The evaluation of suspected ulnar neuropathy at the elbow. Normal conduction study values.

Local compression of the ulnar nerve occurs at several points, with the elbow region being the most common. Nerve conduction studies can be useful in identifying and localizing such lesions; however, the specifics of the technique, including normal values, have not been firmly established. We evaluated the effect of elbow position on segmental conduction velocities (CVs), the influence of elbow, nerve segment length on CV calculations, the change in compound action potential amplitude at sites along the nerve, and the use of performing segmental sensory CVs. Conductions done with the elbow flexed produced less segment-to-segment CV variation than those obtained with the elbow extended. The influence of using overlapping nerve segments compared with short adjacent ones for segmental CV comparison is discussed.

The description of motor unit potentials in electromyography.

It has been suggested that the findings on needle electromyography should be described by abbreviations such as "SSAP" rather than "myopathic." The patterns of changes that may occur and their pathophysiologic basis make both of these terms unsuitable. Quantitative measurements are needed.

Spinal cord infarction: another cause of "lumbosacral polyradiculopathy".

An elderly woman with leg weakness and sensory loss had fibrillation potentials in her legs and at multiple lumbosacral levels of paraspinal muscles. Clinical and myelographic studies showed occlusion of an anterior spinal artery due to an arteriovenous malformation of the spinal cord. EMG aided in the diagnosis and localization of this anterior spinal cord lesion.

Lumbosacral spinal evoked potentials in humans.

Evoked potentials in response to submaximal electrical stimuli to the peroneal or tibial nerves were recorded from the lumbosacral region in 18 normal subjects. Averaging of 128 responses from recording electrodes over spinous processes S1 to T11, with a reference electrode on the contralateral iliac crest, demonstrated potentials of 0.5 to 1.8 microV, with two well-defined negative peaks having latencies proportional to the distance between the stimulating and recording electrodes. The first peak originated from a traveling wave of depolarization in afferent fibers in the cauda equina, and the second peak originated in the spinal cord. F waves, H reflexes, microreflexes, and volume-conducted muscle responses did not contribute to these potentials.

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.

Neuropathy in the Miller Fisher syndrome: clinical and electrophysiologic findings.

The clinical and electrophysiologic findings in 10 patients with Miller Fisher syndrome (ataxia, ophthalmoplegia, and areflexia) were reviewed. All patients had motor and sensory nerve conduction studies and EMG in the arm and the leg, and seven patients had cranial nerve conduction studies. Electrodiagnostic abnormalities were found in all patients and were characteristic of an axonal neuropathy or a neuronopathy with predominant sensory nerve changes in the limbs and motor damage in the cranial nerves. The pattern of abnormalities was distinct from the usual features seen in the major form of acute inflammatory polyneuropathy, the Guillain-Barré syndrome.

Deep branch ulnar neuropathy due to giant cell tumor: report of a case.

Electrophysiologic studies indicated a lesion of the deep branch of the ulnar nerve in the palm of a 42-year-old man with painless weakness and wasting of ulnar-innervated intrinsic hand muscles. Magnetic resonance imaging of this region demonstrated a soft-tissue mass in the palm distal to Guyon's canal. Surgical exploration disclosed a giant cell tumor of the tendon sheath, compressing the deep branch of the ulnar nerve.

A clinical and electrophysiological evaluation of myoclonus.

The records of 23 consecutive patients with myoclonus who were seen during a 16-month period were analyzed prospectively. The patients were divided into two groups: epileptic and nonepileptic. The epileptic patients had focal and stimulus-elicitable myoclonus with enlarged somatosensory evoked potentials and enhanced long-loop reflexes, and they responded well to anticonvulsants, especially clonazepam and valproic acid. The nonepileptic group had massive and spontaneous jerks with normal-sized somatosensory evoked potentials and long-loop reflexes, and they responded poorly to anticonvulsants. Evaluation of these clinical and electrophysiologic characteristics can help in the classification of obscure movement disorders and in predicting responses to therapy.

How frequently does classic amyotrophic lateral sclerosis develop in survivors of poliomyelitis?

There is a paucity of reports of classic amyotrophic lateral sclerosis (ALS) developing in survivors of paralytic poliomyelitis. We describe a patient with classic ALS and an antecedent paralytic disease thought to have been poliomyelitis from which she recovered completely. If the paucity of ALS preceded by true poliomyelitis is not merely a matter of underreporting, antecedent paralytic poliomyelitis may have a protective role against the development of ALS. This has implications relevant to pathogenesis and to projected secular trends of ALS incidence since the introduction of poliomyelitis vaccines. There is a need to establish the incidence of cases of classic ALS in patients with antecedent poliomyelitis.

Stationary waves recorded at the shoulder after median nerve stimulation.

A new recording method with a reference electrode on the stimulated arm defined two discrete far-field potentials just before the propagated near-field nerve action potential was recorded at Erb's point. Both potentials were stationary waves with the same latency at all recording sites. The first potential had the same onset and peak latencies as the propagated wave at the axilla; it corresponded to the first component of the P9 far-field potential recorded with scalp to noncephalic reference montages. The latency of the second potential coincided with that of the propagated wave entering the neck and corresponded to the peak of the P9 potential. The occurrence of these potentials where there are significant changes in the morphology of the volume conductor suggests that the P9 far-field potential is due to a change in the conducting medium that surrounds the nerve.

Facial myokymia with polyradiculoneuropathy.

Two patients had bilateral facial myokymia in association with polyradiculoneuropathy. Characteristic electromyographic findings allow polyradiculoneuropathy to be differentiated from other causes of facial movements, and support the possibility that extraaxial facial nerve involvement is another cause of facial myokymia.

The syndrome of acute sensory neuropathy: clinical features and electrophysiologic and pathologic changes.

We followed 42 patients with clinically defined pure sensory neuropathy of acute or subacute onset for 2 to 35 years. The symptoms began in the upper limbs in 23 patients, in the lower limbs in 13, symmetrically in all 4 limbs in 4, and the face was 1st affected in 2. For 19 patients, the symptoms began asymmetrically. Electrophysiologic testing typically showed absence of sensory potentials. Spinal fluid was usually acellular with a normal protein level. Sural nerve biopsy in 22 patients showed loss of large myelinated fibers and axonal atrophy without inflammation. Six of the patients died: 4 of unrelated causes and 2 of subdural hemorrhages. Only 2 patients had severe functional impairment. Twenty-two had significant sensory deficit but were able to carry out most of their usual activities. In 8, the symptoms had resolved completely. The acute, often focal onset suggests an immune-mediated or vascular process at the level of the posterior root or dorsal root ganglion.

Peripheral neuropathic syndromes in giant cell (temporal) arteritis.

Of 166 consecutive patients with histologically confirmed giant cell (temporal) arteritis (GCA) seen during a 3-year period, 23 (14%) had clinically diagnosed peripheral neuropathic syndromes temporally coincident with clinically active GCA. Electromyography and nerve conduction studies were performed in 16, confirming abnormalities in all. Of the 23 patients, 11 had a generalized peripheral neuropathy, nine had multiple mononeuropathies, and three had a mononeuropathy. The nerves affected as mononeuropathies were the median, ulnar, peroneal, tibial, and sural nerves, and the C-5 and L-5 nerve roots. Angiography, performed in two patients, demonstrated widespread arteritis involving the lower limbs and, after 3 months of oral corticosteroid treatment in one of these patients, an amputation specimen showed chronic arteritis.

Effect of artificial pancreas treatment on peripheral nerve function in diabetes.

To determine whether the complete correction of hyperglycemia of diabetes can rapidly improve abnormal peripheral nerve function, eight hyperglycemic insulin-requiring diabetics underwent 3 days of glucose control with an artificial endocrine pancreas, the BIOSTATOR Glucose Controller. Comparison of neurologic assessment before and after BIOSTATOR treatment showed improvement only in ulnar sensory conduction velocity (+ 3.2 +/- 1.4 meters per second, p less than 0.032) and no significant changes in 24 other nerve conduction measurements, computer-assisted examination, and scored neurologic assessment. Any significant beneficial effect on nerve function resulting from correction of hyperglycemia probably requires more than 3 days to be manifested.

When is an apparent excess of neurologic cases epidemiologically significant?

To conserve clinical and public health resources, it is necessary to screen reports from the community of an excess or cluster of cases of chronic neurologic diseases for potential epidemiologic significance, ie, to identify those clusters that may have occurred owing to the operation of an underlying etiologic cause rather than to chance alone. Traditionally, the probability that such a cluster has occurred by chance within the reporting community is computed, ignoring the fact that many other similar communities have not reported a cluster. We propose a modified approach that takes this larger universe of communities into account, thereby raising the threshold for potential epidemiologic significance. As a result, the lowest value for the ratio of observed-to-expected cases that may be considered of epidemiologic significance should be increased by factors of 2 for small clusters (one to three expected cases), 1.5 for intermediate clusters (seven to 30 expected cases), and 1.3 for large clusters (60 to 90 expected cases). Consequently, case ascertainment and full field investigations can be reserved for only those reports that, if confirmed, would represent a cluster not due to chance alone. We illustrate this with a case from our own experience.

Epidemiologic correlates of sporadic amyotrophic lateral sclerosis.

We evaluated 74 selected patients with amyotrophic lateral sclerosis (ALS) and 201 matched controls for risk factors for ALS by a case-control design and a sequential questionnaire/interview technique to quantitate biographic data. We analyzed occupational and recreational data only for 47 male patients and 47 corresponding patient controls; data for women were insufficient. We used nonparametric analyses to evaluate five primary comparisons of ALS patients with controls: (1) more hard physical labor, p not significant (NS); (2) greater frequency of neurodegenerative disease in family members, p NS; (3) greater exposure to lead, p less than 0.05; (4) more years lived in a rural community, p NS; and (5) more trauma or major surgery, p NS. Men with ALS had worked more frequently at blue-collar jobs (although not a statistically significant difference, p = 0.10) and at welding or soldering (p less than 0.01). These results suggest that there may be an association between ALS in men and exposure to lead vapor. The limited nature of the association favors a multifactorial etiologic mechanism of ALS.

Lack of progression of neurologic deficit in survivors of paralytic polio: a 5-year prospective population-based study.

We completed a prospective, population-based cohort study of polio survivors in Olmsted County, Minnesota, between 1986 and 1993. We identified 50 individuals who had had paralytic polio between 1935 and 1960, as representative of all 300 cases of paralytic polio in the county. We completed detailed quantitative clinical and electrophysiologic studies at entry and after 5 years. These studies demonstrated stable neuromuscular function within the cohort, although 60% of the individuals were symptomatic. In two-thirds of the symptomatic patients, the causes of their symptoms were unrelated to earlier polio. For the 20% of patients who had unexplained muscle pain, perception of weakness, and fatigue, a mechanical disorder most likely underlies their symptoms.

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.

Late effects of paralytic poliomyelitis in Olmsted County, Minnesota.

We identified a cohort of 300 individuals who had paralytic polio between 1935 and 1955. All lived in Olmsted County, Minnesota. From the 247 survivors, we selected 50 subjects for detailed historical, functional, psychological, clinical, and electrophysiologic evaluation. Sixty-four percent of these 50 survivors complained of new symptoms of muscle pain, fatigue, and weakness after a period of prolonged stability. This led to changes in lifestyle or activity in only 18%. The likelihood of expressing new complaints was not related to present age or interval since polio, and electrophysiologic testing did not distinguish between those with or without new problems. The development of new difficulties in a limb was most strongly predicted by significant paralysis of that limb at the time of the acute illness. Patients with leg weakness were twice as likely to complain of new problems compared to those with arm weakness. Elevated creatine kinase levels were present only in those with new complaints.

Monitoring of cortical evoked potentials during surgical procedures on the cervical spine.

We reviewed the results of intraoperative monitoring of short-latency cortical evoked potentials in 81 patients who underwent surgical procedures of the cervical spine. Of these patients, 43 had baseline somatosensory evoked potentials from stimulation of the upper and lower extremities, intraoperative monitoring for at least 3 hours, and absence of an intrinsic lesion of the spinal cord. Major reductions in amplitude of the ulnar and tibial cortical evoked potentials occurred shortly after induction of anesthesia in 12% of patients. Latencies gradually increased during the operation as the concentration of volatile anesthetic agents increased. In patients with preoperative evidence of cervical cord damage, the cortical responses showed more fluctuations and could be lost without major changes in the concentration of the anesthetic agent or surgical manipulation. In one patient, intraoperative monitoring of the cervical cord function prevented a postoperative neurologic deficit. Ulnar and tibial cortical evoked potentials were successfully monitored throughout operation in all patients in whom baseline scalp responses could be obtained, but careful monitoring of anesthetic effect is necessary for proper interpretation.