Short-term exposure to a 1.5 tesla static magnetic field does not affect somato-sensory-evoked potentials in man

The literature is contradictory regarding the effect of static magnetic fields on the function of the central nervous system of mammals. Since human subjects are exposed to intense static magnetic fields during magnetic resonance imaging, it is important to determine if the static magnetic field adversely affects the nervous system of man. Therefore, somato-sensory evoked potentials (SEPs) elicited from median nerve stimulation were measured in 11 normal subjects before and during short-term exposure to a 1.5 Tesla static magnetic field. Specially modified instrumentation was used to record SEPs that were unperturbed by the static magnetic field. There were no statistically significant differences in the N20 or P25 latencies or in the amplitude from N20 negative peak to P25 positive peak of the SEPs obtained before compared to those recorded during exposure to the static magnetic field. In addition, there were no changes in the waveforms associated with exposure to the static magnetic field. We conclude that short-term exposure to a 1.5 Tesla static magnetic field does not affect SEPs (i.e., nerve conduction and synaptic transmission were within normal limits) in normal human subjects.

Local steroid injection: its effect on the recovery of nerve conduction in experimental neuropathy

This study was designed to investigate the effectiveness of local steroid injection on the recovery of nerve conduction in acute compression neuropathy. Experimental neuropathy with complete conduction block was produced by mechanical compression of the caudal nerves of 24 rats. Five days after compression, the compression site was injected with 0.2 mL Dexamethasone acetate (8 mg/mL suspension) in eight rats (group A), and 0.2 mL normal saline in another eight rats (group B). The remaining eight rats (group C) received no injection. Motor nerve conduction velocity (NCV) over the compressed segment, as well as amplitude of the evoked compound muscle action potential (CMAP) recorded from the segmental tail muscles, were measured before nerve compression and three times per week after nerve compression. The recovery rates of NCV of the caudal nerve were not significantly different among the three groups. The recovery rate of amplitude of CMAP in group A was significantly higher than that in groups B or C (p less than 0.01). However, there was no significant difference in recovery rate of the amplitude of CMAP between groups B and C. It is concluded that local steroid injection to the site of nerve compression may facilitate the recovery of nerve conduction block but not the recovery of demyelinative lesion.

Peroneal nerve entrapment at the knee localized by short segment stimulation

The purpose of this study was to evaluate the usefulness of short segment stimulation (SSS) of the peroneal nerve at the knee in order to localize the site of compression and/or entrapment of the nerve. Eighteen patients with suspected peroneal nerve palsy and 28 controls were studied by SSS of the peroneal nerve across the knee. Compound muscle action potentials (CMAPs) were obtained from the extensor digitorum brevis muscle after successive supramaximal stimuli of the nerve at 2 cm intervals, starting 4 cm distal (D4 and D2) and ending 6 cm proximal (P2, P4, and P6) to the fibular head prominence (P). In patients the average conduction times from D2 to P, P to P2, and P2 to P4 were significantly (P less than 0.05) longer and the average amplitude of CMAPs at P, P2, P4, and P6 significantly (P less than 0.05) lower than those of controls. Fourteen patients showed statistically significant reduction in amplitude and prolongation of conduction time in one or more short segments. Three patients had prolongation of conduction time only and one patient had reduction in amplitude only. When nerve conduction of the entire 10-cm segment across the knee was tested by the conventional method, only nine showed reduction in amplitude from proximal stimulation, or slowing of motor conduction velocity across the 10-cm segment or both. It was concluded that the SSS technique is a sensitive and reliable procedure for the detection of mild compression or entrapment of the peroneal nerve around the knee.

Increased skin temperature after vibratory stimulation

The skin temperature effect of vibratory stimulation was studied in 28 healthy subjects. Vibration (50 Hz or 100 Hz) was applied to the volar surface of the left forearm for 15 min. Skin temperature of the bilateral forearms was measured before and immediately after cessation of vibration and at 5 and 10 min postvibration. Vibration at 100 Hz for 15 min on all 28 subjects was associated with a temperature increase of 4.20 +/- 0.79 degrees F that was significantly (P less than 0.01) higher than that in the controls (0.38 +/- 0.33 degrees F). Skin temperature decreased to previbration levels by 50 min of postvibration. The 11 subjects who received 50-Hz vibration for 15 min showed a skin temperature increase (0.75 +/- 0.23 degrees F) in the vibrated forearm significantly (P less than 0.01) higher than that in the control forearm (0.11 +/- 0.17 degrees F). All measurements decreased to previbration skin temperatures by 10-min postvibration. Vibration at 100 Hz also produced skin erythema in all subjects, whereas 50-Hz vibration produced no erythema. The mechanism by which 100-Hz vibration relieves pain is largely unclear, but it could be associated with increased skin temperature and erythema.

Early smooth horizontal eye movement: a favorable prognostic sign in patients with locked-in syndrome

Locked-in Syndrome (LIS) is a rare clinical entity consisting of quadriplegia, paralysis of lower cranial nerves, mutism, and bilateral paresis of horizontal gaze. The prognosis is usually poor. Most patients who do survive have severe residual impairment or develop chronic LIS. Review of the literature shows that recovery has been reported but not systematically studied, particularly with respect to early prognostic signs. We report a case of LIS with bilateral pontine infarctions shown by MRI. Severe neurological deficits included quadriplegia, paresis of horizontal gaze, facial paralysis, and bulbar palsy. Horizontal eye movements were present and smooth by the second week after onset. The patient had almost full functional motor recovery within four months, after a comprehensive rehabilitation program. Fourteen other reported cases of LIS with full recovery had documented recovery of lateral gaze in the early stage. In addition, smooth horizontal gaze is the most frequent activity in incomplete LIS. Early recovery of horizontal eye movement may indicate that the brain lesion is limited and may be a good prognostic sign in LIS.

Electrophysiologic recovery of acute conduction block of rat tail nerve

The recovery of experimental compression neuropathy with prolonged conduction block of the caudal nerve was studied electrophysiologically in 48 adult Sprague-Dawley albino rats divided equally into six groups. The pressure applied in groups A, B, C, D, E, and F was approximately 20kg/cm2 for 20 minutes, 20kg/cm2 for 10 minutes, 20kg/cm2 for 5 minutes, 10kg/cm2 for 20 minutes, 20kg/cm2 for 10 minutes, and 10kg/cm2 for 5 minutes, respectively. The motor nerve conduction velocity (NCV) and the amplitude of the evoked compound muscle action potential (CMAP) were measured before and periodically after nerve compression. The period of initial complete block was significantly longer in the high pressure groups than in the lower ones, and also significantly longer in the nerves compressed for 20 minutes than for those compressed for five or ten minutes. Thus, the severity of conduction block seems to be related to both pressure and duration of compression. Once the conduction block began to recover, the recovery rate of conduction block (recovery rate of amplitude ratio of CMAP, proximal/distal) was not significantly different. The recovery rate of demyelinative lesion (NCV recovery rate) was also not significantly different among the six groups. The degree of compression seems to determine the severity of the initial conduction block, but not the subsequent recovery rate of conduction.

Averaged axillary F-loop latency of median and ulnar nerves

Axillary F-loop latencies (AFLL) were measured on median and ulnar nerves of 54 normal volunteers. The median and ulnar nerves were stimulated at the wrist and at the axilla 25cm distal to the sternal notch. The compound muscle action potentials were recorded from thenar and hypothenar muscles. Averaged tracings from 32 consecutive stimuli at the wrist were obtained. The averaged F-wave latencies were measured to the peak (Fwp) of the averaged F-wave. The M-wave latencies from wrist and axilla stimulation were measured to the onset of the wave (Mw and Ma, respectively). The averaged AFLL (a-AFLL) was calculated as (Fwp + Mw)-2 Ma. The average values of a-AFLL were 14.12 +/- 0.88msec for median nerve, and 13.97 +/- 0.90msec for ulnar nerve. There was no significant difference between male and female subjects, nor between the right and left sides. Seven subjects with EMG evidence of C8 or C8 to T1 radiculopathy, although manifesting normal AFLL gauged by the regular method (ie, measured to the onset of the shortest F-wave latency among eight tracings), had significantly longer "averaged AFLL" in both median and ulnar nerves of the affected side than the a-AFLL obtained from the normal side. It is concluded that the a-AFLL is a more sensitive measure than the "regular AFLL" in the assessment of proximal nerve lesion (especially C8 or C8 to T1 radiculopathy).

Averaged F-wave conduction velocity of peroneal nerve

Averaged F-wave conduction velocities (a-FWCV) of peroneal nerve were measured on 38 healthy volunteers and 22 patients with clinical and electromyographic evidence of unilateral L5 or L5 + S1 radiculopathy. The peroneal nerve was stimulated supramaximally at the fibular head and the compound muscle action potential was recorded from the extensor digitorum brevis muscle. Averaged tracings from 32 consecutive stimuli were obtained. The averaged F-wave latency (Fp) and M-wave latency (Mp) were measured from the stimulating artifact to the peak of the waves. The distance (D) between the stimulating point and the T12 spinous process was measured. The value of a-FWCV was calculated as 2D/(Fp-Mp-1) m/second. In normal subjects, the average value of a-FWCV was 56 +/- 4, and there was no significant difference between males and females, nor between the right and left sides. The differences among the tests administered at different times on the same subject were also statistically insignificant. Of the 22 patients, 17 had subnormal value of a-FWCV if the lower normal limits were defined as mean minus 2.5 SD (i.e., 46 m/second) calculated from the normal control value. However, only one of them had subnormal value of FWCV calculated by the conventional method (without averaging technique). All the patients with two root (L5 + S1) involvement had subnormal a-FWCV. It is concluded that the a-FWCV is a more sensitive measure than the conventional FWCV in the assessment of L5 radiculopathy.

Ultrasound thermotherapy effect on the recovery of nerve conduction in experimental compression neuropathy

Bilateral tibial nerves of 18 albino rats were mechanically compressed between knee and ankle. Beginning on the fifth day after compression, ultrasound thermotherapy of 0.5 or 1.0watt/cm2 was applied over the area of nerve compression in one limb for one minute three times per week. The other side (control) was not treated. Motor distal latency (DL), motor nerve conduction velocity (NCV) of the segment with nerve compression, and amplitude of the evoked compound muscle action potential (ACMAP) were measured before and immediately after nerve compression and two or three times per week after compression. The recovery rates of NCV and ACMAP of the tibial nerve treated with ultrasound of 0.5watt/cm2 were significantly faster than those of the control nerve. There was no significant change in the recovery rate of DL. However, if ultrasound of 1.0watt/cm2 was applied, the recovery rate of ACMAP of the treated nerve was slower than that of the control nerve. There were no significant changes in the recovery rates of DL and NCV. Low doses of ultrasound thermotherapy may facilitate recovery of compression neuropathy, but higher doses may induce an adverse effect.

Electrophysiologic studies of the median nerve and its palmar cutaneous branches after nerve grafting

Electromyography (EMG) and nerve conduction studies were performed on a patient with an incomplete lesion of the median nerve involving the motor fibers to the thenar muscles, the palmar cutaneous branches, and the sensory fibers to the index finger. The studies were done before, and 13 weeks, 16 weeks, and one year after grafting. The preoperative electrodiagnostic evaluation showed abnormalities involving the median motor fibers and the palmar cutaneous branch. Electromyography of the opponens pollicis and abductor pollicis brevis before surgery showed severe active denervation. Thirteen weeks after nerve grafting, the median motor distal latency was prolonged and the amplitude of the evoked potential of the median motor and index finger digital sensory nerves were decreased. At 16 weeks, both the latency and amplitude showed improvement, as did EMG of the affected muscles. One year later, the electrophysiologic findings were normal except for a slightly prolonged median motor distal latency. Clinical and functional improvement after grafting correlated well with the electrophysiologic findings. We conclude that EMG and nerve conduction studies are useful tools for following the progression of recovery after nerve grafting.

Learning ability of young rats is unaffected by repeated exposure to a static electromagnetic field in early life

Infant albino rats were exposed to a static electromagnetic field of 0.0 Tesla (control) or 0.5 Tesla (experimental) for 14 postnatal days. Following a 1-month rest period, the experimental (13 males and 10 females) and control (11 males and 14 females) rats were trained on four successive reversals of a position habit in a single-unit enclosed T-maze that was adapted for the use of escape-avoidance of mild foot shock as a motive. There was no significant difference in learning ability between the experimental and control groups in terms of total (initial combined with repetitive) errors committed over the four reversal problems. While the females tended to make more errors than the males, this difference was likewise insignificant.

Rehabilitation in dual disability of hemiplegia and upper extremity amputation: two case reports

Dual disability involving amputation and hemiplegia is relatively rare. The vast majority of these cases involve lower extremity amputations. In this report two patients sustained a right-sided hemiplegia complicating an old left upper extremity amputation. Through the comprehensive rehabilitation program these two patients were able to make gains, especially in some activities of daily living and in lower extremity functions. Since some of the upper extremity activities, such as dressing or bathing, could not be accomplished, it appears that patients with upper extremity amputation who have a contralateral hemiplegia have a poorer prognosis for achieving functional independence than patients with lower extremity amputation and similar neurologic loss.

Static magnetic field influence on human nerve function

In an attempt to understand the possible neural mechanism mediating the effects of a static magnetic field (SMF), nerve conduction velocity (NCV) and excitability index (EI), measured as the ratio of the amplitude of the submaximally evoked compound muscle action potential during or after magnetic exposure to that before exposure from the same intensity of stimulation of the motor nerve, were studied on ten normal volunteers (aged 17 to 39), when the nerve was exposed to an SMF of 1 tesla (T) for 15 seconds. NCV and EI were measured before, during (5, 10, and 15 sec) and three minutes after magnetic exposure. Both NCV and EI were measured on median nerve in all ten subjects, the peroneal nerve in seven subjects, while the ulnar nerve was measured for only EI in eight subjects. There was no significant change in NCV over the segment exposed to the magnetic field. However, EI was significantly increased during the magnetic exposure in all three nerves. The effects were observed as early as five seconds after exposure and disappeared by three minutes after exposure. It is concluded that the excitability of the motor nerve is increased when it is exposed to an SMF with a density of 1T.

Static magnetic field influence on rat tail nerve function

Motor nerve conduction and excitability were measured on the tail nerve of anesthetized rats before and after the nerve was exposed perpendicularly to a static electromagnetic field of various intensities and durations. There was no significant change in either the distal latencies or the amplitudes of the compound muscle action potential (CMAP) measured from stimulating the tail nerve after it was exposed to the electromagnetic field with a density up to 1.2 Tesla (T) for a duration of 60 seconds. However, the nerve excitability expressed as changes of the amplitudes of the submaximally evoked CMAP increased significantly when the tail nerve was exposed to a magnetic field with a density higher than 0.5T for more than 30 seconds. The finding that an electromagnetic field increases motor nerve excitability suggests a possible mechanism of its therapeutic effects.

Cervical radiculopathy. Clinical, radiographic and EMG findings

This retrospective study reviewed clinical, radiographic, and electromyographic (EMG) findings in 108 patients with cervical radiculopathy. Radiographic evaluation included measurements of the size of the intervertebral foramina and the space for the intervertebral disk. The results showed that the clinical findings correlated well with the EMG abnormalities but not with the radiographic findings. The extent of the intervertebral foramen and the disk space narrowing correlated poorly with the severity of EMG abnormalities. It is suggested that radiographic findings alone may be an inadequate basis for a diagnosis of cervical radiculopathy. EMG examination may be very helpful in such a diagnosis and may be more accurate in assessing radiculopathy than the plain films in certain cases.

Geophysical variables and behavior: XXVII. Magnetic necklace: its therapeutic effectiveness on neck and shoulder pain: 2. Psychological assessment

The efficacy of magnetic necklaces (maximum static magnetic field 0.13 T) in controlling chronic neck and shoulder pain was studied. A double-blind experiment was performed on four groups of human adults (Total N = 101). The experimental design involved 52 subjects with chronic pain (35 women, 17 men) and 49 without symptoms of pain (20 women, 29 men). They were assigned in near-equal numbers into subgroups in which magnetic or nonmagnetic necklaces were worn 24 hr. a day for 4 wk. Subjective reports and psychological testing indicated that there were no statistically significant differences among treatment subgroups before treatment. Subjects in the pain group reported a statistically significant reduction in frequency and severity of pain immediately after treatment. However, treatment condition (magnetic vs nonmagnetic) did not significantly affect subjective reports, indicating that the reported improvement is attributable to the placebo effect.

Metabolic effects of exhaustive training of athletes

Sixteen athletes (11 men, 5 women), averaging 21 years of age, were studied before and after four weeks of daily exhaustive exercise (six days/week) during an endurance training course. In comparing blood chemistries before and after training, concentrations of blood glucose, total serum lipids, serum triglycerides, and serum cholesterol were significantly reduced; serum free fatty acid ( SFFA ) level was significantly increased; and serum protein and serum phospholipid concentrations remained unchanged. It was concluded that exhaustive training produces reduced blood glucose (but not clinically significant hypoglycemia) with increased fat utilization as a result of depletion of carbohydrate storage and that such training reduces the resting levels of serum cholesterol and serum triglycerides. The increased hematocrit, serum Na+, and serum K+ concentrations observed were presumably due to plasma water loss from excessive perspiration. Concentrations of blood urea nitrogen (BUN) and serum glutamic-oxaloacetic transaminase (SGOT) were increased significantly; serum glutamic-pyruvic transaminase (SGPT) and serum creatinine showed no significant changes. None of the athletes showed evidences of water-electrolyte deficiency syndrome, renal dysfunction, or liver cell damage, despite a persistent mild degree of dehydration and catabolic state noted after training.

Magnetic necklace: its therapeutic effectiveness on neck and shoulder pain

The effect of the magnetic necklace on chronic neck and shoulder pain was studied on 101 volunteers, 46 males and 55 females. A double-blind method was applied on 4 divided groups (with pain vs without pain matched with magnetic vs nonmagnetic necklace). All the subjects wore the necklace 24 hours per day for 3 weeks. Subjective evaluation from the subjects with pain, either with magnetic or nonmagnetic treatment, was performed before and 3 weeks after the necklace treatment, and revealed a significant placebo effect in terms of decrease in intensity or frequency of pain. The objective tests with electrodiagnostic procedures were done before the treatment and at 3 weekly intervals. The proximal conduction time of the ulnar nerve was significantly reduced by magnetic treatment in the subjects without pain but was not changed in the subjects with pain. There was no significant change in the excitation threshold of the suprascapular nerve in all subjects. The possible mechanism of magnetic effects on pain and the prospect of magnetotherapy for pain relief in physical medicine are discussed.

Axillary F-loop latency of ulnar nerve in normal young adults

F waves were studied with stimulation of the ulnar nerve in normal subjects (25 men and 15 women, with an average age of 26.5 years) using an EMG machine that permits the simultaneous display of 8 sweeps. The axillary F-loop latency (AFLL), defined at the conduction time between the axilla (25cm from the sternal notch) and the spinal cord, was 9.17 +/- 0.81msec when 8 F responses were measured but was 8.57 +/- 1.00msec when 40 F responses were used. Data from men and women showed no significant statistical difference. The mean plus 2 standard deviations were 10.8 and 10.6msec for 8 and 40 responses, respectively. On the basis of these findings, an AFLL longer than 11msec should be considered abnormal in the young adult. Four measures repeated at weekly intervals showed no significant difference from week to week, indicating that the technique can be consistently and reliably applied at different times. The average duration of the F complex was 15.78 +/- 2.55msec and was about 80% of the average duration of the M wave.