Neuromuscular Ultrasonography May Have Potential in Assessing SLE

Ultrasound measurement of the cross-sectional area (CSA) of peripheral nerves can be a helpful and patient-friendly tool, and the combination of nerve conduction study (NCS) with neuromuscular ultrasonography (NMUS) can provide a detailed analysis of nerve changes in patients with systemic lupus erythematosus (SLE), according to a new study.

The report was published in Lupus Science & Medicine.

The authors explained that peripheral neuropathy (PN) is a common finding among patients with SLE and that NMUS has become a prevalent means of evaluating various neuropathies because it is more sensitive and less expensive than traditional MRI. The use of NMUS to assess parameters, like CSA, of peripheral nerves has been supported by research in other clinical areas, but the investigators said no such study has investigated the morphological features of PN among patients with SLE.

They constructed a cross-sectional study of 37 patients with SLE and 18 healthy controls. Multiple nerves in each patient were examined bilaterally, using NMUS to estimate the CSA.

Overall, the investigators evaluated 370 nerves in the 37 patients with SLE. NCS showed all but one patient with SLE had polyneuropathy, and most (80.6%) had mixed-type polyneuropathy. The remaining 19.4% had sensory polyneuropathy.

The study showed significant mean CSA enlargement in the following areas:

• Ulnar nerve at the Guyon’s canal and mid-humerus (both P = .001)
• Tibial nerve at the distal leg and proximal to the tarsal tunnel (P = .003 and P = .001, respectively)
• Peroneal nerve at the popliteal fossa (P = .042)

NMUS images were evaluated by 3 expert rheumatologists who were blinded to clinical and electrophysiological results in order to prevent bias and ensure agreement.

The authors added that the mean CSA measurement showed high specificity compared with NCS. “Our data show that the sonographically measured CSA of the peripheral nerves might be a helpful supplementary test to NCS in diagnosing PN in patients with SLE,” they wrote.

In addition, previous research has focused on whether peripheral nerve syndrome is caused by SLE. However, the new study suggests PN plays a larger role than previously thought. The authors noted only 37.8% of patients in their study received a PN diagnosis during clinical examination, but 97.3% were found to have PN when the diagnosis was done by NCS.

“This discrepancy may be attributed to well-known high sensitivity, reliability, and detective power of [electrodiagnosis] versus clinical diagnosis,” they wrote.

The investigators said NMUS advances suggest it can be a complement or alternative to electrodiagnosis, and CSA is considered a “suitable and reliable” quantitative parameter for evaluating nerve sizes. Still, they recommended further studies to look at CSA values of different nerves is a larger population in order to develop nation-based reference values

“Another recommendation is to study other nerve parameters, such as echogenicity, mobility, and vascularity, in addition to CSA, while examining the peripheral nerves using NMUS,” they concluded.

Reference

Mahran SA, Galluccio F, Khedr TM, et al. Peripheral neuropathy in systemic lupus erythematosus: what can neuromuscular ultrasonography (NMUS) tell us? A cross-sectional study. Lupus Sci Med. 2021;8(1):e000521. doi:10.1136/lupus-2021-000521