IMPROVED SENSORY RELEARNING AFTER NERVE REPAIR INDUCED BY SELECTIVE TEMPORARY ANAESTHESIA – A NEW CONCEPT IN HAND REHABILITATION B. ROSE ´ N, A. BJO ¨ RKMAN and G. LUNDBORG From the Department of Hand Surgery, Lund University, University Hospital Malmo¨, Malmo¨, Sweden The outcome after nerve repair in adults is generally poor. We hypothesized that forearm deafferentation would enhance the sensory outcome by increasing the cortical hand representation. A prospective, randomized, double-blind study was designed to investigate the effects of cutaneous forearm anaesthesia combined with sensory re-education on the outcome after ulnar or median nerve repair. During a 2 week period, a local anaesthetic cream (EMLA s ) ðn ¼ 7Þ or placebo ðn ¼ 6Þ was applied repeatedly onto the flexor aspect of the forearm of the injured arm and combined with sensory re-education. Evaluation of sensory function was carried out at regular intervals and at 4 weeks after the last EMLA s /placebo session. The EMLA s group showed significant improvement compared to placebo in perception of touch/pressure, tactile gnosis and in the summarized outcome after 6 weeks. These results suggest that cutaneous forearm anaesthesia of the injured limb, in combination with sensory re-education, can enhance sensory recovery after nerve repair. Journal of Hand Surgery (British and European Volume, 2006) 31B: 2: 126–132 Keywords: nerve injury, anaesthesia, sensory relearning, hand function INTRODUCTION The outcome after a peripheral nerve injury and repair depends on several factors, both in the peripheral and central nervous system (Lundborg, 2003, 2004). In spite of refined surgical technique, the clinical outcome in adults is generally poor with persisting sensory dysfunc- tion and pain problems (Lundborg, 2003, 2004). A major reason for this is the profound cortical functional changes which are induced by a peripheral nerve injury, based on the misdirection of regenerating axons which follows surgical repair (Chen et al., 2002; Lundborg, 2004). Generally, children with nerve injury have a better functional outcome, presumably because of the superior ability of the young brain to adapt to the cortical reorganization. This adaptability is reduced, although not lost, in the older brain (Almquist et al., 1983; Birch and Raji, 1991; Lundborg, 2004; Lundborg and Rose´n, 2001). The ‘‘new language’’ that the hand speaks to the brain after a nerve repair is difficult to interpret and the functional result – impairment in tactile gnosis (func- tional sensibility) – is a serious problem for the patient, taking into account the accompanying motor and pain problems (Jerosch-Herold, 2000; Lundborg et al., 2004; Rose´n, 1996; Wynn-Parry, 1986). Therefore, we have to look for new ways to improve the outcome after nerve repair, focusing on the central nervous system. Strate- gies to improve the functional results should focus on a refinement of current sensory re-educational pro- grammes in consideration of evolving neuroscientific concepts, utilizing the capacity for rapid and long-term cortical remodelling that is possible not only in the young brain but also in the adult brain (Chen et al., 2002; Lundborg, 2004; Rose´n et al., 2003; Wall et al., 2002). Experimental deafferentation using tourniquet-in- duced anaesthesia, or an anaesthetic block, has been shown to induce cortical changes in both brain hemi- spheres (Calford and Tweedale, 1990; Chen et al., 2002; Werhahn et al., 2002a, b). In healthy persons and patients with peripheral nerve injuries, a temporary deafferentation of one hand with a nerve block, or a tourniquet, induced a rapid improvement in hand function on the contralateral side (Bjorkman et al., 2004b; Werhahn et al., 2002b). Selective deafferentation may also have effects on sensorimotor functions in the ipsilateral arm. Anaesthetic block of upper cervical roots in stroke patients results in increased grip strength in the hand being innervated by the lower cervical roots (Muellbacher et al., 2002). By analogy, a selective cutaneous anaesthesia of the forearm on healthy persons has been shown to induce improved hand sensation in the ipsilateral hand (Bjo¨rkman et al., 2004a). This is probably due to expansion of cortical territories adjacent to the denervated forearm representation, including the hand representation (Bjo¨rkman et al., 2004b; Muellbacher et al., 2002; Werhahn et al., 2002b). Our hypothesis was that deafferentation of the forearm would also allow an expansion of the cortical representation of the adjacent hand in nerve-injured patients and that this might enhance the effectiveness of sensory re-education. Accordingly, the aim of the present study was to investigate the effects on sensory ARTICLE IN PRESS 126