Purpose: Stellate ganglion block (SGB) is a procedure that uses ultrasound to guide a needle near a group of nerves in the neck called the stellate ganglion. A local anesthetic is then injected to block pain signals. This procedure has recently shown promise as a treatment for cervical radicular pain - pain that travels from the neck down into the arm, usually caused by a pinched nerve in the spine.

While SGB appears to be effective for many patients, not all patients respond equally well. Currently, there is no way to predict before the procedure which patients are likely to benefit and which are not. Identifying such predictors would help doctors select the right patients for this treatment and avoid unnecessary procedures.

Study Question: This study aimed to determine whether specific clinical characteristics or imaging findings on MRI could predict whether a patient would have a successful pain response after receiving SGB for cervical radicular pain.

Methods: This was a retrospective study that reviewed the medical records of patients who received ultrasound-guided SGB at a single medical center between October 2018 and April 2023. Patients were included if they had one-sided arm pain caused by a pinched nerve confirmed on MRI and had not improved after at least one month of standard treatments such as medication and physical therapy.

Information collected from medical records included patient age, sex, body mass index, presence of diabetes or hypertension, pain severity (measured on a 0-to-10 scale), duration of symptoms, and neck disability scores. Imaging findings from cervical MRI were also evaluated, including the degree of nerve compression, the cause of the compression (soft disc herniation versus bony overgrowth), the condition of the spinal canal, disc degeneration, and the amount of fatty changes in the small muscles along the back of the neck (called the multifidus muscles).

Hypothesis: The study hypothesized that certain imaging-based factors - specifically, significant fatty degeneration of the cervical multifidus muscles and bony overgrowth as the main cause of nerve compression - would be associated with a poorer response to SGB at 3 months after the procedure.

Inclusion Criteria:

• Unilateral cervical radicular pain
• Evidence of cervical foraminal stenosis on magnetic resonance imaging (MRI) consistent with radicular pain
• Age ≥ 19 years
• Symptoms unresponsive to at least 1 month of conservative treatment, including medication and physical therapy

Exclusion Criteria:

• History of cervical spine surgery
• Bilateral symptoms or involvement of three or more segments
• Neck pain intensity greater than arm-pain intensity
• Other conditions, such as facet joint syndrome or myofascial pain syndrome, contributing to the symptoms
• Insufficient documentation in the electronic medical records

Patients aged 19 years or older with unilateral cervical radicular pain who underwent ultrasound-guided stellate ganglion block at the pain clinic of Asan Medical Center, Seoul, Korea, between October 2018 and April 2023. All patients had MRI-confirmed cervical foraminal stenosis consistent with their symptoms and had failed at least 1 month of conservative treatment including medication and physical therapy. Patients were excluded if they had a history of cervical spine surgery, bilateral or multi-segment involvement, neck pain exceeding arm pain, other contributing pain conditions, or insufficient medical records.