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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
PubMed1998

Clinical and electrophysiological findings in critical illness polyneuropathy.

Sixty two patients with critical illness polyneuropathy (CIP) were studied prospectively to determine the clinical and electrophysiological profile, to assess the prognostic value of respiratory electrophysiology in determining the duration of ventilation and to analyze the role of neuromuscular blocking agents (NMBA) and steroids. Limb motor and sensory nerve conductions, bilateral phrenic nerve onset latencies, bilateral diaphragmatic compound muscle action potentials (CMAP), unilateral diaphragmatic needle electromyography (EMG), limb muscle EMG, time on the ventilator, time in the intensive care unit (ICU), dosage of NMBA and steroids were analyzed in 62 patients. The diagnosis of CIP was made by clinical criteria, electrophysiological criteria and exclusion of any other condition suspicious of an axonal neuropathy. The results of phrenic nerve conduction studies and diaphragmatic EMG were compared to normal mean values in 25 healthy subjects. The most common finding in our study were reduced CMAPs and abnormal spontaneous activity in muscle, occuring in 100%. Forty per cent had reduced CMAPs but normal sensory nerve action potentials (SNAP). These patients had normal CK-levels and normal findings, unspecific changes, type 2 fibre atrophy or denervation atrophy on muscle biopsy. Seventy seven per cent of patients had abnormal diaphragmatic CMAPs and spontaneous activity in the diaphragm indicating denervation of the diaphragm is common in CIP. There was no statistically significant relationship to the dosage of NMBA and steroids, and the respiratory electrophysiological studies, duration of ventilation and stay in the ICU.

Adolescent↗
PubMed1998

Diagnostic difficulties in myasthenia gravis.

Four patients with myasthenia gravis presented with severe, largely isolated, bulbar and respiratory muscles weakness. Tensilon tests were positive and antiacetylcholine receptor (anti-AChR) antibody titers were negative in all patients. Only 1 patient had a greater than 10% decremental response during the period of respiratory failure. Although routine nerve conduction studies were normal, all had very low-amplitude diaphragmatic compound muscle action potentials. Three patients had abundant fibrillation potentials and positive sharp waves largely restricted to respiratory muscles. Clinical and electrophysiological findings improved with corticosteroids, and surprisingly, decremental responses became positive in all patients. The assessment of patients with largely isolated bulbar and respiratory muscle weakness due to myasthenia gravis may be difficult and misleading, as anti-AChR antibody titers may be negative, decremental responses may be absent, and electrophysiological assessment atypical. Due consideration of clinical symptomatology, a Tensilon test, and a trial of immunosuppression may be necessary to establish the diagnosis.

Adult↗
PubMed1998

Electromyography of the diaphragm in neuromuscular disease.

We compared the diaphragmatic electromyographic (EMG) recordings from 32 patients with known neuromuscular disease and respiratory symptoms (23 neuropathies, 9 myopathies) to recordings from 23 normal subjects. Turns analysis of 219-ms sections, or epochs, of the EMG demonstrated a significant overlap between diagnostic groups, although some epochs from neuromuscular patients were significantly different from normal. Empirical rules were derived to infer neuropathic and myopathic involvement of the diaphragmatic EMG.

Diaphragm↗
PubMed1998

Genotype/phenotype correlation in affected individuals of a family with a deletion of the entire coding sequence of the connexin 32 gene.

X-linked Charcot-Marie-Tooth disease (CMTX) is a peripheral nerve disorder that has been linked to mutations in the connexin 32 gene (Cx32). These mutations have been shown to be genetically heterogeneous, though recurrences of specific mutations in apparently unrelated families have been seen. The majority of mutations have been shown to be missense, resulting in non-conservative amino acid changes. A few mutations resulting in a premature termination of protein translation, including both nonsense mutations as well as frameshifting microdeletions, have been documented. We would like to report a deletion mutation that appears to eliminate the entire coding sequence of the Cx32 gene, but which has been shown to segregate with a clinical phenotype not unlike that seen in individuals with a less severe alteration of the Cx32 gene. The causes at a cellular level of the CMTX phenotype are still not fully clear, though there has been speculation that these may involve a dominant negative effect where the mutant connexin 32 suppresses the function of other connexins. Studies of kindreds such as this, where in CMTX-affected males the Cx32 gene product is totally absent, will help us to better understand the molecular mechanisms underlying the clinical phenotype associated with this disorder.

Aged↗
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↗
PubMed1997

Novel measurement for automated interference pattern analysis of the diaphragm.

The automated interference pattern analysis for limb muscles was modified to take into account the unique features of the needle EMG of the diaphragm. The modification was successful in recording more accurately the number of small and large segments and the activity levels with inspiratory effort. "Clouds" were generated in ten healthy subjects. The techniques may prove useful in electrophysiological investigations.

Diaphragm↗
PubMed1997

Repetitive phrenic nerve stimulation study in normal subjects.

In patients with myasthenia gravis (MG), it may be difficult to determine by clinical methods if respiratory insufficiency is due to a defect in neuromuscular transmission. We therefore studied the technique of repetitive electrical stimulation of the phrenic nerve in 6 healthy subjects. It was easily performed and quite reproducible. Responses at 3-Hz stimulation were recorded from surface electrodes of the ipsilateral hemidiaphragm, before and after exercise. We analyzed the percent decrement of the negative peak (NP) amplitude, area, and duration of the diaphragmatic compound muscle action potential (CMAP) between the first and the fifth or sixth potentials. The mean percentage change of the area was -2.2% (+/-4.3), and in all tests the change was <10.6%, yielding a normal range of <11%. The change in the NP amplitude was 12.1% (+/-8.3); in duration, the change was -8.7% (+/-9.6). Producing diaphragm fatigue did not change these results. The increase in amplitude and decrease in duration with little change in area, termed pseudofacilitation, may be due to shifts in the position of the diaphragm affecting volume conduction. The technique is a promising tool in the diagnosis of respiratory involvement from neuromuscular transmission disorders.

Action Potentials↗
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↗