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J R Daube

Publications and source records attributed to J R Daube.

At least 37 records · Page 2Linked to original sources
PubMed1995

Estimating the number of motor units in a muscle.

A loss of motor units is the primary defect in many neurogenic disorders. The number of motor units remaining in a muscle or group of muscles can be estimated by a number of methods on either needle electromyography or as part of nerve-conduction studies. Comparison of the methods of motor unit number estimates (MUNE) and their underlying assumptions shows that each method can provide reliable and useful clinical information. Each method relies on obtaining an estimate of the average size of single motor units, and compares that size with the size of a maximal compound muscle action potential in which all motor units are activated. The potential errors of all the methods are similar and relate primarily to adequacy of sampling of the size of single motor units. The method of statistical estimates of MUNE does not attempt to isolate and measure individual motor unit potential sizes. Rather it estimates the size of single motor units from the variation in size of a muscle action potential when individual motor units in a group of motor units fire randomly.

Electromyography↗
PubMed1994

Cranial nerve conduction and needle electromyography in patients with acoustic neuromas: a model of compression neuropathy.

Of 45 patients with acoustic neuromas (0.3-5.0 cm), 73% had facial nerve impairment on electrophysiologic testing, but only 16% had facial weakness. Cranial nerve conduction was the most sensitive measurement, especially prolongation of the ipsilateral R1 latency of the blink reflex compared with that of the contralateral reflex. The severity of nerve conduction abnormality was highly correlated with tumor size. Our results confirm and quantitate the sensitivity of nerve action potential latency in response to chronic nerve compression.

Adult↗
PubMed1993

Long-term follow-up of 121 patients with benign fasciculations.

Using the case records of Mayo Clinic patients, 121 patients with a diagnosis of benign fasciculations were identified. All had a normal neurological examination and normal electrophysiological studies, except for fasciculation potentials. Interviews by telephone were conducted 2 to 32 years after diagnosis. None of the patients developed symptomatic motor neuron disease. Forty individuals were in health care careers. A subset of 19 patients described acute onset of fasciculations following a viral infection. Benign fasciculations are not a preclude to progressive motor neuron disease.

Adult↗
PubMed1993

Muscle innervation.

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Electromyography↗
PubMed1992

Effect of BAEP monitoring on hearing preservation during acoustic neuroma resection.

We measured the effect of brainstem auditory evoked potential (BAEP) monitoring on hearing preservation in acoustic neuroma resection in 90 consecutive patients with monitoring compared with 90 historical controls matched for tumor size and preoperative hearing status. In small tumors (less than 2 cm), BAEP monitoring was associated with a higher rate of hearing preservation and a greater chance that the hearing preserved was clinically useful. Changes in the BAEP intraoperatively showed a good correlation with postoperative hearing status.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1992

Interaction of random electromyographic activity with averaged sensory evoked potentials.

We averaged sensory nerve action potentials (SNAP) of the median nerve recorded at the wrist, forearm, and elbow with up to 6,000 trials in the presence of quantitated levels of background EMG activity in six normal volunteers. The SNAP could be recorded reproducibly with averaging when the EMG amplitude was up to 50 times the SNAP amplitude. EMG amplitudes of greater than 100 times the SNAP amplitude produced continuous variation in the averaged waveform that did not stabilize, probably because of the quasi-random, large, triphasic potentials that make up the EMG. Monitoring and reduction of background EMG activity can improve reliability of somatosensory evoked potential recording.

Adult↗
PubMed1992

Effect of partial neuromuscular blockade on intraoperative electromyography in patients undergoing resection of acoustic neuromas.

Intraoperative electromyographic monitoring of the facial nerve during acoustic neuroma excision provides early detection of nerve injury and improved outcome. To determine whether a useful level of peripheral neuromuscular blockade could be achieved without compromise of facial electromyographic monitoring, we studied 10 patients undergoing resection of acoustic neuroma. Facial nerve monitoring was accomplished by placement of wire electrodes in the orbicularis oris, orbicularis occuli, and mentalis muscles. Peripheral neuromuscular blockade was assessed by recording unprocessed hypothenar compound muscle action potentials (CMAPs). After induction of anesthesia, an infusion of atracurium (1.0 micrograms.kg-1.min-1) accompanied by a bolus dose of 50 micrograms/kg was administered. The infusion was then increased in increments of 0.5 micrograms.kg-1.min-1 until a 50% reduction in hypothenar single-twitch CMAP was obtained. Facial nerve function was continuously monitored by comparison of facial CMAPs produced by stimulation of the nerve proximal and distal to the tumor bed. The mean (+/- SD) infusion rate of atracurium was 2.55 +/- 0.75 micrograms.kg-1.min-1. Decrements in facial nerve CMAPs were detected in 6 of 10 patients, and all demonstrated moderate to severe facial nerve dysfunction. In no patient was an unexpected deficit present postoperatively. Moderate degrees of peripheral neuromuscular blockade can be achieved without compromising facial nerve electromyographic monitoring.

Action Potentials↗
PubMed1992

Spinal cord injury in experimental thoracic aortic occlusion: investigation of combined methods of protection.

The efficacy of combined methods of spinal cord protection during thoracoabdominal aortic reconstruction was evaluated because a recent clinical study failed to substantiate the value of cerebrospinal fluid drainage when used alone in the prevention of paraplegia. The effect of cerebrospinal fluid drainage and aortofemoral shunting were analyzed with regard to neurologic outcome and spinal cord blood flow in a model of thoracic aortic occlusion. In addition, we studied the use of motor-evoked potentials as compared with somatosensory-evoked potentials in monitoring cord perfusion. Thirty-two dogs underwent proximal and distal thoracic aortic occlusion for 60 minutes. The control group (n = 8) underwent thoracic aortic cross-clamping only. Spinal cord protection was used in three groups: cerebrospinal fluid drainage alone (n = 8), aortofemoral shunting alone (n = 8), and cerebrospinal fluid drainage and aortofemoral shunting (n = 8). Neurologic outcome improved in all treatment groups as compared with controls (p less than 0.001). The addition of cerebrospinal fluid drainage to aortofemoral shunting did not further improve neurologic outcome. Spinal cord blood flow measured with microspheres in the lumbar gray matter was significantly higher in the dogs with aortofemoral shunting (+/- cerebrospinal fluid drainage) as compared with those with cerebrospinal fluid drainage alone (p less than 0.05) or the controls (p less than 0.001). Aortofemoral shunting also prevented the development of acidosis and hyperglycemia. Loss or changes in amplitude and latency of motor-evoked potentials did not distinguish between the groups. Loss of somatosensory-evoked potentials had a high sensitivity (92%) but lower specificity (68%) in predicting neurologic injury, whereas loss of motor-evoked potentials had a high specificity (100%) but a very low sensitivity (16%). We conclude that cerebrospinal fluid drainage or aortofemoral shunting significantly improve spinal cord blood flow and neurologic outcome. The greatest increase in spinal cord blood flow was seen with aortofemoral shunting, which also prevented metabolic disturbances of reperfusion. Although the addition of cerebrospinal fluid drainage to aortofemoral shunting was the only group in which no neurologic injury occurred, this group did not have a significant improvement in outcome when compared with aortofemoral shunting alone. Spinal cord ischemia was more accurately detected with somatosensory-evoked potentials when aortofemoral shunting was used, whereas motor-evoked potentials recorded from the spinal cord were not sensitive enough to predict neurologic injury.

Analysis of Variance↗
PubMed1991

Acute peripheral arterial occlusion: electrophysiologic study of 32 cases.

Thirty patients with 32 acute peripheral arterial occlusions underwent nerve conduction and electromyographic studies at a mean of 12.4 months after the vascular occlusion. Compound action potentials showed greater reduction than conduction velocity (26% to 75% vs 8% to 13% lower than normal). All changes were more prominent in the legs than arms, including fibrillation potentials (64% vs 28%). Short motor unit potentials were seen in 13% of patients; this group also had signs of severe nerve damage. The extent of abnormality varied with location of occlusion. Signs of nerve damage were significantly decreased in patients who had early revascularization. The electrophysiologic findings suggested axonal destruction rather than demyelination.

Action Potentials↗
PubMed1991

AAEM minimonograph #11: Needle examination in clinical electromyography.

The physiologic and histologic principles underlying clinical electromyographic studies are briefly reviewed as an introduction to the normal and abnormal findings in human subjects. Technical aspects of recordings as well as the specific types of discharges and their significance are discussed.

Action Potentials↗