Ultrasound of cervical nerve root enlargement in polyneuropathy is not confounded by neuroforaminal stenoses

•Common age-related cervical neuroforaminal stenoses on MRI/CT are not per se associated with nerve root enlargement on ultrasound.•Degeneration of the cervical spine is unlikely to confound the ultrasound assessment of cervical nerve roots in polyneuropathy.•Older age is associated with neuroforaminal stenosis, but is not a significant covariate of nerve root diameter in this cohort. Ultrasound can detect enlargement of cervical nerve roots, which has been described in polyneuropathies (PNP), mainly of demyelinating pathology. This study investigates whether neuroforaminal stenosis, as a common but often asymptomatic degenerative change, is associated with nerve root enlargement on ultrasound and whether neuroforaminal stenosis thus confounds cervical nerve root ultrasound findings in the diagnostic assessment of PNP. We retrospectively studied 182 patients (62 demyelinating, 71 axonal PNP; 49 without evidence of PNP) who had undergone ultrasound of the cervical nerve roots C5 and C6 and magnetic resonance or computed tomography of the cervical spine that was reviewed with respect to neuroforaminal stenoses. 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 stenoses. Neuroforaminal stenosis per se does not entail relevant cervical nerve root enlargement detectable by nerve ultrasound. Ultrasound assessment of cervical nerve root size in the diagnostic evaluation of PNP is unlikely to be confounded by common degenerative changes of the cervical spine.