemispheres) or even absent (uvula, culmen). CONCLUSION: The differential effects of fixation suppression on this complex pattern of cerebellar activation in part allow us to separate visual and attentional from ocular motor processing. Our data agree with behavioral and physiologic animal data about ocular motor processes and motor learning in the vestibulospinal and optokinetic reflex. This suggests that hemispheric cerebellar activity may be mainly associated with changes in attention, whereas vermal activity seems to be associated with ocular motor control, and activity of the dentate nuclei and the cerebellar peduncles seems to be associated with both.

Adult↗
PubMed1999

Cortical activation patterns during voluntary blinks and voluntary saccades.

OBJECTIVE: To investigate the activation of frontal, parietal, and occipital areas in normal volunteers during voluntary blinks and during voluntary saccades using functional MRI (fMRI). BACKGROUND: A previous fMRI study revealed the activation of the precentral and posterior middle frontal gyrus ("frontal eye field" [FEF]), the medial part of the superior frontal gyrus ("supplementary eye field" [SEF]), and the visual cortex. The parietal cortex was not included in this study. Frontal and occipital cortical areas involved in voluntary blinking have not been shown previously using fMRI. METHODS: A 1.5-T standard clinical scanner was used for both anatomic and functional studies in 12 observers. To conduct data analyses the authors used voxel-by-voxel cross-correlation. RESULTS: Voluntary blinks led to the activation (p < 0.05) of the FEF, the SEF, the posterior parietal cortex ("parietal eye field" [PEF]), and the visual cortex. Voluntary blinking produced activity in the same cerebral structures as voluntary saccades. However, the number of activated voxels was smaller during voluntary blinking than during voluntary saccades in the visual cortex and in the FEF (p < 0.01). In contrast, the extent of activation was significantly higher (p < 0.003) in the SEF and in the PEF during voluntary blinking. CONCLUSIONS: Voluntary blinks and saccades are associated with similar loci of activation patterns; however, the quantitative distribution of activation suggests that the middle part of the frontal gyrus and posterior parietal cortex are of special significance for voluntary blinks. The results argue for the importance of considering quantitative distributional properties of parallel cortical activities associated with saccades and blinks.

Adult↗
PubMed1999

MR findings in a patient with Kernicterus.

We report on a 2.5-year-old boy with severe mental retardation, choreoathetosis, dystonia, muscle rigidity, opisthotonus and severe hearing impairment. He had history of severe hyperbilirubinaemia immediately after birth presumably due to ABO incompatibility. The history and the clinical picture suggested the diagnosis of Kernicterus. The MR imaging examination upon admission revealed bilateral signal intensity increase in the globus pallidum on T2-weighted sequences. Additionally, our patient showed signal intensity changes within the subthalamic nuclei, which is known to be another characteristic area of bilirubin deposition in Kernicterus.

Abnormalities, Multiple↗
PubMed1998

Bilateral functional MRI activation of the basal ganglia and middle temporal/medial superior temporal motion-sensitive areas: optokinetic stimulation in homonymous hemianopia.

OBJECTIVE: To determine to what extent sensorimotor control is achieved for each hemisphere separately or interactively during small-field optokinetic stimulation in patients with complete homonymous hemianopia. DESIGN: Functional and structural neuroimaging using high-resolution magnetic resonance imaging. SETTING: University medical center research facility. PATIENTS: Three patients with complete homonymous hemianopia after acute infarction of the right posterior cerebral artery. MAIN OUTCOME MEASURES: Anatomical location of activated structures during horizontal optokinetic stimulation and T2-weighted anatomical magnetic resonance imaging. RESULTS: Occipitotemporal cortical areas (Brodmann areas 39 and 40) were the only activated cortical structures that showed statistically significant (P<.01) activation on the affected hemisphere. Of the subcortical areas, activation of thalamic nuclei appeared to be missing on the affected side, whereas the basal ganglia (putamen, globus pallidus, and caudate nucleus) were bilaterally activated. CONCLUSIONS: Bilateral activation of the basal ganglia confirms the concept of the basal ganglia-thalamocortical motor loop and of the efference copy of oculomotor pathways from each hemisphere. Our findings suggest 2 possible explanations for the activation of occipitotemporal areas (the human homolog of middle temporal/medial superior temporal areas) on the infarcted hemisphere: involvement of direct extrastriatal visual pathways or interhemispheric callosal connections between right and left middle temporal/medial superior temporal areas.

Aged↗
PubMed1998

Horizontal or vertical optokinetic stimulation activates visual motion-sensitive, ocular motor and vestibular cortex areas with right hemispheric dominance. An fMRI study.

The differential effects of optokinetic stimulation with and without fixation suppression were analysed in an fMRI study in 10 right-handed healthy subjects. Horizontal and vertical small-field optokinetic stimulation activated the same multiple visual, ocular motor and vestibular cortical and subcortical areas in both hemispheres. The extent of activation in each hemisphere was independent of the stimulus direction. All activated areas representing cortical (occipitotemporal cortex, posterior parietal cortex, precentral and posterior median frontal gyrus, prefrontal cortex, medial part of the superior frontal gyrus) and subcortical (caudate nucleus, putamen, globus pallidus and paramedian thalamus) ocular motor structures were activated during optokinetic stimulation as well as during fixation suppression of optokinetic nystagmus. However, the activation was significantly stronger with optokinetc nystagmus compared with fixation suppression. The only relatively increased activity during fixation suppression was seen in the medial part of the superior frontal gyrus (supplementary eye field) and the anterior cingulate gyrus. The anterior insula and the posterior insula (human homologue of the parieto-insular vestibular cortex) were activated during optokinetic nystagmus but not during fixation suppression. A significant right hemispheric predominance (regardless of stimulus direction) was found under both conditions in the visual motion-sensitive and ocular motor areas of the cortex, except the supplementary eye field and anterior cingulate gyrus. This was most prominent in the occipitotemporal cortex, but did not occur in the primary visual cortex and in subcortical ocular motor structures (putamen, globus pallidus and caudate nucleus). Thus, cortical and subcortical activation patterns did not differ for horizontal and vertical optokinetic stimulation, and there was distinct right-hemisphere dominance for visual motion-sensitive and cortical ocular motor areas and the thalamus. Fixation suppression of optokinetic nystagmus yielded four different results: (i) increased activation in the supplementary eye field and anterior cingulate gyrus; (ii) unchanged activation in the visual cortex; (iii) decreased activation in most of the ocular motor areas; and (iv) suppressed activation in the anterior and posterior insula and the thalamus. Activation of the parieto-insular vestibular cortex may be related to ocular motor function rather than self-motion perception.

Adult↗
PubMed1997

Activation mapping in essential tremor with functional magnetic resonance imaging.

We used functional magnetic resonance imaging (FMRI) to study possible cerebral activation patterns associated with unilateral postural tremor in 12 patients with essential tremor (ET), with mimicked postural tremor in 15 control subjects, and with passive wrist oscillation in both groups. During essential tremor, patients showed mainly contralateral activation of the primary motor and primary sensory areas, the globus pallidus, and the thalamus, but bilateral activation of the nucleus dentatus, the cerebellar hemispheres, and the red nucleus. Only 2 patients presented with activity in the medulla close to the olivary nucleus. Unilateral passive wrist oscillation of ET patients resulted in only unilateral activation of the cerebellum, nuclei dentati, and red nuclei. In contrast to the involuntary tremor condition of ET patients, the mimicked tremor condition of the control subjects was not associated with bilateral activity in the cerebellum, nuclei dentati, or red nuclei. Involuntary tremor of ET patients was associated with a significantly larger extent of activation in the cerebellar hemispheres and the red nucleus (p < 0.003) compared with mimicked tremor in the control group. Our FMRI study indicates that ET is mainly associated with an additional contralateral cerebellar pathway activation and overactivity in the cerebellum, red nucleus, and globus pallidus without significant intrinsic olivary activation.

Aged↗
PubMed1997

Cerebral generators involved in the pathogenesis of the restless legs syndrome.

The pathophysiology of periodic limb movements and sensory leg discomfort in the restless legs syndrome is unknown. With high-resolution functional magnetic resonance imaging, we localized for the first time cerebral generators associated with sensory leg discomfort and periodic limb movements in 19 patients with restless legs syndrome. During sensory leg discomfort there was mainly bilateral activation of the cerebellum and contralateral activation of the thalamus. During the combined periodic limb movement and sensory leg discomfort conditions, patients also showed activity in the cerebellum and thalamus. In contrast to the sensory leg discomfort condition alone, the combined condition was associated with additional activation in the red nuclei and brainstem close to the reticular formation. Voluntary imitation of periodic limb movements by patients and control subjects was not associated with brainstem activity, but with additional activation in the globus pallidus and motor cortex. These findings indicate that cerebellar and thalamic activation may occur because of sensory leg discomfort and that the red nucleus and brainstem are involved in the generation of periodic limb movements in patients with restless legs syndrome.

Aged↗
PubMed1997

Postoperative spiral computed tomography and magnetic resonance angiography after aneurysm clipping with titanium clips.

OBJECTIVE: To reduce morbidity and mortality after subarachnoid hemorrhage, it is imperative to evaluate the results of the surgical treatment of cerebral aneurysms. We investigated the usefulness of spiral computed tomography (CT) and magnetic resonance angiography as postoperative control examinations after cerebral aneurysms were clipped with titanium clips. METHODS: Eleven patients with 13 treated aneurysms were studied prospectively with postoperative digital subtraction angiography, spiral CT, and magnetic resonance angiography. The occlusion of the dome of the aneurysm, the presence of a remnant of the neck, the patency of the parent vessels and other major vessels, and the presence of vasospasm were investigated. RESULTS: The different parameters could all be well evaluated by postoperative spiral CT. The artifacts caused by the titanium clips, although relatively small compared with artifacts from other clips, precluded evaluating the dome and the neck of the aneurysm with magnetic resonance angiography. CONCLUSION: In our opinion, spiral CT promises to become a valuable aid in in the postoperative evaluation of clipped aneurysms, and we recommend its routine performance. Postoperative digital subtraction angiography remains the gold standard and has to be performed when spiral CT reveals abnormalities, when the neck of the aneurysm cannot be evaluated because the clip overlays it, or when, intraoperatively, imperfect clipping is suspected and intraoperative angiography cannot be performed.

Adolescent↗
PubMed1997

Radical resection of meningiomas and arteriovenous fistulas involving critical dural sinus segments: experience with intraoperative sinus pressure monitoring and elective sinus reconstruction in 10 patients.

OBJECTIVE: Radical resection of meningiomas and dural arteriovenous fistulas involving functional major dural sinuses entails the risk of intracranial hypertension and venous infarction. Surgical reconstruction of dural sinuses and bridging veins increases the spectrum of dural sinus conditions that can be treated by complete resection, but indications for venous reconstructions and associated risks are still not well defined. We report our experience with sinus reconstruction based on the intraoperative assessment of collateral venous flow. METHODS: Radical resection of meningiomas (n = 5) or dural arteriovenous fistulas (n = 5) involving critical segments of dural sinuses was performed in 10 patients. All but two patients were suffering from recurrent disease after incomplete treatment. Tolerance of sinus occlusion was assessed intraoperatively by measuring stump pressure in the superior sagittal sinus during test clamping of the involved sinus segment. RESULTS: In five patients, the results of pressure monitoring suggested that occlusion of the sinus might not be tolerated. In two other patients, major bridging veins entered the diseased segment. In these patients, the resected sinus segment was reconstructed and bridging veins were reinserted as far as possible. Postoperative graft occlusion occurred in two patients. One patient who was managed without reconstruction sustained a transient postoperative neurological deficit resulting from venous congestion in the vein of Labbé. Postoperative imaging confirmed total elimination of the pathological process in all 10 patients. There was no recurrence of disease during follow-up periods of up to 8 years. CONCLUSION: The monitoring of sinus pressure, together with the possible reconstruction of the diseased sinus, allows complete surgical treatment of dural sinus abnormalities and involves acceptable risk.

Adolescent↗
PubMed1997

Functional MRI mapping of occipital and frontal cortical activity during voluntary and imagined saccades.

We investigated the activation of frontal and occipital cortical areas in 14 normal volunteers during voluntary saccades in light or dark and during imagined saccades using functional magnetic resonance imaging (FMRI) with electro-oculogram monitoring. Voluntary saccades in light or dark and imagined saccades led to a significant activation (p < 0.005) of the precentral and posterior medial frontal gyrus (frontal eye field). The medial part of the superior frontal gyrus (supplementary eye field) also showed significant activity during voluntary saccades in all subjects, but only in four subjects during imagined saccades. In addition to frontal activity we found an activated primary visual cortex during voluntary saccades, both in light and in dark. In contrast to executed saccades, imagined eye movements revealed to occipital response under either condition. Our FMRI study supports the concept of frontal eye fields during voluntary saccades and demonstrates that occipital areas are associated with the generation of voluntary eye movements. However, the primary visual cortex is not active when eye movement is only imagined.

Adult↗
PubMed1997

Sensorimotor cerebral activation during optokinetic nystagmus. A functional MRI study.

Self-motion or object motion can elicit optokinetic nystagmus (OKN), which is an integral part of dynamic spatial orientation. We used functional MR imaging during horizontal OKN to study cerebral activation patterns in sensory and ocular motor areas in 10 subjects. We found activation bilaterally in the primary visual cortex, the motion-sensitive areas in the occipitotemporal cortex (the middle temporal and medial superior temporal areas), and in areas known to control several types of saccades such as the precentral and posterior median frontal gyrus, the posterior parietal cortex, and the medial part of the superior frontal gyrus (frontal, parietal, and supplementary eye fields). Additionally, we observed cortical activation in the anterior and posterior parts of the insula and in the prefrontal cortex. Bilateral activation of subcortical structures such as the putamen, globus pallidus, caudate nucleus, and the thalamus traced the efferent pathways of OKN down to the brainstem. Functional MRI during OKN revealed a complex cerebral network of sensorimotor cortical and subcortical activation.

Adult↗
PubMed1997

[A comparison of ultrafast computed tomography, magnetic resonance angiography and selective angiography for the detection of coronary bypass patency].

PURPOSE: Validation of ultrafast-CT and MR-angiography (MRA) in comparison with angiography for detection of early postsurgical arterial and venous coronary artery bypass graft (CABG) patency. METHODS: 21 patients with a total of 55 CABG (34 venous and 21 arterial) were studied with angiography, ultrafast-CT (EBT), and MRA. RESULTS: With EBT, patency of 43/45 angiographically patent CABG could be correctly assessed (sensitivity: 96%). With MRA 26 CABG (17 venous and 9 arterial) were identified as patent (sensitivity: 67%). It was not possible to quantify proximal stenosis of three grafts (> 40%) and to evaluate the distal bypass anastomosis with both EBT and MRA. CONCLUSIONS: Ultrafast-CT is a promising minimal invasive screening method for the evaluation of venous and arterial CABG patency. The diagnostic significance of MRA is remarkably reduced.

Aged↗
PubMed1996

Pallidal lesions. Structural and functional magnetic resonance imaging.

OBJECTIVE: To study noninvasively the functional anatomy and pathophysiologic characteristics of the globus pallidus external (GPe) and internal (GPi) divisions. DESIGN: Structural and functional neuroimaging using high-resolution magnetic resonance imaging. SETTING: University medical center research facility. SUBJECTS. Seven patients with pallidal lesions, 4 with an akinetic-rigid syndrome and 3 with a dystonic syndrome, and 15 age-matched volunteers. MAIN OUTCOME MEASURES: T2-weighted anatomical magnetic resonance imaging and number of activated voxels in the GP during rapid supination and pronation of the hand. RESULTS: T2-weighted images showed hyperintense bilateral lesions in the GP of all patients. Patients with dystonic syndromes had isolated lesions in the GPi. Patients with signs of akinetic-rigid syndromes showed abnormalities in the GPe or in central portions of the GP (GPc). Patients with lesions in both parts of the GP had akinetic-rigid or dystonic syndromes. All patients showed activation in the areas of the lesions. The number of activated voxels in the GP was significantly smaller (P < .005, Wilcoxon signed rank test) in patients than in control subjects. Activation of the GP was predominantly contralateral to the moving hand. CONCLUSIONS: Lesions in the GPi result in a loss of inhibitory pallidal projections to the thalamus, which may explain the hyperkinetic signs. Lesions in the GPe lead to an increased inhibition of the thalamus, which may explain the hypokinetic signs. Neuronal activation in lesion sites suggests the presence of remaining functionally vital tissue.

Aged↗
PubMed1995

Effects of nuclear magnetic resonance imaging on cardiac pacemakers.

Patients with cardiac pacemakers are currently restricted from nuclear magnetic resonance imaging (MRI). The aim of the study was to analyze the influence of MRI on new generation pacemakers. Tests were performed using a phantom model with seven dual chamber and two single chamber systems in a 0.5 Tesla MRI scanner. Monitoring by telemetry and oscillography were used during the standard clinical scan sequences as well as a pacemaker inquiry after each sequence. Spin echo, gradient echo, and fast field echo sequences were performed with the following stimulation modes: VVI, VVIR, VOO, DDD, DDDR, and DOO. On entering the static magnetic field, the reed switch was activated followed by asynchronous stimulation. The subsequent scan showed no influence on the stimulation function nor on the pacemaker program. Event counter function remained intact. Pacemakers with automatic mode switching to demand pacing or programmed inactivation of the reed switch were triggered in the dual chamber mode and were inhibited in the one chamber mode during the scan. Alterations of pacemaker program or rapid pacing were not observed. MRI scan could induce voltage as high as intracardiac signals, but the stimulation threshold of the heart was not reached. Thus, pacemakers should be programmed in the asynchronous mode during scan to avoid inhibition and trigger mechanism.

Acrylic Resins↗