Magnetic resonance neurography findings in herpetic brachial plexopathy

Abstract

Brachial plexus neuritis was originally diagnosed by clinical signs and symptoms in addition to electrophysiological studies [1–5]. Therefore, initially, brachial plexopathy was misdiagnosed as a shoulder disorder, cervical radiculopathy, or myelopathy [4]. Herpes zoster brachioplexopathy is a rare complication characterized by motor weakness of the arm, which may occur in limbs affected by herpes zoster. Varicella zoster virus can induce inflammatory brachial plexopathy [1–4, 6]. It is still under-recognized by clinicians and misdiagnosis or delay in treatment can occur as a consequence. Magnetic resonance (MR) imaging studies have been attempted for diagnosis of brachial plexus disorders [6–9]. However, there are very few reports about MR neurography for zoster-induced brachial neuritis [6]. We present a 68-yearold male patient with monoparesis resulting from brachial plexopathy caused by varicella zoster virus infection and report the findings of MR neurography in this patient. A 68-year-old man noted a skin rash, vesicles, and pain in his left arm. At that time, he was not treated. Four days later, he developed weakness in his left arm and visited the emergency department at our hospital for this complaint. Upon admission, the patient had multiple erythematous crusted plaques on the left arm (Fig. 1). Neurologic examination revealed weakness of shoulder abduction (grade 2/5) and elbow flexion (grade 2/5), and the left biceps reflex was diminished. He had dysesthesia and hyperalgesia over the left C6–7 dermatomes. The level of IgG antibodies against varicella zoster virus was elevated. However, the IgM antibody level against varicella zoster was negative. We performed MR neurography of the brachial plexus with a 1.5-T MR imaging system (Gyroscan Intera, Philips Medical Systems, Netherlands) 10 days after admission. Among the MR neurography images, the coronal short tau inversion recovery (STIR, TR/TE: 3558.39/60.00, time inversion: 160 ms) image depicted edema and thickening of the superior trunk of the left brachial plexus compared to the unaffected right side (Fig. 2). MR imaging also showed denervation edema of the left supraspinatus muscle (Fig. 3). Needle electromyography showed fibrillations and positive sharp waves in the left deltoid and biceps muscles and only positive sharp waves in the left supraspinatus muscle. The patient was treated with intravenous acyclovir and physical therapy for his left arm. After discharge, he was followed in the outpatient department for 6 months. His left-arm weakness improved to grade 3. Herpes zoster brachial plexus neuritis-associated motor weakness may be due to a demyelinating process related to inflammation [1–3, 5, 6]. Inflammatory changes in the brachial plexus result in swelling and thickening of divisions or cords of the brachial plexus. MRI can demonstrate inflammatory changes in neural tissue and MR neurography can detect inflammatory changes in the brachial plexus and denervation edema of affected muscle [6–9]. Especially STIR images from MR neurography have been used for evaluation of pathological lesions of the brachial plexus such as neuralgic amyotrophy [7, 8]. In our case, we evaluated the STIR images of the brachial plexus and they D. H. Heo Y. J. Cho (&) Department of Neurosurgery, Peripheral Nerve Disorder Clinic, Chuncheon Sacred Heart Hospital, Hallym University Medical Center, 153 Kyo-dong, Chuncheon-shi, Kangwon-do, Korea e-mail: nssur771@hallym.or.kr