The double crush in nerve entrapment syndromes

Regeneration following tibial nerve crush in the rabbit: the effect of proximal constriction

In order to test the regenerative capacity of atrophic axons, a constricting ligature was placed around the proximal tibial nerve of the rabbit, and the nerve crushed at the ankle one week later. Axonal atrophy with altered g ratios was subsequently confirmed in fibres distal to the site of ligature and proximal to the site of crush. In nerves with tight proximal ligatures the reinnervation of plantar muscles and the subsequent recovery of distal motor latency were delayed, indicating impaired regeneration. This result may be relevant to the "double-crush" theory of nerve damage.

Graded inhibition of retrograde axonal transport by compression of rabbit vagus nerve

Effects of experimental compression at different pressures on retrograde axonal transport were studied in rabbit vagus nerve. Proteins in the sensory neurones were radiolabelled by injection of [3H]leucine into the nodose ganglion. Sixteen hours after labelling, a small compression chamber and/or ligatures were applied around the cervical part of the vagus nerve for 8 h. Compression of the vagus nerve at 20, 30 and 200 mm Hg pressure induced a graded inhibition of both retrograde and anterograde transport of the radiolabelled proteins. Neither retrograde nor anterograde transport was affected by the presence of the non-inflated chamber. The results indicate that compression at pressures similar to those found in human carpal tunnel syndrome can block retrograde axonal transport. The consequences of inhibition of retrograde and anterograde axonal transport for the metabolism in the nerve cell bodies are discussed.

Increase of vibration threshold during wrist flexion in patients with carpal tunnel syndrome

The most prominent symptoms of carpal tunnel syndrome (CTS) are sensory, with intermittent numbness, paraesthesiae and pain in the fingers innervated by the median nerve. No consistent signs are found by neurological examination, however. Conventional sensibility tests are positive in only about 50% of the cases. This applies also to quantitative tests such as measurement of the perception threshold for vibration (VT). In an attempt to find a more reliable indication and improve the diagnostic value of sensory testing, determination of VT was combined with provocation by means of wrist flexion. In a patient group with neurophysiologically verified CTS, all patients exhibited an increase to at least twice the VT value in the fingers innervated by the median nerve. No increase was seen in the little finger or in a control group of patients with digital paraesthesiae but with normal neurophysiological findings. It is concluded that VT measurements during wrist flexion can be used as a supplementary or alternative diagnostic criterion to indicate that the nerve dysfunction is located in the carpal tunnel.

Radial sensory nerve entrapment in the forearm

A group of 51 patients with complaints related to entrapment of the superficial sensory branch of the radial nerve is described. Symptoms included altered sensibility over the dorsoradial aspect of the hand and dorsoradial cutaneous pain with ulnar flexion of the wrist or with gripping and pinching. Pertinent history included compressive or crushing forearm injuries, work activities requiring frequent pronation and wrist hyperextension, and associated illnesses, such as diabetes. Physical examination included abnormal touch perception, abnormal moving two-point discrimination over the dorsoradial area of the hand, a positive Tinel sign in the forearm, and aggravation of the patient's symptoms with forced forearm pronation and wrist ulnar flexion. Seven (37%) of 19 patients treated with nonoperative modalities after a mean of 28 months from the onset of symptoms or their injury were improved. Of the 32 patients treated with surgery with a mean follow-up of 10 months (range of 6 to 29 months), there has been excellent subjective improvement in 37%, good subjective improvement in 49%, and fair subjective improvement in 6%, and 8% were not improved. Of this group of surgically treated patients, 43% have returned to their regular jobs, and 22% are in either vocational rehabilitation or working at a different job.

Effects of nerve compression on fast axonal transport in streptozotocin-induced diabetes mellitus. An experimental study in the sciatic nerve of rats

The hypothesis that nerves in diabetes mellitus exhibit an increased susceptibility to compression was experimentally tested. Inhibition of fast axonal transport was induced by local compression in sciatic nerves of rats with streptozotocin-induced diabetes mellitus. Fast anterograde axonal transport was measured after application of 3H-leucine to the motor neurone cell bodies in the spinal cord. The sciatic nerve was subjected to local, graded compression in vivo by a small compression chamber. The amount of accumulation of proteins was quantified by calculation of a transport block ratio. Compression at 30 mm Hg for 3 h induced a significantly greater (p less than 0.05) accumulation of axonally transported proteins at the site of compression in nerves of diabetic animals (transport block ratio: 1.01 +/- 0.35; n = 7) than in nerves of controls (0.67 +/- 0.16; n = 7). Accumulation was significantly higher in ligature experiments of both control (1.34 +/- 0.44; n = 8; p less than 0.01) and diabetic animals (1.45 +/- 0.30; n = 8; p less than 0.05), indicating that the block of transport in compressed nerves was incomplete. Neither sham compressed diabetic (0.50 +/- 0.09; n = 6) nor control (0.49 +/- 0.11; n = 6) nerves showed any block of axonal transport. The possible causes of the increased inhibition of fast axonal transport in diabetic rats are discussed. The results indicate that diabetes may lead to an increased susceptibility of peripheral nerves to compression.

Effects of graded experimental compression on slow and fast axonal transport in rabbit vagus nerve

Effects of compression at low pressures on slow and fast axonal transport was investigated in rabbit vagus nerve. Proteins in the sensory fibres were radiolabelled by injection of [3H]leucine or [35S]methionine into the nodose ganglion. A small compression chamber and/or ligatures were applied around the cervical part of the vagus nerve for 8 h, at an appropriate time for the subsequent analysis of the effects of compression on both slow and fast transport of radiolabelled proteins. In normal nerves there were two waves of slowly transported proteins with rates of about 12-15 and 25-30 mm/day, respectively. SDS-polyacrylamide gel electrophoresis was used and confirmed that the main proteins which accumulated proximal to the ligatures had a molecular weight of 54 000-56 000. Neither compression of the nerve at 20 mm Hg nor sham-compression induced any statistically significant accumulation of slowly transported proteins at the site of compression. A higher pressure, i.e. 30 mm Hg, induced a marked but incomplete accumulation of slowly transported proteins. Fast transport was partially inhibited in some, but not all, nerves, when 20 mm Hg was applied for 8 h, in contrast to the lack of effect found previously with the same pressure applied for only 2 h. Despite these slight differences, the results indicate that both slow and fast transport are impaired by low pressure levels of around 20-30 mm Hg, which are comparable with those found in human compression neuropathies. The impaired provision of cytoskeletal elements to the distal axon may be of significance in the pathophysiology of nerve entrapment syndromes.

Entrapment of the ulnar nerve by the deep flexor-pronator aponeurosis

A study of eight patients and 20 cadaveric limbs identified the deep aponeurosis of the flexor carpi ulnaris as a potential site for constriction of the ulnar nerve. The ulnar nerve passes through this aponeurosis approximately 5 cm distal to the medial epicondyle and 2 to 3 cm distal to the cubital tunnel. In two cases of isolated compression at this level, local decompression was successful in relieving the symptoms of ulnar nerve compression. Submuscular transposition is also effective because it places the ulnar nerve deep to this aponeurosis throughout its entire course.

Electrodiagnostic abnormalities in 15 patients with posttraumatic syringomyelia: pre- and postoperative studies

A review of 15 patients with posttraumatic syringomyelia indicates that the most reliable electrodiagnostic criteria for the diagnosis of syrinx are the loss of motor unit numbers with increase in motor unit amplitude and duration nd synchronous firing. Prolongation of F wave latency in a previously stable patient is a useful observation. Return of function and improvement of F wave latencies can occur rapidly following decompression of the syrinx. Forty per cent of the patients studied had concomitant involvement of at least one peripheral nerve as one would expect invoking the double crush hypothesis.

Pyridoxine as an adjunct in the treatment of carpal tunnel syndrome

Nineteen consecutive patients with carpal tunnel syndrome were treated with pyridoxine. Two thirds of the patients who specifically presented symptoms of median neuropathy eventually required surgical release. Although pyridoxine may have a place alongside other nonsurgical modalities in the treatment of carpal tunnel syndrome, surgical release continues to be indicated in many patients with carpal tunnel syndrome.

Ulnar nerve entrapment at the elbow. Tailoring the treatment to the cause

Ulnar nerve entrapment at the elbow is a common cause of arm and hand pain, paresthesias, and weakness. Its characteristics and the appropriate diagnostic tests should be known to all primary care physicians. An understanding of the surgical treatment of this common disorder is helpful in providing informed medical care.

Carpal tunnel syndrome. Avoiding poor treatment results

Carpal tunnel syndrome is one of the most common causes of paresthesias, pain, and weakness of the hands. All physicians should be aware of the typical presentation of the syndrome, its differential diagnosis, and the various options for treatment. The prognosis with surgical treatment is excellent if significant muscle atrophy has not occurred.

Carpal tunnel syndrome: a review

Compression of the median nerve in the crowded carpal tunnel is common and frequently incapacitating. Its causes and associated clinical conditions are multiple. Diagnosis is made by the typical history, three frequently positive physical signs at the wrist, and, if necessary by median nerve conduction velocity impairment. Most patients can be managed medically; when surgery is required it can be done usually without general anesthesia on an outpatient basis with gratifying results.

Abnormalities of the innervation of the urethral striated sphincter musculature in incontinence

Perineal nerve and transcutaneous spinal cord stimulation have been used to study 17 patients with idiopathic neurogenic faecal incontinence, 12 of whom also had urinary incontinence. Significant increases in spinal, perineal and pudendal nerve motor latencies were demonstrated in all 17 patients. These results suggest that there is damage to the nerves innervating both the urethral and perianal sphincter musculature in these patients, including those with isolated faecal incontinence. There was evidence of both a distal (perineal nerve) and a proximal (sacral root) component to the damage to the nerve supply of the urethral striated sphincter muscle in half of the patients.

Changes in fast axonal transport during experimental nerve compression at low pressures

The minimal pressure for impairment of fast anterograde axonal transport was determined in rabbit vagus nerve. Proteins, transported by fast anterograde axonal transport, were labeled by a microinjection of [3H]leucine into the nodose ganglion, and a small compression chamber was applied around the cervical vagus nerve. In this way the nerve was subjected to acute, graded compression. Compression at 20 mm Hg for 2 h as well as sham compression did not induce accumulation of axonally transported proteins at the level of compression. However, a pressure of 30 mm Hg for 2 h induced a block of axonal transport at the site of compression. The causes of the axonal transport block are discussed as well as the minimal pressure level in relation to pressures found in clinical nerve compression lesions.

Double-entrapment radial tunnel syndrome

A symptomatic double-level entrapment of the posterior interosseous branch of the radial nerve is described. In addition to the more common level of compression at its entrance into the supinator, the posterior interosseous nerve may be entrapped at its exit from the supinator or at multiple levels.

Upper extremity neuropathies following median sternotomy

The status of 958 patients who underwent median sternotomy between January, 1978, and May, 1981, was analyzed. Fifty-four patients had an upper extremity neuropathy. Among 38 patients who underwent further evaluation, motor and sensory nerve conduction studies localized the injury to the level of the elbow in 13, to the brachial plexus in 10, and to both locations in 6. Ninety-two percent of these 38 patients were asymptomatic 3 months after operation.

Anterior submuscular transposition of the ulnar nerves by the Learmonth technique

Thirty-eight patients with progressive posttraumatic ulnar neuropathy at the elbow underwent anterior submuscular transposition of their nerves. Multiple mechanical causes of neuropathy were identified. Fourteen patients had undergone previous surgery for ulnar neuropathy, while 24 had not. Postsurgical follow-up averaged 23.1 months. The operative technique is described and illustrated in detail. Complications attributable to surgery were minimal. No absolute prognostic factors could be identified, and even those patients with significant muscular atrophy or time delay before operation were generally benefited. If prior surgery had induced significant scarring and neural damage, the prognosis for recovery was considerably worse, as it also was for patients who had severe preoperative dysesthesia or pain. Four patients thought to represent examples of double crush or compression syndrome were identified.

[Carpal tunnel syndrome: electroneuromyographic study of 135 cases]

One hundred thirty five patients with carpal tunnel syndrome were studied trough electrophysiological techniques. Nerve sensory conductions, motor conductions and electromyography were performed in all patients and the results discussed. The authors call the attention for the technic of sensory conduction stimulating palma and picking up the potentials on the wrist as the most sensitive technic for the early detection of carpal tunnel syndrome.

Blockage of axonal transport induced by acute, graded compression of the rabbit vagus nerve

Rapid axonal transport in rabbit vagus nerve was studied during and after graded nerve compression. Proteins of the rapid axonal transport were labelled by micro-injection of 3H-leucine into the nodose ganglion and the cervical vagus nerve was subjected to graded compression by a small "mini-cuff" applied directly to the exposed nerve trunk. The results showed that even slight trauma to the nerve, in this model represented by a pressure at 50 mmHg applied for two hours, may induce accumulation of axonally transported proteins at the level of compression. This transport block was, however, reversible within one day. 200 mmHg and 400 mmHg applied for two hours similarly induced a block of axonal transport persisting up to at least one and three days respectively after the compression. Time for recovery of normal transport was correlated with the magnitude of the pressure applied to the nerve. The results indicate that axons may survive, that is not undergo Wallerian degeneration, after blockage of rapid axonal transport persisting at least one day after the compression trauma.

Reduced motor conduction velocity of the ulnar nerve in spinal cord injured patients

Twelve male patients with spinal cord injury were studied. The purpose of this study was to determine if ulnar nerve damage occurs in patients with spinal cord injury who are wheelchair bound and if so at which segment of the ulnar nerve. The results showed significant drop in ulnar nerve conduction velocity in both segments, mid-arm to below elbow and below to the wrist. There was no significant difference between quadriplegic and paraplegic. No significant correlation was found between ulnar nerve impairment and the duration of spinal cord injury.

Electromyographic diagnosis of the carpal tunnel syndrome

Sensory conduction velocities of the median nerve were studied from digit to palm and from palm to wrist in normal subjects and in patients with the carpal tunnel syndrome. Definite slowing was noted in the palm to wrist segment, even in the early carpal tunnel syndrome. It was noted that 37% of normal women over 40 years of age had electrophysiological evidence of the carpal tunnel syndrome.

Ulnar neuropathies in rheumatoid arthritis

A loss of functional motor axons in the median and ulnar nerves occurred in half of thirty-three patients with rheumatoid arthritis. Weakness of small hand muscles may predispose to the development of ulnar deviation of the fingers in patients with joint disease at the radio-ulnar and metacarpophalangeal joints. There is no evidence that spasm of small hand muscles is a significant cause of ulnar deviation of the fingers in rheumatoid arthritis. Ulnar deviation of the fingers in rheumatoid arthritis is not due to selective impairment of the ulnar nerve or the deep palmar branch of the ulnar nerve even though ulnar deviation of the fingers can occur in association with such lesions and in the absence of joint disease.

Regeneration distal to a prolonged conduction block

In 6 baboons a tourniquet round the knee was used to produce a prolonged local conduction block. This was followed, within a few days, by a surgical crush of the tibial or deep peroneal nerve at the ankle, in order to produce Wallerian degeneration distally. Electrophysiological recordings from small foot muscles were then used to study the time-course of regeneration in motor fibres. When the results were compared with those from crushed but unblocked nerves of the opposite leg, there was no evidence that either reinnervation of muscles or the subsequent maturation of the regenerating motor nerve fibres was delayed by the prolonged proximal conduction block.

Carpal tunnel syndrome, humeral epicondylitis, and the cervical spine: a study of clinical and dimensional relations

Forty-three patients with idiopathic carpal tunnel syndrome, confirmed by nerve conduction studies and treated by surgery, were compared clinically and radiologically with 43 age- and sex-matched control patients. Patients with carpal tunnel syndrome had a significantly greater prevalence of lateral humeral epicondylitis (tennis elbow) (33%) than controls (7%). Randomised reading of the cervical spine radiographs in ignorance of the groups to which they belonged showed no significant difference in the prevalence of either intervertebral disc degeneration or intraforaminal osteophyte protruion using conventional grading methods. Measurement of the minimum anteroposterior diameter of the cervical spinal canal, the anteroposterior diameters of the cervical vertebral bodies, and the ratio of intervertebral disc height to adjacent vertebral body height in the cervical spine, however, showed a consistent trend to smaller measurements in the carpal tunnel group. Differences were significant at several vertebral levels in each of these dimensions. The narrowing of the intervertebral discs relative to the vertebral bodies in patients with carpal tunnel syndrome may indicate connective tissue changes, which might also occur in the common extensor origin at the elbow or in the contents of the carpal tunnel.

Longitudinal sliding of the median nerve during movements of the upper limb

An incidental finding during recordings from the median nerve was that the nerve trunk slides longitudinally in its bed when the limb is moved. The amount of movement has been measured in 19 subjects. The observations are discussed with reference to the pathology of entrapment neuropathies and it is suggested that, where longitudinal movement of a peripheral nerve is restricted, continual trauma results from normal movements of the limb.

Patterns of motoneuron dysfunction and recovery

Electrophysiological studies have been carried out on five patients with neuropathies of different etiologies. In each patient serial estimates were made of the numbers of functioning motor units in various muscles. It was found that the intensity of the neuropathic process and the rate of recovery differed in a consistent way among the motoneuron pools investigated. The lesion was more severe in extensor digitorum brevis neurons than in thenar neurons, while the hypothenar ones were least affected. A stage of partial synaptic failure has been recognized in which a motoneuron appears to be no longer able to excite a muscle fiber, but still capable of maintaining certain trophic activities. By comparing the number of functioning motor units with the size of the maximum evoked muscle response it has been possible to detect the adoption of denervated muscle fibers by axonal sprouts from 'healthy' surviving neurons (collateral reinnervation). Lastly, in some muscles it appears that the adopted muscle fibers may subsequently be recaptured by the original motoneurons following recovery of the latter from the neurotoxic insult.

The neurapraxic lesion: a clinical contribution to the study of trophic mechanisms

Four patients with neurapraxic lesions are described; in spite of the absence of impulse activity in muscle fibers no other signs of denervation could be detected. These observations are interpreted as indirect evidence for the role o f a non-impulsive (axoplasmic flow) system in certain trophic phenomena. The relationship of the present findings to the spectrum of neuropathic lesions is considered.