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Biomedical subjects

M D Devous

Publications and source records attributed to M D Devous.

At least 37 records · Page 2Linked to original sources
PubMed1992

Brain blood flow related to acoustic laryngeal reaction time in adult developmental stutterers.

The 1980s witnessed renewed interest in the relation between developmental stuttering and central nervous system (CNS) abnormalities. We have reported differences between nonstutterers and developmental stutterers on electrophysiologic (QTE) and metabolic (rCBF) measures of brain function. A critical step in the interpretation of results of functional brain imaging studies is to determine the relation, if any, of identified CNS abnormalities to speech motor control in persons who stutter. In this study we addressed the interpretation of rCBF findings by asking whether we could identify patterns of impaired acoustic laryngeal reaction time (LRT) as a function of response complexity parallel to rCBF findings. Stutterer subgroups determined by clinical severity ratings were not differentiated by LRT values as a function of response complexity. Stutterers with relative blood flow asymmetry below the normal median value involving both left superior and middle temporal regions of interest (ROIs) showed significantly longer LRT for the complex response than did normal speakers and stutterers with above-normal median relative flow values to at least one of these temporal ROIs. Stutterer subgroups based on reduced cingulate flow alone were not differentiated by LRT values. Findings are consistent with Goldberg's (1985) model of CNS premotor processing. Findings also suggest that stutterer subgroups might be distinguished by the presence, loci, and relative magnitude of cortical and/or subcortical rCBF abnormality in regions that subserve a fluency-generating system.

Adult↗
PubMed1992

The use of acetazolamide-enhanced regional cerebral blood flow measurement to predict risk to arteriovenous malformation patients.

Regional hemodynamic disturbances may complicate the treatment of certain cerebral arteriovenous malformations (AVM) and occasionally produce life-threatening situations. Acetazolamide-enhanced quantitative regional cerebral blood flow studies were performed preoperatively in 35 patients to determine if patterns of vasoreactivity could be identified that might be markers for postoperative morbidity. Ipsilateral and contralateral regions of hypoperfusion were identified on resting studies, and a steal index was calculated by dividing the regional cerebral blood flow in the steal region by the flow in a normal cerebellar region. Flow in these regions of interest was again quantitated after the administration of acetazolamide, a known cerebral vasodilator. A delta value was calculated by subtracting the resting index values from the acetazolamide indices. Abnormally enhanced vasoreactivity (vasodilation) to acetazolamide stimulation was noted in these threatened territories in AVM that had perforating vessel feeding and angiographic steal phenomena, that developed hyperemic disturbances, and that resulted in poor outcomes. These findings call into question traditional theories of AVM-related hemodynamic decompensation and suggest unique smooth muscle derangements in cerebral vasculature in some AVM patients.

Acetazolamide↗
PubMed1992

Dual-isotope brain SPECT imaging with technetium-99m and iodine-123: clinical validation using xenon-133 SPECT.

Our phantom studies indicate that the energy resolution (9.7% FWHM) of a new three-headed single-photon tomograph (PRISM-3000) separates the distribution of 99mTc from 123I for 10% asymmetric or 15% or 10% centered 99mTc windows when combined with a 10% asymmetric 123I window. This technique is now applied to the simultaneous measurement of resting rCBF and changes induced by vasodilation (1 g acetazolamide) in 10 subjects with cerebrovascular disease. Resting and vasodilated 133Xe SPECT images were obtained first. Within 48 hr, 99mTc HMPAO was given at rest, acetazolamide injected, and after 20 min either [123I] IMP or [123I] HIPDM was administered. Subjects were scanned for 99mTc and 123I simultaneously using 10% asymmetric windows. Regression analyses demonstrated a linear relationship between 133Xe SPECT and dual-isotope SPECT measurements of lesion-to-cerebellum ratios in baseline (r = 0.92), vasodilated (r = 0.86) and rest-minus-vasodilated data (r = 0.85). Technetium-99m and 123I images obtained through dual-isotope imaging are by definition in perfect anatomic registration.

Acetazolamide↗
PubMed1992

Dual-isotope brain SPECT imaging with technetium-99m and iodine-123: validation by phantom studies.

Phantom studies were employed to determine whether the enhanced energy resolution (9.7% FWHM) of a new high-resolution, three-headed single-photon emission computed tomograph might permit the simultaneous acquisition of 99mTc and (123)I. Various window widths (15% and 10%) and positions (centered and asymmetric to the photopeak) were used to examine cross-contamination between these two isotopes. Brain phantom experiments using a 15% centered 99mTc window in conjunction with a 10% asymmetric (123)I window (upper half of the (123)I photopeak) demonstrated that approximately 95% of observed counts were derived from the isotope of interest. Shifting the (123)I window from asymmetric to centered resulted in a significant increase in contamination of the (123)I window. Shifting the 99mTc window from centered to asymmetric did not significantly alter image quality for 99mTc. Separate experiments employing vials with varying isotope concentrations demonstrated that quantitative recovery from mixed 99mTc and (123)I sources was equivalent to that from matched single-isotope sources (r2 > or = to 0.90).

Brain↗
PubMed1992

Comparison of SPECT applications in neurology and psychiatry.

The following presentation provides an overview of SPECT brain imaging applications in both neurologic and psychiatric disorders. Specific findings in cerebrovascular disease, dementia, and epilepsy are described in order to highlight the role SPECT plays in distinguishing primary organic disease from primary psychopathology. Through case examples, new applications of three-dimensional SPECT rCBF imaging that could play a major role in defining CNS network abnormalities in major depressive disorder and obsessive compulsive disorder are elucidated. The role of network imaging analysis across groups in psychiatric subjects is contrasted to its roles in neurologic disorders. The degree to which both neurologic and psychiatric pathology seen on SPECT exceeds that observed through structural modalities is defined.

Brain↗
PubMed1991

Heterogeneity in spasmodic dysphonia. Neurologic and voice findings.

Spasmodic dysphonia is a disturbance of phonation with laryngeal spasms. We report voice and neurologic examination findings in 45 subjects. Neurologic abnormalities were found in 32 subjects (71.1%). Rapid alternating movement abnormalities, weakness, and tremor were common. Incoordination and spasticity were rare. Lower extremity findings were frequent. Abnormalities were bilateral. Spasmodic dysphonia severity was related to age. Type, severity, and duration of vocal symptoms were not different for subjects with or without neurologic abnormalities. Vocal tremor was more frequent in neurologically abnormal subjects. Involvement of a pallidothalamic-supplementary motor area system could account for neurologic findings, brain imaging findings, and clinical heterogeneity. The view emerging is that spasmodic dysphonia is a manifestation of disordered motor control involving systems of neurons rather than single anatomical sites.

Adult↗
PubMed1991

Regional cerebral blood flow in developmental stutterers.

Stuttering is a poorly understood communication disorder with a 1% global prevalence. Recently, there has been a resurgence of interest in a neurogenic origin for the disorder, although no research has established clear neurological differences between "developmental" (stuttering onset in childhood) stutterers and nonstutterers. We have used xenon 133 single-photon emission computed tomography to study regional cerebral blood flow (rCBF) in 20 stutterers. Analysis revealed global, absolute flow reductions. Relative flow asymmetries (left less than right) were identified in three hemispheric regions: anterior cingulate and superior and middle temporal gyri. Milder changes were found in the left inferior frontal gyrus. Stutterers had rCBF values below median for either anterior cingulate or middle temporal gyri. With one exception, severe stutterers had rCBF values below median for the anterior cingulate gyrus. All stutterers with rCBF values above median in the cingulate gyrus had rCBF values below median in the middle temporal gyrus, and severity of their disorder was either mild or moderate. Our findings suggest that stuttering is a neurogenic disorder involving recognized cortical regions of speech-motor control.

Adult↗
PubMed1991

Laryngeal reaction time profiles in spasmodic dysphonia: relationship to cortical electrophysiologic abnormality.

This study combines measures of linguistic and vocal performance and long-latency auditory electrophysiology to investigate task-dependent variability in spasmodic dysphonia (SD). Linguistic performance was evaluated using several measures of relatively complex linguistic ability (i.e., discourse analysis). Vocal performance was evaluated by measuring acoustic laryngeal reaction time (LRT) for tasks that differ in complexity. Normal structure of the cortex and subcortex was confirmed by magnetic resonance imaging. Cortical function was measured using multichannel quantitative auditory evoked potentials (AEPs). As a group, SD subjects who demonstrated subtle linguistic deficits also demonstrated prolonged LRT for the complex task and repeated and persistent auditory electrophysiologic abnormalities over the anterior quadrant of the left hemisphere. As a group, linguistically normal SD subjects demonstrated no significant increase in LRT for the complex task and no recurrent electrophysiologic abnormalities over the left anterior cortex relative to normal controls. Results support a neurogenic origin of SD and suggest that some aspects of inter- and intrasubject variability may be related to differences in loci and magnitude of cortical abnormalities.

Adult↗
PubMed1990

Hypofrontality and cognitive impairment in schizophrenia: dynamic single-photon tomography and neuropsychological assessment of schizophrenic brain function.

Regional cerebral blood flow (rCBF) was assessed in 40 chronic male schizophrenic patients (20 medicated, 20 unmedicated) and 31 matched normal controls with Dynamic Single-photon Emission Computed Tomography (D-SPECT). Blind analyses of normalized color-coded tomograms revealed significant bifrontal and bitemporal rCBF deficits in the patient group. Frontal flow deficits were most prominent in paranoid patients (n = 21) and right temporal deficits were most prominent in nonparanoid patients (n = 19). These relative regional declines were observed within the context of significantly elevated hemispheric blood flow in schizophrenics compared with controls. Reduced left frontal rCBF was associated with neuropsychological impairment on the Wisconsin Card Sorting Test and Luria-Nebraska Battery. Increased hemispheric CBF was correlated with the presence of positive schizophrenic symptoms. Medication status was unrelated to rCBF. These findings demonstrate that hypofrontality has important implications for cognitive function in some schizophrenic individuals.

Adult↗
PubMed1990

Evidence for cortical dysfunction in spasmodic dysphonia: regional cerebral blood flow and quantitative electrophysiology.

Cortical function was evaluated in 26 subjects with spasmodic dysphonia. Quantitative topographic electrophysiologic mapping (QTE) was employed to provide quantitative analyses of EEG spectra and auditory and visual long-latency evoked potentials. Single-photon emission computed tomography (SPECT) of the cerebral transit of Xenon-133 was used to evaluate regional cerebral blood flow. Left hemispheric abnormalities in cortical function were found by both techniques in 10 subjects and by at least one technique in 18 subjects. Right hemispheric abnormalities were observed by both techniques in 8 subjects and by at least one technique in 18 subjects. Most patients with cortical dysfunction in one hemisphere had cortical dysfunction in the other, while only 4 subjects had unilateral lesions as found by one of the two techniques. Eight subjects were normal by all measurements. Underlying structural abnormalities were detected by magnetic resonance imaging in 5/24 subjects. However, functional abnormalities (SPECT or QTE) were not observed at sites of structural abnormalities. SPECT and QTE were significantly related in identification of left hemispheric dysfunction (p = .037) with a trend in the right hemisphere (p = .070), and a significant congruence of SPECT and QTE findings occurred in the left anterior cortical quadrant (p = .011). These findings indicate that dysfunction of cortical perfusion and/or cortical electrophysiology is associated with spasmodic dysphonia in the majority of subjects studied.

Adult↗
PubMed1990

Single photon emission computed tomography in epilepsy.

Functional brain imaging by either single photon emission computed tomography (SPECT) or positron emission tomography (PET) is now a well-established technique in the diagnosis and evaluation of the epilepsies. Perhaps only in stroke have these emerging technologies proven of greater significance. Scalp, cortical, or depth electroencephalographic (EEG) data previously have been the gold standards for the localization and subcharacterization of epileptic activity in the human brain. Yet, they are fraught with difficult interpretations, technical difficulties, and limitations in sampling accuracy. Both SPECT and PET have localizing power approaching that of combined scalp and depth EEG. In the following discussion, a brief overview of the results of PET investigations in epilepsy is presented as background and comparative material for the concurrent and, more recently, dominant role of SPECT in evaluating patients with seizure activity. SPECT results in the interictal state in partial and generalized seizure activity are reviewed followed by an analysis of the role of ictal SPECT imaging in epilepsy. Next, relationships among interictal hypoperfusion (or hypometabolism) and computed tomography, magnetic resonance imaging, neuropathology, clinical severity, and cognitive function are discussed. The role of perfusion or metabolism imaging in the management of antiepileptic pharmacotherapy is also discussed, and the potential for receptor imaging in the evaluation of the epilepsies is examined. Finally, application in pediatric epilepsy are presented.

Epilepsy↗
PubMed1989

Cognitive function and regional cerebral blood flow in partial seizures.

Patients with partial seizures have cognitive function impairments that have been attributed to the toxic side effects of anticonvulsants and structural cerebral damage. However, even when these factors are absent, neuropsychological (NP) deficits have been demonstrated, although of milder degree than in structurally brain-damaged patients. Assessment of cerebral metabolism using positron emission tomography and cerebral blood flow with single photon emission computed tomography (SPECT) reveals focal physiologic deficits in structurally normal areas. Using both SPECT and NP assessment with the Halstead-Reitan Battery, we evaluated 50 patients with partial seizures. Comparison of the location of visually identified regional cerebral blood flow (rCBF) deficits in these patients with the location of the NP deficits revealed a significant correlation. Additional analyses indicated that rCBF quantification in visually identified areas of hypoperfusion was significantly lower than in "normal" areas and that quantified NP variables significantly discriminated patients with and without visual rCBF deficits in temporal and frontal brain regions.

Adult↗
PubMed1989

Regional cerebral function and blood flow: complementary single photon emission computed tomography of the brain using xenon-133 and [123I]iodoamphetamine.

Regional cerebral function and blood flow can be imaged using isopropyl[123I]iodoamphetamine (IMP), or 133Xe (DSPECT), respectively. Both of these essentially non-invasive, quantitative, methods are suitable for many nuclear medicine laboratories. This study assessed the in vivo information about intracerebral disease provided by IMP and DSPECT techniques to determine the optimal diagnostic use of these modalities. Single photon emission computed tomograms of 53 subjects were acquired using similar displays for IMP and DSPECT data. Lobar tracer distributions were graded by three experienced observers and analyzed using a kappa statistic to eliminate chance agreements. Overall, both IMP and DSPECT had similar patterns. However, while similar, one or the other technique often displayed abnormalities not present on both. Although technical factors may account for some differences between the modalities, a case of arteriovenous malformation proves that discordant findings can result directly from tracer localization properties. Thus at least some discordances provide truly complementary diagnostic information lacking in either single study taken alone.

Adult↗
PubMed1989

The effect of acetazolamide on regional cerebral blood flow in patients with Alzheimer's disease or stroke as measured by single-photon emission computed tomography.

Regional cerebral blood flow (rCBF) was assessed in 35 patients with possible or probable Alzheimer's disease (AD) and in 16 patients known to have had at least one stroke. Patients were evaluated before and after the administration of 1 g acetazolamide (ACZ) by means of a rotating four-detector single-photon emission computed tomograph (SPECT) and inhaled Xe-133. RCBF values in mL/minute/100 g were derived from eight cortical regions of interest (ROI), and from the whole transverse section as a measure of whole brain flow (WBF). ROI/WBF ratios were calculated for each ROI in paired determinations done before and 15 minutes after the administration of ACZ. Results were compared with those previously obtained in a study of 15 normal, healthy volunteer subjects. ROI/WBF ratios greater than 2 standard deviations (SD) below the mean for a given ROI in the normal group were regarded as probably abnormal, whereas ratios greater than 4 SD below the mean were considered definitely abnormal. After ACZ administration, the number of ROI greater than 2 SD below the normal mean decreased significantly in the AD group and was unchanged in the stroke patients. However, the number of ROI/WBF ratios greater than 4 SD below the normal mean fell in the AD group and rose in the stroke group, with the difference in behavior highly statistically significant. Thus, the response of low-flow areas to ACZ differs in AD and in stroke, which could be of ultimate diagnostic significance.

Acetazolamide↗
PubMed1989

Microfibrillar collagen model of canine cerebral infarction.

A new canine model of focal cerebral ischemia has been developed employing intravascular delivery of microfibrillar collagen via femoral catheterization. In 13 dogs, dose-effect studies showed neurologic deficits (ranging from mild hemiparesis to death) related to the dose of microfibrillar collagen delivered. In another 10 dogs, 0.5 ml of 60 mg/ml microfibrillar collagen was injected into the common carotid artery; neurologic assessment over 48 hours revealed a survivable stroke syndrome in seven dogs, death at 40 hours in one dog and at less than 12 hours in another, and no clinical effect in one dog. The eight surviving dogs were sacrificed at 48 hours; nine of the 10 dogs had middle cerebral artery distribution infarcts (two grossly hemorrhagic and five grossly nonhemorrhagic) on histologic examination. Angiography in three dogs demonstrated no significant major vascular occlusion. All seven dogs with survivable strokes demonstrated a dense hemiparesis at 24 hours that improved to ambulatory status at 48 hours. The use of microfibrillar collagen to produce middle cerebral artery strokes in dogs provides a new opportunity to study cerebral ischemia without surgery involving the cervical or cranial vasculature. Dogs have larger brains than other common animal models and thus are more amenable to study with imaging modalities. A model with a measurable but survivable insult provides an opportunity for short- and long-term clinical follow-up and for the investigation of therapeutic interventions.

Animals↗
PubMed1989

Reversible middle cerebral artery embolization in dogs without intracranial surgery.

Using dogs, we developed an intravascular model for reversible middle cerebral artery occlusion that does not involve intracranial surgery or enucleation. Using silicone plastic plugs with a suture embedded within them, we embolized the middle cerebral artery in 19 dogs via the cervical carotid artery. The free end of the suture remained accessible in the neck, and after variable dwell times traction was placed on the suture and the plug was withdrawn. Placement of the plug in the middle cerebral artery produced ischemia in the basal ganglia. The degree and distribution of cortical ischemia were variable as evidence by the pathologically documented scattered nature of infarcts that resulted when the plug was left permanently in the middle cerebral artery and when it was removed after 1 or 2 hours. Angiography demonstrated occlusion of the middle cerebral artery with the plug in place as well as reperfusion when the plug was withdrawn. This modification of a previously described model of middle cerebral artery occlusion provides an opportunity to study structural, physiologic, and biochemical events occurring in acutely hypoperfused cerebral tissue as well as critical changes leading to irreversible injury without the disadvantages of surgical manipulation required by all previous models of reversible cerebral ischemia.

Animals↗