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D G Darby

Publications and source records attributed to D G Darby.

28 records · Page 2Linked to original sources
PubMed1996

Cortical activation in the human brain during lateral saccades using EPISTAR functional magnetic resonance imaging.

The location of the human cortical substrate underlying simple horizontal saccadic eye movements was investigated using echoplanar functional magnetic resonance imaging (fMRI) in young healthy volunteers. Echoplanar imaging with signal targeting and alternating radiofrequency (EPISTAR), a novel perfusion technique, measured signal intensity changes in one to four contiguous 10-mm slices centered to include both striate cortex and putative frontal eye fields during horizontal saccade and fixation conditions. Subtraction images of self-paced visually guided saccadic versus fixation conditions showed bilateral marked and statistically significant localized signal increases in the precentral region (Brodmann areas 4, 6) and peristriate cortex (areas 17, 18, 19) and qualitative increases in the superior medial frontal region, as identified by a Talairach-Tournoux generalized template in the brain slices that were scanned. Additional parietal activation occurred during a target-guided saccade task. Our data (i) support the localization of the human FEF, as identified by simple, nonexploratory saccadic eye movements, in the precentral motor strip and premotor cortex, (ii) show individual variability in the exact anatomical location of saccade-related activations, and (iii) confirm that the EPISTAR technique can demonstrate localized signal increases during a behavioral task.

Adult↗
PubMed1996

D-cycloserine added to clozapine for patients with schizophrenia.

OBJECTIVE: The effects of D-cycloserine added to clozapine were assessed and compared with previous results for D-cycloserine plus conventional neuroleptics. METHOD: Ten schizophrenic outpatients receiving clozapine entered consecutive 2-week trials of placebo and D-cycloserine at 5, 15, 50, and 250 mg/day. Clinical evaluations were videotaped and scored by a rater blind to the sequence of assessments. RESULTS: There was a significant dose effect of D-cycloserine on scores on the Scale for the Assessment of Negative Symptoms (SANS); the 50-mg dose produced a mean 21% increase in SANS score. The patients had significantly higher baseline serum glutamate concentrations than the patients receiving typical neuroleptics in the previous trial. Baseline glutamate level and change in glycine level significantly correlated with response of negative symptoms to 50-mg D-cycloserine. CONCLUSIONS: The improvement of negative symptoms with D-cycloserine previously observed in patients receiving typical neuroleptics did not occur in patients treated with clozapine.

Adult↗
PubMed1996

EEG-triggered echo-planar functional MRI in epilepsy.

We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2) subclinical epileptic discharges could be used to trigger ultrafast functional MRI images, (3) artifact-free functional MRI images could be obtained while the patient was having the EEG monitored, and (4) the functional MRI images so obtained would show focal signal increases in relation to epileptic discharges. We report our results in two patients who showed focally higher signal intensity, reflective of increased local blood flow, in ultrafast functional MRI timed to epileptic discharges recorded while the patients were in the imager and compared with images not associated with discharges. One patient showed a focal increase despite a clinical and EEG history of generalized discharges. This approach may have the potential to identify brain regions activated during brief focal epileptic discharges.

Adult↗
PubMed1995

Brain lesions in patients with multiple sclerosis: detection with echo-planar imaging.

PURPOSE: To evaluate the detection of brain lesions with echo-planar imaging relative to conventional spin-echo (SE) imaging. MATERIALS AND METHODS: In 17 patients (three men, 14 women; mean age, 31 years) with multiple sclerosis, the following were compared: single-shot proton-density- and T2-weighted and thin-section T2-weighted echo-planar, proton-density- and T2-weighted multishot echo-planar, and conventional SE sequences. Quantitative and qualitative criteria as well as lesion detectability were evaluated. The proton-density-weighted SE sequence was used as the standard of reference. RESULTS: Multishot sequences were superior to single-shot sequences in image quality and lesion detectability. With the multishot proton-density-weighted sequence, 53 of 54 large lesions and 23 of 30 small lesions were detected; with the single-shot proton-density-weighted sequence, 38 of 54 large lesions and five of 30 small lesions were detected. CONCLUSION: With multishot echo-planar sequences, detectability of large lesions is similar to that with conventional SE imaging. Susceptibility artifact is diminished in comparison to single-shot echo-planar sequences.

Adult↗
PubMed1994

Qualitative mapping of cerebral blood flow and functional localization with echo-planar MR imaging and signal targeting with alternating radio frequency.

PURPOSE: To create qualitative maps of cerebral blood flow (CBF) with the EPISTAR (echo-planar imaging and signal targeting with alternating radio frequency) technique. MATERIALS AND METHODS: The EPISTAR technique was performed in a pig model of hypercapnia and then tested in 26 volunteers by using various paradigms for cortical activation. Echo-planar images were acquired with and without use of a radio-frequency inversion pulse applied to inflowing arterial spins. A qualitative map of CBF was then created by subtracting the image obtained without the radio-frequency pulse from that obtained with the radio-frequency pulse. RESULTS: Progressively more distal portions of the tagged vessels were seen as the inflow time was lengthened until cortical enhancement was seen for inflow times of approximately 1 second or longer. Signal intensity increases from rest to sensorimotor activation ranged from 13% to 193%. CBF changes in the motor strip, primary visual cortex, and the motor area for eye movements were well localized to the cortical gray matter ribbon. CONCLUSION: The EPISTAR technique is a rapid, noninvasive means for creating qualitative maps of CBF.

Animals↗
PubMed1993

Lateralization of verbal memory and unilateral hippocampal sclerosis: evidence of task-specific effects.

This study retrospectively investigated the effect of left (LHS) versus right (RHS) hippocampal sclerosis on verbal memory, measured by means of the Paired Associate Learning and Logical Memory subtests of the Wechsler Memory Scale (WMS) administered as part of a routine preoperative assessment. Patients were selected for the presence of unilateral hippocampal sclerosis by means of preoperative magnetic resonance imaging (MRI) and postoperative neuropathology. The LHS patients (n = 20) were significantly worse on paired associate learning than RHS patients (n = 18), the performance of RHS patients being consistent with normative standards. In contrast, no laterality effect was seen on the immediate and delayed recall of passages; the evidence suggests that both groups performed at a mildly impaired level. It was suggested that the laterality of verbal memory is conditional upon specific task demands in patients with damage to mesial temporal structures.

Adult↗
PubMed1993

Sensory aprosodia: a clinical clue to lesions of the inferior division of the right middle cerebral artery?

Isolated infarction in the territory of the inferior division of the right middle cerebral artery (MCA) is often associated with subtle clinical features. Sensory aprosodia, a disorder of emotional speech (affective prosody) with impaired prosodo-affective comprehension and repetition (but relatively spared expression) and added impairment of identification of emotional gesturing, has been advanced as a potential clinically useful marker for such lesions. We examine this hypothesis in a prospective serial study of native Anglophones with a recent initial unilateral cerebral infarction demonstrated on CT. There were four patients with inferior divisional infarctions of the right MCA among 42 with infarctions involving the MCA territory (27 right, 16 left). Sensory aprosodia was present acutely in four patients: two inferior divisional right MCA lesions, one more extensive right MCA lesion (with neurologic signs consistent with predominant inferior division of right MCA impairment), and one left MCA infarction. At approximately 20 days postinfarction, there were three patients with sensory aprosodia, including two with inferior divisional right MCA lesions and another with superior divisional right MCA infarction. No healthy controls or lacunar infarction patients showed this profile. We conclude that sensory aprosodia (1) is identifiable with standardized, objective methodology, (2) is an acute marker of inferior divisional infarction in the right MCA territory, (3) is less specific several weeks after infarction, and (4) is not associated with lacunar infarction.

Aged↗
PubMed1988

Primary intraventricular hemorrhage: clinical and neuropsychological findings in a prospective stroke series.

Seven cases of primary intraventricular hemorrhage (PIVH) constituted 3.1% of intracerebral hemorrhages in a prospective stroke series of 2,950 patients. All patients collapsed suddenly and had a depressed state of consciousness. Focal signs, if present, were minimal and contralateral to the major site of hematoma. Angiography in four patients revealed three intracranial arteriovenous malformations and one moyamoya. We conclude that PIVH may be readily diagnosed radiologically and underlying vessel malformations should be sought by angiography. Survival is common (five of seven cases), but a severe amnesic state may be a persisting deficit.

Brain↗
PubMed1984

Metabolic disorders presenting as stroke.

In a series of 1460 consecutive patients admitted to an "acute" stroke unit, 10 patients (0.7%) were found to have a metabolic encephalopathy which mimicked stroke. Of these, three had hypoglycaemia, four had hyperglycaemia, three had hyponatraemia, and one had suffered from hypoxia. Metabolic disorders should be excluded in all patients with a diagnosis of suspected stroke, especially if the presentation is associated with a confusional state or focal seizures. The conventional symptoms and signs of the metabolic disorders may be minimal or absent. The relative rarity of these disorders among patients with suspected stroke is overshadowed by the importance of early recognition and treatment, in order to minimize morbidity and mortality.

Aged↗