Science News: Ultrasound of Cervical Nerve Root Enlargement in Polyneuropathy is not Confounded by Neuroforaminal Stenosis

Submitted by: Eman Tawfik, MD
Edited by: Nakul Katyal, MD

Härtig K, Kronlage C, Wittlinger J, Hauser TK, Grimm A. Ultrasound of cervical nerve root enlargement in polyneuropathy is not confounded by neuroforaminal stenoses. Clin Neurophysiol. 2022;141:34-41.

Summary: In this study, the authors aimed to investigate whether neuroforaminal cervical stenosis is associated with cervical root enlargements detectable by ultrasound.

The authors retrospectively analyzed the clinical, electrophysiological, laboratory, and radiological data of patients with suspected polyneuropathy (PNP) who underwent C5, C6 root ultrasound and cervical MRI/or CT within 2 years before or after ultrasound examination. They classified the patients as having demyelinating or axonal polyneuropathy based on clinical, electrophysiological, and laboratory findings. The control group included patients with no evidence of large fiber polyneuropathy after exclusion of diseases that may cause cervical root enlargements like neurofibromatosis, and inflammatory nerve disorders.

Cervical root diameter was measured in the longitudinal view and neuroforaminal stenosis was rated: absent (Grade 0) or, if present, severe (Grade 3) vs. non-severe (Grade 1 and 2).

The analysis included 182 patients who met the inclusion criteria and were included in the analysis. Of the 182, 62 patients were found to have demyelinating PNP, 71 had axonal PNP and 49 had no evidence of polyneuropathies (PNP). Patients with demyelinating PNP had larger nerve roots than those with axonal/without PNP. No significant differences in cervical nerve root diameters were found between groups with vs. without neuroforaminal stenosis. The diagnostic performance of the discrimination of PNP subtypes based on ultrasound nerve root measurements did not differ significantly when including or excluding subjects with neuroforaminal stenosis.

In conclusion, cervical foraminal stenosis as a radiological finding per see without evidence of symptomatic radiculopathy is not associated with sonographic changes in cervical root size, and thus is not a possible source of confusion when examining patients with PNPs. Note that this finding mainly applies to asymptomatic cervical stenosis.

Comments: The utility of neuromuscular ultrasound in the diagnostic workup of PNPy is increasingly gaining interest. Nerve enlargement is the hallmark sonographic abnormality in most of the nerve disorders, but the pattern of the nerve enlargements varies in different disorders. In addition to enlargements of the peripheral nerves, enlargement of cervical roots has been documented in PNPs particularly the demyelinating types and has been included in suggested ultrasound scores for PNPs like ultrasound pattern sum score. However, it remains the question whether the cervical root enlargements are entirely related to PNPs, or it could be seen also in neuroforaminal stenosis-a common degenerative disc disorder- which if true may limit the utility of ultrasound in the assessment of demyelinating PNPs.

The research question is valid and needed in the neuromuscular ultrasound field. The findings are interesting and important to know. However, it should be noted that this finding primarily applies to asymptomatic cervical stenosis. As the authors noted, this contrasts with symptomatic cervical radiculopathy, which can lead to cervical root enlargements as shown in previous studies.

Articles of similar Interest: Kim E, Yoon JS, Kang HJ. Ultrasonographic cross-sectional area of spinal nerve roots in cervical radiculopathy: a pilot study. Am J Phys Med Rehabil. 2015;94(2):159-164.