Manual stimulation of forearm muscles does not improve recovery of motor function after injury to a mixed peripheral nerve

Exp Brain Res (2008) 185:469483 DOI 10.1007/s00221-007-1174-y

RESEARCH ARTICLE

Manual stimulation of forearm muscles does not improve recovery of motor function after injury to a mixed peripheral nerve

N. Sinis O. Guntinas-Lichius A. Irintchev E. Skouras S. Kuerten S. P. Pavlov H. E. Schaller S. A. Dunlop D. N. Angelov

Received: 10 August 2007 / Accepted: 7 October 2007 / Published online: 23 October 2007 Springer-Verlag 2007

Abstract Transection and re-anastomosis of the purely motor facial nerve leads to poor functional recovery. However, we have recently shown in rat that manual stimulation (MS) of denervated vibrissal muscles reduces the number of polyinnervated motor endplates and promotes full recovery of whisking. Here, we examined whether MS of denervated rat forearm muscles would also improve recovery following transection and suture of the mixed (sensory and motor) median nerve (medianmedian anastomosis, MMA). Following MMA of the right median nerve, animals received no postoperative treatment, daily MS of the forearm muscles or handling only. An almost identical level of functional recovery, measured by the force of grip in grams, was reached in all animals by the sixth postoperative week and maintained till 3 months following surgery regardless of the postoperative treatment. Also, we found no diVerences among the groups in the degree of axonal

sprouting, the extent of motor endplate polyinnervation and in the soma size of regenerated motoneurons. Taken together, we show that while MS is beneWcial following motor nerve injury, combined strategies will be required for functional recovery following mixed nerve injury.

Keywords Motoneuron Axotomy Median nerve Axonal sprouting Forearm muscles Motor endplates Polyinnervation

Introduction

Although mammalian peripheral nerves have an innate capacity to regenerate, functional recovery is often poor and persistent pareses, synkineses and dysreXexia are inevitable (Hall 2005; Lundborg 2005). Advances in reconstructive microsurgery have provided some signiWcant improvements in encouraging axon regeneration per se but

S. A. Dunlop and D. N. Angelov contributed equally and share last authorship.

N. Sinis H. E. SchallerDepartment of Hand-, Plastic-,and Reconstructive Surgery with Burn Unit, BG-Trauma Centre, University of Tuebingen, Tuebingen, Germany

O. Guntinas-LichiusDepartment of Otorhinolaryngology, Friedrich-Schiller University Jena, 07740 Jena, Germany

A. IrintchevCentre for Molecular Neurobiology, University of Hamburg, Hamburg, Germany

E. SkourasDepartment of Trauma, Hand and Reconstructive Surgery, University of Cologne, Cologne, Germany

S. Kuerten D....