Intravenous immunoglobulin for multifocal motor neuropathy.
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Female↗
Biomedical subjects
W M Carroll
Publications and source records attributed to W M Carroll.
Late radiation associated neurological injury.
Late radiation-associated neurological injury is a recognised and often fatal complication of therapeutic ionising radiation. This retrospective study outlines its highly variable presentation, radiological findings and prognosis over a 6 year period in a major teaching hospital.
Acute Disease↗
Saccade onset and offset lambda waves: relation to pattern movement visually evoked potentials.
The lambda (lambda) wave is an occipital EEG potential which occurs when saccadic eye movements are made against an illuminated contrast background. There is some disagreement concerning the presence of sub-components to the lambda-wave, and its relationship to visually evoked potentials. In the present study, lambda-waves were recorded with saccades of different durations (30-110 ms) and compared to VEPs associated with pattern movements of similar durations and velocity. It was found that the lambda-wave consisted of a saccade onset component with positive sub-components at 59 and 100 ms after saccade onset, and a saccade offset component with a positive potential at 74 ms after saccade offset. With small saccades of 30 ms duration or less, these components superimposed to form a single lambda-wave. In the case of pattern movement VEPs, a movement onset component of latency 110 ms following movement onset, and a movement offset component at 89 ms after movement offset, were identified. The similar behaviour of the lambda-wave and VEP under these conditions supports the view that the lambda-wave is a visually evoked potential resulting from movement of the visual field across the retina during a saccadic eye movement.
Adult↗
Intraoperative spinal cord monitoring.
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Electrophysiology↗
The origin of remyelinating oligodendrocytes in antiserum-mediated demyelinative optic neuropathy.
The origin of the remyelinating oligodendrocyte in a focal antigalactocerebroside-induced demyelinating lesion of the cat optic nerve was studied with detailed correlative electron microscopy and immunocytochemistry using a panel of antigenic markers. Within 10 days of the destruction of all endogenous oligodendrocytes and demyelination of all axons in the lesion, a new population of small glial cells appeared coincident with division of the residual astrocytes and developed a process-bearing axon-embracing morphology. The processes of these small glial cells (SGCs) contained intermediate filaments composed not of glial fibrillary acidic protein but of vimentin and over the ensuing 14 days these cells confirmed their oligodendrocyte destiny by differentiating to lose the intermediate filaments, form myelin and acquire the acquire the typical oligodendrocyte antigenic phenotype. It is suggested that the extensive remyelination of this lesion is sponsored by the new population of SGCs which in turn are generated either by dedifferentiated reactive astrocytes or by as yet unidentified precursor cells.
Animals↗
Blink reflexes and magnetic resonance imaging in focal unilateral central trigeminal pathway demyelination.
The electrically elicited blink reflex allows quantitative analysis of the corneal reflex which traverses the trigeminal and facial nerves and the brainstem. Two patients presenting with symptomatic unilateral trigeminal lesions are described, in whom the blink reflexes showed conduction block and slowing at predictable sites in the central pathways, and magnetic resonance imaging confirmed precisely the clinical and electrophysiological localisation.
Adult↗
Spinal cord lesions induced by antigalactocerebroside serum.
The spinal cord lesions induced by micro-injection of high titre anti-galactocerebroside serum (anti-GC) into the dorsal columns of the rat were studied by light and electron microscopy. The lesions typically comprised a central zone of Wallerian-type degeneration surrounded by pockets of primary demyelination. Both oligodendrocytes and astrocytes were reduced in the lesions. Demyelination also occurred in the dorsal roots. Evidence of remyelination by oligodendrocytes and by Schwann cells was found in the 10 to 12 day cord lesions. The dorsal column lesions differ from the optic nerve lesions induced by anti-GC which are almost exclusively demyelinative, and in which astrocytes are largely spared and remyelination is more prominent.
Animals↗
"Alien hand" and loss of bimanual coordination after dominant anterior cerebral artery territory infarction.
Three patients with dominant anterior cerebral artery territory infarction demonstrated a severe disturbance of upper limb motor control with impaired bimanual coordination, the "alien hand" sign, and intermanual conflict, in addition to signs of callosal interruption and a transcortical motor aphasia. Recordings of movement-related potentials in one patient showed an attenuated Bereitschaftspotential and a greater asymmetry of the NS' component of the premotor negativity with left finger than with right finger movement. The impairment of bimanual motor control and associated abnormal motor behaviour of the right hand in these cases are postulated to be due to involvement of the supplementary motor area and related areas of the medial frontal cortex.
Aged↗
Reactive glial cells in CNS demyelination contain both GC and GFAP.
The glial cell response to anti-galactocerebroside (GC) induced demyelination of the cat optic nerve was studied using electron microscopy and immunocytochemistry. Oligodendrocytes, which are a primary target for anti-GC, were depleted in the early lesions but astrocytes survived and showed reactive changes. Astrocytic processes exhibited dual staining for both GC and glialfibrillary acidic protein, a feature not seen in astrocytes outside the lesion or in normal optic nerve. These reactive astrocytes did not stain for anti-myelin basic protein, nor did they contain myelin debris, making it unlikely that the GC immunoreactivity was due to phagocytosis of myelin. Rather, it is postulated that the presence of GC in these cells represents a process of dedifferentiation to a more primitive state in which both astrocytic and oligodendrocytic determinants are synthesised, and that these reactive glial cells may be precursors of a new population of remyelinating oligodendrocytes.
Animals↗
Crossed facilitation and post-contraction depression of abductor pollicis brevis motor neurons.
Crossed facilitation of abductor pollicis brevis (APB) motor neurons by voluntary contraction of the contralateral APB was investigated using F response analysis. The integrated F response EMG showed a mean 4-fold increase during contraction. This enhancement was maintained until the onset of subjective fatigue and then declined. After isometric or isotonic contraction of the ipsilateral APB there was a significant depression of F responses with a progressive return to baseline values over a 6 minute period. The significance of the findings is discussed.
Adult↗
Averaging, spatio-temporal mapping and dipole modelling of focal epileptic spikes.
A computer-based technique is described for the acquisition, spatio-temporal mapping and dipole modelling of epileptic spike events. Spike acquisition is operator-controlled and subsequent data processing is performed off-line. Preliminary averaging and topographical display of wave forms provide complementary information on the spike field. The method promises to be a useful adjunct to conventional EEG in spike analysis.
Brain↗
Effects of hyperventilation on pattern-reversal visual evoked potentials in patients with demyelination.
The effects of hyperventilation on the pattern-reversal visual evoked potential (VEP) were studied in seven normal subjects and 13 multiple sclerosis patients with visual pathway involvement. Significantly greater reductions in P100 latency occurred in the multiple sclerosis patients than in controls and normalisation of the half-field response topography occurred in one patient after hyperventilation. The VEP changes are attributed to improved impulse transmission in demyelinated fibres in the visual pathway as a result of the alkalosis and changes in ionised calcium levels induced by hyperventilation.
Adult↗
Anterior ischaemic optic neuropathy. A correlative clinical and visual evoked potential study of 18 patients.
The clinical and visual evoked potential (VEP) findings were analysed in 18 patients with anterior ischaemic optic neuropathy. The VEP studies showed a variety of abnormalities which could be interpreted as being the result of subcomponent interaction consequent upon loss or attenuation of the normal macular-derived P100 component. Delay of normal VEP subcomponents was not seen. The VEP findings were non-specific but pointed to a severe disturbance of transmission in optic nerve fibres subserving central vision. No significant changes were observed with time in most cases indicating a static monophasic process with no significant recovery.
Aged↗
Galactocerebroside antiserum causes demyelination of cat optic nerve.
A model of immune-mediated optic nerve demyelination is described. Micro-injection of small volumes (less than 5 microliter) of high titer polyclonal anti-Gal-C serum into the cat optic nerve resulted in a focal, highly selective demyelinative lesion followed by remyelination. Demyelination appears to be due to a dual effect on myelin and on oligodendrocytes. The numbers of these cells within the lesion were initially reduced but subsequently increased as remyelination occurred.
Animals↗
Dipole source derivation. Application to the half-field pattern evoked potential.
Dipole modelling is a technique for estimating the location of sources of electrical activity in the brain responsible for the generation of surface recorded potentials on the human scalp. A detailed description of this technique is given with a modification that allows for possible activity at the reference electrode during the surface potential measurement. The application of this technique to localisation of the source of the principal components of the left half-field pattern visual evoked potential is described.
Adult↗
Cerebral potentials accompanying visually triggered finger movement in man.
The cerebral potentials associated with visually triggered movements of the right index finger were studied in 5 normal subjects using multichannel scalp recordings and separate stimulus and movement-locked averaging. The visually locked wave forms showed enhanced components of the passive visual evoked potential (P1-N1) with a more widespread distribution than the VEP. The amplitude of the P1-N1 complex was influenced by the reaction time but its timing was independent of the timing of the movement. In a 'move'/'no move' choice paradigm, the positive components following the P1-N1 complex were attenuated with movement and subtraction of the 'move' and 'no move' wave forms showed a movement-related negativity building up over the contralateral parietal and central regions. With movement-locked averaging, a pre-motor negativity (PMN) of comparable topography and timing to the readiness potential was found when the timing of the cuing stimulus was regular. With randomly timed stimuli, the PMN still developed but then plateaued prior to movement. It is suggested that in this situation the PMN is related to an increasing level of arousal, anticipation and preparedness to move which is then maintained pending the arrival of the stimulus and the final motor command.
Adult↗
Management of extra-sellar pituitary tumours with bromocriptine: comparison of prolactin secreting and non-functioning tumours using half-field visual evoked potentials and computerised tomography.
To determine whether prolactin secreting and non-functioning pituitary tumours respond differently in terms of shrinkage to bromocriptine, we prospectively studied ten consecutive patients (five with prolactinomas and five with non-functioning tumours) complicated by extra-sellar extensions. No patient had received prior radiotherapy or bromocriptine and the mean dose and duration of bromocriptine treatment were identical in the two groups of patients. Objective evidence of tumour shrinkage was provided by serial half-field visual evoked potentials (VEPs) and computerised tomography (CT). All five prolactinomas were shown to shrink as assessed by improvement in VEP and four of the five as assessed by CT. In contrast, only one of the five patients with non-functioning tumours showed any improvement in VEP or CT. Macroprolactinomas frequently shrink rapidly when treated with bromocriptine, whereas non-functioning tumours seldom show such a dramatic response.
Adult↗
The effects of conditioning stimuli on the F-response.
The effect of conditioning stimuli on the F-response was investigated in normal subjects using stimulus pairs with interstimulus intervals of 1 to 400 ms. The "recovery curve" for the F-response was found to be similar to that for the H-reflex but differences were found between male and female subjects. The significance of these findings is discussed.
Adult↗