Armin Kraus

An improved electrophysiological method to study peripheral nerve regeneration in rats.

After restitution of motor function the grasping test alone is insufficient to figure out any further differences of axonal nerve regeneration of the median nerve in rats. To avoid this problem we developed a standardized electrophysiologic method for testing median nerve regeneration. Threshold, latency, compound muscle action potentials (CMAP) and velocity of neuromuscular transduction were recorded in 54 rats 20 weeks post-operatively. Animals of group 1 served as control group, no transection of the median nerve was carried out. Animals of groups 2 and 3 underwent either primary nerve coaptation or autologous nerve grafting after transection of the median nerve. To ensure validity of the method additional correlation between all parameters was investigated. Reliable electrophysiological results were observed in all animals. As expected, group 1 animals showed lowest threshold and latency and highest CMAP levels. Transection of the median nerve and additional nerve repair leads to significant increase of threshold and latency as well as reduction of CMAP. Furthermore, animals of group 3 showed higher levels for threshold and latency and reduced CMAP levels compared with animals of group 2. The grasping test alone could not demonstrate these slight differences 20 weeks post-operatively. Additionally, we observed strong correlations between threshold, latency and CMAP using the Spearman correlation ranking. We describe the usage of motor neurography as a reproducible and valid tool which should be mandatory for detailed analysis of regeneration in the rat median nerve model.

Efficacy of various durations of in vitro predegeneration on the cell count and purity of rat Schwann-cell cultures.

The efficacy of Schwann-cell cultivation can be enhanced by in vitro predegeneration of the harvested cells compared to immediate culture. The aim of this study was to improve Schwann-cell culture efficacy by comparing three different durations of predegeneration. The sciatic and median nerves of 6-8-week-old Lewis rats were harvested and subjected to either 2-day, 7-day, or 14-day predegeneration in Dulbeccos Modified Eagles Medium supplemented with 10% fetal calf serum and 1% Penicillin/Streptomycin. Afterward, tissue was enzymatically dissociated and placed in a modified melanocyte growth medium. The cell count was determined immediately after dissociation while the cell purity was determined one subculture/trypsinization cycle later after cell attachment to the culture plate by means of optical microscopy and immunocytochemistry. Particular attention was then paid to the Schwann-cell-to-fibroblast relation. The cumulative cell count in the culture was 5.8 x 10(5) for 2-day, 1.12 x 10(6) for 7-day, and 1.48 x 10(6) for 14-day predegeneration. The culture purity was approximately equal for 2- and 7-day predegeneration (88% Schwann cells, 12% fibroblasts after 2 days; 85% Schwann cells, 15% fibroblasts after 7 days). After 14 days, however, cell cultures were significantly debased by fibroblast proliferation (57% Schwann cells, 43% fibroblasts). In vitro predegeneration is a particularly suitable procedural method to increase the cultural Schwann-cell yield. The number of cultivated rat Schwann cells is doubled by 7-day in vitro predegeneration in comparison to 2-day predegeneration. After 14-day predegeneration, however, the culture is significantly debased by fibroblasts. Therefore, 7-day in vitro predegeneration is an advisable predegeneration period.

Functional recovery after implantation of artificial nerve grafts in the rat- a systematic review

Purpose The aim of this study was to compare functional data of different nerve-gap bridging materials evaluated in rat experiments by means of a systematic review. Materials and methods A systematic review was conducted, searching MEDLINE, HTS and CENTRAL to identify all trials evaluating functional recovery of artificial nerve conduits in the rat model. Results There was a trend towards a favourable outcome of conduits coated with Schwann-cells compared to the plain synthetics. Histomorphometry, electrophysiology and muscle-weight correlated poorly with functional outcome. Conclusion Schwann-cell coated conduits showed promising results concerning functional recovery. Further standardization in outcome reporting is encouraged.

Nervenrekonstruktion und Nervenersatzoperationen

The surgical treatment of peripheral nerve injuries is still a challenging and highly demanding procedure. Past results have been improved upon by different advances in microsurgical techniques and algorithms. Nevertheless, results are not always satisfying, making secondary procedures necessary. Thus, these secondary procedures such as tendon transfers and arthrodesis of different joints must be taken into account during reconstructive planning. This review gives an overview of peripheral nerve reconstruction (nerve grafting, nerve repair) and the pertinent secondary procedures.ZusammenfassungDie Versorgung von Nervenverletzungen und Nervendefekten stellt eine anspruchsvolle chirurgische Maßnahme dar. Verschiedene Techniken und Algorithmen haben in den vergangenen Jahren zu einer Verbesserung der chirurgischen Ergebnisse geführt. Trotz dieser Verfahren kommt es allerdings immer wieder zu einer Persistenz von Ausfällen und Lähmungserscheinungen. Daher ist es unabdingbar, dass der rekonstruktive Plan des Chirurgen auch so genannte Sekundär- oder Palliativmaßnahmen berücksichtigt, die sekundär zum Einsatz kommen können. Der vorliegende Beitrag gibt eine kurze Übersicht über die Versorgung peripherer Nervenverletzungen, die Nerventransplantation und verschiedene palliative Maßnahmen (Arthrodesen, motorische Ersatzoperationen usw.), die sekundär eingesetzt werden können.AbstractThe surgical treatment of peripheral nerve injuries is still a challenging and highly demanding procedure. Past results have been improved upon by different advances in microsurgical techniques and algorithms. Nevertheless, results are not always satisfying, making secondary procedures necessary. Thus, these secondary procedures such as tendon transfers and arthrodesis of different joints must be taken into account during reconstructive planning. This review gives an overview of peripheral nerve reconstruction (nerve grafting, nerve repair) and the pertinent secondary procedures.

Restoration of shoulder abduction function by direct muscular neurotization with the phrenic nerve fascicles and nerve grafts: A case report

In this report, we describe the first case of using the partial phrenic nerve transfer and direct muscular implantation into the deltoid muscle for restoration of the shoulder function and stability. A patient suffering from the partial brachial plexus injury with absent axillary nerve underwent reconstructive surgery by an end‐to‐end nerve coaptation using two fascicles of the phrenic nerve and two autologous nerve grafts, and direct implantation of nerve grafts into the deltoid muscle. Eighteen months after the procedure, we found a functioning biceps with 90° elbow flexion against gravity and 40° shoulder abduction with satisfactory shoulder stability. Electrophysiology revealed reinnervation potentials in the deltoid and biceps muscle. This case demonstrates a satisfactory result after using transfer of the partial ipsilateral phrenic nerve in combination with muscular implantation to restore shoulder abduction and stability. We recommend the described techniques in cases without other reconstructive options.

Local administration of DFO-loaded lipid particles improves recovery after end-to-end reconstruction of rat median nerve.

PURPOSE The improvement of regeneration and functional recovery after peripheral nerve injury is a major challenge in neurosurgery. Although microsurgical techniques for nerve reconstruction have seen great advancements over the last years, the clinical outcome with patients is often unsatisfactory. The aim of the present study was to investigate if administration of the iron chelator Deferroxamine (DFO), can improve postoperative outcome in the rat median nerve reconstruction model. METHODS After complete transection, the right median nerve was repaired by end-to-end neurorrhaphy. The suture site was wrapped by a 1-cm-long external jugular vein segment, either empty or filled with DFO-loaded lipid particles (Perineurin or with a vehicle (unloaded lipid particles) alone. Functional testing was carried out weekly by means of the grasping test. At the time of withdrawal, 12 weeks post-operatively, muscle tropism recovery was assessed by weighing flexor digitorum sublimis muscle that is innervated by the median nerve only. Before harvesting of the nerve specimens electrophysiological analyses were performed with measuring the latency, the threshold and the conduction velocity. Finally, the repaired nerves were withdrawn for immunocytochemistry with a neurofilament antibody and axon quantitative morphology. RESULTS The comparison between the groups showed that intraoperative application of the DFO-loaded lipid particles at the neurorrhaphy site led to a significant increase in the density of regenerating axons as well as to an accelerated recovery of both muscle tropism and motor function. The electrophysiological results demonstrated a decrease of the threshold, a lower latency, and a higher conduction velocity in the Perineurin-treated animals. CONCLUSIONS The results of the present study suggest that local administration of Perineurin might have a therapeutic potential for improving the postoperative outcome after microsurgical nerve reconstruction in patients.

Non-viral genetic transfection of rat Schwann cells with FuGENE HD © lipofection and AMAXA © nucleofection is feasible but impairs cell viability

PURPOSE To determine transfection efficiency of FuGENE HD© lipofection and AMAXA© nucleofection on rat Schwann cells (SC). METHODS The ischiadic and median nerves of 6-8 week old Lewis rats were cultured in modified melanocyte-growth medium. SCs were genetically transfected with green fluorescent protein (GFP) as reporter gene using FuGENE HD© lipofection and AMAXA© nucleofection. Transfection rates were determined by visualization of GFP fluorescence under fluorescence microscopy and cell counting. Transfected cell to non-transfected cell relation was determined. RESULTS Purity of Schwann cell culture was 88% as determined by immunohistologic staining. Transfection rate of FuGENE HD© lipofection was 2%, transfection rate of AMAXA© nucleofection was 10%. With both methods, Schwann cells showed pronounced aggregation behavior which made them unfeasible for further cultivation. Settling of Schwann cells on laminin and poly-L-ornithine coated plates was compromised by either method. CONCLUSION Non-viral transfection of rat SC with FuGENE HD© lipofection and AMAXA© nucleofection is basically possible with a higher transfection rate for nucleofection than for lipofection. As cell viability is compromised by either method however, viral transfection is to be considered if higher efficiency is required.

Aggressive digital papillary adenocarcinoma – a rare malignant tumor of the sweat glands: two case reports and a review of the literature

Aggressive digital papillary adenocarcinomas are rare malignant tumors often located on the digits of the hand. Due to lack of pain, slow growth, and an inconspicuous appearance, diagnosis is often missed or delayed. We report two cases and review the present literature to give recommendations for diagnosis and treatment.

Chapter 23: Manual stimulation of target muscles has different impact on functional recovery after injury of pure motor or mixed nerves.

Direct coaptation and interpositional nerve grafting (IPNG) of an injured peripheral nerve is still associated with poor functional recovery. Main reasons for that are thought to be an extensive collateral axonal branching at the site of transection and the polyinnervation of motor endplates due to terminal axonal and intramuscular sprouting. Moreover, severe changes occurring within the muscle after long-term denervation, like loss of muscle bulk and circulation as well as progressive fibrosis, have a negative effect on the quality of functional recovery after reinnervation. We have recently shown that manual stimulation (MS) of paralyzed vibrissal muscles in rat promotes full recovery after facial nerve coaptation. Furthermore, MS improved functional recovery after hypoglossal nerve repair, hypoglossal-facial IPNG of the facial nerve in rat. In contrary, MS did not improve recovery after injury of the median nerve in rat, which is however a mixed peripheral nerve comparing to the facial nerve. It is speculated that manually stimulated recovery of motor function requires an intact sensory input, which is affected in case of mixed peripheral nerves but not in case of pure motor nerves. In this article, we summarize our results of MS in several peripheral nerve injury models in order to illustrate the application potential of this method and to give insights into further investigations on that field.

Is intraoperative luxation of the ulnar nerve a criterion for transposition

BACKGROUND The relevance of subcutaneous transposition of the ulnar nerve in the therapy of cubital tunnel syndrome is still under debate. The aim of this study was to compare the results after decompression to additional transposition in cases of intraoperative luxation. METHODS A total of 54 cases after surgery of cubital tunnel syndrome between 2000 and 2006 were analyzed. Nerve transposition was performed in cases of intraoperatively apparent nerve luxation. RESULTS Of the patients 12 were treated by decompression alone and 42 by additional subcutaneous transposition. There was no significant difference concerning symptom amelioration, usage properties of the hand, sensation impairment and duration of disability. Force measurements of grip strength and pinch strength revealed no significant differences between either hand in both groups. The 2-point discrimination ability of the 8th to 10th finger nerves was not significantly different between the groups either. CONCLUSION Nerve transposition revealed no benefits in the treatment of cubital tunnel syndrome when performed in cases of intraoperative nerve luxation.