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Biomedical subjects

R K Fulbright

Publications and source records attributed to R K Fulbright.

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

MR of hereditary hemorrhagic telangiectasia: prevalence and spectrum of cerebrovascular malformations.

PURPOSE: Our goal was to describe the prevalence and types of cerebral vascular malformations (CVMs) seen with MR imaging in patients with hereditary hemorrhagic telangiectasia (HHT). METHODS: We reviewed retrospectively the brain MR images of 184 consecutive patients with HHT. Catheter angiography was performed in 17 patients with CVMs detected on MR images. RESULTS: MR imaging revealed 63 CVMs in 42 patients. Classic arteriovenous malformations (n = 10) had a conspicuous network of vessels with flow voids and enlarged adjacent pial vessels. Apparent venous malformations (n = 5) were best seen after administration of contrast material as a prominent vessel coursing through normal brain parenchyma. Indeterminate vascular malformations (n = 48) had a spectrum of appearances characterized by variable combinations of heterogeneous signal intensity, enhancement, or hemosiderin. Angiography in 17 patients revealed 47 CVMs. Forty-six were arteriovenous malformations (AVMs), including 25 CVMs not seen with MR imaging and 21 CVMs that by MR criteria included 8 AVMs and 13 indeterminate vascular malformations. Angiography confirmed 1 venous malformation seen with MR imaging but failed to detect 3 indeterminate lesions revealed by MR imaging. CONCLUSION: MR imaging of a large cohort of consecutive patients with HHT revealed a CVM prevalence of 23% (42/184). Most CVMs (48/63) have an atypical appearance for vascular malformations on MR images. Angiographic correlation suggests that MR imaging underestimates the prevalence of CVMs and that the majority of indeterminate CVMs, despite their variable MR appearance, are AVMs.

Cerebral Angiography↗
PubMed1998

Functional MR imaging of regional brain responses to pleasant and unpleasant odors.

BACKGROUND AND PURPOSE: Odors can elicit a range of behaviors and emotions. Our purpose was to identify regional activation of the human cerebral cortex in response to pleasant (positive hedonic value) and unpleasant (negative hedonic value) odors. METHODS: Thirteen neurologically normal adults underwent functional MR imaging of frontal and anterior temporal brain regions with a gradient-echo echo-planar technique. Eleven candidate regions of interest (ROIs) were identified on the first half of the data set based on t-map comparisons of signal intensities during administration of clementine (pleasant odor), isovaleric acid (unpleasant odor), and clear air (control odor). These ROIs were applied to the second half of the data set, and the number of voxels activated with the odorants was compared with the number of voxels activated during clear air trials, using independent t-tests. RESULTS: Clementine activated five cortical areas: Brodmann's area (BA) 8, BA 32 (lateralized to left), BA 46/9, BA 6 (lateralized to right), and the insula. Isovaleric acid activated four of the five regions without lateralization; no BA 8 activity was seen. Clementine produced more activity than isovaleric acid in the left insula, and isovaleric acid produced more activity than clementine in the left BA 6. No activation was detected in the orbitofrontal cortex or in the medial temporal lobes. Subjects rated clementine, isovaleric acid, and clear air as being pleasant, unpleasant, and neutral, respectively. CONCLUSION: Activation in frontal regions may represent brain processes linked to olfactory networks. There may be regional specialization based on odorant hedonic values.

Adult↗
PubMed1997

An fMRI study of the human cortical motor system response to increasing functional demands.

Functional magnetic resonance imaging (fMRI) was used to study activation changes in the human primary motor-sensory areas (MAs), supplementary motor areas (SMAs), premotor areas (PMAs) and the superior and inferior parietal areas (SPAs, IPAs) during right hand finger movements as the rate, force and complexity of movement were varied. A preliminary reproducibility study of a single subject doing the same repetitive index finger movements in nine different sessions over a six week period demonstrated highly consistent and highly localized activation in the contralateral MA. ANOVAs demonstrated highly significant main effects of increasing the force and complexity of movement, thereby illustrating the distributed and integrated systemic character of the cortical motor system. Interactions between brain region and the rate and complexity of movements suggested functional specialization of some components of the system. Increasing the rate of movement led to increased activity only in the contralateral MA; increasing complexity led to greater increases in activity in the left and right SPAs and the left IPA than in other areas. Although activation was evident in varying degree throughout the multiple motor areas, only the MAs showed consistent lateralization of activation.

Adult↗
PubMed1997

Economic impact of replacing CT with MR imaging for refractory epilepsy.

PURPOSE: To evaluate the economic costs of using computed tomography (CT) vs. magnetic resonance (MR) imaging in the preoperative evaluation of refractory epilepsy patients. METHODS: Preoperative CT and MR imaging findings from 117 patients who underwent surgery for medically refractory epilepsy during a 3.5-year period were reviewed. Cost savings were based on the paradigm that intracranial electroencephalogram monitoring (costing about $50,000) would have been necessary for preoperative localization of the epileptogenic zone in those patients without positive imaging findings. Savings attributed to replacing CT with MR were based on patients with positive MR and normal CT. A similar paradigm was used to calculate savings for replacing MR with CT. National savings were based solely on patients with neoplasms or vascular lesions because paradigms for other lesions vary considerable depending on institutional philosophy. RESULTS: Replacing CT with MR imaging would have eliminated preoperative intracranial electrode procedures in 29 of 117 patients, with potential savings of $1,450,000 at our institution. In the 37 patients with neoplastic or vascular substrates, MR would have eliminated 10 invasive electrode procedures with estimated savings of $0.5 million institutionally and $3 to $4 million per year nationally. There were no cases to support replacing MR with CT. CONCLUSION: Replacing CT with MR decreases health costs associated with preoperative evaluation of intractable epilepsy requiring surgical amelioration.

Adolescent↗
PubMed1997

Predicting reading performance from neuroimaging profiles: the cerebral basis of phonological effects in printed word identification.

This study linked 2 experimental paradigms for the analytic study of reading that heretofore have been used separately. Measures on a lexical decision task designed to isolate phonological effects in the identification of printed words were examined in young adults. The results were related to previously obtained measures of brain activation patterns for these participants derived from functional magnetic resonance imaging (fMRI). The fMRI measures were taken as the participants performed tasks that were designed to isolate orthographic, phonological, and lexical-semantic processes in reading. Individual differences in the magnitude of phonological effects in word recognition, as indicated by spelling-to-sound regularity effects on lexical decision latencies and by sensitivity to stimulus length effects, were strongly related to differences in the degree of hemispheric lateralization in 2 cortical regions.

Adult↗
PubMed1997

Functional magnetic resonance imaging assessment of the human brain auditory cortex response to increasing word presentation rates.

In an investigation of the auditory cortex response to speech, six subjects were studied using echo-planar functional magnetic resonance imaging (fMRI) at 2.1T. The subjects were asked to listen to English nouns presented at various rates ranging from 0 words per minute (wpm) to 130 wpm while fMRI images encompassing their primary and posterior superior secondary auditory cortices were acquired. An asymmetric spin echo imaging sequence was used with an induced T2 weighting of 50 ms to allow for transverse relaxation effects. Images were acquired in two or four axial-oblique slices with a repetition time of 3.75 or 7.5 s, in plane resolution of 6 x 3 mm, and a slice thickness of 5 mm. Localized activation centered over grey matter was consistently observed in all subjects in the transverse temporal gyrus (TTG), the transverse temporal sulcus (TTS), and the posterior superior aspect of the superior temporal gyrus (STG). The total activate volume and the integrated signal response in bilateral primary and posterior superior secondary auditory cortices increased with increasing rate of word presentation, peaking at 90 wpm (with some intersubject variability) with a subsequent fall at 130 wpm. There were no significant differences in the rate dependence of the signal response in bilateral primary and bilateral posterior superior secondary auditory cortices (P < 0.05).

Adult↗
PubMed1997

Cerebral vascular malformations adjacent to sensorimotor and visual cortex. Functional magnetic resonance imaging studies before and after therapeutic intervention.

BACKGROUND AND PURPOSE: It is not known how cerebral vascular malformations affect the function of the surrounding brain. Functional magnetic resonance imaging (fMRI) can provide information about normal functional neuroanatomy and its alteration by vascular lesions and therapeutic intervention. METHODS: We performed fMRI studies in 24 patients harboring vascular malformations adjacent to primary somatosensory, motor, and visual cortex. The fMRI studies consisted of the acquisition of an image time series coupled with functional activation of motor, sensory, or visual cortex in both hemispheres. Activated voxels were identified using frequency domain analyses, and their number and anatomic location were compared between the affected and unaffected hemispheres. RESULTS: Every patient capable of performing the desired task showed functional activation. Eight patients without neurological deficits showed a symmetrical pattern of activation between the hemispheres. Each had a vascular malformation located one or more gyri from the functional region imaged. Three patients showed hemispheric symmetry in the location of activated cortex but with a marked asymmetry in the number of activated voxels. Each harbored vascular malformations located within one gyrus of the functional region and showed either subtle or no neurological deficit. Eleven patients showed hemispheric asymmetry in the location of activated cortex. In 6, the anatomic displacement appeared to be due to a mass effect of the lesion. In 5, the activation occurred at a different anatomic locale, and the patients exhibited gross neurological deficit in the respective function. Posttherapeutic changes in functional activation reflected elimination of the mass effect or recovery of clinical function. CONCLUSIONS: Systematic fMRI studies are possible in patients with vascular malformations in brain regions adjacent to primary somatosensory, motor, and visual cortex. Displacement of the activated region and hemispheric asymmetry in the number of activated voxels in the functional regions appear to reflect the anatomic and physiological impact of the vascular malformation. Changes in fMRI findings after intervention reflect the consequences of therapy and parallel clinical recovery.

Adolescent↗
PubMed1997

A systematic approach for interpreting MR images of the seizure patient.

A systematic approach needs to be used to review MR scans in epilepsy patients to avoid the common pitfalls engendered by the subtle nature of many epileptogenic lesions. One should always evaluate the hippocampus regardless of other MR findings to avoid missing dual abnormalities. False-positive and false-negative diagnosis of hippocampal sclerosis can be avoided by evaluating the hippocampus after correcting for head rotation [by assessing the internal auditory canals and atria). Periventricular heterotopia can be successfully diagnosed by systematically studying the periventricular regions, especially those adjacent to the atria of the lateral ventricles. Gray matter lateral to the ventricles (excluding the caudate nucleus) is always an abnormal finding. Sulcal and cortical morphologic abnormalities are particularly difficult to diagnose unless a high index of suspicion is maintained. Cortical thickening is indicative of a developmental anomaly and should be screened in an organized manner. Because epilepsy is generally a cortical process, one must search for subtle cortical abnormalities, including focal atrophic abnormalities and lesions without mass effect. Diligence will offer its own rewards.

Adult↗
PubMed1997

Qualitative MR imaging of refractory temporal lobe epilepsy requiring surgery: correlation with pathology and seizure outcome after surgery.

OBJECTIVE: The purpose of this study was to compare MR imaging findings with histologic findings of either hippocampal sclerosis or gliosis in patients with intractable temporal lobe epilepsy requiring surgery and to correlate MR imaging findings with seizure outcome after surgery and with clinical parameters such as febrile seizure history. MATERIALS AND METHODS: A retrospective study of MR scans of 66 patients with medically refractory temporal lobe epilepsy requiring surgery was performed. Qualitative diagnosis was done by visual inspection of MR images. MR imaging findings of hippocampal atrophy, signal intensity changes, and segmental findings were correlated with histopathology and with neuronal density. The final MR imaging diagnosis was also correlated with seizure outcome after surgery and with febrile seizure history. RESULTS: Histologic findings consisted of hippocampal sclerosis in 55 patients and nonspecific gliosis in 11 patients. Two variables, MR imaging findings of hippocampal sclerosis (hippocampal atrophy or signal intensity change) and a febrile seizure history, were significantly associated with hippocampal sclerosis. MR images of nonspecific gliosis usually showed normal findings, although some cases showed mild hippocampal atrophy. When comparing MR imaging findings with histology, our observers achieved sensitivities of 87-98% and specificities of 45-100%. In patients with successful outcomes after surgery, sensitivity ranged from 85% to 98% for MR imaging findings suggesting hippocampal sclerosis, specificity ranged from 17% to 85%, and positive predictive values ranged from 82% to 90%. CONCLUSION: Qualitative visual analysis of MR images correlates well with histologic findings, febrile seizure history, and seizure outcome after surgery. MR imaging findings and febrile seizure history help differentiate between hippocampal sclerosis and nonspecific gliosis, two similar clinical conditions associated with temporal lobe epilepsy that often have different outcomes after surgery.

Adolescent↗
PubMed1997

Embryology of the human fetal hippocampus: MR imaging, anatomy, and histology.

PURPOSE: To identify changes in the embryology of the hippocampus responsible for its adult anatomy. METHODS: Ten human fetal specimens ranging from 13 to 24 weeks' gestational age were examined with MR imaging. Dissections and histologic sections of 10 different specimens of similar ages were compared with MR imaging findings. RESULTS: At 13 to 14 weeks' gestation, the unfolded hippocampus, on the medial surface of the temporal lobe, surrounds a widely open hippocampal sulcus (hippocampal fissure). At 15 to 16 weeks, the dentate gyrus and cornu ammonis have started to infold. The hippocampal sulcus remains open. The parahippocampal gyrus is larger and more medially positioned. The CA1, CA2, and CA3 fields of the cornu ammonis are arranged linearly. The dentate gyrus has a narrow U shape. By 18 to 20 weeks, the hippocampus begins to resemble the adult hippocampus. The dentate gyrus and cornu ammonis have folded into the temporal lobe. The hippocampus and subiculum approximate each other across a narrow hippocampal sulcus. The CA1-3 fields form an arc and the CA4 field has increased in size within the widened arch of the dentate gyrus. CONCLUSION: MR imaging of fetuses provides a developmental basis for understanding hippocampal anatomy.

Adult↗
PubMed1996

Auditory selective attention: an fMRI investigation.

In the present experiment, 25 adult subjects discriminated speech tokens ([ba]/[da]) or made pitch judgments on tone stimuli (rising/falling) under both binaural and dichotic listening conditions. We observed that when listeners performed tasks under the dichotic conditions, during which greater demands are made on auditory selective attention, activation within the posterior (parietal) attention system and at primary processing sites in the superior temporal and inferior frontal regions was increased. The cingulate gyrus within the anterior attention system was not influenced by this manipulation. Hemispheric differences between speech and nonspeech tasks were also observed, both at Broca's Area within the inferior frontal gyrus and in the middle temporal gyrus.

Adult↗
PubMed1996

Cerebral organization of component processes in reading.

The cerebral organization of word identification processes in reading was examined using functional magnetic resonance imaging (fMRI). Changes in fMRI signal intensities were measured in 38 subjects (19 males and 19 females) during visual (line judgement), orthographic (letter case judgement), phonological (nonword rhyme judgement) and semantic (semantic category judgement) tasks. A strategy of multiple subtractions was employed in order to validate relationships between structure and function. Orthographic processing made maximum demands on extrastriate sites, phonological processing on a number of frontal and temporal sites, and lexical-semantic processing was most strongly associated with middle and superior temporal sites. Significant sex differences in the cerebral organization of reading-related processes were also observed.

Adult↗
PubMed1996

Refractory epilepsy: comparison of MR imaging, CT, and histopathologic findings in 117 patients.

PURPOSE: We compared computed tomography (CT) and magnetic resonance (MR) imaging for the detection of abnormalities underlying epilepsy. MATERIALS AND METHODS: CT and MR imaging findings in 117 patients (56 female, 61 male patients; age at surgery, 12-56 years) who underwent surgery for medically refractory epilepsy were compared with histopathologic findings by using the McNemar and chi 2 statistics. RESULTS: Sensitivities for detecting abnormalities were 95% (104 of 109) for MR imaging and 32% (35 of 109) for CT; specificities were 87% (13 of 15) for MR imaging and 93% (14 of 15) for CT (P < .001 for MR versus histopathologic findings). In the subgroup of 113 patients with solitary findings, MR imaging depicted an abnormality at the surgical site in 86% (n = 97) of 113 patients compared to 28% (n = 32) for CT (P < .001). In this same subgroup, histopathologic findings were predicted by using MR imaging in 88% (n = 99) of 113 patients versus 35% (n = 40) with CT (P < .001). Multiple findings were observed in 3% of CT (three of 117) and 17% of MR (20 of 117) images. CONCLUSION: CT has no role in the diagnostic evaluation of medically refractory epilepsy. Even in patients with medically controlled epilepsy, use of less costly CT instead of MR imaging seems imprudent.

Adolescent↗
PubMed1996

Exceptional multiplicity of cerebral arteriovenous malformations associated with hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome).

PURPOSE: To describe the clinical and imaging features of seven patients with hereditary hemorrhagic telangiectasia and an exceptional number of cerebral arteriovenous malformations (AVMs). METHODS: One hundred thirty-six patients from a dedicated hereditary hemorrhagic telangiectasia clinic were screened systematically for cerebral AVMs by means of MR imaging. Thirty-one were found to have abnormalities suggestive of a vascular malformation. Eighteen of these 31 patients subsequently underwent diagnostic cerebral angiography. RESULTS: Of the 18 patients who had cerebral angiography, all were found to have at least one AVM and seven were found to have three or more AVMs. The number of cerebral AVMs detected ranged from three to nine. At angiography, the AVMs varied in size from 3 to 25 mm in maximal dimension and consisted of a poorly defined plexiform nidus that typically had a single arterial feeding pedicle and a single draining vein. The two largest AVMs (20- and 25-mm nidus, respectively) contained intranidal aneurysms. Treatment included embolization, surgical excision, or follow-up management. CONCLUSIONS: Multiple cerebral AVMs are associated with hereditary hemorrhagic telangiectasia and further highlight the uniqueness of central nervous system involvement by this systemic angiodysplasia. MR imaging can underestimate the number and size of cerebral AVMs; therefore, catheter angiography is necessary to establish the extent of central nervous system involvement in this disorder.

Adult↗
PubMed1995

Sex differences in the functional organization of the brain for language.

A much debated question is whether sex differences exist in the functional organization of the brain for language. A long-held hypothesis posits that language functions are more likely to be highly lateralized in males and to be represented in both cerebral hemispheres in females, but attempts to demonstrate this have been inconclusive. Here we use echo-planar functional magnetic resonance imaging to study 38 right-handed subjects (19 males and 19 females) during orthographic (letter recognition), phonological (rhyme) and semantic (semantic category) tasks. During phonological tasks, brain activation in males is lateralized to the left inferior frontal gyrus regions; in females the pattern of activation is very different, engaging more diffuse neural systems that involve both the left and right inferior frontal gyrus. Our data provide clear evidence for a sex difference in the functional organization of the brain for language and indicate that these variations exist at the level of phonological processing.

Adult↗
PubMed1995

MR characteristics of neoplasms and vascular malformations associated with epilepsy.

We assessed the magnetic resonance (MR) imaging characteristics of two categories of epileptogenic substrates, neoplasms, and vascular malformations, to determine MR sensitivity and typical imaging features. A blinded retrospective analysis was performed on MR scans from 41 patients who had a neoplasm or vascular malformation surgically resected as treatment for medically refractory epilepsy. Abnormalities were assessed for sensitivity of MR detection, prediction of pathologic category, location, calvarial remodelling, signal intensity, and effect on adjacent tissue. Pathologic findings consisted of 33 tumors and 8 vascular malformations. We correctly localized 100% of the 41 lesions and predicted the correct pathologic category for 95% of these lesions. Neoplastic and vascular lesions (NVLs) associated with epilepsy had certain characteristic features. The temporal lobe was the most common site for NVL, involved in 68%. NVL were located in the brain periphery in 85% and remodelled the calvarium in 32%. NVL were associated with mass effect in 61%, volume loss in 1%, and no effect on adjacent tissue in 37%. NVL associated with epilepsy can be detected with high sensitivity using MR imaging. The temporal lobe location, cortical involvement, and calvarial remodelling are findings typical of NVL. MR characteristics can successfully predict the pathologic substrate of these lesions.

Brain Neoplasms↗
PubMed1995

Cranial nerve enhancement in the Guillain-Barré syndrome.

We report a case of Guillain-Barré syndrome with enhancement of multiple cranial nerves seen with postcontrast MR imaging. Clinical symptoms and electrodiagnostic studies reflected abnormalities of some but not all of the enhancing cranial nerves.

Cranial Nerve Diseases↗