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Biomedical subjects

Philip D Thompson

Publications and source records attributed to Philip D Thompson.

18 recordsLinked to original sources
PubMed2006

Early investigation and treatment of obstructive sleep apnoea after acute stroke.

Obstructive sleep apnoea (OSA) is an independent risk factor for hypertension, which is a major cause of stroke. The prevalence and associations of OSA in a cohort of stroke patients were studied. The safety and tolerability of early treatment with nasal continuous airways pressure (nCPAP) was also assessed. Consecutive subjects admitted with acute stroke were assessed clinically, radiologically and with scales assessing prior OSA risk, dysphagia and disability. Sleep studies were performed within the first few days of admission using a portable diagnostic system. Twenty-nine of 55 (53%) subjects had evidence of OSA, using an apnoea-hypopnoea index (AHI) of 10 or greater. The AHI was significantly associated with an index of prior OSA symptoms, but not with history of hypertension, degree of dysphagia, or type and severity of stroke. Use of a portable diagnostic system for detecting OSA in the acute stroke setting was well tolerated. OSA is common after acute stroke and exceeds rates seen in control populations of similar age (53% vs. 11%). Early treatment with nCPAP was effective and well tolerated.

Acute Disease↗
PubMed2005

Immunohistochemical staining of epoxy resin sections of peripheral nerve.

The authors describe a simple and cost-effective method of immunostaining semithin epoxy resin sections of peripheral nerve for light microscopy with antibodies to myelin protein zero, peripheral myelin protein 22, myelin basic protein, and neurofilament protein 200 using a combined technique of surface etching with sodium ethoxide and heat-induced antigen retrieval.

Antibodies↗
PubMed2004

Interhemispheric coupling of corticospinal excitability is suppressed during voluntary muscle activation.

Motor-evoked potentials (MEPs) after transcranial magnetic stimulation (TMS) show a trial-to-trial variation in size at rest that is positively correlated for muscles of the same, and opposite, upper limbs. To investigate the mechanisms responsible for this we have examined the effect of voluntary activation on the correlated fluctuations of MEP size. In 8 subjects TMS was concurrently applied to the motor cortex of each hemisphere using 2 figure-8 coils. MEPs (n = 50) were recorded from left and right first dorsal interosseous (FDI), abductor digiti minimi (ADM), and extensor digitorum communis. At rest, MEPs were significantly positively correlated for pairs of muscles of the same (75% of comparisons) and opposite limb (56% of comparisons). The correlation for within-limb muscle pairs was strongest for FDI and ADM. In contrast, between-limb MEP correlations showed no somatotopic organization. Voluntary activation reduced the strength of MEP correlations between limbs, even for muscle pairs that remained at rest while a remote upper limb muscle was active. In contrast, activation of a remote muscle did not affect the strength of MEP correlation for muscle pairs within the same limb that remained at rest. For within-limb comparisons, activation of one or both muscles of a pair reduced the strength of the MEP correlation, but to a lesser extent than for between-limb pairs. It is concluded that the process linking corticospinal excitability in the two hemispheres is suppressed during voluntary activation, and that different processes contribute to common fluctuations in MEP size for muscles within the same limb.

Adult↗
PubMed2004

Peripheral nervous system and central nervous system pathology in rapidly progressive lower motor neuron syndrome with immunoglobulin M anti-GM1 ganglioside antibody.

Pathological studies, including novel teased peripheral nerve fiber studies, were performed in a patient who presented with a rapidly progressive, lower motor neuron syndrome and high titer of immunoglobulin M anti-GM1 ganglioside antibody. In the central nervous system, there was a severe loss of motor neurons and central chromatolysis with ubiquitin immunopositive cytoplasmic inclusions in residual motor neurons. In the peripheral nervous system, axonal degeneration of myelinated fibers in the anterior nerve roots was evident. Pathologic evidence of sensory nerve involvement was also found despite the absence of clinical or electrophysiological sensory abnormalities. Sectional studies of single myelinated nerve fibers from an antemortem sural nerve biopsy showed remyelination and globular paranodal swellings due to focal complex myelin folding and degeneration in 13% of fibers. Postmortem studies of the sural nerves 4 weeks later showed paranodal demyelination (90% of fibers), but no paranodal swellings and similar findings were present in samples of the ulnar, radial, median, tibial, and common peroneal nerves. Paranodal abnormalities of enlargement of the adaxonal space, myelin degeneration, and axonal compaction were found on cross-sectional studies of individual teased fibers, which on conventional light microscopic assessment appeared normal. These changes suggest a disturbance of paranodal axonal-myelin adhesion due to binding of the anti-GM1 ganglioside antibody to the common epitope known to be present on the myelin sheath and nodal axolemma in the paranodal region of both motor and sensory nerves.

Adult↗
PubMed2003

Is the long-latency stretch reflex in human masseter transcortical?

A long-latency stretch reflex (LLSR) has been described in the human masseter muscle, but its pathway remains uncertain. To investigate this, the excitability of corticomotoneuronal (CM) cells projecting to masseter motoneurons during the LLSR was assessed with transcranial magnetic stimulation (TMS). A facilitated response to TMS would be evidence of a LLSR pathway that traverses the motor cortex. Surface electromyogram electrodes were placed over the left or right masseter, and subjects ( n=10) bit on bars with their incisor teeth at 10% of maximal electromyographic activity (EMG). Servo-controlled displacements were imposed on the lower jaw to evoke a short- and long-latency stretch reflex in masseter. TMS intensity was just suprathreshold for a response in contralateral masseter. Trials consisted of: (1) stretch alone, (2) TMS alone, and (3) TMS with a preceding conditioning stretch at varied conditioning-testing (C-T) intervals chosen to combine TMS with the short-latency stretch reflex (3 ms, 5 ms) and the LLSR (23-41 ms). Masseter EMG was rectified and averaged. With TMS alone, mean (+/- SE) MEP area above baseline was 56+/-9%. The area of masseter MEPs above baseline in the C-T trials was calculated from each EMG average following subtraction of the response to stretch alone. Conditioning muscle stretch had no significant effect on masseter MEPs evoked by TMS with any C-T interval (ANOVA; P=0.90). In addition, subjects were unable to modify the SLSR or LLSR by voluntary command. It is concluded that the long-latency stretch reflex in the masseter does not involve the motor cortex and is not influenced by "motor set".

Adult↗
PubMed2003

Prolonged peripheral nerve stimulation induces persistent changes in excitability of human motor cortex.

This study sought to determine whether prolonged peripheral nerve stimulation was effective in inducing persistent "plastic" changes in the excitability of the human motor cortex. The amplitude of the electromyographic response evoked in resting intrinsic hand muscles by focal transcranial magnetic stimulation (TMS) was taken as an index of motor cortical excitability. Twelve subjects were stimulated with each of three protocols, one of which was given on each of three separate occasions. The protocols consisted of various schedules of electrical stimulation of the radial and ulnar nerves or the motor point of the first dorsal interosseous muscle (FDI), or stimulation of FDI motor point paired with low-frequency TMS. Amplitudes of TMS-elicited motor evoked potentials (MEPs) were measured before peripheral stimulation and for 2 h after stimulation. The data from one subject were unusable. In every other subject, all three protocols induced a prolonged, significant facilitation of MEPs in at least some of the three intrinsic hand muscles used. In some instances, MEPs were not enlarged and occasionally were significantly depressed. Different protocols based on peripheral afferent stimulation can induce plastic changes in the organisation of the motor cortex that persist for at least 2 h.

Adult↗
PubMed2003

Responses of single motor units in human masseter to transcranial magnetic stimulation of either hemisphere.

The corticobulbar inputs to single masseter motoneurons from the contra- and ipsilateral motor cortex were examined using focal transcranial magnetic stimulation (TMS) with a figure-of-eight stimulating coil. Fine-wire electrodes were inserted into the masseter muscle of six subjects, and the responses of 30 motor units were examined. All were tested with contralateral TMS, and 87 % showed a short-latency excitation in the peristimulus time histogram at 7.0 +/- 0.3 ms. The response was a single peak of 1.5 +/- 0.2 ms duration, consistent with monosynaptic excitation via a single D- or I1-wave volley elicited by the stimulus. Increased TMS intensity produced a higher response probability (n = 13, paired t test, P < 0.05) but did not affect response latency. Of the remaining motor units tested with contralateral TMS, 7 % did not respond at intensities tested, and 7 % had reduced firing probability without any preceding excitation. Sixteen of these motor units were also tested with ipsilateral TMS and four (25 %) showed short-latency excitation at 6.7 +/- 0.6 ms, with a duration of 1.5 +/- 0.3 ms. Latency and duration of excitatory peaks for these four motor units did not differ significantly with ipsilateral vs. contralateral TMS (paired t tests, P > 0.05). Of the motor units tested with ipsilateral TMS, 56 % responded with a reduced firing probability without a preceding excitation, and 19 % did not respond. These data suggest that masseter motoneurons receive monosynaptic input from the motor cortex that is asymmetrical from each hemisphere, with most low threshold motoneurons receiving short-latency excitatory input from the contralateral hemisphere only.

Adult↗
PubMed2003

Time to hospital admission for acute stroke: an observational study.

OBJECTIVES: To determine the time from symptom onset to hospital admission of patients with suspected acute stroke, final diagnoses and patient eligibility for thrombolytic therapy. DESIGN: Hospital-based, prospective, observational study. SETTING: Royal Adelaide Hospital Stroke Unit, South Australia. PATIENTS: All patients admitted to the unit with suspected acute stroke over 11 months (11 April to 10 October 2000 and 20 August 2001 to 19 January 2002). MAIN OUTCOME MEASURES: Time from symptom onset to admission; final diagnosis. RESULTS: Of 284 patients admitted, 39 (14%) had diagnoses other than stroke (including eight with transient ischaemic attacks), 42 (15%) had haemorrhagic stroke and 203 (71%) had ischaemic stroke. Median time to admission after symptom onset was 6 hours (range, 30 min to 13 days), with 100 patients admitted within 3 hours of symptom onset (35%), and 80 within 2 hours (28%). Thirty-seven patients (13%) could have been considered for thrombolysis (diagnosis of non-severe but disabling ischaemic stroke and admission time < 3 hours). Location at stroke onset was the only independent predictor of time to admission. CONCLUSIONS: Most patients with stroke do not present urgently to the emergency department, rendering them less likely to be considered for thrombolytic therapy.

Adult↗
PubMed2003

Myoclonus in spinal dysraphism.

Two cases of segmental myoclonus occurring in association with spinal dysraphism are described. In one, myoclonus of paralysed legs arose below a region of spinal cord lacking any normal function, illustrating the capacity of the isolated spinal cord to generate and maintain rhythmic activity independent of supraspinal influences.

Adolescent↗
PubMed2003

Brainstem myoclonus in generalised tetanus.

Electrophysiological studies of stimulus sensitive myoclonus in a man with generalised tetanus revealed features characteristic of hyperekplexia or brainstem myoclonus.

Brain Stem↗
PubMed2002

Induction of persistent changes in the organisation of the human motor cortex.

Motor learning must involve changes in the organisation of the brain, and it seems axiomatic that afferent signals generated during repeated motor practice contribute to this. In this study, motor-point stimulation of the first dorsal interosseous (FDI) muscle was paired with transcranial magnetic stimulation of the human motor cortex on three successive days to determine whether repeated stimulation sessions result in enduring reorganisation of the motor cortex. This repeated "dual" stimulation induced significant changes in the excitability of the motor cortex together with expansion of the area of scalp from which these responses were elicited. The expansion in muscle representation was accompanied by large movements in the centre of gravity (CoG), suggesting a true reorganisation of the underlying cortical representational zone. The changes persisted for at least 2 days following the last stimulation session. It is concluded that repeated dual stimulation is capable of inducing long-lasting reorganisation within the motor cortex. These changes may be similar in nature to those seen in the motor cortex during motor learning. Moreover, these observations suggest that it may be possible to induce the motor cortex of patients who have suffered strokes to reorganise in a way that improves the voluntary control of the weakened muscles.

Adult↗
PubMed2002

Disordered respiration as a levodopa-induced dyskinesia in Parkinson's disease.

Symptomatic respiratory disturbance as a consequence of levodopa (L-dopa) therapy for Parkinson's disease (PD) has been described only rarely and may be underrecognized in clinical practice. We report on two patients with PD in whom the introduction or augmentation of L-dopa therapy was associated with the development of irregular and rapid breathing. Analysis of breathing patterns before and after L-dopa demonstrated a striking change in respiratory rate after administration of L-dopa, with the emergence of irregular tachypnea alternating with brief periods of apnea, in a pattern consistent with a central origin. In both cases, the temporal relationship of the respiratory disturbance to the administration of L-dopa suggested a peak-dose drug effect. Previous reports of L-dopa-induced respiratory dyskinesia are reviewed, and the potential mechanisms whereby L-dopa might influence the central control of respiration to produce irregular breathing patterns are discussed.

Aged↗
PubMed2002

Stiff man syndrome and related conditions.

The stiff man syndrome (SMS) and its variants, focal SMS, stiff limb (or leg) syndrome (SLS), jerking SMS, and progressive encephalomyelitis with rigidity and myoclonus (PERM), appear to occur more frequently than hitherto thought. A characteristic ensemble of symptoms and signs allows a tentative clinical diagnosis. Supportive ancillary findings include (1) the demonstration of continuous muscle activity in trunk and proximal limb muscles despite attempted relaxation, (2) enhanced exteroceptive reflexes, and (3) antibodies to glutamic acid decarboxylase (GAD) in both serum and spinal fluid. Antibodies to GAD are not diagnostic or specific for SMS and the role of these autoantibodies in the pathogenesis of SMS/SLS/PERM is the subject of debate and difficult to reconcile on the basis of our present knowledge. Nevertheless, evidence is emerging to suggest that SMS/SLS/PERM are manifestations of an immune-mediated chronic encephalomyelitis and immunomodulation is an effective therapeutic approach.

Adult↗
PubMed2002

Rhabdomyolysis: a review.

Rhabdomyolysis, a syndrome of skeletal muscle breakdown with leakage of muscle contents, is frequently accompanied by myoglobinuria, and if sufficiently severe, acute renal failure with potentially life-threatening metabolic derangements may ensue. A diverse spectrum of inherited and acquired disorders affecting muscle membranes, membrane ion channels, and muscle energy supply causes rhabdomyolysis. Common final pathophysiological mechanisms among these causes of rhabdomyolysis include an uncontrolled rise in free intracellular calcium and activation of calcium-dependent proteases, which lead to destruction of myofibrils and lysosomal digestion of muscle fiber contents. Recent advances in molecular genetics and muscle enzyme histochemistry may enable a specific metabolic diagnosis in many patients with idiopathic recurrent rhabdomyolysis.

Humans↗
PubMed2002

Tomacula in MAG-deficient mice.

The pathogenesis of tomacula in mice with a null mutation of the myelin-associated glycoprotein (MAG) gene is not well understood. This study, using a novel teased nerve fiber technique, demonstrates that tomacula in MAG-deficient mice are formed by redundant myelin infoldings and outfoldings in the paranodal regions as early as 4 weeks after birth and increase in size and frequency with age. Although tomacula show degenerative changes with increasing age, there was no significant evidence of demyelination/remyelination. Longitudinal sections of normal teased nerve fibers show early redundant myelin foldings in externally normal paranodal regions. These data and the absence of internodal tomacula support a role for MAG in the maintenance of myelin at the paranodal regions.

Animals↗
PubMed2002

Pathological evidence of encephalomyelitis in the stiff man syndrome with anti-GAD antibodies.

We report the case of a 57 year old woman with typical clinical features of the stiff man syndrome (SMS) and antibodies to glutamic acid decarboxylase (antiGADAb), who developed a supranuclear gaze palsy, ileus and died of bronchopneumonia eight years after the onset of illness. Post mortem examination revealed perivascular lymphocyte cuffing throughout the cerebral hemispheres, brainstem and spinal cord and neuronal loss in medial anterior horns of the cervical spinal cord. These findings support the notion that the SMS and progressive encephalomyelitis with rigidity (PER) form a clinical and pathologic continuum.

Antibodies↗
PubMed1999

An 'annoying' foot: unilateral painful legs and moving toes syndrome.

The syndrome of painful legs and moving toes is an uncommon condition causing distressing leg pain and is recognised chiefly by the characteristic involuntary movements. This case report describes an unusual unilateral clinical presentation, which led to a delay in diagnosis.

Aged↗