UCSF UC San Francisco Previously Published Works Title Central Adaptation following Brachial Plexus Injury. Permalink https://escholarship.org/uc/item/2ds5z53m Authors Simon, Neil G Franz, Colin K Gupta, Nalin et al. Publication Date 2016 DOI 10.1016/j.wneu.2015.09.027 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Literature Reviews Central Adaptation following Brachial Plexus Injury Neil G. Simon1, Colin K. Franz2,3, Nalin Gupta4, Tord Alden5,6, Michel Kliot6 Key words Brachial plexus trauma (BPT) often affects young patients and may result in - Apraxia lasting functional deficits. Standard care following BPT involves monitoring for - Brachial plexus injury - Central adaptation clinical and electrophysiological evidence of muscle reinnervation, with sur- - Nerve trauma gical treatment decisions based on the presence or absence of spontaneous - Neuroplasticity recovery. Data are emerging to suggest that central and peripheral adaptation may play a role in recovery following BPT. The present review highlights Abbreviations and Acronyms BPT: Brachial plexus trauma adaptive and maladaptive mechanisms of central and peripheral nervous system CIMT: Constraint-induced movement therapy changes following BPT that may contribute to functional outcomes. Rehabili- CNS: Central nervous system tation and other treatment strategies that harness or modulate these intrinsic EMG: Electromyography adaptive mechanisms may improve functional outcomes following BPT. ES: Electrical stimulation H-reflex: Hoffman reflex MRI: Magnetic resonance imaging OBPP: Obstetric brachial plexus palsy PNI: Peripheral nerve injury RECOVERY FROM BPT functional recovery, with no residual def- fi Recovery of nerve tracts following BPT icits identi ed on serial clinician or phys- 1St. Vincent’s Clinical School, University of New South 1 2 relies on a complex cascade of peripheral iotherapist review. However up to 15% of Wales, Australia; Department of Physical Medicine and fi Rehabilitation, Northwestern University, and 3Sensory Motor nerve regenerative processes, culminating patients have persisting signi cant fi 1 Performance Program, Rehabilitation Institute of Chicago, in target muscle reinnervation.3 In de cits, and the proportion of patients 4 Illinois, USA; Departments of Neurological Surgery and instances of severe injury to the brachial with spontaneous functional recovery Pediatrics, University of California, San Francisco, California, may be overestimated.11 5 plexus or nerve roots, successful nerve USA; Division of Neurosurgery, Ann and Robert H. Lurie In patients with residual deficits, a Children’s Hospital of Chicago, and 6Department of regeneration might not be possible Neurological Surgery, Northwestern University Feinberg without surgical brachial plexus pattern of recovery may be seen, with most fi School of Medicine, Chicago, Illinois, USA. reconstruction.4,5 de cits seen in C5- to C7-innervated To whom correspondence should be addressed: Even patients in whom regenerating muscles. Forearm pronation typically 12 Michel Kliot, M.D. nerve fibers reach the target muscles, improves before forearm supination. The [E-mail: [email protected]] there are substantial barriers to a good degree of recovery of shoulder external Citation: World Neurosurg. (2016) 85:325-332. fl functional outcome. The process of axonal rotation, elbow exion, and forearm http://dx.doi.org/10.1016/j.wneu.2015.09.027 regeneration is inefficient, and sprouting supination at 3 months predicts which Journal homepage: www.WORLDNEUROSURGERY.org fibers may not reconnect with the appro- children will retain persistent functional Available online: www.sciencedirect.com fi 12 priate fascicle beyond the injured de cits. In children with residual ª 1878-8750/$ - see front matter 2016 Elsevier Inc. segment.6,7 Fibers that reach the target impairment, functional tasks can typically All rights reserved. muscle do so in substantially reduced be performed using the injured limb, but numbers, resulting in incomplete rein- with asymmetric movement relative to fl nervation and a reduced number of func- the uninvolved limb. Elbow exion and INTRODUCTION tional motor units.8 Although the shoulder abduction are the functional Brachial plexus trauma (BPT) occurs in dynamics of motor unit recruitment can movements that prove most challenging two different age groups. Obstetric recover from nerve injury if the muscle is in patients after severe OBPP, but brachial plexus palsy (OBPP) is a recog- reinnervated by the same motor nerve,9 shoulder external rotation and forearm nized complication of childbirth, with an aberrant reinnervation can affect this supination are usually the most affected 1 12,13 incidence of 0.3% of deliveries. The next process.10 movements and recover last. These peak in the incidence of BPT is in described patterns of recovery and younger (usually male) adults, and it is Maladaptive Central Processes following residual functional impairment inform often caused by motor vehicle accidents BPT rehabilitation strategies, although therapy 2 or penetrating wounds. Beyond peripheral nerve regeneration, paradigms are largely empiric and are fl BPT can result in severe and lasting central processes are involved in deter- based on splinting of ail wrists and neurologic impairments, and because the mining successful or failed functional elbows to prevent dislocation and passive affected patients are young, it has a long- recovery following BPT. range-of-motion exercises to prevent term effect on work and societal roles. contractures. As such, optimizing recovery from Developmental Apraxia. The majority of In a small subgroup of patients with brachial plexus injury is critical. patients with OBPP make an excellent residual symptoms, electromyography WORLD NEUROSURGERY 85: 325-332, JANUARY 2016 www.WORLDNEUROSURGERY.org 325 LITERATURE REVIEWS NEIL G. SIMON ET AL. RECOVERY FROM BRACHIAL PLEXUS INJURY (EMG) studies of the affected limb Investigations of patients with develop- avulsion. EMG showed no voluntary units demonstrate active motor units in weak mental apraxia identified that reduction of in his left biceps and shoulder abductor muscles, suggesting at least partial rein- motor skills and muscle strength were muscles, but little active muscle denerva- nervation, but clinical function remains exaggerated when compared with neuro- tion. A postganglionic injury of the left poor.14 This unique issue has been termed physiological and physical muscle responses upper trunk was diagnosed. developmental apraxia and is considered to to peripheral nerve stimulation.15 This He was taken to surgery and after being be an example of maladaptive central finding was interpreted as being indicative anesthetized, electrodiagnostic testing motor programming early in infancy of impaired voluntary motor unit was performed. Transcutaneous stimula- following OBPP.15 The presence of EMG activation, suggesting defective motor tion of his left Erb’s region gave rise to activity in these clinically weak muscles programming development in early infancy. contraction of his left biceps, supra- has been apportioned to “luxury A separate study used transcranial spinatus, infraspinatus, and deltoid mus- innervation,” which refers to the magnetic stimulation to examine a cohort cles. Transcranial electrical stimulation phenomenon of additional muscle of patients with OBPP without evidence of (ES) of the right motor cortex also gave innervation from spinal segments beyond functional recovery.18 Motor evoked rise to motor evoked potential responses those typical for the individual muscle. potentials were recordable in all patients, in these muscles (Figure 1). As such, a typically C5- and C6- confirming the presence of an intact He underwent surgical exploration innervated muscle, such as biceps, may connection between the motor cortex of his infraclavicular brachial plexus. A have luxury innervation from C7, resulting and muscle, and suggesting that the supraclavicular brachial plexus exploration in the presence of active motor units on failure of functional recovery could be was not performed. Direct stimulation of EMG with minimal functional movement. due to abnormalities of central motor the left musculocutaneous nerve gave rise Luxury innervation begins between weeks control processes. to contraction in the biceps muscle. 16 and 25 of gestation and is usually lost Similarly, direct stimulation of the axillary after the age of 3 months.16,17 Limb Illustrative Case 1: Developmental nerve gave rise to a contraction in deltoid. immobilization in the period of sensory Apraxia Because of a lack of functional recovery in and motor brain organization, such as A 17-month-old baby boy suffered a severe elbow flexion, a side-to-side median to following OBPP, can result in incomplete left brachial plexus injury at birth resulting musculocutaneous nerve repair was per- realization of this reserve function, and in a complete upper trunk palsy on clinical formed to provide a supplementary source harnessing this reserve capacity may examination. Magnetic resonance imaging of axons to biceps with minimal iatrogenic benefit recovery.18 (MRI) showed no evidence of nerve root neurological morbidity.19 Postoperatively he Figure 1. Developmental apraxia following obstetric brachial plexus palsy (Illustrative Case 1). Intraoperative electrophysiology (A, B) identified retained responses from biceps to brachial plexus and cortical stimulation in the absence of voluntary activity of the muscle. (C) Three