Introduction>
Herpes zoster (HZ) is a reactivation of the latent varicella-zoster virus. The most common complication of HZ is post-herpetic neuralgia, but segmental zoster paresis is a rare complication of HZ infection. Zoster-associated limb paresis is characterized by focal, asymmetric motor weakness in the myotome that corresponds to the dermatome of the rash. Zoster-paresis (ZP) could be induced by the injury of the root, or plexus, but the pathophysiology is still unclear. There are few reports of brachial plexopathy following onset of HZ skin rash. Therefore, we describe a case with zoster-associated brachial plexopathy demonstrated by MRI findings and electrodiagnostic studies (EDX).
Case>
A 52-year-old man visited the local orthopedic center two months ago because of sudden onset of left shoulder pain and was treated with injection treatment. A few days later, Symptom developed blister lesions on the skin along the left arm. He was diagnosed with HZ by visiting a dermatologist and was given antiviral medications. A month after that, he had an additional weakness in the left shoulder muscle and was referred to University Hospital for further evaluation and management. He was diagnosed with left C5 nerve lesion through C-spine MRI and EDX and was treated with nerve root block, but there was no symptom improvement after injection. Manual muscle test revealed a score of 1/5 on left shoulder flexion and abduction, and 4/5 on elbow flexion and physical exam revealed muscular atrophy of left deltoid, supraspinatus (SST), and infraspinatus (IST) area and limited Range of Motion (ROM) of left shoulder. C-spine MRI showed multilevel diffuse bulging disc and mild foraminal stenosis (Figure 1). Brachial plexus MRI showed shows slightly high signals at upper trunk of brachial plexus and severe swelling with a subtle enhancement of left SST, IST, and deltoid muscles (Figure 2). Nerve conduction study (NCS) and electromyography (EMG) were conducted a month after symptom onset (Table 1). Motor NCS demonstrated no-response of the left axillary nerve and low amplitude of compound motor unit action potential (CMAP) of the left musculocutaneous (MC) nerve and suprascapular (SS) nerve. EMG demonstrated abnormal spontaneous activities and reduced motor unit recruitments in the left deltoid, SST, IST, and biceps brachii muscles. EDX was suggestive of left brachial plexus injury (Mainly upper trunk lesion). Conservative treatments including therapeutic modalities (Deep heat, Electrical stimulation therapy, ROM exercise) and shoulder muscle strengthening exercises were administered for 2months. A follow-up EDX exhibited some improvements: increased recruitments in previous abnormal muscles and amplitude increments of CMAPs of the left axillary, MC, and SS nerve.
Conclusion>
We present a case of zoster-induced brachial plexopathy, which involved the upper trunk of motor segment and demonstrates that EDX, as well as MRI, can be helpful for the diagnosis of ZP.
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Figure 1. Cervical spine MRI shows that degenerative spondylosis and diffuse bulging disc with dural sac indentation in C3-4, C4-5 C5-6 and C6-7 (A) Saggital T2-weighted view (B) Axial T2-weighted view at level of C5-6.
Figure 2. MRI findings of post-herpetic brachial plexopathy. Brachial-plexus MRI scan was taken 7-8weeks after the onset of motor weakness (A) Coronal T2-weighted image shows slightly high signals (arrow) at upper trunk of brachial plexus (B) Saggital T2-weighted image demonstrates severe swelling with subtle enhancement (arrow) of left supraspinatus, infraspinatus, clavicular part of deltoid muscles.
Table 1. Results of Nerve Conduction Study (NCS) and Needle Electromyography (EMG)
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