Functional recovery after transection of the sciatic nerve at an early age: a pilot study in rats

Abstract

It is often clinically noted that peripheral nerve transections in infants and very young children seem to show better functional recovery after nerve repair compared with adult patients. There can be several reasons for this (e.g. outgrowing axons might have maintained their potential to locate their genuine target muscle, the distance from the lesion site to the target organ is shorter, or there is enhanced compensational capacity of central brain areas at early stages of development). We decided to study the effects on walking performance of sciatic nerve transection and repair in nine rats at the youngest age at which appreciable numbers of motoneurons survive transaction (10th day of life). The follow-up period was 52 weeks. Walking movements were recorded on video and performance was qualitatively assessed. The stance factor and the sciatic function index were calculated and abnormalities such as automutilation of the toes or flexion contractures were noted. Postmortem inspection aimed to examine the continuity of the regenerated nerve and the presence of neuromas. Nine days after the transection and nerve repair, walking performance in all rats was close to the level in rats that had not undergone the procedure. Exorotation of the hind leg on the operated side was observed in only two rats. However, 20 days after lesioning the walking performance started to deteriorate, and walking patterns in all but one rat showed severe disability until the end of the observations. Only one out of the nine animals walked relatively undisturbed, with a sciatic function index approaching normal values but with an abnormal stance factor. We conclude that a sciatic nerve transection in rats aged 10 days leads to long-term impairments in walking patterns.Clinical evidence has suggested that peripheral nerve lesions or transections at neonatal and young age may lead to less severe impairments than similar lesions at adult age, 1 and comparable results have been reported in infant monkeys. 2 Others, however, have questioned this optimism. 3 There is only scant evidence from animal experiments. The effects of transection and repair of the posterior tibial nerve at 6 and 22 days in rats has been studied; 4 walking in the animals operated at the 6th day was more impaired than in rats operated at the 22nd day.Adult motoneuronal axons have the capacity to grow out towards the distal stump of a severed sciatic nerve. However, when arriving at the target area, the outgrowing axons obviously are unable to relocate their muscles of origin and they randomly reinnervate these muscles. 5 Retrograde labelling of motoneurons showed different neurons within one and the same motoneuronal pool but innervating antagonistic muscles. This, and the drastic effects on the properties of the denervated and reinnervated muscles, are the main reasons for maladaptive functioning. 6 It might be hypothesized that nerve transections at early stages of development have less severe consequences. The outgrowing axons might still have maintained their potenti...

Revitalizing the common peroneal function index for assessing functional recovery following nerve injury

“…The use of PFI (Ruiter et al., 2007; Chen et al., 2009; Wong et al., 2011; Hare et al., 1992) is less common than SFI (Bittner et al., 2012; Chen et al., 2007, 2009, 2010; Clavijo‐Alvarez et al, 2007; Dinh et al., 2009; Hare et al., 1992; Kim et al., 2007; Lee et al., 2013; Matsuda et al., 2010; Meek et al., 2007; Monte‐Raso et al., 2006, 2008; Nagao et al., 2011; Nie et al., 2007; Penna et al., 2012; Ruiter et al., 2007; Whitlock et al., 2009; Wong et al., 2011; Wood et al., 2010; Xu et al., 2012), and several problems with walking tracks are still apparent in the literature, such as contracture, related to loss of function of tarsal flexor/digital extensor muscles (Chen et al., 2009; Hare et al., 1992; Wong et al., 2011), or other causes of poor print quality (Maeda et al., 1993; Medinaceli et al., 1982; Meek et al., 1996). Other problems have been suggested, but not investigated, such as alteration of contralateral limb prints as a result of compensatory strategies during locomotion (Hare et al., 1992), and the effect of velocity on walking track analysis (Shenaq et al., 1989; Varejão et al., 2001; Walker et al., 1994).…”