James Howells

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This study investigated whether there are changes in the excitability of motor axons in peripheral nerves of patients with corticospinal lesions, reflecting plasticity of the motoneuron due to altered descending drives and/or changes in afferent feedback. The excitability of motor and sensory axons in peripheral nerves of the affected limb of 11 patients(More)
HCN channels are responsible for I(h), a voltage-gated inwardly rectifying current activated by hyperpolarization. This current appears to be more active in human sensory axons than motor and may play a role in the determination of threshold. Differences in I(h) are likely to be responsible for the high variability in accommodation to hyperpolarization seen(More)
Subthreshold electrical stimuli can generate a long-lasting increase in axonal excitability, superficially resembling the phase of superexcitability that follows a conditioning nerve impulse. This phenomenon of 'subthreshold superexcitability' has been investigated in single motor axons in six healthy human subjects, by tracking the excitability changes(More)
Abstract  Hyperthermia challenges the nervous system's ability to transmit action potentials faithfully. Neuromuscular diseases, particularly those involving demyelination have an impaired safety margin for action potential generation and propagation, and symptoms are commonly accentuated by increases in temperature. The aim of this study was to examine the(More)
Conventional paired-pulse transcranial magnetic stimulation (TMS) techniques of assessing cortical excitability are limited by fluctuations in the motor evoked potential (MEP) amplitude. The aim of the present study was to determine the feasibility of threshold tracking TMS for assessing cortical excitability in a clinical setting and to establish normative(More)
Spinal lesions produce plastic changes in motoneuron properties. We have documented the excitability of motor axons in the median nerve of 12 patients with multiple sclerosis and 50 normal subjects, hypothesizing that plastic changes in the properties of spinal motoneurons might be reflected in the properties of peripheral motor axons and be demonstrable in(More)
PURPOSE To compare the effect of flap-off epi-LASIK versus automated brush epithelial removal on pain and wound healing in low myopic photorefractive keratectomy (PRK). METHODS In this prospective intraindividual study 60 patients received surface ablation in each eye. Epithelial removal was performed by an automated brush technique in one eye (brush(More)
A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast K(+) channels, at least in patients with demyelinating diseases. This study investigates the genesis of(More)
1 Watson PG, Jakeman C, Ozturk M, et al. The complications of trabeculectomy (a 20-year followup). Eye 1990;4:425–38. 2 Chiou AGY, Mermoud A, Hédiguer SEA, et al. Ultrasound biomicroscopy of eyes undergoing deep sclerectomy with collagen implant. Br J Ophthalmol 1996;80:541–4. 3 Sacks ZS, Kurtz RM, Juhasz T, et al. High precision subsurface photodisruption(More)
OBJECTIVE Potassium (K(+)) has been implicated as a factor in the development of uraemic neuropathy. This study was undertaken to investigate whether hyperkalaemia plays a causal role in axonal dysfunction in end-stage kidney disease (ESKD). METHODS Median motor nerve excitability studies were undertaken in four haemodialysis patients during a modified(More)