Electromyography and clinical neurophysiology
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Electromyogr Clin Neurophysiol · Dec 1999
Muscle compound motor action potentials from esophago-vertebral electrical stimulation of the spinal cord in the normal awake man.
In 15 normal alert subjects, electrical stimulation of the spinal cord at various levels by a nasopharyngeal probe (cathode) and a vertebral surface electrode (anode) was performed with different orientation of the stimulating dipole. Maximum spinal cord compound motor action potentials (SCCMAPmax) simultaneously recorded from homologous muscles of the upper arm of both sides were not significantly different in amplitude and latency. By stimulating the spinal cord at the cervico-dorsal level it was possible to obtain simultaneous recordings of SCCMAP from muscles of the upper and lower limbs and trunk at a stimulus intensity of 50-70 mA. ⋯ Central latency of the F wave exceeded by 0.5 to 0.7 ms that of the SCCMAP, suggesting that esophago-vertebral stimulation is able to directly excite the motor neurons. By threshold current intensity, it is possible to obtain a threshold SCCMAP (SCCMAPth) of the same latency as SCCMAPmax and different in shape, duration and amplitude from the CMAP obtained by cortical stimulation with threshold magnetic stimuli. SCCMAPth was different in shape from the motor unit action potential activated at weak voluntary effort, SCCMAPth latency and amplitude were unchanged after voluntary homo- and contralateral activation.
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Electromyogr Clin Neurophysiol · Jan 1999
Diaphragmatic denervation in intensive care unit patients.
The causes of prolonged requirement for mechanical ventilation in the intensive care unit (ICU) are currently a subject of investigation. Critical illness polyneuropathy (CIP), an axonal polyneuropathy that frequently occurs with prolonged sepsis and multi-organ failure, has been cited as a frequent cause of difficulty with weaning from a ventilator. The relative contribution of diaphragmatic denervation in ICU patients with and without CIP has not been definitively determined. ⋯ Electrodiagnostic studies included diaphragmatic needle electromyography (EMG) to evaluate for diaphragmatic denervation. The medical charts of the patients with diaphragmatic denervation were reviewed for etiologies other than CIP for the diaphragmatic denervation. Our results suggest: 1) Respiratory impairment in ICU patients may often be unrelated to either CIP or diaphragmatic denervation; 2) Only about half of ventilator dependent CIP patients have diaphragmatic denervation; 3) Diaphragmatic denervation in ICU patients frequently may be attributable to causes other than CIP.
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Electromyogr Clin Neurophysiol · Oct 1998
Case ReportsSacral plexopathy and sciatic neuropathy after total knee arthroplasty.
While peroneal and tibial neuropathies have been described as a complication of total knee arthroplasty (TKA), a computerized literature search failed to reveal any previously reported cases of associated sacral plexopathy or sciatic neuropathy. This case report describes the diagnosis and management of a patient found to have evidence of a right sacral plexopathy and a left sciatic neuropathy, following bilateral TKA. This case suggests that these may be rare complications of TKA.
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Electromyogr Clin Neurophysiol · Apr 1997
Evaluation of diaphragm electromyogram contamination during progressive inspiratory maneuvers in humans.
The diaphragm electromyogram (EMGdi) is susceptible to contamination by non-diaphragm related electrical signals such as the ECG, electrode motion artifacts, and other sources of noise. It is difficult to distinguish between these contaminating signals and those that are representative of the non-contaminated EMGdi, especially during periods when the EMGdi amplitude is relatively small, as during mild contractions of the diaphragm. The aim of the present study was to evaluate how contaminating signals influence the EMGdi power spectrum center frequency (CF) during progressive inspiratory maneuvers. ⋯ This was expressed by a factor of 4 reduction in the coefficient of variation of the CF values. The majority of the excluded EMGdi signals (i.e. not satisfying the spectral deformation index inclusion levels), had low CF values mainly due to the presence of electrode motion artifacts. It was concluded that: 1) The majority of EMGdi power spectrums are deformed early on during unloaded inspirations, and their CF values should be carefully interpreted as being representative of diaphragm function. 2) The relative contribution of contaminating signals in the EMGdi decreases proportionally throughout the first two thirds of an inspiration to IC. 3) The use of visual inspection of the signal in the time domain is questionable as a method to discriminate non-contaminated signals. 4) Analysis of the signal in the frequency domain makes it possible to detect the influence of signal contamination.
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Electromyogr Clin Neurophysiol · Sep 1996
Case ReportsElectrodiagnostic evidence for cervical radiculopathy and suprascapular neuropathy in shoulder pain.
Patients diagnosed with a shoulder impingement syndrome occasionally do not respond to techniques used for treatment of soft tissue injury. The neurologic examination may be only partially abnormal or incomplete due to pain limitation so that peripheral nerve or nerve root abnormalities are overlooked. This study was undertaken to investigate the frequency of cervical radiculopathy and suprascapular neuropathy in patients with shoulder pain who were initially diagnosed with a musculoskeletal syndrome. ⋯ Of the 11 subjects with abnormal electrodiagnostic studies, the neurological examination in 7 (63.6%) was normal except for pain-limited manual muscle testing, and the other 4 (36.4%) had an abnormality in either sensation testing, muscle bulk, or muscle stretch reflexes. One case of a patient with an initial diagnosis of soft tissue injury is presented. In patients undergoing evaluation for shoulder pain, cervical radiculopathy as a possible etiology should be considered, even when there is an equivocal clinical examination.