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Biomedical subjects

C F Bolton

Publications and source records attributed to C F Bolton.

At least 19 recordsLinked to original sources
PubMed1997

Subacute uremic and diabetic polyneuropathy.

We present 4 patients who had a subacute, predominantly motor polyneuropathy associated with diabetes mellitus and end-stage renal disease. Electrophysiological studies and muscle biopsy indicated a primary axonal degeneration of nerve with secondary segmental demyelination, and mild to moderate, acute and chronic denervation of muscle. A relative absence of denervation potentials on needle electromyography was an unusual feature. Three of our patients improved with a switch from conventional to high-flux hemodialysis. We speculate on possible mechanisms.

Aged↗
PubMed1996

Needle EMG of the human diaphragm: power spectral analysis in normal subjects.

Needle EMG of the diaphragm was performed in 43 diaphragms in 23 healthy volunteers. The mean +/- standard deviation for the median frequency (MF) of the power spectrum was 233.3 +/- 58.1 Hz. The MF increased with age and showed a negative correlation with the forced vital capacity (FVC), but there was no correlation with other anthropometric measures or the results of phrenic nerve conduction study. The higher MF in older subjects may be due to early recruitment of larger units. The negative correlation between MF and FVC is likely secondary to a lower level of contraction required for normal breathing in subjects with high FVC. The integrated EMG (iEMG) of each inspiration strongly correlated with the tidal volume and the duration of inspiration. Power spectral analysis of diaphragmatic EMG is feasible and reliable. It can be used to assess respiratory muscle fatigue and may help in the diagnosis of neuromuscular disorders affecting the diaphragm.

Adult↗
PubMed1996

Transcortical and cervical magnetic stimulation with recording of the diaphragm.

Transcortical and cervical magnetic stimulation is a potential method of examining the central inspiratory pathway to phrenic motor neurons. The reliability and accuracy of this technique were studied. We performed magnetic stimulations of the cortex and cervical spinal cord with recording from both hemidiaphragms in 35 normal subjects using two different stimulation coils (90-mm circular coil and 70-mm figure-of-eight coil). Needle electrode recordings and ultrasound real-time documentation in 2 subjects excluded volume-conducted contaminations from adjacent chest wall and abdominal muscles. The effect of diaphragmatic facilitation (stimulation at the end of a deep breath) on latency, and amplitude were compared to the effect of hypothenar muscle facilitation. Normal ranges were established for: latency; central motor conduction time; amplitude; amplitude ratio between between peripheral and both cortical and cervical amplitude; and excitability threshold. The latencies were similar for both coils. The amplitudes were significantly higher, and excitability thresholds significantly lower for the 90-mm circular coil, indicating that this coil is preferable for transcortical diaphragmatic stimulations. The effect of facilitation was greater for hypothenar than diaphragmatic recordings. There was excellent right-left agreement for all measurements. Transcortical and cervical magnetic stimulation with recording from the diaphragm can be used routinely to diagnose and monitor patients with impaired central respiratory drive.

Action Potentials↗
PubMed1996

Lambert-Eaton myasthenic syndrome presenting with severe respiratory failure.

Two cases of Lambert-Eaton myasthenic syndrome (LEMS) who presented with primary respiratory failure are reported. In each case, although not initially suspected clinically, the electrophysiological findings, which included reduced compound muscle action potential amplitudes, decrement to 3-Hz stimulation, and potentiation after 40-Hz stimulation, led to the diagnosis in the critical care unit. Electrophysiological studies of the respiratory system, including repetitive nerve stimulation of the phrenic nerve, were extremely valuable in management. As shown by these cases, the severe respiratory failure in LEMS is reversible with treatment. Thus, LEMS should be considered in cases of unexplained respiratory failure, other clinical features of the disorder sought, and the electrophysiological hallmarks looked for including studies of the respiratory system.

Action Potentials↗
PubMed1996

Brain mapping of median nerve somatosensory evoked potentials with combined 99mTc-ECD single-photon emission tomography and magnetic resonance imaging.

Single-photon emission tomography (SPET) was performed during electrical median nerve stimulation and used to detect focal neuronal activation in the somatosensory pathways. Intravenously administered technetium-99m ethyl cysteinate dimer (ECD) was used as a blood flow tracer to obtain baseline and activated images in each of three subjects. After image registration, baseline images were compared voxel by voxel with the activation images. In addition, the mean summation of the activated-state images of the subjects was compared with the mean summation of the baseline-state images of ten normal subjects. Discrete brain regions occupying 0.9%-1.6% of total brain volume showed an increase in signal from 33.6% to 35.0%. For further anatomical localization of regional increases in signal, the MRI scan of each subject was registered and superimposed on the activated-state SPET image. This method may be used to localize lesions in various disorders of the central nervous system.

Adult↗
PubMed1996

Plasma-exchange therapy in chronic inflammatory demyelinating polyneuropathy. A double-blind, sham-controlled, cross-over study.

Eighteen patients with definite, untreated chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) of chronic progressive (nine patients) or relapsing course (nine patients) were randomized prospectively to receive 10 plasma-exchange (PE) or sham plasma-exchange (SPE) treatments over 4 weeks in a double-blind trial. After a wash-out period of 5 weeks or when they returned to baseline scores, patients were crossed over to the alternate treatments. Neurological function was assessed serially using a quantitative neurological disability score (NDS), a functional clinical grade (CG) and grip strength (GS) measurements. Electrophysiological studies were done at the beginning and end of each treatment. A primary 'intention to treat' analysis showed significant improvement with PE in all clinical outcome measures: NDS by 38 points, P < 0.001; CG by 1.6 points, P < 0.001; GS by +13 kg, P < 0.003 and in selected electrophysiological measurements, sigma proximal CMAP, P < 0.01; sigma motor conduction velocities, P < 0.006; sigma distal motor latencies, P < 0.01. Fifteen patients completed the trial and of those, 12 patients (80%) improved substantially with PE; i.e. five out of seven patients with chronic progressive course and seven out of eight patients with relapsing CIDP improved. There were three drop-outs; one patient lost venous access; one patient suffered a stroke and one patient left the trial to receive open treatment elsewhere. The improvement in motor functions correlated with the electrophysiological data, i.e. with improved motor conduction velocities and reversal of conduction block. Eight of 12 PE responders (66%) relapsed within 7-14 days after stopping PE. All improved with subsequent open label PE; all but two patients required long-term immunosuppressive drug therapy for stabilization. The PE non-responders improved with prednisone. We conclude that PE is a very effective adjuvant therapy for CIDP of both chronic progressive and relapsing course; concurrent immunosuppressive drug treatment is required. Exchange treatments should be given two to three times per week until improvement is established; the treatment frequency should then be tapered over several months.

Adolescent↗
PubMed1996

Intravenous immunoglobulin treatment in chronic inflammatory demyelinating polyneuropathy. A double-blind, placebo-controlled, cross-over study.

Thirty patients with definite or probable chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) of chronic progressive (16 patients) or relapsing (14 patients) course were randomly assigned to receive intravenous immunoglobulin (IvIg) 0.4 g per kg body weight or a placebo treatment on 5 consecutive days in a double-blind, cross-over trial. Neurological function was monitored by serial quantitative assessments [neurological disability score (NDS); clinical grade (CG) and grip strength (GS) measurements] and by electrophysiological studies before and after each treatment period. Twenty-five patients completed both treatment periods. A comparison of the observed changes in clinical outcome measures revealed statistically significant differences in favour of IvIg, with (mean +/- SD) improvements in NDS by 24.4 +/- 5.4 points (P < 0.002) in CG by 1 +/- 0.3 points (P < 0.001) in GS by +6.3 +/- 1.7 kg (P < 0.005), whereas scores were unchanged or worse with placebo. A secondary two-groups analysis of the first trial period included all 30 patients; 16 patients had been randomly assigned to IvIg and 14 to placebo treatments. Again significant differences in favour of IvIg were observed in all the clinical end-points: improvement in NDS was 35.6 +/- 25 points (P < 0.0001), in CG it was 1.3 +/- 1.9 points (P < 0.002) and in GS +9.8 +/- 7.7 kg (P < 0.001), whereas all scores worsened with placebo. Of the 30 patients, 19 (63%) improved with IvIg treatments; nine out of 16 patients (56%) with chronic progressive CIDP, and 10 out of 14 patients (71%) with relapsing CIDP (differences were not statistically significant). A placebo response was seen in five patients. Comparison of paired electrophysiological measurements before and 4 weeks after IvIg treatments revealed statistically significant improvements in the summed motor conduction velocities (sigma MCV; P < -0.0001) and in the summed compound muscle action potentials (CMAP) evoked with proximal stimulation (sigma proximal CMAP, P < 0.03) of median, ulnar, peroneal and tibial nerves. Eight of nine IvIg responders with chronic progressive CIDP improved gradually to normal function with a single 5 day course of IvIg; in five of these, small doses of prednisone were prescribed during follow-up. In 10 IvIg responders with relapsing CIDP, improvements lasted a median 6 weeks (range 3-22 weeks) and was reproducible with open label treatments. All 10 patients have been maintained and stabilized with IvIg pulse therapy of 1 g per kg body weight or less, given as a single infusion prior to the expected relapse. A beneficial response to IvIg was found to be most likely in patients with acute relapse or with disease of one year or less. Patients with predominantly sensory signs did not improve.

Adolescent↗
PubMed1996

Central and peripheral respiratory electrophysiological studies in myotonic dystrophy.

Acute and chronic respiratory failure is a common and potentially life-threatening feature in patients with myotonic dystrophy (MD). The causes may be varied, and can involve both the central and peripheral nervous system. To evaluate the incidence of respiratory muscle involvement and the function of the central motor inspiratory pathway to phrenic motor neurons we performed magnetic stimulation of the cortex and cervical spinal cord, phrenic nerve conduction studies and needle EMG of diaphragm and intercostal muscles in 25 patients with MD. The results were compared with those from 35 healthy subjects. In addition, pulmonary function tests, blood gas analyses and static mouth pressures were evaluated. Abnormalities in response to magnetic stimulation, including a reduced compound muscle action potential (CMAP) from the diaphragm and increased excitability threshold, indicated impaired central inspiratory drive in 20% of cases. Phrenic nerve conduction showed a reduced diaphragmatic CMAP amplitude in 20%, and a delayed negative peak onset latency in 4% of cases. Abnormalities in diaphragm and intercostal muscle needle EMG were found in 76% of cases, these were mainly myotonic discharges (68%) and a decrease in the number of active motor units (36%). Patients with abnormal respiratory electrophysiological parameters had a significantly lower functional vital capacity (FVC; P = 0.005). The duration of the disease correlated negatively with diaphragmatic CMAP amplitude to phrenic nerve, but not magnetic, stimulation. Our results demonstrate that the involvement of the central inspiratory pathway is common in MD patients. Central and peripheral electrophysiological studies of the diaphragm should be considered in the diagnosis and management of patients with MD and dyspnoea.

Adult↗
PubMed1996

Prediction of outcome in patients with anoxic coma: a clinical and electrophysiologic study.

OBJECTIVE: To evaluate and compare the predictive powers of clinical examination, electroencephalography (EEG), and studies of short-latency somatosensory evoked potentials in determining the prognosis in anoxic coma. DESIGN: Prospective case series of patients in anoxic coma, whose prognoses were uncertain based on previously established clinical criteria. The clinical features, EEG, and somatosensory evoked potentials results were correlated with outcome. SETTING: A 40-bed intensive care unit in a university teaching hospital. PATIENTS: Thirty-four consecutive patients admitted over a 2-yr period with anoxic coma as the principal diagnosis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Twenty-seven (79%) patients never recovered consciousness and seven (21%) patients made a good recovery. One of six patients whose pupillary reflexes were present but whose other cranial nerve reflexes were absent on day 1 recovered, but none of the seven patients with these features still present on day 3 survived. None of the patients with motor responses of extension to painful stimuli or worse on days 1 or 3 recovered. The EEGs were classified into benign, uncertain, and malignant categories. The results of both EEG and somatosensory evoked potentials studies were strongly associated with outcome. With malignant EEG, the sensitivity was 74%, the specificity was 71%, and the positive predictive value was 90% [corrected] for the prediction of no recovery (death or persistent vegetative state). However, two patients with an initially malignant EEG eventually made a good recovery. The sensitivity for low amplitude or absent somatosensory evoked potentials for prediction of no recovery was 66%. There were no falsely pessimistic predictions with somatosensory evoked potentials, as all 18 patients with absent or low-amplitude responses had no recovery (specificity and positive predictive value were 100%). EEG and somatosensory evoked potentials studies were complementary to clinical examination in the determination of prognosis. Using a combined clinical and electrophysiologic approach, 63% of patients who had no recovery could be identified by day 3. Repeat EEG and somatosensory evoked potentials studies were of value in patients whose prognoses were uncertain, as their evolution invariably correlated with outcome. CONCLUSIONS: Based on the present data and a literature review, we propose that clinical examination combined with the results of EEG and somatosensory evoked potentials can be used to establish an early, definitive prognosis in a significant proportion of patients in anoxic coma. On day 3 or thereafter, patients with motor response of extension to pain or worse and malignant EEG, or those patients with flexor posturing or worse and bilaterally absent cortical somatosensory evoked potentials invariably have poor outcome. However, some patients with initially malignant EEG and normal somatosensory evoked potentials may recover and should be supported until their prognoses become more definitive.

Adolescent↗
PubMed1996

Sepsis and the systemic inflammatory response syndrome: neuromuscular manifestations.

OBJECTIVE: To describe the various conditions of peripheral nerve, neuromuscular junction, and muscle associated with the systemic inflammatory response syndrome (SIRS). DATA SOURCES: Publications in the scientific literature and personal observations during the last 15 yrs. DATA EXTRACTION: Computer search of the literature and review of patient records relating to polyneuropathy, neuromuscular transmission defects, and myopathies associated with sepsis, the septic syndrome, and SIRS. SYNTHESIS: SIRS is a new concept in which infection and trauma induce a systemic inflammatory response affecting the microcirculation to organs throughout the body. The nervous system is commonly affected in the forms of septic encephalopathy and critical illness polyneuropathy. Neuromuscular blocking agents and corticosteroids may have additional toxic effects on the neuromuscular system that are manifest as transient neuromuscular blockade, an axonal motor neuropathy, or a thick filament myopathy. Clinical examination in the critical care unit is often unreliable and electrophysiologic studies, at times accompanied by magnetic resonance imaging of the spinal cord, measurement of the circulating creatine phosphokinase concentration, and muscle biopsy, are often necessary to establish the diagnosis. Variants of critical illness polyneuropathy may occur outside the critical care unit. The precise mechanism of these neuromuscular conditions is not known, and further basic research is needed. CONCLUSIONS: A variety of neuromuscular conditions complicates SIRS. The identification of these conditions is important in patient management and in rendering a prognosis.

Critical Care↗
PubMed1996

Respiratory electrophysiological studies in Guillain-Barré syndrome.

Respiratory failure is a common and potentially life threatening complication in patients with Guillain-Barré syndrome. The incidence of phrenic nerve involvement and the predictive value of phrenic nerve conduction and diaphragmatic needle EMG were studied in 40 patients with Guillain-Barré syndrome within the first three days of admission to hospital. The negative peak onset latency of the diaphragmatic compound muscle action potential (CMAP), and its amplitude, duration, and area were abnormal in 83%. The need for ventilation was correlated with diaphragmatic CMAP amplitude (P = 0.005), and area (P = 0.001), but not with latency or duration. Abnormalities in diaphragmatic needle EMG were found in 45%, mainly a decreased number of motor unit potentials. The abnormalities correlated with the need for ventilation (P = 0.013). Of the 40% who required ventilation, all had either abnormal phrenic conduction, abnormal diaphragmatic needle EMG, or both. Eighty one per cent of the ventilated patients had abnormal forced vital capacity on the day of the electrophysiological examination. The results indicate that phrenic nerve conduction studies and diaphragmatic EMG are useful in detecting respiratory involvement in patients with Guillain-Barré syndrome and in identifying those at risk of respiratory failure.

Adolescent↗
PubMed1996

Motor neuron disease presenting as acute respiratory failure: a clinical and pathological study.

Respiratory failure is rarely a presenting symptom of motor neuron disease. Seven patients with motor neuron disease who presented with acute respiratory failure of unknown cause and required mechanical ventilation were studied. They all had symptoms and signs suggestive of diaphragmatic weakness. Respiratory involvement seemed disproportionately severe, as six were ambulatory and only three noted limb weakness. Only one had tongue weakness and none had swallowing difficulty. Electrophysiological studies showed widespread denervation and, in particular, diaphragmatic involvement to explain the severe respiratory failure. Weaning from the ventilator was unsuccessful in all cases. The four patients examined at necropsy showed severe loss of anterior horns cells in the cervical cord, with only minimal upper motor neuron involvement. Motor neuron disease should be recognised as a cause of acute respiratory failure, secondary to diaphragmatic paralysis from involvement of phrenic motor neurons.

Acute Disease↗
PubMed1996

The cortical representation of somatosensory evoked potentials of the phrenic nerve.

Respiratory electrophysiological studies are of essential value in diagnosing and managing patients with respiratory failure, but assessment of the sensory phrenic nerve fibres has been neglected. We recorded phrenic nerve somatosensory evoked potentials (SSEPs) by combining neurophysiological and neuroimaging techniques in three healthy subjects. Evoked potentials of the phrenic nerve showed the highest amplitude at CP3, determined by the modified 10-20 EEG system, and occurred at a constant latency, PI at 12.0 +/- 0.6 ms, and NI at 17.3 +/- 0.8 ms. Single photon emission computer tomography (SPECT) performed during phrenic nerve stimulation revealed focal neuronal activation in the somatosensory pathways. Intravenously administered Tc-99m Ethyl Cysteinate Dimer (ECD) was used as a blood flow tracer to obtain baseline and activated images. After image registration, baseline images were compared voxel-by-voxel with the activation images. The mean inter-subject summation image of the activated state was compared with that of the baseline state using ten normal subjects. The extent of the total voxel volume increase on the mean images of the 3 activated SPECT images was 0.7%, and a mean signal increase of 22%. For further anatomic localization of regional increases in signal, the magnetic resonance image (MRI) scan of each subject was registered and superimposed on the activated stage SPECT image. This method may be used clinically to study the pathophysiology of impaired central respiratory drive.

Adult↗
PubMed1995

Phrenic nerve conduction study in normal subjects.

Phrenic nerve conduction studies were performed in 50 phrenic nerves from 25 normal subjects using a technique modified from previously described methods. The normal ranges for latency, amplitude, negative peak area, and duration were established. The latency correlates with age and the amplitude increases with chest circumference. With our method, the amplitude increases and the duration decreases with lung volume. We found good right-left agreement and reproducibility. Therefore, the unaffected side can be used as a reference in unilateral phrenic nerve lesions and previous studies can be used for comparison in serial studies. We recommend that phrenic nerve conduction studies be used routinely to diagnose and monitor patients with respiratory involvement from neuromuscular diseases.

Action Potentials↗