Diagnostic value of lower extremity ultrasonographic nerve enlargement for differentiating demyelinating Charcot-Marie-Tooth disease from chronic inflammatory demyelinating polyneuropathy.

BACKGROUND AND PURPOSE: We previously reported that nerve enlargement assessment by nerve ultrasonography of the intermediate upper limb is applicable for distinguishing demyelinating Charcot-Marie-Tooth disease (CMT) from chronic inflammatory demyelinating polyneuropathy (CIDP). However, differences in the severity and distribution patterns of lower extremity nerve enlargement have not been established for either disease. Therefore, we examined the utility of lower extremity nerve ultrasonography for differentiating between CMT and CIDP. METHODS: Twelve patients with demyelinating CMT and 17 patients with CIDP were evaluated. The median, ulnar, tibial, and fibular nerves were evaluated in three regions: the distal upper extremity, intermediate upper extremity, and lower extremity. Of the 14 selected screening sites, the number of sites that exhibited nerve enlargement (enlargement site number, ESN) in each region was determined. RESULTS: The screening ESNs in the intermediate region and lower extremities were greater in patients with demyelinating CMT than in patients with CIDP and greater than the ESN in the distal region (p = 0.010, p = 0.001, and p = 0.101, respectively). The ESNs in the intermediate region and lower extremities significantly differed among patients with typical CIDP, CIDP variants, and demyelinating CMT (p = 0.084 and p < 0.001). Among the 14 selected screening sites, the combined upper and lower extremity ESNs exhibited the highest AUC (0.92; p < 0.001). CONCLUSIONS: Combining the upper and lower extremities for ultrasonographic nerve measurement more accurately distinguishes CIDP from demyelinating CMT.

Nerve Ultrasonography for the Diagnosis and Evaluation of Neuralgic Amyotrophy.

Neuralgic amyotrophy (NA) is a peripheral nervous system disorder involving multifocal distribution. Although nerve ultrasonography has shown potential for detecting NA lesions, no established detection method exists for distal forearm NA. A 59-year-old man presented with weakness of the muscles innervated by the left posterior interosseous nerve (PIN), median nerve (MN), anterior interosseous nerve (AIN), and ulnar nerve (UN), following severe left shoulder pain. This case suggests that nerve ultrasonography can help accurately diagnose distal forearm NA.

Impact of anatomical variations on ultrasonographic reference values of lower extremity peripheral nerves.

INTRODUCTION/AIMS: Cross-sectional area (CSA) reference values using ultrasonography vary widely for lower extremity peripheral nerves. In addition, there is a lack of data on the muscular branches of the tibial nerve and the anatomical variations of the sural nerve. We aimed to evaluate the ultrasonographic reference values for lower extremity peripheral nerves considering different anatomical variations and physical factors. METHODS: The CSA of the lower extremity nerve was measured at 10 sites. In addition to establishing reference values, differences in the CSA owing to anatomical variations were verified. The relationship between CSA and physical factors, such as age, height, weight, body mass index, and ankle circumference, was also examined. RESULTS: A total of 100 healthy Japanese volunteers were recruited. The mean CSA of the sural nerve significantly differed depending on its formation pattern (1.4-1.8 mm2 ). The mean decreases in CSAs from the proximal to distal tibial and fibular nerves within the popliteal region significantly differed based on the fine branching pattern. The maximum value of the mean decreases in CSAs in the tibial and fibular nerves reached 7.2 and 2.5 mm2 , respectively. With respect to physical factors, age and ankle circumferences were associated with CSA at several measurement sites. DISCUSSION: Fine branching from the tibial and fibular nerves and sural nerve formation may affect CSA measurements. The establishment of accurate CSA reference values requires consideration of anatomical variations in the peripheral nerves of the lower extremity.