Median and ulnar nerve conduction studies among workers: normative values

To determine normative values for nerve conduction studies among workers, we selected a subset of 326 workers from 955 subjects who participated in medical surveys in the workplace. The reference cohort was composed exclusively of active workers, in contrast to the typical convenience samples. Nerve conduction measures included bilateral median and ulnar sensory amplitude and latency (onset and peak). Workers with upper extremity symptoms, medical conditions that could adversely affect peripheral nerve function, low hand temperature, or highly repetitive jobs were excluded from the "normal" cohort. Linear regression models explained between 21% and 51% of the variance in nerve function, with covariates of age, sex, hand temperature, and anthropometric factors. The most robust models were fitted for sensory amplitudes in the median and ulnar nerves for dominant and nondominant hands. The median-ulnar difference was least sensitive to adjustment, indicating it is the best measure to use if corrections are not made to account for relevant covariates. A key point was that the magnitude of variance increased with age and anthropometric factors. These findings provide strong evidence that to improve diagnostic accuracy, electrodiagnostic testing should control for relevant covariates, particularly age, sex, hand temperature, and anthropometric factors.     

Sensory and mixed nerve conduction studies in the evaluation of ulnar neuropathy at the elbow

The relative sensitivities of sensory, mixed nerve, and motor conduction studies in assessing ulnar neuropathy at the elbow have not yet been established. Using surface electrodes, we performed conduction studies across the elbow segment in 43 patients with symptoms referable to the ulnar nerve and 40 control subjects. Segmental slowing of motor conduction localized the lesion to the elbow in 14 of 21 patients (67%) with clear evidence of ulnar neuropathy on physical examination but only in 2 of 22 (9%) with subtle or no physical examination abnormalities. The diagnostic yield was increased by the finding of segmental slowing of sensory or mixed nerve conduction across the elbow to 86% and 68%, respectively, for each of the groups. We conclude that surface-recorded sensory and mixed nerve conduction studies appear to be more sensitive than motor studies in the electrodiagnosis of ulnar neuropathy at the elbow and are especially valuable in patients with subtle clinical involvement.     

Chronic double-level cauda equina compression. An experimental study on the dog cauda equina with analyses of nerve conduction velocity

STUDY DESIGN: Nerve conduction velocity was studied in the dog cauda equina subjected to chronic double-level compression. OBJECTIVES: To analyze the effects of chronic double-level cauda equina compression. SUMMARY OF BACKGROUND DATA: Double-level cauda equina compression produces more symptoms in patients and more changes in acute experimental set-ups than does single-level compression. However, there have been no controlled, experimental studies on chronic double-level compression. METHODS: A total of 20 dogs were anesthetized. Two balloons were placed under the lamina of the seventh lumbar vertebra and the first sacral vertebra, respectively. One week (10 mm Hg, n = 5; 0 mm Hg, n = 5) and 1 month (10 mm Hg, n = 5; 0 mm Hg, n = 5) after inflation with a viscous substance, nerve conduction velocity was studied by local electrical stimulation and recording of muscle action potentials in the tail muscles. RESULTS: Nerve conduction velocity was determined over the cranial balloon, the caudal balloon, and both balloons. The data were similar for all three recordings. After 1 week there was a significant reduction in nerve conduction velocity induced by 10 mm Hg, compared with that induced by 0 mm Hg, which showed normal conditions. However, after 1 month this initial reduction in nerve conduction velocity had recovered partially. The reduction was similar to that described for single-level compression in a previous study in which the same compression model was used. CONCLUSIONS: Unlike the acute situation, chronic double-level compression does not induce more changes than single-level compression after 1 week, although the recovery after 1 month of compression is less complete after double-level compression. This less complete recovery may be a result of an adaptation of the nerve tissue and the vascularization of the cauda equina nerve roots to the applied pressure.     

Symmetry of normal motor and sensory nerve conduction measurements

Nerve conduction measurements in normal subjects are assumed to be symmetric, but the normal limits of symmetry have not been determined. Full data on the limits of symmetry for commonly studied nerves are important in the clinical interpretation of nerve conduction data. We selected normal electrodiagnostic studies from archived electromyographic laboratory reports that included bilateral measurements of motor and sensory nerves. Symmetry of nerve conduction measures was confirmed, and only the median and ulnar sensory nerves had significant deviations from symmetry, supporting subclinical nerve damage in the most common dominant hand. The limits of symmetry were determined by calculating the 95th percentile for the differences between sides. For motor and sensory nerves, the range of 95th percentile limits was narrower for measures in upper extremity nerves compared to lower extremity nerves. Several reasons are offered for the wider limits of symmetry in lower extremity nerves.     

Statistical methods of computing reference values for side-to-side differences in nerve conduction studies

OBJECTIVE: To evaluate the utility of surgery in the treatment of peptic ulcer disease. METHODS: The clinical history of patients operated for peptic ulcer disease in a 15 year period were reviewed. The demographic data, indications for surgery, surgical procedure, morbidity, mortality and long term results, were analyzed. RESULTS: 349 patients were operated for peptic ulcer disease or its complications, 56% male. In 78% surgery was elective, mostly due to pyloric obstruction. In the remaining 22% perforation or bleeding ulcer were the main causes for emergency surgery. The most frequent elective procedure was vagotomy and drainage (66%); in urgent surgery, a definitive procedure was done in 35% of the perforations and in 94% of the bleeding ulcers. The 30-day mortality in urgent surgery was 14%; in elective surgery there was no mortality. A satisfactory long term result was obtained in 80% of the patients. CONCLUSIONS: An indication for surgical treatment of complicated peptic ulcer disease was above 50%, and 90 per cent in recent years. The frequency of urgent surgery is increasing and reached 60% of surgeries for this disease. Whenever possible, a definitive procedure is recommended.     

Neural conduction velocity of the human auditory nerve: bipolar recordings from the exposed intracranial portion of the eighth nerve during vestibular nerve section

We measured the conduction velocity of the intracranial portion of the auditory nerve in 3 patients undergoing vestibular nerve section to treat Ménière's disease. The conduction velocity varied from patient to patient, with an average value of 15.1 m/sec. The latency of peak III of the brain-stem auditory evoked potentials (BAEPs) increased by an average of 0.5 msec as a result of exposure of the eighth nerve, and if that increase is assumed to affect the entire length of the auditory nerve (2.6 cm) evenly, then the corrected estimate of conduction velocity would be 22.0 m/sec. Estimates of conduction velocity based on the interpeak latencies of peaks I and II of the BAEP, assuming that peak II is generated by the mid-portion of the intracranial segment of the auditory nerve, yielded similar values of conduction velocities (about 20 m/sec).     

Carbon disulfide neurotoxicity in rats: VI. Electrophysiological examination of caudal tail nerve compound action potentials and nerve conduction velocity

The effects of subchronic exposure to carbon disulfide (CS2) on ventral caudal tail nerve compound nerve action potential (CNAP) amplitudes and latencies, and nerve conduction velocity (NCV) in rats were examined. Male and female Fischer 344 rats were exposed to 0, 50, 500, or 800 ppm CS2 for 6 hrs/day, 5 days/week. Using separate groups, exposure duration was 2, 4, 8, or 13 weeks. Exposure to 500 or 800 ppm CS2 for 13 weeks decreased NCV compared to the 50 ppm CS2 group. CNAP amplitudes were increased, and peak P1P2 interpeak latency decreased, after exposure to 500 or 800 ppm CS2 for 13 weeks. Most of the changes in NCV and CNAPs were not attributable to differences in tail or colonic temperature. However, the increases in peak P1 amplitude may relate to the proximity of the electrodes to the tail nerves. Assessment of tail nerve morphology after 13 weeks exposure to 800 ppm CS2 revealed only minor changes compared to the extent of axonal swelling and degeneration observed in the muscular branch of the tibial nerve and axonal swelling in the spinal cord. As anticipated, in older animals the NCV increased, the CNAP amplitudes increased, and the CNAP latencies decreased. The biological basis for the changes in CNAPs produced by CS2 is under investigation. Future studies will focus on electrophysiological evaluation of spinal nerve function, to allow better correlation with pathological and behavioral endpoints.     

The cutaneous innervation of the palm: an anatomic study of the ulnar and median nerves

Twenty-five fresh-frozen cadaveric hands without obvious deformity were dissected using 3.5x loupe magnification. Median and ulnar nerves were identified in the proximal forearm and dissected distally to the midpalm. Cutaneous branches of median and ulnar nerves were described relative to an incision for carpal tunnel release. The palmar cutaneous branch of the median nerve was present in all 25 specimens. In a single specimen, the palmar cutaneous branch of the median nerve was isolated as it crossed the incision, and in another two specimens, the terminal branches of the nerve were identified at the margin of the incision. In 4 hands, a classic palmar cutaneous branch of the ulnar nerve was found an average of 4.9 cm proximal to the pisiform. In 10 specimens, a nerve of Henle arose an average of 14.0 cm proximal to the pisiform and traveled with the ulnar neurovascular bundle to the wrist flexion crease. In 24 specimens, at least one-usually multiple-transverse palmar cutaneous branch was identified originating an average of 3 mm distal to the pisiform within Guyon's canal. The origin and destination of these nerves was highly variable. In 16 specimens, an incision in the axis of the ring finger would likely have encountered at least one branch of the ulnar-based cutaneous innervation to the palm. Cutaneous branches of the ulnar nerve would be expected to cross the line of dissection frequently during open carpal tunnel release. Decreased levels of discomfort in patients undergoing endoscopic and subcutaneous types of carpal tunnel release may be in part due to the preservation of the crossing cutaneous nerves with these procedures.     

Surgical treatment of the ulnar nerve entrapment neuropathy: submuscular anterior transposition or simple decompression of the ulnar nerve? Long-term results in 79 cases

The surgical treatment of the ulnar nerve entrapment neuropathy at the elbow is controversial. None of the presently advocated procedures (simple decompression of the ulnar nerve, medial epicondylectomy, subcutaneous or submuscular anterior transposition of the ulnar nerve) has proven optimal regarding long-term results. We studied the outcome in 79 patients whose ulnar nerve had been operated on for the first time, either by simple decompression (31 cases) or by submuscular anterior transposition (48 cases). The mean follow-up was 76 months. Patients were classified according to McGowan pre- and postoperatively; we also applied a more detailed scoring system of our own. Preoperatively, the patients were distributed almost equally between the three McGowan classes. Postoperatively, about one out of three patients in both treatment groups experienced a distinct improvement, i.e. was upgraded to a better McGowan class. Using our own scoring system, the overall rate of objective improvement was 73% after transposition and 55% after simple decompression. Irrespective of the surgical method, roughly 90% of the patients considered their postoperative condition to be improved. However, one specific group of patients (people with habitual ulnar luxation or subluxation of the ulnar nerve) experienced a distinctly better result when treated by anterior transposition than by simple decompression. Our results show that simple decompression of the ulnar nerve can be recommended in all patients without cubital (sub)luxation of the nerve, whereas people with a tendency of cubital (sub)luxation of the ulnar nerve should be treated by submuscular anterior transposition.     

Segmental motor conduction time for abductor of the fifth finger muscle: methods and normative values

Electrical stimulation of the ulnar nerves (60 nerves) and magnetic stimulation of the roots (C7) and motor cortex were performed on 30 normal controls. The muscle responses and F wave (peripheral stimulation) were recorded from abductor digiti minimi muscle (60 muscles). The parameters of examined potentials were measured and the central, root, peripheral motor conduction times were estimated. The normative values were established as well as formulae of linear regression within the observed correlations with height. The method may be used for electrophysiological diagnosis of patients with motor pathway impairment at the different levels.     

Sensory and cognitive factors in the processing of visual velocity.

A symmetrical 6?×?6 factorial design of distances and durations served to produce either 36 different moving stimuli (real movement condition) or 36 static displays separately containing the respective stimulus components (cognitive movement condition). Different metric rules underlay the two types of velocity judgments: Perceptual estimations of real movement obeyed a ratio model, whereas conscious estimations of implied movement obeyed an additive model. Valuation operations differed, too; the scales underlying real velocity were nonlinearly related to the even more compressive scales that underlay cognitive velocity. Implications of these results for velocity research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Traumatic forearm amputation with avulsions of the ulnar and median nerves from the brachial plexus

A case of a traumatic forearm amputation and associated complete avulsions of the ulnar and median nerves from the brachial plexus due to a crush-traction injury of the distal part of the right forearm is reported. The patient also suffered a traumatic head injury. The injury of the upper limb and the general condition of the patient were so serious that an amputation at the 1/3 middle part of the forearm had to be performed.     

Nerve conduction velocity in man: influence of glucose, somatostatin and electrolytes

Insufficient metabolic control in diabetes mellitus is associated with a reversible reduction in nerve conduction velocity, but the mechanism behind this phenomenon is unknown. To examine the effect of acute hyperglycaemia on nerve conduction eight non-diabetic men (20-49 years of age) with no signs of peripheral neuropathy were studied before and after 3 h of hyperglycaemic clamping (plasma glucose approximately 15 mmol/l), while insulin secretion was suppressed by somatostatin [Study 1]. Nerve conduction velocity, as determined in the proximal part of the median nerve, fell by 2.8 +/- 3.0 m/s (2p-value: 0.033). However, during euglycaemic clamping (plasma glucose approximately 5 mmol/l) in five non-diabetic men (19-38 years of age) infused solely with somatostatin [Study 2], a comparable decrement in nerve conduction velocity was found (1.7 +/- 1.3 m/s, 2p-value: 0.043). In both studies relative hypoinsulinaemia was present. Serum-sodium decreased significantly (143 +/- 1 mmol/l vs 137 +/- 1 mmol/l [Study 1] and 143 +/- 1 mmol/l vs 142 +/- 2 mmol/l [Study 2]), while serum-potassium increased. In conclusion, the slight but significant reduction in nerve conduction velocity observed in both studies appears to be correlated to electrolyte changes. However, an effect of hypersomatostatinaemia or the hormonal changes associated with this cannot be excluded, while short-term hyperglycaemia per se seems to be without effect on nerve conduction velocity.     

Electrophysiologic analysis of the lumbosacral radiculopathy using nerve root conduction velocity (NRCV) and cauda equina action potentials (CEAP)

Nerve root conduction velocity (NRCV) and cauda equina action potential (CEAP) have been measured to assess the severity of lumbosacral radiculopathy, the level-specific diagnosis of the symptomatic roots, and to predict the outcome. This study included 71 patients (40 males, 31 females, average age of 54 years at the time of surgery) who underwent decompressive surgery for lumbar radiculopathy. The NRCV and CEAP were directly measured during the operation. The NRCV decreased significantly with progression of radicular symptoms. The NRCV showed a marked reduction in the nerve roots of the patients with a two years or longer history of radicular symptoms; or those with compression of the nerve roots on the imaging examinations; or nerve roots that were considered to have been subjected to persistent compression over a prolonged period with severe inflammation and adhesions. Multivariative analyses suggested that the NRCV correlated closely to the postoperative neurologic recovery, and the outcome of the lumbosacral radiculopathy could be predicted to some extent by measurements of NRCV. The level-specific diagnosis of the radiculopathy could be determined when the CEAP showed a more than 30% left-right potentials difference.     

Electrophysiologic mapping and cadaveric dissection of the lateral foot: implications for tibial motor nerve conduction studies

OBJECTIVE: To clarify, through electrophysiologic mapping and cadaveric dissection of the lateral foot, the previously published "proximal" and "distal" recording sites for tibial motor nerve conduction studies. DESIGN: Observational. SETTING: Electromyography laboratory; anatomy laboratory. PATIENTS OR OTHER PARTICIPANTS: Ten asymptomatic feet; eight cadaveric feet. MAIN OUTCOME MEASURES: (1) Amplitudes and onset latencies of compound muscle action potentials (CMAPs) recorded over a grid on the lateral foot that included the "proximal" and "distal" recording sites; (2) nerve supply and anatomic boundaries of the abductor digiti minimi pedis (ADMP) and nearby muscles, particularly as they relate to the above recording sites. RESULTS: (1) Relatively large CMAPs were recorded at and around the "proximal" and "distal" sites, with significantly shorter "proximal" latencies. (2) In all cadaveric feet, ADMP was innervated by only the inferior calcaneal nerve (ICN) and was located deep to the "proximal" site, with virtually no muscle fibers deep to the "distal" site. The flexor digiti minimi brevis (FDMB) was conspicuously located immediately deep to the "distal" site and was innervated by only the lateral plantar nerve (LPN). CONCLUSIONS: This study strongly suggests that the "proximal" site records predominantly from the ICN-innervated ADMP, whereas the "distal" site predominantly records from the LPN-innervated FDMB.