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Sex-related differences in the regeneration of sensory axons and recovery of nociception after peripheral nerve crush in the rat

Sex-related differences regarding the regeneration of nociceptive axons and the recovery of nociception after sural nerve crush injury were examined in rats. The elongation rate of the fastest regenerating sensory axons in females started to increase after the first 6 days. This resulted in about 15% greater axon elongation distance at 8 days after crush in female than in male rats as determined by the nerve pinch test. The number of regenerating sensory axons in female and male rats, however, was not different. The recovery of nociception in the instep started earlier and was more extensive in females than in males during the entire 24-week recovery period, so that the pain sensitive area was finally about 20% larger in females than in males. Although ovariectomy significantly reduced plasma estradiol concentration in female rats, it did not change the elongation distance of regenerating nociceptive axons, which remained significantly greater than in male rats. Elimination of the cells in the distal nerve segment by freezing revealed that a more effective cell support in the distal nerve segment is probably responsible for faster regeneration of nociceptive axons in females than in males, rather than the circulating female sex hormones.

Aging impairs collateral sprouting of nociceptive axons in the rat

Sprouting of uninjured nociceptive axons was examined in young adult, middle aged and aged rats. Axon sprouting from the spared sural nerve, both into adjacent denervated skin and into end-to-side coapted nerve graft, was significantly higher in young rats than in aged rats. Cross-transplantations of the end-to-side coapted nerve grafts between young and aged rats demonstrated that axon sprouting from young recipient nerves into aged donor nerve grafts was significantly deteriorated, whereas the axon sprouting from aged recipient nerves into young donor nerve grafts was not statistically significantly affected. The levels of laminin polypeptides in peripheral nerves were 50-100% higher in young adult than in aged rats. However, the levels of peripherin, NGF isoforms and TrkA in skin, peripheral nerves and DRG, respectively, were not significantly reduced in aged rats. Therefore, impaired sprouting of nociceptive axons in aged rats is due rather to the alterations in peripheral neural pathways, than to the limited sprouting capacity of aged sensory neurons. Decreased levels of extracellular matrix components might be important in this respect.

Influence of Breaching the Connective Sheaths of the Donor Nerve on Its Myelinated Sensory Axons and on Their Sprouting into the End-to-Side Coapted Nerve in the Rat

The influence of breaching the connective sheaths of the donor sural nerve on axonal sprouting into the end-to-side coapted peroneal nerve was examined in the rat. In parallel, the effect of these procedures on the donor nerve was assessed. The sheaths of the donor nerve at the coaptation site were either left completely intact (group A) or they were breached by epineurial sutures (group B), an epineurial window (group C), or a perineurial window (group D). In group A, the compound action potential (CAP) of sensory axons was detected in ~10% and 40% of the recipient nerves at 4 and 8 weeks, respectively, which was significantly less frequently than in group D at both recovery periods. In addition, the number of myelinated axons in the recipient nerve was significantly larger in group D than in other groups at 4 weeks. At 8 weeks, the number of axons in group A was only ~15% of the axon numbers in other groups (p<0.05). Focal subepineurial degenerative changes in the donor nerves were only seen after 4 weeks, but not later. The average CAP area and the total number of myelinated axons in the donor nerves were not different among the experimental groups. In conclusion, myelinated sensory axons are able to penetrate the epiperineurium of donor nerves after end-to-side nerve coaption; however, their ingrowth into recipient nerves is significantly enhanced by breaching the epiperineurial sheets at the coaptation site. Breaching does not cause permanent injury to the donor nerve.

Use of 3D visualisation of medical images for planning and intraoperative localisation of superficial brain tumours: our experience

Background. In the present article, we assessed the role, adequacy and application accuracy of intraoperative visual guidance based on the computer 3D visualisation of preoperative medical images in the surgery of superficial brain tumours. Materials and methods. For 30 consecutive patients with convexity meningioma or cortical/subcortical brain tumour, we used 3D visualisation of post-contrast fast spoiled gradient recalled (FSPGR) MR images to plan optimal positions for the trepanation opening and/or corticotomy site. At the beginning of the surgery, planned positions were transferred to the scalp and the cortical surface of the patient by visually matching the 3D surfaces with the operative field. The feasibility of visual matching was assessed by counting the number of cases in which this was possible. On the exposed cortical surface, we measured the mismatch between the centre of the actual trepanation opening and the planned corticotomy site, where possible. Results. During computer-assisted 3D planning, the centre of the trepanation opening, initially defined on the basis of 2D diagnostic images, was redefined in all our cases by an average repositioning distance of 19.7 mm ± 7.6 mm. During surgery, the transfer of the planned centre of the trepanation opening and the corticotomy site was possible in all (30/30) and in 70% (19/27) of the cases, respectively. Where assessable, the mismatch between the centre of the actual trepanation opening and the planned corticotomy site was less than 1 cm in 70% of cases (12/17) and more than 2 cm in 6% (1/17) of cases. Conclusions. Intraoperative visual guidance based on 3D visualisation proved to be adequate and accurate for locating superficial brain tumours in cases where transfer of planned surgical targets to the surgical field was possible. Decision about its use should be based on preoperative computer-assisted 3D planning, in which the feasibility of visual matching during surgery can and must be assessed.

Which myelinated sensory axons sprout into an end-to-side coapted peripheral nerve in the rat?

BACKGROUND The high-threshold sensory afferents, which express trkA, are predominantly involved in terminal collateral sprouting in the skin of adult mammals. We explored which sensory axons are capable of sprouting into the end-to-side coapted nerve in the rat. METHOD The distal stump of the transected peroneal nerve was sutured to the side of the uninjured sural nerve. After 36 weeks, sprouting of sensory axons into the end-to-side coapted nerve was assessed by the electrophysiologic measurements of compound action potential and by counting the myelinated axons. The neurons in the dorsal root ganglia (DRG) L5 whose axons sprouted into the end-to-side coapted nerve were retrogradely labelled by the fluorescent dye Fluorogold. The expression of trkA in sprouting DRG neurons was investigated by immunohistochemistry. FINDINGS Predominantly thin myelinated axons were found in the end-to-side coapted peroneal nerve. Their mean conduction velocity (CV) was between the average CVs of the Adelta and Abeta fibres in the normal sural nerves. About 90% of the sprouting DRG neurons were small and medium sized, and about 10% were large. About 85% of sprouting DRG neurons was immunoreactive to trkA, but the rest were not. CONCLUSIONS Mostly the high-threshold sensory afferents sprouted into the end-to-side coapted nerve, which resembles the collateral sprouting of sensory axons in the skin. However, our results suggest that also some low-threshold mechanoreceptors can sprout after the end-to-side nerve repair.

Concurrent intradural meningioma and schwannoma at the same lumbar level in a patient without neurofibromatosis: a case report

Abstract Spinal schwannomas coexisting with meningiomas in patient without neurofibromatosis are extremely rare lesions. Here we present a case of 59-year-old patient with concurrent spinal meningioma and schwannoma at L1-L2 spinal level. This is the first case of the concurrent intradural tumours at the same lumbar level.