Paraspinal muscle involvement in herpes zoster-induced abdominal wall pseudohernia revealed by electrophysiological and radiological studies.

Segmental zoster paresis is an uncommon complication of herpes zoster, and abdominal wall pseudohernia is rare. Previous reports have emphasized the involvement of anterior rami of spinal nerves, while the involvement of posterior rami has been less frequently reported. We aimed to elucidate the involvement of posterior rami of spinal nerves in abdominal wall pseudohernia. Four patients with a diagnosis of abdominal wall pseudohernia underwent needle electromyography (nEMG) and magnetic resonance imaging (MRI). In three patients, nEMG of affected paraspinal muscles showed denervation potentials, and MRI showed hyperintensity of these muscles on short T1 inversion recovery imaging. These results suggested involvement of paraspinal muscles, and indicated that posterior rami of spinal nerves are also often affected in abdominal wall pseudohernia. MRI as well as nEMG could be useful for evaluating paraspinal muscle involvement and for the diagnosis.