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R A Macdonell

Publications and source records attributed to R A Macdonell.

28 records · Page 2Linked to original sources
PubMed1991

Hemispheric threshold differences for motor evoked potentials produced by magnetic coil stimulation.

A brief monophasic pulse through an electromagnetic coil preferentially activates motor pathways of each hemisphere, depending on the direction of coil current flow. Using the preferred direction for each hemisphere, the minimum stimulus intensity (threshold) that evoked compound muscle action potentials in the contralateral abductor digiti minimi (ADM) muscle was significantly less for the left hemisphere than the right. Threshold for biceps on each side was significantly higher than ADM, but there was no side-to-side difference. Assessing handedness using a standard handedness index, those who had less tendency to use the right hand for everyday tasks had greater differences between hemispheres for ADM thresholds. The lower threshold of the left-hemisphere projection to hand muscles is probably related to the asymmetry of corticomotoneuronal monosynaptic connections; a greater number project to the motor neuron pool of the right- than left-hand muscles.

Action Potentials↗
PubMed1990

Carpal tunnel syndrome: which finger should be tested? An analysis of sensory conduction in digital branches of the median nerve.

Each digital branch of the median nerve was stimulated in turn in 34 women (55 hands) with carpal tunnel syndrome (CTS). The amplitude and conduction velocity of the sensory nerve action potential (SNAP) recorded at the wrist, and the threshold for patient perception of the electrical stimulus on the median innervated sides of each digit, were compared with the corresponding values in a group of asymptomatic, age-matched women. Sensory conduction velocity or SNAP amplitude were abnormal in more than 80% of all digital nerves studied apart from those in the index finger. Stimulation of digital nerves in the index finger proved the least sensitive means of detecting the electrophysiological abnormality. We conclude that selective digital nerve stimulation is a sensitive technique in the diagnosis of CTS. If ring electrodes are preferred, our results suggest that the middle rather than the index finger should be used.

Action Potentials↗
PubMed1989

A comparison of somatosensory evoked and motor evoked potentials in stroke.

Nineteen patients with radiologically confirmed stroke, and varying degrees of hemiparesis, were studied using somatosensory evoked potentials and the recently developed technique of transcutaneous motor cortex stimulation. The functional deficit caused by stroke was assessed at the time of evoked potential testing and again on follow-up 2 months after stroke. Stroke location and degree of recovery were compared with the evoked potentials elicited an average of 8 days after the acute event. The motor response was better (p less than 0.01) than somatosensory response at predicting an outcome in terms of functional recovery, both overall and when comparing patients with similar degrees of weakness. Normal somatosensory evoked potentials also predicted recovery but were not as sensitive as the motor evoked potentials (0.01 less than p less than 0.05). Motor evoked potentials in conjunction with clinical assessment may offer a means of more accurately predicting functional outcome following stroke than can be achieved with clinical assessment, with or without somatosensory evoked potentials. The additional finding that cortically evoked motor evoked potentials were delayed only by subcortical lesions is of interest and may extend the understanding of the pathophysiological mechanism of this response in humans.

Aged↗
PubMed1989

Intrathecal baclofen and the H-reflex.

Baclofen was given intrathecally to six patients with severe lower limb spasticity due to traumatic spinal cord injury. The effects of the drug on spasticity and the ratio between the maximum amplitude of the H reflex and the M response from the soleus (Hmax/Mmax ratio) were assessed. In each patient, spasticity was reduced following intrathecal baclofen and in four patients there was a reduction in the amplitude of the H reflex and Hmax/Mmax ratio. These results suggest that the Hmax/Mmax ratio may be helpful in establishing optimum drug dosage, particularly when the drug is used on a chronic basis.

Adult↗
PubMed1988

The electroencephalogram and acute ischemic stroke. Distinguishing cortical from lacunar infarction.

One hundred consecutive cases of clinically diagnosed, acute forebrain infarction were studied using computerized tomography (CT) and electroencephalography (EEG). Computed tomography confirmed brain infarction in 91 patients and was normal in the remaining nine. Each EEG was read independently by two experienced electroencephalographers without knowledge of CT or clinical details and their findings were compared with those of CT. Lateralized theta and/or delta activity predicted ipsilateral cortical infarction with a sensitivity of 76% and specificity of 82%. In contrast, cerebral hemisphere lacunae produced similar EEG abnormalities in only a few cases (9%). Electroencephalography is particularly useful following stroke if the initial CT excludes hemorrhage but does not detect infarction. In conjunction with clinical details, the EEG can then be used to indicate the likelihood of cortical involvement and thus suggest the likely pathophysiologic mechanism of infarction.

Acute Disease↗
PubMed1987

Otocerebral mucormycosis--a case report.

Mucormycosis is an often fatal infection caused by ubiquitous organisms of the order Mucorales. Infection is most commonly seen in the immunocompromised host, particularly in the setting of diabetic ketoacidosis. The most common presentation is with rhinocerebral involvement. We here report a case of otocerebral mucormycosis occurring in an elderly man with maturity onset diabetes who was not acidotic. The unusual site of infection delayed diagnosis until the pons had been invaded by the infecting organism which was demonstrated as a hypodense area on CT scan. Consequently radical excision of infected tissue was not feasible and the patient died. At post-mortem examination there was extensive infection and infarction of the parotid gland, inner ear and pons associated with arterial invasion by the fungus and septic cavernous sinus thrombosis. The case is described to demonstrate the existence of other modes of neurological presentation of mucormycosis apart from the well recognized rhinocerebral form. Early diagnosis is the key to successful therapy.

Aged↗
PubMedDate not supplied

Serial changes in somatosensory evoked potentials following cerebral infarction.

The relationship between somatosensory evoked potentials (SEPs) and recovery from stroke was investigated in 12 patients. All had suffered recent cerebral infarction. SEPs were performed within the first week, 6 weeks, 3 months and 6 months after stroke onset. Improvement of initially abnormal SEPs was maximal in the first 6 weeks and this correlated closely with the period of maximum clinical improvement. The results of this study suggest that the major effect of stroke on SEPs occurs acutely and is little affected by secondary degenerative processes.

Aged↗
PubMedDate not supplied

Interrater reliability of the National Institutes of Health Stroke Scale: rating by neurologists and nurses in a community-based stroke incidence study.

The reliability of the National Institutes of Health Stroke Scale (NIHSS) for use by trained neurologists in clinical trials of acute stroke has been established in several hospital-based studies. However, it also has the potential for application in community-based settings and to be used by nonneurologists: issues which have not been explored before. Hence, we aimed to determine the reliability of the NIHSS when administered by research nurses within the existing North Eastern Melbourne Stroke Incidence Study. Using the NIHSS, thirty-one consecutively registered stroke patients were assessed by 2 neurologists and 1 of 2 trained research nurses. The interrater reliability of observations was compared using weighted and unweighted kappa statistics and intraclass correlation coefficients (ICC). There was a high level of agreement for total scores between the 2 neurologists (ICC = 0.95) and between each neurologist and research nurse (ICC = 0.92 and 0.96). While there was moderate to excellent agreement among neurologists and research nurse (weighted kappa > 0.4) for the majority of the NIHSS items, there was poor agreement for the component 'limb ataxia'. Overall, agreement between nurse and neurologist for individual items was not significantly different from agreement between neurologists. It appears that in both hospital and community settings, trained research nurses can administer the NIHSS with a reliability similar to stroke-trained neurologists. This ability could be used to advantage in large community-based trials and epidemiological studies.

Australia↗
PubMedDate not supplied

Cerebellar infarction: natural history, prognosis, and pathology.

Using clinical and computed tomography (CT) criteria, an analysis of 2,000 consecutive stroke unit patients from 1977 to 1984 revealed 30 patients with cerebellar infarction. The case fatality rate was 23%, higher than for any other location of brain infarction studied over the same period. Death was most often due to concomitant brainstem infarction. Obstructive hydrocephalus occurred in 4 patients (13%), and in 2 cases diagnosis, facilitated by urgent CT scanning, allowed early surgical intervention that was life saving. Patients who survived the acute phase were followed for an average of 21 months, and over that time 22% sustained further brainstem infarction, representing a 13% stroke rate per year. Over the latter 3 years of the clinical study, an autopsy survey revealed 11 cases of cerebellar infarction that had been clinically unrecognized. None of these died as a direct result of their infarction. Mechanisms of infarction inferred from autopsy included in situ thrombosis, embolism, watershed, and lacunar infarction, with in situ thrombosis being the most common. We conclude that the case fatality rate of cerebellar infarction is greater than of any other form of brain infarction, but it may be reduced by prompt recognition of those patients who will benefit from surgical decompression. In survivors, a high risk of subsequent hindbrain stroke exists. More attention needs to be paid to this entity in terms of early diagnosis and prevention of subsequent stroke.

Aged↗