s95 ClinicalNeurology andNeurosurgery, 9.5 (SuppI.) (1993) S95s102 0 1993 Elsevier Science Publishers B.V. All rights reserved 0303-8467/93/%06.00 CLINEU 002.59 Respiration-related activity in the biceps brachii muscle after intercostal-musculocutaneous nerve transfer M.J.A. Malessya, J.G. van Dijk” and R.T.W.M. Thomet$ Departments of aNeuroswgety and bNeurology and Clinical Neurophysiology, University ofleidq Leiden, TheNetherlands Key words: Brachial plexus; Nerve transfer; Intercostal nerves; Respiration; EMG zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Summary Needle EMG and polygraphic recordings of respiration and biceps activity were obtained in 7 patients who had undergone intercostal to musculocu~neous nerve transfer because of severe traumatic injury to the brachial plexus. EMG activity during expiration and inspiration was assessed during quiet breathing, deep breathing, and during sustained inspiration and expiration, and compared to the clinical strength of the biceps muscle. Biceps activity was consistently found during both expiration and inspiration, and in either case separately related to the flexion force levels. Initially this relationship appeared equally strong for both phases. With time, control over flexion changes from a completely respiratory-driven control to a conscious volitional control; however, involuntary effects of respiration always remained present in polygraphic recordings. Theoretical explana- tions for the change in control are put forward. Introduction Aims of the study Intercostal nerves (ICNs) can be used for nerve transfers in lesions of the brachial plexus (BP), in an attempt to regain elbow flexion in avulsions of all roots or in avulsions of the upper two or three roots [l]. Following intercos~l-musculo- cutaneous (ICN-MC) nerve transfer, about half of the pa- tients regain elbow flexion with force levels of M grades 4 PI- The ICNs of the third to sixth thoracic segments used for this purpose originally innervate 5 different thoracic respira- tory muscles. Dorsally, they give off branches to the serratus posterior superior muscle and the external interosseous inter- costal muscles. Further branches to the latter muscle and branches to the internal interosseous intercostal muscle split off in the axillary fine. At the level of the costal cartilage branches go off to the internal interchondral intercostal mus- cle and just parastemally to the triangularis sterni muscle. Some of these muscles are active in inspiration and others in expiration; fu~he~ore, these muscles play a complex role in thoracic movements [3,4]. Axons with essentially Corrtqwzdence to: M.J.A. Malessy, M.D., Department of Neu~urgery, L&den University Hospital, P.O.Box %1X3,2300 RC Leiden, The Netherlands. Phone: (+31)-71263957; FAX: (+31)-71-157536. antagonistic functions, i.e. inspiration and expiration, are present in ICNs. As both types of motor neurons may be involved in a ICN-MC nerve transfer, both may reach the biceps muscle. It is not yet known if, and to what extent, this antagonism influences the re-establishment of voluntary control over elbow function. This study had a threefold purpose: to provide a review of the physiology of the muscles innervated by ICNs, to review reports on inspiratory versus expiratory activity in ICN-MC nerve transfer, and finally to perform a preliminary analysis of results in 7 patients after ICN-MC nerve transfer. Functions of ICN-innervated muscles The internal interchondral intercostal muscles show EMG activity only during inspiration 13,541, and are always ac- tive during inspiration [7]. The internal interchondral inter- costal muscles in the upper interspaces show more activity than those in lower spaces [8]. Increased activation is asso- ciated with changing from a supine to an erect posture, with increasing the frequency of breathing, and with increasing lung volume above the normal quiet breathing level [9,10]. The external interosseous intercostal muscles contract during inspiration. Inspiratory activation of these muscles predominates in the cranial interspaces. They are readily recruited sequentially along a cranio~udal gradient by deeper inspiration [3,11].