Diagnostic accuracy of nerve ultrasonography for the detection of peripheral neuropathy in type 2 diabetes

Abstract

Background and purpose Nerve conduction studies (NCS) are the current objective measure for diagnosis of peripheral neuropathy in type 2 diabetes but do not assess nerve structure. This study investigated the utility of peripheral nerve ultrasound as a marker of the presence and severity of peripheral neuropathy in type 2 diabetes. Methods A total of 156 patients were recruited, and nerve ultrasound was undertaken on distal tibial and distal median nerves. Neuropathy severity was graded using the modified Toronto Clinical Neuropathy Scale (mTCNS) and Total Neuropathy Score (TNS). Studies were undertaken by a single ultrasonographer blinded to nerve conduction results. Results A stepwise increase in tibial nerve cross‐sectional area (CSA) was noted with increasing TNS grade (p < 0.001) and each mTCNS quartile (p < 0.001). Regression analysis demonstrated a correlation between tibial nerve CSA and neuropathy severity (p < 0.001). Using receiver operator curve analysis, tibial nerve CSA of >12.88 mm yielded a sensitivity of 70.5% and specificity of 85.7% for neuropathy detection. Binary logistic regression revealed that tibial nerve CSA was a predictor of abnormal sural sensory nerve action potential amplitude (odds ratio = 1.239, 95% confidence interval [CI] = 1.142–1.345) and abnormal neuropathy score (odds ratio = 1.537, 95% confidence interval [CI] = 1.286–1.838). Conclusions Tibial nerve ultrasound has good specificity and sensitivity for neuropathy diagnosis in type 2 diabetes. The study demonstrates that tibial nerve CSA correlates with neuropathy severity. Future serial studies using both ultrasound and NCS may be useful in determining whether changes in ultrasound occur prior to development of nerve conduction abnormalities and neuropathic symptoms.

Hindsight for ultrasound imaging/measurement of the tibial nerve

“…We congratulate the authors for their great effort in evaluating the specificity and sensitivity of tibial nerve ultrasound imaging for the diagnosis of neuropathy in type 2 diabetes. Indeed, the authors have demonstrated the correlation between the tibial nerve cross-sectional area (CSA) and the severity of neuropathy [1]. Herein, we would like to comment on their Figure 2 which represents transverse ultrasound imaging to measure the tibial nerve CSA.…”

“…We have read with great interest the article recently published in the European Journal of Neurology by Dhanapalaratnam et al [1].…”

“…First, the authors have assessed the tibial nerve 5 cm proximal to the medial malleolus in each and every patient [1]. Herewith, the muscle belly of flexor hallucis longus is clearly visible in Figure 2(c) but not in Figure 2(d).…”

Hindsight for ultrasound imaging/measurement of the tibial nerve (answer)

“…We are grateful to Ricci et al for their interest in our work [ 1 ]. They make valid points on limitations of peripheral nerve ultrasonography and measurement of cross‐sectional area (CSA) in individual patients, particularly where there may be anatomical variations.…”

“…The sonographer must be aware of local anatomy and avoid taking measurement at the bifurcation site to avoid false representation of CSA. As described in Methods, we took measurements at 5 cm proximal to the medial malleolus [ 1 ]. Three measurements were taken at this site from each observer, and the mean value was used for data analysis.…”