Ultrasonographic Findings in Chronic Inflammatory Demyelinating Polyneuropathy

A 35-yr-old man with a previous diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) was evaluated at the authors’ outpatient clinic. His diagnosis had been based on characteristic symptoms, including progressive symmetric motor weakness and sensory dysfunction in the proximal and distal limbs, electrophysiologic studies, and cerebrospinal fluid findings. His motor weakness had been dramatically improved by corticosteroid treatment; in addition, intravenous immunoglobulin was regularly used for maintenance. He was in remission when he had a recurrence of progressive weakness and dysesthesias in all four limbs approximately 6 mos before presentation. A nerve conduction study revealed prolonged distal latency and decreased amplitude of compound muscle action potentials in both median motor nerves. Neither compound muscle action potentials nor sensory nerve action potentials could be evoked in the ulnar, tibial, peroneal, and sural nerves in the limbs bilaterally. Ultrasound examination was performed using an L12-5 linear array probe (Fig. 1A, B). The cross-sectional area (CSA) of each nerve was measured bilaterally at various points in the upper and lower limbs and found to be significantly increased in all examined nerves, compared with reference values.1 In addition, overall echogenicity appeared decreased. The CSA of the right ulnar nerve at the outlet of the cubital tunnel was 0.226 cm2, and the CSA of the right median nerve at the wrist, forearm, and elbow were 0.159 cm2, 0.165 cm2, and 0.252 cm2, respectively. The CSA of the peroneal and tibial nerves at the popliteal fossa were 0.337 cm2 and 0.494 cm2, respectively. The gastrocnemius muscle showed increased muscle echogenicity with atrophic change.FIGURE 1: Ultrasound imaging of various nerves and muscle in a patient with chronic inflammatory demyelinating polyneuropathy. Transverse sectional ultrasound image of various nerves shows an enlarged and hypoechoic structure surrounded by hyperechoic rims and thinning muscular atrophic change compared with healthy subjects. (A) Median nerve (M) at forearm level. (B) Peroneal nerve (P) and tibial nerve (T) at popliteal fossa level.The diagnosis of CIDP is made through clinical features and laboratory studies.2 The cardinal feature of CIDP is demyelination revealed by functional and structural examination. Electrophysiologic studies provide functional assessment of demyelination and are an essential diagnostic test. To evaluate structural changes in CIDP, nerve biopsy has been performed in the past. However, magnetic resonance imaging studies in CIDP have been performed for the last two decades, and magnetic resonance imaging enhancement or hypertrophy of the plexus or roots have been recognized as supportive criteria in recent guidelines.3 High-resolution ultrasonography has some advantages over magnetic resonance imaging, in that it can evaluate both proximal and distal regions in all four limbs at the same time. Previous ultrasonographic study in patients with CIDP suggested that enlarged CSAs of the median and ulnar nerves are more common than in axonal neuropathies, and these differences may reflect pathologic findings related to repeated demyelination and remyelination.4 In conclusion, we suggest that the diffuse nerve enlargement seen on ultrasonography may represent structural change in CIDP and could be a helpful feature in the diagnosis of CIDP.