Change in cross-sectional area of the median nerve with age in neonates, infants and children analyzed by high-resolution ultrasound imaging.

AIM: To analyze age dependencies in the cross-sectional area (CSA) of the median nerve during early childhood. METHOD: A total of 43 participants (32 of whom were children younger than 2 years) were included in this cross-sectional study to analyze the age dependency of the CSA of the median nerve at three locations (wrist, forearm and upper arm) using high-resolution ultrasound images. RESULTS: A strong and highly significant correlation was found between age and CSA (p < 0.001). When plotted, the relationship followed a logarithmic curve (p < 0.001) with a growth rate that decreases with age. Based on the regression analysis, a temporally similar increase in CSA for all three locations was found. The nerve reaches 70% of its final CSA by 2 years of age at all three locations. INTERPRETATION: Similar to the nerve conduction speed, the increase in CSA is greatest during the first 2 years of life. Then, the rate gradually and synchronously slows at the proximal and distal locations. Measurement of the CSA in the clinical setting might offer a new method to assess the maturation of the nervous system in infants with minimal interference.

The Use of a Hypoallergenic Dermal Matrix for Wrapping in Peripheral Nerve Lesions Regeneration: Functional and Quantitative Morphological Analysis in an Experimental Animal Model.

INTRODUCTION: The aim of this research was to test, in an animal model, the nerve regeneration technique with a hypoallergenic acellular dermal matrix used to wrap the microsurgical neural suture. MATERIALS AND METHODS: Two groups of rats received the cut of limb right median nerves. The regeneration technique considers for both groups an end-to-end nerve suture. In the experimental group (A) was used also a wrapping protocol by a conduit of collagen matrix currently used in oral surgery. The animals underwent functional grasping tests (at 1, 3, 5, and 7 months) and a histological and quantitative analysis of distal nerve was performed at the end of experimental time. RESULT: After seven months, the grasping test reveals functional recovery in each tested animal; this improvement is more evident in Group A. The fibers appear well organized with restored myelin sheaths in both groups. Group A showed a great quantity of connective tissue surrounding the nerve. The quantitative morphology analysis in both groups shows a similar fibers density, fiber diameter, and myelin thickness. The differences between the groups in axon mean diameter are significant. In Group A M/d, D/d, and g-ratio is significantly higher compared to control group. CONCLUSIONS: Histological and functional assessments show a functional recovery of the injured nerve in the test groups, stressed by the results of the grasping tests and the meaningful increasing in fiber diameter and higher g-ratio. Moreover, a connective tissue cuff distinguishes the distal portion of the injured nerve. Considering the easy availability and handling of the material used in this study we can conclude that this experimental technique can be considered as a valid alternative to protect nerves in nerve wrap surgery.

Retalho tenar adipofascial reverso para cobertura do nervo mediano hipertrofiado em macrodactilia / The reverse adipofascial thenar flap for coverage of the hypertrophied median nerve in macrodactyly

A macrodactilia é uma anomalia congênita infrequente, caracterizada pelo crescimento desproporcional dos tecidos ósseo, gorduroso, nervoso, vascular e dérmico nos dedos das mãos ou dos pés. Existem muitas teorias sobre a sua etiopatogenia, sendo a mais aceita a hiperestimulação por fatores de crescimento enviados através dos nervos. Foram descritos alguns casos associados com a síndrome do túnel do carpo. Apresenta-se um caso clínico de síndrome do túnel do carpo por hipertrofia do nervo mediano, evidenciando um aumento de conteúdo dentro do retináculo flexor, o qual foi tratado cirurgicamente com sucesso pela realização de uma retinaculotomia do ligamento anular do carpo junto a um retalho de transposição tenar adipofascial reverso da região tenariana hipertrofiada visando à cobertura do nervo mediano na região do punho.

Macrodactyly is a rare congenital anomaly characterized by the disproportionate growth of bone, fat, nervous, vascular, and dermal tissue in the digits . There are many different theories about its etiopathogenesis, the most accepted being a hyperstimulation by growth factors conducted through nerves. A few cases have been described in conjunction with carpal tunnel syndrome. Here, a clinical case of carpal tunnel syndrome due to hypertrophy of the median nerve is presented, showing an increase of content within the flexor retinaculum. Successful surgical treatment was accomplished by conducting a retinaculotomy of the anterior annular ligament along with a reverse transposition adipofascial flap of the hypertrophied thenar region for coverage of the median nerve at the wrist.

The effects of restricting afferent input during early ontogenesis on evoked activity of projection neurons depend on the maturity of the sensory inputs.

Experiments were performed on 28 Wistar rats, of which 14 were subjected to unilateral denervation of the forelimb (by dissection of the median nerve) on day 13 of postnatal ontogenesis. The effects of restriction of sensory input on baseline and evoked somatosensory cortex neuron activity in the areas corresponding to the representation of the intact fore- and hindlimbs were studied. According to the proximal-distal rule of maturation, the sensory input from the forelimbs was completely formed by the moment at which deafferentation was performed, while the sensory input from the hindlimbs was still incompletely mature. Opposite changes were found to occur in areas receiving more or less mature afferent inputs. In the projection zone of the less mature input (from the hindlimbs), neurons showed a lower frequency of baseline activity and stimulation of the sciatic nerve evoked significantly more activatory responses and an increase in the duration of short-latency activatory responses. In the projection zone of the more mature sensory input (from the forelimb), stimulation of the intact median nerve evoked significantly more inhibitory responses and fewer complex responses. Thus, normal formation of normal brain neuron activity requires an adequate sensory input.

Maturation of near-field and far-field somatosensory evoked potentials after median nerve stimulation in children under 4 years of age.

OBJECTIVES: The maturation of subcortical SEPs in young children. METHODS: Median nerve SEPs were recorded during sleep in 42 subjects aged 0-48 months. Active electrodes were at the ipsilateral Erb's point, the lower and upper dorsal neck, and the frontal and contralateral centroparietal scalp; reference electrodes were at the contralateral Erb's point, the ipsilateral earlobe and the frontal scalp; bandpass was 10-3000 Hz. The peaks were labelled by their latencies in adults. RESULTS: The peak latencies of N9 (brachial plexus potential) decreased exponentially with age during the first year, but increased with height thereafter. The interpeak latencies (IPLs) N9-N11, which measure conduction between brachial plexus and dorsal column, decreased with age (linear regression). The IPLs N11-P13 and N11-N13b, which measure conduction between the dorsal column and approximately the cervico-medullary junction, did not change across this age range. The IPLs N13a-N20, N13b-N20 and P13-N20, which measure central conduction, showed negative exponential regressions with rapidly decreasing latencies during the first year of life and slowly decreasing latencies thereafter. CONCLUSIONS: Maturation of the peripheral segments of the somatosensory pathway progresses more rapidly than that of the central segments. The maturation of central conduction is not completed within the first 4 years of age. Our maturational data may serve as a reference source for subsequent developmental and clinical studies.

Effects of insulin-like growth factor-1 in motor nerve regeneration after nerve transection and repair vs. nerve crushing injury in the rat.

Despite highest standards in nerve repair, functional recovery following nerve transection still remains unsatisfactory. Non-specific re-innervation of target organs are regarded as one reason for a poor functional outcome. Insulin-like growth factor-1 (IGF-1) has demonstrated promoting effects on sciatic nerve regeneration after crushing injury. Similarly, IGF-1 has shown a direct inductive effect on motoneuron growth associated protein-43 (GAP-43) which is believed to play a role in axon guidance during development. Based on this fact we have examined the trophic effects of recombinant human IGF-1 on peripheral motor nerve regeneration following transection and epineural repair in rats median nerve. RhIGF-1 (0.5 mg/kg/rat) was administered subcutaneously to the neck of the repaired side for 14 days postoperation. Accuracy of re-innervation of the flexor carpi radialis muscle motoneuron pool was studied by sequential retrograde double labelling technique. Motor recovery was tested with the grasping test. No significant differences between experimental and control animals in accuracy of re-innervation and in recovery of muscle power could be demonstrated. Non-specific re-innervation of the flexor carpi radialis muscle was found in 23.2% in the experimental group and in 24.2% in the control group. These results demonstrate that systemically applied rhIGF-1 failed to improve functional motor recovery after nerve transection and repair in the rat as it was demonstrated after nerve crushing injury in several studies. Furthermore, systemically applied IGF-1 did not improve accuracy of re-innervation after axotomy and repair in adult rats.

Effects of self- and cross-reinnervation on the numbers of motoneurons regenerating to forearm muscles in young and adult rats.

The present study was carried out to compare the ability of motoneurons to regenerate to functionally appropriate and inappropriate muscles, following axotomy at different stages of postnatal development. Five-, 10-, 21-day-old and adult rats of both sexes were used. In one group, the right median and radial nerves were cut and reunited. In a second group, the cut nerves were cross reunited and, in a third group the nerves were merely exposed. Following survival periods of up to one year, the extent of motoneuron regeneration through the repaired nerves was determined by injecting the retrogradely transported tracers horseradish peroxidase (HRP) and Fast Blue into the flexor and extensor muscles of the right forearm. The results were expressed in terms of the difference between the number of labelled motoneurons on the experimental side of the spinal cord and the number on the control side, the latter having been labelled by injection of HRP and Fast Blue into the muscles of the left forearm. Comparisons were then made between the groups with respect to the age at which axotomy occurred, and the target of regeneration. The results showed that when axotomy was performed in 5- and 10-day-old rats, significantly fewer motoneurons were labelled, irrespective of whether or not the target was functionally appropriate, than when axotomy was performed in adulthood. The difference was most likely due to a lower survival rate of motoneurons following axotomy in neonates. No difference was found, however, between the numbers of labelled median and radial nerve motoneurons following self- versus cross-reinnervation in any age group. This suggests that, in both adult and neonatal rats, motoneurons which survive axotomy are able to regenerate equally well to functionally appropriate or inappropriate muscles.

Loss of motor neurons from the median nerve motor nucleus of the mutant mouse 'wobbler'.

This paper describes the location and number of motor neurons in the median nerve pool of wobbler mice and normal littermates as determined by retrograde labelling of the cut median nerve with horseradish peroxidase (HRP) in animals from 3 weeks to 1-year-old. The median nerve motor nucleus is located in spinal segments C5-T1, and in normal animals contains 199 (6) (mean (SEM] motor neurons. Three-week-old wobbler mice have the same number of labelled neurons as control animals, and this number falls to 75% of normal values by 4 weeks of age, and to approximately 60% by 6 weeks of age and older. Numerous swollen, pale and frequently vacuolated perikarya are present in the same 3-6-week-old mice. In the 3-week-old mutants these comprise on average 17% of the total large (greater than 20 microns) neuronal cell bodies counted in segments C5-T1. By 6 weeks this figure has fallen to 10%, and to less than 4% in adult wobblers. We conclude that the most active period in the expression of the wobbler phenotype is from 3 to 6 weeks of age.

[Some elements of the internal structure of the median nerve in the post-fetal life of man]. / Niektóre elementy wewnetrznej budowy nerwu posrodkowego w przebiegu zycia pozaplodowego czlowieka.

The studies were carried out on 240 median nerves taken bilaterally from cadavers of 60 men and 60 women aged from 1 day to 86 years. The number of fascicles in the place where it leaves the brachial plexus, in the upper 1/3 part of the arm, in the lower 1/3 part of the arm and in the cubital area were determined. The magnitude of the surface area of cross-section of the fascicles forming the medical nerve in the lower 1/3 part of the arm were studied. Some of the changes occurring within these elements in the post-fetal life in man were also determined.