Effects of elbow flexion on radial nerve motor conduction velocity.

The position of the elbow while conducting motor studies of the radial nerve is generally extended (15) or slightly flexed (10), but little is known about the effects of elbow flexion on the radial motor conduction velocity. We attempted to measure the effects of the elbow position on the radial motor conduction velocity, as well as directly measure the change in the length of the nerve at different elbow positions in the cadaver. In addition, we established normal values for the radial F-wave with the recording electrode on the extensor indicis proprius muscle. Radial motor nerve conduction was studied in 25 normal subjects to evaluate the effect of 3 different elbow positions (0 degree, 45 degrees, and 90 degrees) on motor conduction velocity (MCV) across the elbow. Direct (in situ) radial nerve measurements were performed on four cadaver specimens to compare changes in nerve length during elbow flexion. Normal values for radial F-wave latencies recording from the extensor indicis proprius muscle were also determined in 23 subjects. The radial MCV decreased significantly as the elbow flexed from 0 degree to 90 degrees. The normal range of values for radial motor nerve conduction at 0 degree of elbow flexion was 71.7 +/- 4.7 m/s, 68.9 +/- 4.9 at 45 degrees of elbow flexion, and 62.0 +/- 6.4 m/s at 90 degrees elbow flexion. Actual (in situ) radial nerve measurements were also found to decrease in length as the elbow flexed. The minimal radial F-wave latency was 19.8 +/- 3.7 milliseconds. For routine determination of motor nerve conduction velocity across the elbow, we recommend that the elbow be fully extended, as the distance measurement most accurately reflects the maximum anatomic length of the nerve. We also feel that the radial nerve F-wave latency is readily obtainable from the extensor indicis proprius muscle.

Biased responding: a case series demonstrating a relationship between somatic symptoms and impaired recognition memory performance for traumatic brain injured individuals.

Biased responding on the Sternberg Recognition Memory Test was observed in four patients with traumatic brain injury. None of these individuals met the Diagnostic and Statistical Manual's (DSM-IV) criteria for malingering. Individual recognition memory scores were high shortly after injury, declined to chance or below at the 6- and 12-month evaluations, and then showed substantial recovery by the 24-month evaluation. Recall memory performance actually declined slightly across this same 2-year period. Recognition memory scores were related to the extent to which the patients endorsed somatic items on the Hamilton Rating Scale for Depression (HAM-D). Poor performance was associated with high somatic scores. The relationship between memory and somatic scores on the HAM-D in this case series suggests that unconscious processes can influence memory performance and, because of this, that clinicians should not use such performance as a primary indicator of malingering. More importantly, biased responding and actual memory deficits may coexist. This is indicated in the current cases by the failure of recall memory to improve during the 2 years these patients were followed.

Post-traumatic amnesia after closed head injury: a review of the literature and some suggestions for further research.

Post-traumatic amnesia (PTA) is a transient sequela of closed head injury (CHI). The term PTA has been in clinical use for over half a century, and generally refers to the subacute phase of recovery immediately after unconsciousness following CHI. The duration of PTA predicts functional outcome after CHI, but its pathophysiological mechanism is not known. This paper compares current methods of determining the duration of PTA, summarizes reports on neuropsychological deficits in PTA, reviews available data that allow inferences about its mechanism, and suggests methods for further exploration of its pathophysiology.

The lumbar multifidus muscle in polysegmentally innervated.

We conducted a prospective case study to determine whether the lumbar multifidus muscle is polysegmentally innervated. A 49-year-old man with chronic mechanical low back pain underwent bilateral percutaneous radiofrequency neurotomy of the medial branches of the L3 dorsal rami. Electromyography (EMG) examination was performed in the L2-5 multifidi both prior to and 3 weeks after the procedure. Positive sharp waves and fibrillations appeared in the L3-L5 multifidi after the neurotomy. This study provides electrophysiological evidence in the human lumbar spine that the medial branch of the lumbar root innervates the multifidus muscle at multiple levels, i.e., the lumbar multifidus muscle is polysegmentally innervated. As a result, electromyography of the multifidus cannot identify a specific level of lumbar radiculopathy.

Sensory nerve conduction velocity is inversely related to axonal length.

It was found that the axonal length was inversely related to motor conduction velocity (CV). However, it is not clear that sensory CV is inversely related to axonal length. The nerve lengths of the median sensory fascicles from the C6 and C7 intervertebral foramen to the digital branches of the thumb and middle finger were compared in ten cadavers. Sixty healthy subjects (24 men, 36 women; mean age 35, range 24-54 years) had median sensory CV testing. The median sensory nerve action potentials were obtained antidromically in the thumb and middle finger with wrist and elbow. The CVs across the forearm for the thumb and the middle finger fascicles were then calculated. It was found that the nerve length of C7 was longer than C6 with a difference of 3.6 +/- 0.6 cm. The mean forearm CV for the median sensory axons innervating the middle finger (60.0 +/- 3.9 m/s) was slower than the CV for the median sensory axons innervating the thumb (61.4 +/- 4.1 m/s,p = 0.0012). These results demonstrate that sensory CV is slowed by 3.9 m/s per 10 cm of axon length. This study confirms that the inverse relation of CV and axonal length reported in motor axons also applies to the sensory nerves.

Thoracodorsal nerve conduction study.

There is no nerve conduction study for the thoracodorsal nerve in the literature. A conduction study for this nerve is described. Thirty healthy adults (16 males) with a mean age of 41.5 +/- 10.6 (range, 22-63) years were studied. The thoracodorsal nerve was stimulated at axilla and Erb's point with recording over the latissimus dorsi. The latency was 1.9 +/- 0.4 (range, 1.2-2.7) ms and 3.6 +/- 0.4 (range, 2.8-4.5) ms for the axillary and Erb's stimulations, respectively. The amplitude of the compound muscle action potential was 4.1 +/- 1.8 mv on the right and 3.9 +/- 1.4 mv on the left. The compound muscle action potential ratio was 0.8 +/- 0.12 (range, 0.55-0.99). This study may be useful to evaluate the integrity of the thoracodorsal nerve and to assist in the diagnosis and prognosis of brachial plexus injury.

Mentorship in physical medicine and rehabilitation residencies.

Mentorship is considered by many authorities as being possibly the most important developmental tool for the progression of a professional in training. In recent years, progressively increasing support of mentoring programs has been documented, especially in business, academia, and overall career development. Despite its recognized importance, there is a paucity of literature examining the needs of physicians in residency training programs in regard to mentorship. A 21-item questionnaire was sent to all physical medicine and rehabilitation (PM&R) residents in training in United States residency programs in May of 1993. The objectives of this survey were 3-fold: to assess interest in mentorship among PM&R residents, to determine the effect of preresidency mentorship on candidates choosing PM&R as a specialty, and to identify the factors that establish a successful mentorship in PM&R residency. A response rate of 36.2% (406/1123) was obtained. Analysis of the results indicated that 97.3% (390/401) of the respondents were interested in mentorship programs during PM&R residency; however, only 28.1% (114/406) had a mentor at the time of the survey. Before residency, 35.4% (143/404) of the respondents had a mentor, and of those, 75.9% (107/141) indicated that mentorship had a positive effect on their decision to choose PM&R as a specialty. Regarding the current mentorship, respondents benefited the most in the categories of increased knowledge of PM&R, 72.8% (83/114), and improved clinical skills, 65.8% (75/114). The least satisfaction was with the mentor's assistance with a research project, 46% (52/113), and with the effect of mentorship on the resident's visibility and reputation, 38.6% (44/114). Overall resident satisfaction with mentorship was significantly higher (P < 0.0001) in mentorships formed by free choice compared with those that were formally assigned by the residency program. Success of mentorship significantly correlated (P < 0.0001) with frequency of communication between mentor and protégé, while gender and ethnicity had no effect.

Correlation of EMG, CMAP and SNAP amplitude decrease in mononeuropathies with axonal loss.

We retrospectively reviewed electrodiagnostic studies from 1983 to 1994 and found 48 patients who met our criteria for mononeuropathy with axonal loss (40 ulnar, 4 peroneal, 4 radial). Appropriate diagnostic criteria required bilateral studies with a normal contralateral, sensory nerve action potential (SNAP) amplitude decrease of > 50% compared to contralateral, and/or distal compound muscle action potential (CMAP) amplitude decrease of > 40% compared to contralateral, and/or presence of denervation potentials; and sufficient electrodiagnostic investigation to rule out peripheral polyneuropathy. We conclude that in the electrodiagnosis of mononeuropathy with axonal loss: 1) a significant quantitative correlation between CMAP and SNAP amplitude percentage decrease does not exist (r = 0.274, p = 0.06), 2) SNAP amplitude percentage decrease [75.3 +/- 31.8%] is greater than CMAP amplitude percentage decrease [43.9 +/- 31.3%] (paired t-test, p = 0.0001), and 3) CMAP amplitude decrease is positively correlated with the presence of denervation potentials (Xtrend2 = 6.22, p = 0.013).

Electrodiagnostic 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. Thirty-three subjects with a diagnosis of unilateral or bilateral impingement syndrome were entered into the study. A neurological examination was performed, followed by electromyography on 38 upper extremities and associated cervical paraspinal muscles to search for electrodiagnostic evidence for a suprascapular neuropathy and/or cervical radiculopathy. There were no subjects with electrodiagnostic evidence for suprascapular neuropathy. In two studies (5.3%), there was electrodiagnostic evidence for a C5/6 radiculopathy, and in nine (23.7%) additional subjects, there was electrodiagnostic evidence for a possible cervical radiculopathy. The remaining 27 (71.1%) studies showed no significant electrodiagnostic evidence for a cervical radiculopathy. 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.

The prevalence of lumbar paraspinal spontaneous activity in asymptomatic subjects.

Electrodiagnostic findings of fibrillations and positive sharp waves in the lumbosacral paraspinals in patients without previous back surgery has been generally considered to be abnormal, consistent with posterior rami denervation. In some cases, it is the only abnormality on the electromyographic examination. This study was undertaken to determine the prevalence of abnormal spontaneous activity in lumbosacral paraspinals in asymptomatic individuals. Nine (14.5%) of 62 subjects studied had positive sharp waves or fibrillations noted on the needle examination of bilateral lumbosacral paraspinal muscles. There was a significant increase in the prevalence of abnormal activity with increasing age. This suggests that caution should be taken in attributing radiculopathy as the etiology of low back pain when electromyographic lumbosacral paraspinal abnormalities are the only positive findings in the middle-aged or older individual.

Electromyographic motor Tinel's sign in ulnar mononeuropathies at the elbow.

A novel test for localizing ulnar mononeuropathies (UM), the electromyographic (EMG) motor Tinel's sign, has been developed. While recording with a monopolar needle from the abductor digiti minimi, the ulnar nerve is lightly rolled at multiple sites across the elbow, and the test is considered positive if a burst of EMG activity is observed simultaneously with nerve compression. To determine the use of the EMG Tinel's sign, we evaluated 70 control nerves and 50 clinically suspected UMs. The EMG Tinel's sign had a 78% sensitivity and a 79% specificity for suspected UM at the elbow. The clinical Tinel's sign was present in 68% of suspected UM cases, and the combined sensitivity of the EMG and clinical Tinel's sign was 96%. Using nerve conduction study (NCS) values derived from the control nerves, 62% of UM nerves had abnormal NCS/EMG findings, and 28% of UM nerves had NCS/EMG abnormalities that could be localized to the elbow. The development of motor axon mechanosensitivity at the site of nerve injury is a new finding, not previously observed in electrophysiologic studies of animal nerve injury models or reported in the electrodiagnostic literature.

An EMG case report of lead neuropathy 19 years after a shotgun injury.

The clinical picture of lead neuropathy was classically described as a painless progressive motor neuropathy with axonal loss. The literature review fails to demonstrate a consensus on the site of axonal loss. This is an EMG report of a patient who developed a late lead neuropathy after a shotgun injury. A 69-year-old Filipino, healthy, male nondrinker sustained a shotgun injury to his left elbow. Nineteen years later he developed abdominal pain, followed by generalized weakness, distal greater than proximal in the extremities, and impaired pin-prick, proprioception, and two-point discrimination. He became nonambulatory and totally dependent in daily activities. He was lost to follow-up for 2 years until January 1993 when he presented with a blood lead level of 84 micrograms/dL. EMG examination revealed a sensorimotor peripheral polyneuropathy with severe axonal loss. This case demonstrates that axonal loss is the predominant feature in lead neuropathy and the location of pathology is in the peripheral nerves.

The natural resolution of a lumbar spontaneous epidural hematoma and associated radiculopathy.

This is a report of a 37-year-old man who, while lifting a heavy box, developed severe low-back pain radiating into the right anterior thigh. The only clinical signs were paraspinal muscle spasm and a positive femoral nerve stretch test on the right. An electromyographic study demonstrated denervation in the right L2, L3, and L4 myotomes and paraspinal muscles. Magnetic resonance imaging (MRI) showed a large L1-2 anterior epidural hematoma compressing the spinal cord. The patient's pain gradually improved with conservative management and he returned to light work after 4 weeks. Repeat electromyographic and MRI studies were normal, indicating a resolution of the radiculopathy and hematoma. The diagnosis and management of spontaneous epidural hematomas are discussed.

The absence of brachial plexus injury in stroke.

Brachial plexus injury and proximal mononeuropathy have been reported as a potential complications in the hemiplegic shoulder after a stroke. The diagnosis of brachial plexus injury and proximal mononeuropathy in the hemiplegic extremity is complicated by the upper motor neuron findings on physical examination and by the diffusely abnormal electrodiagnostic test results frequently seen in hemiplegic limbs. This study investigated the incidence of brachial plexus injury and proximal mononeuropathy after a thromboembolic stroke. Hemiplegic patients (n = 50) underwent physical examination, needle electromyography of the hemiplegic extremities and nerve conduction studies across the brachial plexus within 4 months after a stroke. Combining the physical examination and electromyographic findings we were unable to make a diagnosis of brachial plexus injury or proximal mononeuropathy in any hemiplegic patient. Spontaneous electromyographic activity was observed in 68% of the arms and 70% of the legs examined on the hemiplegic side. The severity and incidence of spontaneous activity was evenly distributed in upper and lower trunk muscles. Mean central latencies across the lower brachial plexus were slightly delayed (12.5 +/- 2 v 11.6 +/- 2.2 ms, P < 0.01) compared with the contralateral normal limb, but in no case was the F wave unilaterally unelicitable. The mean hypothenar compound muscle action potential amplitude was diminished (7 +/- 2.7 v 9.2 +/- 4.1 mV, P < 0.01) in the hemiplegic hand compared with the normal side and the degree of amplitude loss inversely corresponded (r = -0.6, P < 0.01) to the amount of spontaneous electromyographic activity observed in the first dorsal interosseus muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Rehabilitation of patients with Hallervorden-Spatz syndrome.

Hallervorden-Spatz Syndrome is an infrequently occurring disorder involving pigmentary degeneration of the globus pallidus, red nucleus, and substantia nigra. Resultant corticospinal and extrapyramidal signs and symptoms predominate early in the course of the disease, with concomitant intellectual deterioration paralleling the developing muscular disorder. To date, there have been no reports in the literature of rehabilitative intervention in patients with this disabling pathology. We report the case of a 43-year-old man whose illness spanned 20 years. He was referred for rehabilitation after a precipitous decline in function over the course of six months. An interdisciplinary team approach was implemented and various medical strategies were used, including the initiation of carbidopa-levodopa. An improvement in functional skills, communication, and the ability to use cognitive strategies was observed. We conclude that a multidisciplinary team approach and in selected cases, the use of carbidopa-levodopa are valid methods for the rehabilitation of patients with Hallervorden-Spatz Syndrome.

Dermatomal somatosensory evoked potentials in brachial plexus injuries.

The dermatomally stimulated somatosensory evoked potential is an essentially painless, noninvasive procedure that can add useful information to the diagnosis of the site and extent of brachial plexus injuries. In this study, 13 patients with unilateral brachial plexus injuries who had previously undergone conventional electromyographic testing underwent somatosensory evoked potential recording with median, ulnar, radial, musculocutaneous nerve and C5, C6, C7, C8 and T1 dermatomal stimulation. There was no significant difference in the peak latencies, interpeak latencies, or amplitudes of the major peaks between the normal values and the values from the affected levels. However, analysis for absence or presence of major peaks from side-to-side was useful in supporting the data from electromyographic and radiologic studies, as well as in providing more specific information as to the level of injury and extent of injury in two of the cases. The accurate diagnosis can provide the information needed to determine patient treatment as well as plan the rehabilitation program of the patient. The dermatomal somatosensory evoked potential can be a useful supplement to the assessment of the patient with a brachial plexus injury.

Nerve conduction and creatinine clearance in aged subjects with periodic movements in sleep.

Periodic leg movements during sleep (PLMs) are non-epileptiform, repetitive limb movements that are highly prevalent among the geriatric population. The mechanisms underlying these movements are poorly understood. In this study we evaluated PLMs of 24 aged volunteers. We hypothesized that the high prevalence of PLMs seen in the aged would be related to (a) lower creatinine clearance and (b) slowed velocities/delayed latencies in the nerve conduction studies of such individuals. Results did not support hypothesis (a) but offered some equivocal support for hypothesis (b), inasmuch as aged subjects with higher levels of PLMs had delayed motor and sensory latencies in the upper limbs (median n., ulnar n.). Results are discussed in terms of central vs peripheral mechanisms involved in the generation of PLMs in elderly persons.