British Journal of Medicine & Medical Research 3(4): 928-952, 2013 SCIENCEDOMAIN international www.sciencedomain.org Brachial Plexopathies Josef Finsterer1*, Raffi Topakian2, Julia Wanschitz3, Stefan Quasthoff4, Gerd Bodner5, Wolfgang Grisold6 and Wolfgang N. Löscher3 1Krankenanstalt Rudolfstiftung, Vienna. 2Neurological Department, Wagner-Jauregg Krankenhaus, Linz. 3Neurological Department, Medical University Innsbruck, Innsbruck. 4Neurological Department, Medical University Graz, Graz. 5Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology. Medical University of Vienna, Vienna. 6Neurological Department, Kaiser-Franz-Josef Spital, Vienna, Austria. Authors’ contributions This work was carried out in collaboration between all authors. Author JF designed the study, performed the evaluation of the data, and wrote the first draft of the manuscript. Authors RT, JW, SQ, GB, WG and WNL contributed to the collection and discussion of the data and supported the writing of the manuscript. All authors read and approved the final manuscript Received 1st January 2013 th Review Article Accepted 6 February 2013 Published 11th March 2013 ABSTRACT Lesions of the brachial plexus are most commonly caused by traumatic injuries. Other causes include infiltration by tumors, intrinsic or extrinsic compressions, damage from radiation therapy, or neuralgic amyotrophy (Parsonage-Turner syndrome). Less frequent causes of brachial plexus lesions include metabolic disease (e.g. diabetes), viral infections, immunological reactions to vaccination or infections, drugs, malignancies, paraneoplastic conditions, or hereditary disease (SEPT9 mutations, HNPP). The diagnosis of brachial plexus lesion is based upon history, clinical examination, and instrumental investigations, particularly, nerve conduction studies, electromyography, evoked potentials, magnetic stimulation, and the MRI. Treatment depends on the cause of the plexus lesion and includes prophylactic measures, physiotherapy, drugs, or surgery. Rarely applied measures include therapeutic magnetic stimulation or pulsed radiofrequency treatment. Outcome of plexus lesions depends on the underlying cause and the effectiveness of the treatment and ranges from favorable to deleterious. The ___________________________________________________________________________________________ *Corresponding author: Email: [email protected]; British Journal of Medicine & Medical Research, 3(4): 928-952, 2013 outcome can be improved if diagnosis is made early and treatment is immediately applied after diagnosis. Keywords: Nerve lesion; neuropathy, plexopathy; compression; immunological; infection; malignancy; trauma; neuralgic amyotrophy. ABBREVIATIONS CMAP: Compound muscle action potential; CSF: Cerebro-spinal fluid; CT: Computed tomography; EMG: Electromyography; FS: Fast spin; GalNAC: N-acetyl-galactosaminyl; GM1 antibodies: Ganglioside antibodies; HIV: Human immunodeficiency virus; HNA: Hereditary neuralgic amyotrophy; HNPP: Hereditary neuropathy with liability to pressure palsies; HPV: Human papilloma virus; MABCN: Medial antebrachial cutaneous nerve; MRI: Magnetic resonance imaging; NSAID: Nonsteroidal-anti-inflammatory drugs; OBPP: Obstetric brachial plexus palsy; PMP22: Peripheral myelin protein 22; PTS: Parsonage- Turner syndrome; SE: Spin echo; SEPT9: Septin-9; SNAP: Sensory nerve action potential; SSEPs: Somatosensory-evoked potentials; STIR: Short tau inversion recovery; TNF: Tumor necrosis factor; TOS: Thoracic outlet syndrome; TSE: Turbo-spin echo; 1. INTRODUCTION The brachial plexus is a complex network of interwoven nerve strands, which are exposed to damage of variable origin. The most common cause of plexus damage is mechanical injury due to compression or tearing. Other causes include neoplastic infiltration, infection, immunological or metabolic disease, damage from radiation therapy, or genetic disease [1]. Diagnostic work-up and treatment of brachial plexus lesions of variable cause have been improved over the last years. Aim of the following review is thus to present and discuss recent advances and future perspectives concerning the clinical presentation, causes, diagnosis and outcome of brachial plexus lesions. 2. ANATOMY OF THE BRACHIAL PLEXUS The brachial plexus is part of the plexus cervicobrachialis and innervates the shoulder girdle and arm muscles [2]. The cervical plexus originates from the spinal roots C1-C4 providing nerves to the occipital head and neck, while the brachial plexus originates from the spinal roots C5-Th1 [2,3]. Roots C4 and Th2 may partially contribute to the brachial plexus but most often this input is not considered (pre-/postfixed brachial plexus) [4]. Generally, variations of the brachial plexus are rather the rule than the exception, and therefore may predispose patients to certain diseases (e.g. thoracic outlet syndrome (TOS)), may cause complications during plexus anesthesia or surgical procedures, and may be best visualised by immediate 3D reformat reconstruction with 3D color imaging [4]. After constitution, the plexus enters into the lateral cervical triangle between the anterior and medial scalenus muscle, passes between clavicle and first rib, and extends until the humerus [5]. The brachial plexus is divided into three primary strands (Fig. 1), also termed trunks, and into three secondary strands, also termed fascicles or cords. Roots C5 and C6 supply the upper trunk of the brachial plexus, root C7 the middle trunk, and roots C8 and Th1 the lower trunk. At the level of the clavicle each of the trunks divides into an anterior and posterior branch [3]. At the level of the axillary artery, the fascicles (lateral, dorsal, and medial fascicle) are formed. 929 British Journal of Medicine & Medical Research, 3(4): 928-952, 2013 Fig. 1. Scheme of the anatomical structure of the brachial plexus and the contribution of motor nerve roots to peripheral nerves originating from the plexus Only two nerves originate directly from a trunk. These are the subclavian (often gives a branch to the phrenic nerve) and the suprascapular nerve, both of which originate from the upper trunk (Fig. 2). Four nerves arise from the dorsal fascicle, the radial, axillaris, subscapular, and the thoracodorsalis nerve (Fig. 2). The medial fascicle forms parts (motor root) of the median nerve (intrinsic hand muscles, distal median-innervated muscles), the ulnar nerve, parts of the pectoral nerve, the medial cutaneous brachii nerve, and the medial cutaneous antebrachii nerve. From the lateral fascicle originate the musculocutaneous nerve, parts (sensory root) of the median nerve (flexor carpi rad., flexor dig. prof. and superfic., sensory portion of the median nerve), and parts of the pectoral nerve (Fig. 2). At the level of the roots, motor fibers deviate to the longus collis muscle, the anterior serratus muscle (long thoracic nerve), the diaphragm (parts of the phrenic nerve), and the rhomboidei muscles (dorsal scapular nerve). Altogether 10 mixed sensory-motor nerves and 2 purely sensory nerves originate from the brachial plexus (Fig. 3) [2]. The ten mixed nerves innervate 47 muscles if double innervated muscles (flexor poll. brevis and flexor dig. prof.) are counted as a half muscle, and if the 7 interossei and 4 lumbricales muscles are counted as a single muscle each (Table 1, Fig. 3). All plexus pathways also carry sympathetic fibers. They originate from the intermediolateral nucleus of the grey matter of the thoracic myelon, leave the myelon via the anterior radices to head via the ramus communicans griseus to the spinal ganglion and accompany plexus fibers after having left the sympathetic trunk via the ramus communicans albus. In the ganglia of the sympathetic trunk the first sympathetic neuron is dissipated to the second neuron, to either follow the peripheral nerves or directly head for inner organs, or dissipation takes place in the secondary paravertebral ganglia. 930 British Journal of Medicine & Medical Research, 3(4): 928-952, 2013 Fig. 2. Trunkal or fascicular origin of the 10 motor and the 2 sensory nerves of the brachial plexus 3. CLINICAL PRESENTATION Clinically, brachial plexus lesions present with weakness, muscle wasting, sensory disturbances, reduced tendon reflexes, pain, or vegetative impairment [6]. The most frequent clinical manifestation of a brachial plexus lesion is muscle weakness and wasting. Weakness may persist during only a few hours or days in case of neurapraxia or persist for longer or even life-long in case of axonal lesions due to tearing or disruption. According to the location of the lesion within the plexus, various types of brachial plexus palsies are differentiated. These include supraclavicular lesions, which affect the trunks (upper, middle and lower trunk (primary strand) lesions), clavicular lesions (level of divisions), and infraclavicular lesions, which affect the fascicles (secondary strand lesions). However, variable combinations of these lesion types may occur. 3.1 Anatomical Correlation 3.1.1 Upper trunk lesion If the upper trunk (C5-6) is exclusively affected, weakness is found for shoulder abduction (deltoid muscle, innervated by the axillary nerve), external shoulder rotation (supra- and infraspinatus muscles, innervated by the suprascapular nerve as well as the subscapular muscle, innervated by the subscapular nerve), supination (supinator muscle, innervated by the radial nerve), lowering of elevated arms (latissimus dorsi, innervated by the thoracodorsal nerve), and elbow flexion (biceps muscle, innervated