Abstract
The functional outcome after a brachial plexus birth injury (BPBI) is based on changes in the peripheral nerve and in the central nervous system. Most patients with a BPBI recover, but residual deficits in shoulder function are not uncommon. The aim of this study was to determine cerebral activation patterns in patients with BPBI and also residual symptoms from the shoulder. In seven patients (six females and one male, aged 17–23 years) with a BPBI and residual shoulder problems (Mallet score IV or lower), the cerebral response to active movement of the shoulder and elbow of the injured and healthy arm was monitored using functional magnetic resonance imaging at 3 T. Movements, i.e., shoulder rotation or elbow flexion and extension, of the injured side resulted in a more pronounced and more extended activation of the contralateral primary sensorimotor cortex compared to the activation seen after moving the healthy shoulder and elbow. In addition, moving the shoulder or elbow on the injured side resulted in increased activation in ipsilateral primary sensorimotor areas an also increased activation in associated sensorimotor areas, in both hemispheres, located further posterior in the parietal lobe, which are known to be important for integration of motor tasks and spatial aspects of motor control. Thus, in this preliminary study based on a small cohort, patients with BPBI and residual shoulder problems show reorganization in sensorimotor areas in both hemispheres of the brain. The increased activation in ipsilateral sensorimotor areas and in areas that deal with both integration of motor tasks and spatial aspects of motor control in both hemispheres indicates altered dynamics between the hemispheres, which may be a cerebral compensation for the injury.
Highlights
Brachial plexus birth injury [brachial plexus birth injury (BPBI); incidence 0.4–5.0 per 1,000 births [1, 2]] is caused by stretching or tearing of the brachial plexus, usually during vaginal delivery
Patients suffering from unilateral BPBI and residual symptoms from the shoulder show increased activation in the primary sensorimotor cortex bilaterally and in associated sensorimotor areas, in both hemispheres, located further posterior in the parietal lobe which are known to be important for integration of motor tasks and spatial aspects of motor control, when using the injured arm compared to when using the healthy arm
A peripheral nerve injury in the forearm or a brachial plexus injury is known to result in substantial reorganization in sensorimotor areas in both brain hemispheres—and in changes in functional connectivity between sensorimotor areas [11, 25]
Summary
Brachial plexus birth injury [BPBI; incidence 0.4–5.0 per 1,000 births [1, 2]] is caused by stretching or tearing of the brachial plexus, usually during vaginal delivery. Most children with BPBI recover spontaneously, but up to 30% may suffer from permanent disability [2, 4], and the number of patients with spontaneous recovery may have been overestimated [5]. The degree of recovery of external rotation of the shoulder, elbow flexion, and supination at 3 months can be used as a predictor of which infants will retain functional deficits [9]. External rotation of the shoulder and forearm supination are most affected and recover last, elbow flexion and shoulder abduction are the functional movements that often prove most challenging in patients with severe BPBI [9]. Depending of the type of residual problems, surgical muscle transfer and osteotomy can improve function in patients with permanent disability [10]. A number of patients have residual shoulder problems that restrict their daily life
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