Severity of foraminal lumbar stenosis and the relation to clinical symptoms and response to periradicular infiltration—introduction of the “melting sign”

Nerve root compression causing symptomatic radiculopathy can occur within the intervertebral foramen. Sagittal magnetic resonance imaging (MRI) sequences are reliable in detection of nerve root contact to intraforaminal disc material, but a clinically relevant classification of degree of contact is lacking. This study aimed to investigate a potential relation of amount of contact between intraforaminal disc material and nerve root to clinical findings and response after periradicular corticosteroid infiltration. A post hoc analysis of a prospective cohort was carried out. Patients who underwent computed tomography (CT)-guided periradicular corticosteroid infiltration (L1–L5) at our institution (January 2014 to May 2016) were included. The medical records and radiographic imaging were reviewed. T2-weighted MRI of the lumbar spine of patients with single-level symptomatic radiculopathy with (responders, n=28) or without (non-responders, n=14) pain relief after periradicular infiltration with corticosteroids were measured and compared by two independent readers to determine the amount of intraforaminal nerve root contact with the intervertebral disc (“melting” of the T2-hypointense signal). Pain relief was defined with a pain level decrease of >50% on a visual analogue scale and lack of pain relief with a pain level decrease of