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Biomedical subjects

G McCarthy

Publications and source records attributed to G McCarthy.

At least 109 records · Page 6Linked to original sources
PubMed1993

Nuclear magnetic resonance imaging and spectroscopy of human brain function.

The techniques of in vivo magnetic resonance (MR) imaging and spectroscopy have been established over the past two decades. Recent applications of these methods to study human brain function have become a rapidly growing area of research. The development of methods using standard MR contrast agents within the cerebral vasculature has allowed measurements of regional cerebral blood volume (rCBV), which are activity dependent. Subsequent investigations linked the MR relaxation properties of brain tissue to blood oxygenation levels which are also modulated by consumption and blood flow (rCBF). These methods have allowed mapping of brain activity in human visual and motor cortex as well as in areas of the frontal lobe involved in language. The methods have high enough spatial and temporal sensitivity to be used in individual subjects. MR spectroscopy of proton and carbon-13 nuclei has been used to measure rates of glucose transport and metabolism in the human brain. The steady-state measurements of brain glucose concentrations can be used to monitor the glycolytic flux, whereas subsequent glucose metabolism--i.e., the flux into the cerebral glutamate pool--can be used to measure tricarboxylic acid cycle flux. Under visual stimulation the concentration of lactate in the visual cortex has been shown to increase by MR spectroscopy. This increase is compatible with an increase of anaerobic glycolysis under these conditions as earlier proposed from positron emission tomography studies. It is shown how MR spectroscopy can extend this understanding of brain metabolism.

Brain↗
PubMed1993

X chromosome linkage studies in familial Rett syndrome.

Four families, each with two individuals affected by Rett Syndrome (RS), were analysed using restriction fragment length polymorphisms and microsatellite markers from the X chromosome. In two of the families, X-linked dominant inheritance of the RS defect from a germinally mosaic mother could be assumed. Therefore, maternal X chromosome markers showing discordant inheritance were used to exclude regions of the X chromosome as locations of the RS gene. Much of the short arm could be excluded, including regions containing three candidate genes, OTC, synapsin 1 and synaptophysin. Although most of the long arm was inherited in common it was possible to exclude a centromeric region. Inheritance of X chromosome markers is also presented for two families with affected aunt-niece pairs, one of which has not been previously studied at the DNA level.

Chromosome Mapping↗
PubMed1993

Functional brain imaging at 1.5 T using conventional gradient echo MR imaging techniques.

There is considerable interest in the use of MR imaging to study brain function. Recently, it has been demonstrated that small changes in signal intensity occur in the visual cortex in T2*-weighted imaging in response to appropriate visual stimuli. Similar responses to activation have also been recorded in motor cortex as well as frontal lobes. To date most of these studies have been carried out at very high field strength or they have used echo planar imaging. We report our preliminary results showing that the effects of activation of visual and motor areas of the brains of normal volunteers can be recorded using conventional MR imaging methods on a standard 1.5 T clinical scanner. Using gradient-echo imaging sequences, we have been able to map activated visual and motor cortex with high spatial resolution in multiple planes, and are using this technique to examine the relationship between physiological response and stimulus parameters. Signal changes of the order of 2-12% in images with TE = 45 msec, TR = 120 msec, and alpha = 40 degrees, permit excellent depiction of the regions affected.

Brain↗
PubMed1993

Anorectal function of children with neurological problems. I: Spina bifida.

Anorectal function was assessed with anorectal manometry in 45 children with spina bifida (21 girls and 24 boys, mean age 11 1/2 years). 24 enuretic children served as controls. The pressure in the first and second centimeters of the anal canal was lower among index children than controls and also lower among those with high spinal lesions compared with those with low lesions. Rectal activity (rectal sensation and trace appearance) during rectal distension appeared to be reduced among index children; sensation was particularly poor among those with high spinal lesions. Manometry may be useful in children with spina bifida as it provides a clearer understanding of sphincter function and leads to a more rational approach to the management of bowel problems.

Adolescent↗
PubMed1993

Deficits in short-term memory in posttraumatic stress disorder.

OBJECTIVE: The purpose of this study was to compare the memory function of patients with posttraumatic stress disorder (PTSD) to that of matched comparison subjects. METHOD: Vietnam veterans with combat-related PTSD (N = 26) were compared to physically healthy comparison subjects (N = 15) matched for age, race, sex, years of education, handedness, socioeconomic status, and alcohol abuse. Memory and intelligence were assessed with a battery of neuropsychological tests, including the Russell revision of the Wechsler Memory Scale, the Selective Reminding Test, and subtests of the Wechsler Adult Intelligence Scale-Revised (WAIS-R). RESULTS: The PTSD patients scored significantly lower than the comparison subjects on the Wechsler Memory Scale logical memory measures for immediate recall (mean = 11.6, SD = 3.3 versus mean = 20.9, SD = 6.6) and delayed recall (mean = 8.0, SD = 3.3 versus mean = 17.8, SD = 6.4). The PTSD patients also scored significantly lower on the total recall, long-term storage, long-term retrieval, and delayed recall measures for the verbal component of the Selective Reminding Test and on the recall, long-term storage, long-term retrieval, and continuous long-term retrieval measures for the visual component of the Selective Reminding Test. There was no significant difference between the PTSD patients and comparison subjects in prorated full-scale IQ as measured by the WAIS-R. CONCLUSIONS: Patients with PTSD may have deficits in short-term memory. Counseling and rehabilitation that address these deficits may be of value for PTSD patients.

Humans↗
PubMed1993

Diagnosis of medial temporal lobe seizure onset: relative specificity and sensitivity of quantitative MRI.

Measurement of hippocampal volume by MRI is a new technique with potential value in the localization of epileptic regions, but whether reduced hippocampal volume predicts the location of electrical seizure onset in mixed patient groups is not known. We examined the sensitivity and specificity of this technique among 56 refractory epileptic patients for the diagnosis of medial temporal lobe epilepsy as judged by intracranial EEG recording of spontaneous seizure onset. Since these patients had intracranial EEG because of inconsistent or insufficient localization by noninvasive electrophysiologic, functional, and structural assessment, this patient population can be considered the most difficult to localize. Hippocampal atrophy by MRI volumetry was 75% sensitive to, and 64% specific for, ipsilateral medial temporal lobe seizure onset in this group. Hippocampal atrophy was significantly correlated with longer duration of epilepsy. MRI compared favorably with all other noninvasive means of localization, which had 41 to 73% sensitivity and 45 to 65% specificity to medial temporal ictal onset; of these, none had as acceptable a combination of both adequate sensitivity and specificity. We conclude that MRI volumetry of the hippocampus is a valuable, noninvasive localization method in chronic epilepsy, with a yield and accuracy surpassing all other noninvasive studies used to predict the presence of medial temporal seizure onset.

Atrophy↗
PubMed1993

Localization of the face area of human sensorimotor cortex by intracranial recording of somatosensory evoked potentials.

The authors describe a method of localizing the sensory and motor peri-rolandic cortex representing the face and intraoral structures. Somatosensory evoked potentials (SEP's) to stimulation of the chin, lips, tongue, and palate were recorded in 37 patients studied intraoperatively under general anesthesia or following chronic implantation of cortical surface electrodes. Localization by trigeminal SEP recording was validated by SEP localization of the hand area with median nerve stimulation, and by cortical stimulation of the hand and face areas. The following conclusions were drawn regarding the implementation of face area localization: 1) in general agreement with the results of cortical stimulation in humans and single-unit recordings in monkeys, there is a medial-to-lateral representation in somatosensory cortex of the hand, chin, upper lip, lower lip, tongue, and palate; 2) the chin and lip representations overlap, are adjacent to the hand area, and provide little additional localizing information if the hand area has been identified; 3) stimulation of the tongue and palate evokes reliable, large-amplitude SEP's useful for localization; 4) palatal SEP's allow localization near the sylvian sulcus; 5) for any type of trigeminal stimulation, the largest SEP's are recorded from the somatosensory cortex and provide the most consistent criterion for its identification; and 6) polarity inversion of potentials across the sulcus (a reliable localizing criterion for median nerve SEP's) is a less reliable criterion for trigeminal SEP's.

Adolescent↗
PubMed1993

Anorectal function of children with neurological problems. II: cerebral palsy.

In response to the frequent complaint of difficulties with defecation experienced by children with cerebral palsy, 34 children (13 girls and 21 boys, mean age 10 years) with cerebral palsy were investigated by questionnaire and anorectal manometry. 24 enuretic children served as controls for the anorectal manometry. Constipation affected 26 of 29, defecation distress eight and faecal incontinence 16 of the index children, but incontinence was mild in most cases. Index children had a low resting pressure in the first centimetre of the anal canal, slow anal rhythmical activity and a pressure increase in the first centimetre during maximum rectal distension. These findings suggest anal sphincter and/or pelvic floor muscle incoordination, but no evidence of abnormal rectal function. The authors conclude that surgical intervention was not indicated for the index children, but that medical treatment could be improved.

Adolescent↗
PubMed1992

Dynamic mapping of the human visual cortex by high-speed magnetic resonance imaging.

We report the use of high-speed magnetic resonance imaging to follow the changes in image intensity in the human visual cortex during stimulation by a flashing checkerboard stimulus. Measurements were made in a 2.1-T, 1-m-diameter magnet, part of a Bruker Biospec spectrometer that we had programmed to do echo-planar imaging. A 15-cm-diameter surface coil was used to transmit and receive signals. Images were acquired during periods of stimulation from 2 s to 180 s. Images were acquired in 65.5 ms in a 10-mm slice with in-plane voxel size of 6 x 3 mm. Repetition time (TR) was generally 2 s, although for the long flashing periods, TR = 8 s was used. Voxels were located onto an inversion recovery image taken with 2 x 2 mm in-plane resolution. Image intensity increased after onset of the stimulus. The mean change in signal relative to the prestimulation level (delta S/S) was 9.7% (SD = 2.8%, n = 20) with an echo time of 70 ms. Irrespective of the period of stimulation, the increase in magnetic resonance signal intensity was delayed relative to the stimulus. The mean delay measured from the start of stimulation for each protocol was as follows: 2-s stimulation, delay = 3.5 s (SD = 0.5 s, n = 10) (the delay exceeds stimulus duration); 20- to 24-s stimulation, delay = 5 s (SD = 2 s, n = 20).

Brain Mapping↗
PubMed1992

Quantitative magnetic resonance imaging in temporal lobe epilepsy: relationship to neuropathology and neuropsychological function.

Magnetic resonance images (MRIs) were obtained from 25 patients with medically refractory epilepsy of temporal lobe origin (12 on the left, 13 on the right) and 14 right-handed control subjects. The hippocampi and temporal lobes were traced by computer on successive coronal images and the resulting measurements of area were summed for each region. The left and right hippocampi were symmetrical in the control subjects; however, for patients the hippocampus was smaller on the side of the seizure focus. Moreover, the left-right hippocampal ratio significantly differentiated the control subjects from each patient group. The left temporal lobe was significantly smaller than the right in control subjects. The epileptics' temporal lobes were smaller on the side of the seizure focus, compared to the temporal lobes in the control subjects. MRI hippocampal measurements were compared to hippocampal neuronal densities obtained postoperatively. Significant correlations were obtained between the ratio (side ipsilateral to focus/side contralateral to focus) of MRI hippocampal measurements and neuronal densities in all hippocampal subfields except CA2. Prior to surgery, patients were administered the Wechsler Memory Scale and the verbal Selective Reminding Test. Significant correlations existed between MRI measurements of the left hippocampus and the Wechsler logical memory percent retention scores and between the left temporal lobe measurements and the verbal Selective Reminding Test scores for patients with seizure foci in the left temporal lobe.

Adolescent↗
PubMed1992

Tactile interference differentiates sub-components of N20, P20 and P29 in the human cortical surface somatosensory evoked potential.

Somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded from up to 64 locations on the exposed cortical surface in 19 patients undergoing intracranial surgery for epilepsy and/or tumour removal. In view of previously described 'interference' effects on scalp SEPs, a continuous light tactile stimulus was applied to the palm and the first 3 digits of the stimulated hand in order to try to differentiate components due to input from cutaneous and other sensory receptors. The first cortically generated potentials, N20 at postcentral locations and P20 precentrally, could each be resolved into 2 subcomponents separated by about 2.5 msec. The later subcomponent was consistently the more attenuated by the interfering stimulus and is postulated to be due to input from rapidly adapting cutaneous mechanoreceptors. The earlier subcomponent could be due to input from muscle afferents or from slowly adapting cutaneous receptors which the interfering stimulus would have activated to a lesser degree. In 2 cases the P29 potentials recorded from regions of the postcentral gyrus were dissociated. In one case the potentials recorded at adjacent electrodes were attenuated to differing degrees, and in the other the effect was maximal at different locations when the thumb, index and middle fingers were stimulated separately. The method therefore appears capable of distinguishing regions of the postcentral gyrus concerned with cutaneous input from different parts of the hand.

Adolescent↗
PubMed1992

Management of oral health in persons with HIV infection.

Prevention and treatment of oral disease is required to maintain quality of life and to improve prognosis of patients infected with the human immunodeficiency virus (HIV). Management requires a team approach, and close collaboration with the appropriate responsible physicians and other health care workers is necessary. Oral infection is frequent and usually opportunistic, and management is based on certain principles. Infections may disseminate and can be persistent and severe; multiple concurrent or consecutive infections with different microorganisms are frequent; fungal, viral, and parasitic infections are rarely curable; and long-term antimicrobial therapy may be required. This article reviews the management of oral candidiasis, hairy leukoplakia, and infections with herpes simplex virus, varicella-zoster virus, and cytomegalovirus. The management of Kaposi's sarcoma, lymphomas, aphthous ulceration, gangrenous stomatitis, bleeding, xerostomia, and adverse drug reactions is also described. Treatment should avoid further immunosuppression and inducement of xerostomia or caries, and should be designed to avoid adverse drug reactions and possible drug interactions.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Effect of doxapram on the rate of recovery from atracurium and vecuronium neuromuscular block.

We have studied the effect of doxapram on the rates of spontaneous and neostigmine-induced recovery from neuromuscular block with atracurium and vecuronium, by measurement of the time to recovery of T1 (first twitch in the train-of-four) from 25 to 75% of control (recovery index, RI). After each neuromuscular blocking drug, RI was measured without administering either doxapram or neostigmine (control group), or after administration of doxapram 1 mg kg-1, neostigmine 50 micrograms kg-1 or a combination of doxapram and neostigmine, in groups of 10 patients. RI was significantly longer after vecuronium in the presence of doxapram compared with control (20.1 min vs 14.6 min). There was no significant difference in the RI after atracurium in the presence of doxapram compared with control (12.5 min vs 11.8 min) or when neostigmine was administered with or without doxapram (2.4 min vs 2.4 min, respectively after vecuronium; 3.3 min vs 2.9 min, respectively, after atracurium).

Adolescent↗
PubMed1992

Muscle pains and biochemical changes following suxamethonium administration after six pretreatment regimens.

The incidence of muscle pains and changes in serum concentrations of potassium, calcium and creatine kinase following suxamethonium were investigated after no pretreatment or pretreatment with intravenous tubocurarine 0.05 mg.kg-1, intravenous chlorpromazine 0.1 mg.kg-1, alphatocopherol (vitamin E) 600 mg in three divided doses orally, aspirin 600 mg orally or intravenous calcium chloride 5 mg.kg-1 in groups of 20 patients each. The incidence of myalgia was reduced significantly by tubocurarine, chlorpromazine and alphatocopherol. However, the increase in creatine kinase was attenuated only in the groups of patients who received tubocurarine and chlorpromazine. The changes in serum potassium and calcium concentrations were within acceptable limits. The intubating conditions were not as good in the patients who received tubocurarine as in the other groups. Effectiveness of chlorpromazine in preventing both the myalgia and the biochemical changes suggests the involvement of phospholipases in the pathogenesis of suxamethonium-induced muscle damage.

Adolescent↗
PubMed1992

Onset and duration of action of vecuronium in the elderly: comparison with adults.

The onset and duration of action of vecuronium were studied in young adult (n = 30; mean age 34 +/- 11.1 (s.d.) yr), middle-aged (n = 20; mean age 60 +/- 5.8 yr) and elderly patients (n = 30; mean age 80 +/- 4.6 yr) anaesthetised with thiopentone, nitrous oxide in oxygen and halothane. Neuromuscular block was monitored by applying the train-of-four (TOF) stimulation at 2 Hz to the ulnar nerve every 12 s. Half the patients in each group received 0.08 and the other half 0.12 mg kg-1 of the relaxant. The time to return of T1 (first response in the TOF sequence) to 25% of control was 28 +/- 5.2 (s.d.), 34 +/- 7.1 and 39 +/- 10.2 min following 0.08 mg kg-1 dose (P less than 0.05 between the elderly and young adults) and 45 +/- 9.2, 48 +/- 6.2 and 69 +/- 19.2 min following 0.12 mg kg-1 dose, respectively, in the three age groups (P less than 0.05 between the elderly and the other two groups). The recovery indices (time for 25-75% recovery of T1) after the 0.08 mg kg-1 was 9.6 +/- 3.4, 13.6 +/- 5.1 and 17.4 +/- 6.1 min, respectively (P less than 0.05 between the elderly and young adults). There was no significant difference in any of the parameters between the young adults and the middle-aged. The onset of block at each dose was not significantly different between the three age groups; however, the time to maximum effect was significantly shorter with the higher dose in the young and the middle-aged, but not in the elderly. Regression analysis of the data between age and the duration of action and recovery index suggested a significant prolongation (P less than 0.05) of these parameters in the elderly.

Adult↗
PubMed1992

Event-related potentials elicited by deviant endings to melodies.

Event-related potentials were recorded from scalp electrodes while subjects listened to well-known melodies. The melodies ended either with the expected note or with a different note. This design was a nonlinguistic analogue of the design used by Kutas and Hillyard (1980b), who first reported that anomalous terminal words in sentences elicited N400 potentials. However, Besson and Macar (1987) reported that deviant terminal notes in melodies did not elicit N400 potentials. In the present study, additional time was allowed for expectations to develop for the terminal note. Deviant terminal notes did not elicit N400s. In both studies, however, the deviant notes elicited P300-like waves. This outcome raised the possibility that N400 might have been masked by the positive potential. In a second condition in which P300 amplitude was minimized, N400s were again not evident. These results thus illustrate two additional situations in which nonlinguistic stimuli that deviated from a sequential pattern failed to elicit N400 potentials.

Adult↗
PubMed1992

A new X linked syndrome with mental retardation and craniofacial dysmorphism?

We present a syndrome manifested in two half brothers and their two maternal aunts which is characterised in the two boys by severe mental retardation and craniofacial dysmorphism (broad, coarse features and marked plagiocephaly with flattened occiput), and in the aunts merely by moderate mental retardation without dysmorphic features. The brothers do not seem to fall into any previously described X linked syndrome with mental retardation.

Abnormalities, Multiple↗