Laser-assisted nerve repair in primates

Studies on the peripheral nerves in rats and other species have helped in the development of laser-assisted nerve anastomosis (LANA), but offer little in evaluating the efficacy of this technique in primates. The authors present a study of LANA in the peripheral nerves of rhesus monkeys. Twelve adult rhesus monkeys underwent bilateral resection of a portion of the peroneal nerve followed by placement of autogenous sural nerve interposition fascicular grafts. The grafts were completed with conventional microsurgical suture technique on one side and with LANA on the other. At 5, 8, 10, and 12 months, the grafted nerves were evaluated for continuity, nerve conduction, and histology (both light and electron microscopy). No significant difference in continuity, conduction velocity, nerve degeneration, nerve regeneration, axon fiber number, or axon fiber density was found in any animal between grafts performed by conventional microsuture and LANA grafts. There was no difference in distal or proximal myelinated fiber density between the LANA grafts and the conventional microsuture grafts. It was concluded that LANA is as effective as microsurgical suture nerve anastomosis in a primate model of nerve repair and grafting.

Intra-aortic balloon counterpulsation: a treatment for ischaemic stroke?

Intra-aortic balloon counterpulsation (IABC) augments cardiac output (CO) and pulse pressure (PP) allowing patients with low output heart failure to be supported for a period of time. Augmentation of CO and PP may also be beneficial to the patient with acute cerebral ischaemia. In this paper we investigated the possibility of using IABC to increase local cerebral blood flow (CBF) in ischaemic brain. In 12 anaesthetized mongrel dogs, a canine stroke model was produced by occluding the left internal carotid and middle cerebral arteries with aneurysm clips. Six dogs were then treated with IABC for 2 h, and 6 other dogs acted as controls (no IABC). Haemodynamic data were measured continuously and CBF (microsphere technique) and CO measurements were performed pre- and post-occlusion, and then twice during the treatment period. In the IABC-treated animals, PP increased from 32 +/- 5.9 to 39 +/- 7.8 mmHg (p less than 0.01) but CO and local CBF in the ischaemic brain did not change significantly during IABC. However, in 4 dogs with significant increases in CO due to IABC [1.7 +/- 0.3 to 2.8 +/- 0.7 l/min (p less than 0.05)], local CBF in ischaemic brain also increased significantly from 22 +/- 12 to 26 +/- 11 cc/100 g/min (p less than 0.05). In the control animals, CO and local CBF did not change significantly during the observation period. These data suggest that augmentation of CO and PP by IABC results in an increase in local CBF in ischaemic brain. IABC may be an effective treatment for ischaemic stroke in those patients with compromised cardiac performance whose cardiac output and pulse pressure can be augmented by IABC.

The effects of dose of elemental mercury and first-pass circulation time on exhalation and organ distribution of inorganic mercury in rats

The lung plays a major role in the removal of dissolved elemental mercury (Hg0) from the bloodstream. During the first passage through the lung after an intravenous dose of Hg0 dissolved in aqueous buffer, from 10 to 17% was exhaled depending on the dose (0.11 or 1.1 micrograms Hg/rat) and the injection site (jugular versus tail vein). Furthermore, evidence is presented that subsequent exhalation over the next 50 s, before the rats were killed and the mercury determined in the lung at that time, was largely Hg0-extracted during the first pass. The total mercury extracted during the 60 s period was in the range of 40-49% of the dose. The oxidation of Hg0 to Hg2+ in red cells is important in limiting the availability of Hg0 to certain tissues. Thus, after a short residence time in blood (0.6 s after jugular vein injection), 12.9-17% is exhaled in the first pass as compared to 10.4-12.2% with a longer residence time (1.8 s after tail vein injection). Furthermore, there was a general tendency, even at 60 s after dosing, for certain tissues - lung, brain, and heart - to have higher values after dosing from the jugular vein. It was estimated that the half-time for oxidation was 3.3 s. Our results confirm previous observations that the form of inorganic mercury greatly influences the short-term deposition in certain tissues. Thus as compared to Hg2+, administration of Hg0 increases lung levels 5-10-fold; brain, 4-fold; and heart, 3-fold. Blood levels are lower after Hg0, particularly after the higher dose. Such findings are consistent with a model wherein Hg0 is in part oxidized by red blood cells, the remainder rapidly diffusing in tissues where it is also oxidized to Hg2+.

Surgical exploration of enlarged lymph nodes at the root of the neck

Surgical exploration of presumed enlarged lymph nodes at the root of the neck may sometimes result in the exposure of neurogenic lesions. Careful exposure of the lesion should precede mobilization and excision to prevent unavoidable iatrogenic injury. Experiences with 45 neoplasms in this region are described.

The peripheral nerve allograft: an assessment of regeneration across nerve allografts in rats immunosuppressed with cyclosporin A

Lewis rats (RT1(1] were the recipients of 3-cm nerve grafts from syngeneic Lewis donors or allogeneic ACI (RT1a) donors. Microneurosurgical repair of the nerve graft to the transected sciatic nerve of the recipient animal was performed with 10-0 epineurial sutures. Recipients were randomly allocated to cyclosporin A (CsA) immunosuppressed or untreated groups. Cyclosporin A was administered in the minimal effective dosage to prevent nerve allograft rejection across this major histocompatibility disparity (5 mg/kg per day). Nerve regeneration across the nerve grafts was assessed by sciatic function index (SFI) and toe spread index (TSI) determinations serially and by electrophysiologic, histologic, and morphologic assessments 14 weeks after engraftment. Sciatic nerve regeneration across allogeneic nerve grafts in cyclosporin A immunosuppressed recipients was significantly superior compared to the untreated controls (p less than 0.008) and not significantly different from that across the syngeneic control animals.

Preliminary experiences with brachial plexus exploration in children: birth injury and vehicular trauma

The application of microsurgical techniques to the peripheral nervous system has made possible the reconstruction of the brachial plexus after vehicular and penetrating injuries. We now report our preliminary experiences utilizing these same techniques in the microsurgical management of brachial plexus birth injury. In contrast to other authors and in distinction from our own experiences with vehicular trauma in children, we did not find lesions requiring reconstruction by grafting or neurotization in any of seven plexus explorations for birth injury. The history of the surgical management of brachial plexus birth injury is reviewed, and the rationale for exploration is developed in the context of the natural history of the condition. Differences between our experiences and the existing literature are analyzed, with particular regard for timing of operation and technique of intraoperative assessment of nerve injury. All children with birth injuries of the brachial plexus require careful, repeated neurological evaluation during the first few months of life. Although the great majority make a rapid and satisfactory spontaneous recovery, the minority who do not recover are destined to suffer significant, life-long disability. Microsurgical brachial plexus exploration may benefit this select group of patients.

Shoulder arthrodesis using a pelvic-reconstruction plate. A report of eleven cases

Eleven adults who had a flail shoulder due to brachial plexus palsy had arthrodesis of the shoulder using a single ten-hole pelvic-reconstruction plate. Both the glenohumeral and the acromiohumeral joints were fused with the shoulder in the position of 30 degrees of abduction, 30 degrees of flexion, and 30 degrees of internal rotation. No bone graft was used. The patients were immobilized in a spica cast for six weeks postoperatively. At an average follow-up of twenty-five months after the operation, the position of the arthrodesis had been maintained and solid fusion had occurred in each shoulder. No patient required removal of the plate. The pelvic-reconstruction plate is malleable and is more easily contoured in the operating room than a dynamic-compression plate. We recommend the use of a malleable pelvic-reconstruction plate when performing arthrodesis of the shoulder.

Thoracic outlet syndrome with congenital pseudarthrosis of the clavicle: treatment by brachial plexus decompression, plate fixation and bone grafting

Although a number of cases of congenital pseudarthrosis of the clavicle have been described in the literature, they provide little direction for the treatment of this condition when it is associated with thoracic outlet syndrome. The authors describe their experience with such a case in a 20-year-old woman. Symptoms of pain in the ulnar distribution of the right forearm and discoloration of the hand with abduction of the extremity had developed over 3 years. The radial pulse was obliterated by abduction of the arm. Exploration of the brachial plexus revealed a constricting band arising from the distal fragment of the clavicle running to the first rib which, together with the mass of the pseudarthrosis, comprised the thoracic outlet. The patient was successfully treated by division of the fibrous band, reduction of the clavicle, internal fixation with a plate and iliac crest bone grafting. At follow-up the patient had a full range of motion in the shoulder and was asymptomatic.

An assessment of the effects of internal neurolysis on a chronically compressed rat sciatic nerve

Chronically compressed nerves were treated with three surgical modalities. Simple decompression was compared to internal neurolysis with and without the addition of extrafascicular steroid. Electrophysiologic, histologic, and morphometric assessments were performed. Compressed control nerves demonstrated changes compatible with severe nerve compression (Wallerian degeneration). With simple decompression, improvement in histologic and electrophysiologic parameters occurred. When internal neurolysis was added to the decompression, further improvement in histologic and electrophysiologic parameters was noted. There was no added improvement with the addition of steroids.

A model of chronic nerve compression in the rat

This article describes a model of chronic nerve compression in the rat. The sciatic nerve of adult male Sprague Dawley rats was banded with a 1-cm Silastic tube for varying periods of time. Morphometric analysis, electrodiagnostic studies, and histological evaluation were carried out 3, 5, 8, and 12 months after banding. Histological evaluation at 3 months was normal. At 5 months perineurial thickening was demonstrated. In the periphery of the fascicles, segmental demyelination was noted; central fibers appeared normal. At 8 months there was further epineurial and perineurial thickening. Marked thinning of the myelin was noted in all fibers and evidence of Wallerian degeneration was apparent. Progressive connective tissue and nerve fiber changes were noted at 12 months. Nerve conduction studies after 3 months of compression demonstrated an increase in conduction velocity compared to the normal unbanded control nerves. Progressive slowing of conduction velocity was noted from 5 through 12 months.

Comparison of the protection given by selenite, selenomethionine and biological selenium against the renotoxicity of mercury

The protective effect of selenite, seleno-dl-methionine and biological selenium against the renotoxicity of mercury was tested in rats. As the source of biological selenium, the liver soluble fraction of rats given 60 mumoles/kg selenite 3 days before sacrifice was used. The aim of the experiments was to test whether protective efficiency follows the reported order of ability to form HgSe. Mercury was given subcutaneously in doses of 2.5, 5.0 and 7.5 mumoles/kg HgCl2 and selenium was given in equimolar doses at the same time as Hg2+. Liver soluble fraction, biological selenium or liver soluble fraction supplemented with selenite or seleno-dl-methionine were given orally, while in experiments without liver soluble fraction the two selenium compounds were given subcutaneously. Biological selenium was tested only at the two lower dose levels. Both biological selenium and seleno-dl-methionine decreased the urinary excretion of mercury in the first 48 h, but less so than selenite and only selenite decreased the renal content of mercury at the end of this period. Urinary alkaline phosphatase activity and plasma urea nitrogen at the 2.5 and 5.0 mumoles/kg dose levels decreased in the order of no selenium greater than biological selenium greater than seleno-dl-methionine greater than selenite. As the reported HgSe formation increases in the same order, the experiments support the role of HgSe formation in the protective effect. The degree of necrotic damage in the P2 and P3 regions of the proximal tubular cells increased in the same order as the biochemical indicators at the 5.0 and 7.5 mumoles/kg dose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Injury to the brachial plexus during Putti-Platt and Bristow procedures. A report of eight cases

Eight patients with documented recurrent anterior dislocation of the shoulder sustained iatrogenic brachial plexus injuries during either Putti-Platt or Bristow procedures. Two patients also sustained axillary artery injuries. There were six males and two females. Postoperatively, complete paralysis of the musculocutaneous nerve was noted in six cases and incomplete paralysis in one case. Two patients had complete axillary nerve palsies. There were two cases of partial paralysis of the radial, median, and ulnar nerves, respectively. Seven of the patients underwent brachial plexus exploration an average of 16 weeks following their initial operation (range, 4 to 40). Suture material was removed from around or within two musculocutaneous nerves and one ulnar, one median, and one axillary nerve. Two lacerated musculocutaneous nerves were amenable to delayed primary repair. Two musculocutaneous, one median and one axillary nerve required grafting. Injury to the brachial plexus was associated with inadequate knowledge of regional anatomy, blind clamping of axillary artery lacerations, use of axillary incisions which limited exposure, and failure to identify the musculocutaneous nerve during Bristow procedures. If a brachial plexus injury occurs during a Putti-Platt or a Bristow procedure and the lesion does not rapidly, progressively, and completely recover, the brachial plexus should be explored since there is a high likelihood of structural neurologic injury.

Giant-cell tumor of the middle cranial fossa. Case report

The authors report the case of a 23-year-old man with a giant-cell tumor of the right middle cranial fossa floor. His presentation and management are described, and some aspects of this rare neoplasm of the skull base are reviewed. The role of adjuvant radiotherapy is discussed.

The peripheral nerve allograft: an assessment of regeneration in the immunosuppressed host

Regeneration across the nerve allograft in the immunosuppressed host was assessed using electrical and histologic parameters. The Lewis rat (RTIl) served as the recipient animal, and ACI rats (RTIa) provided the donor nerve allografts. Hydrocortisone and azathioprine were used in various dose schedules as the immunosuppressive agents. Animals were immunosuppressed for either 30 or 100 days. Histologic and electrophysiologic measurements of nerve regeneration were assessed at 30, 100, and 180 days. The degree of nerve regeneration was similar in all experimental groups. Short-term, low-dose immunosuppression was as successful as longer-term, higher-dose immunosuppression therapy. The degree of nerve regeneration in all experimental groups was significantly better than that in the fresh, untreated nerve allograft control group (Lewis/ACI) but was not as good as that seen in the autograft control group (Lewis/Lewis).

A study of neurotrophism in a primate model

This study investigated the existence of neurotrophism in a primate model. In eight adult cynomolgus monkeys the sensory component of the femoral nerve was sectioned and introduced into the proximal channel of a silicone Y chamber. The proximal stump was given distal choices of various tissues inserted into the remaining arms of the silicone Y chamber. The targets presented were combinations of tendon, muscle, intact distal nerve, distal nerve graft, or an empty silicone channel. After 6 weeks, ultrastructural analysis confirmed axonal growth toward distal nerve tissue, while minimal or no nerve regeneration was directed toward tendon, muscle, or the empty silicone channel. The results showed that either a distal nerve stump or a nerve graft will act as a specific target to the regenerating primate proximal nerve stump.

Chronic human nerve compression--a histological assessment

While compression neuropathy is a common clinical problem, the opportunity to study human nerve material is rare. A histological assessment of the superficial radial nerve of four human cases with entrapment syndrome is reported. Changes in the perineurium and the endoneurial microvessels as well as the presence of Renaut bodies were the earliest histological abnormalities noted. Connective tissue changes included epineurial and perineurial fibrosis. Nerve fibre pathology varied from fascicle to fascicle. The myelinated and unmyelinated fibre populations responded differently to this compression. In the myelinated fibre population, marked thinning of the myelin was noted. In the unmyelinated fibre population, a shift in the fibre histogram due to a new population of very small fibres was observed suggesting degeneration with subsequent regeneration of this fibre population.

Perineurioma: a benign peripheral nerve tumor

A unique benign peripheral nerve tumor, called a perineurioma, is described in this report. Light and electron microscopy and immunohistochemistry indicate that this tumor was derived from the perineurial cell. We discuss the ultrastructure, histogenesis, and management of this neoplasm.

Histopathology of compression of the superficial radial nerve in the forearm

A histologic assessment of the radial sensory nerve from a patient with nerve compression is reported. Histologic changes were confined to the region of the nerve compression. Connective tissue changes consisted of an increased thickness of the epineurium and perineurium. Nerve fiber changes consisted of Schwann cell pathology with marked thinning of the myelin noted in the myelinated fibers and evidence of degeneration and regeneration noted in the unmyelinated fiber population. Nerve fiber pathology was not uniform but varied from fascicle to fascicle in the compressed area.

Biomechanical study of full-contact karate contrasted with boxing

It is known that boxers suffer a characteristic cumulative brain injury from repeated blows to the head that correlates well with the number of bouts fought. Much less is known about full-contact karate (kickboxing), which is relatively new. In full-contact karate, punches and kicks are actually landed, rather than being focused to culminate just short of an opponent, as practiced in traditional karate. Although a combatant can win on points, the surest means of victory is a knockout. Consequently, fighters strive to land blows to the head. To investigate the relative force of kicks and punches, a dummy head was mounted 175 cm above the floor (to simulate a 50th-percentile man standing erect) and 125 cm above the floor (to simulate the man in a crouched position) on a universal joint permitting motion about three axes. The mechanism was contrived to provide constant rotational stiffness, and springs provided constant restorative moments about the three axes. The texture of soft tissue was simulated by a mask of visco-elastic foamed materials. Fourteen karate experts punched and kicked the dummy. Accelerometer measurements in the 90- to 120-G range indicated that safety-chops (hand protectors) and safety-kicks (foot padding) did not reduce acceleration of the dummy. Ten-ounce boxing gloves mitigated peak acceleration to some extent. Kicks and punches produced accelerations in the same range. Violent acceleration of the head by any means produces injury. The authors conclude that, if full-contact karate is widely practiced, cases of kickboxer's encephalopathy will soon be reported.

Effect of submuscular versus intramuscular placement of ulnar nerve: experimental model in the primate

A primate model was developed to study the effect of submuscular versus intramuscular placement upon the development of ulnar nerve fibrosis. No significant adherence was found in either location between the ulnar nerve and the flexor-pronator muscle mass. There was no significant difference in the mean nerve fibre diameter or in the percent neural tissue between the ulnar nerves in the two different locations. It is suggested that it is the interaction of the transposed ulnar nerve with other fibrous anatomical structures proximal to, across, and distal to the elbow that causes failure in ulnar nerve transposition procedures, rather than an adverse reaction between the incised flexor-pronator muscle mass and the ulnar nerve.

Hemangioma calcificans of the spinal cord

A 27-year-old woman presented with hemotomyelia during pregnancy. Needle drainage of the spinal cord was followed by relief of symptoms. Symptoms recurred during a second pregnancy 4 years later and she presented with an avascular mass in the midcervical spinal cord. This lesion proved to be hemangioma calcificans, a densely calcified and ossified variant of cavernous angioma.

Selected recent advances in peripheral nerve injury research

Interactions between Schwann cells and growing neurites are reviewed as are the implications of axonal transport studies in shaping the regenerative process. Increased investigative attention will be required to study biochemical changes occurring in the local environment of the injury site even though continued study of the neuronal metabolic process remains critical. Important studies concerning the connective tissue structure of nerve and probable "blood-nerve barrier" sites are reviewed. Factors responsible for connective tissue proliferation and fibroblast alignment after injury are not well understood. Recent experimental studies relating to surgical repair of nerve are reviewed as are a few selected papers reflecting changes in clinical management of the patient with nerve injury.

Alteration of neuroma formation by manipulation of its microenvironment

In a primate model a histologic assessment of neuroma formation is reported. Three experimental groups were defined. Transected sensory nerves left adjacent to the incisional wound in an area of movement (wrist) were considered the control group. In the "proximally cut" group the same sensory nerves were positioned well proximal to the incisional wound. In the "muscle-implantation" group these nerves were placed in adjacent muscles. At 6 months a histologic assessment of the neuroma formation in the three experimental groups was carried out. Implantation of the sensory nerve into muscle significantly altered the regenerative potential of that nerve. The muscle completely surrounded the sensory nerve. The minimal neuroma that formed had significantly less scar tissue and contained nerve fibers that were of a smaller diameter and decreased density than either the control or the proximally cut group. There were no histologic differences between these latter two groups. However, regeneration into the overlying skin that was noted in the control neuromas was not seen in those nerves which had been proximally cut.