After a first stop due to acupuncturists unavailability, the Covid-19 pandemic also impacted on the study time schedule for acupuncture administration and outcomes evaluation.

Pain is one of the most common problems in patients with spinal cord injury (SCI) and persistent pain (that can be of different origin: nociceptive, neuropathic or mixed) is often poorly responsive to pharmacological therapy. Attention has been paid to the use of non-pharmacological therapies and interventional techniques in treating pain in other clinical conditions, and acupuncture has been the treatment most used and appreciated for its effectiveness. However, only few studies are available on the use of acupuncture in SCI patients. The present randomized, comparative trial aims to clarify the efficacy of traditional acupuncture vs. aspecific needle skin stimulation in treating persistent pain in subjects with spinal cord injury, by overcoming the biases reported in previous studies.

About 67% of patients with spinal cord injury (SCI) experience painful symptoms in the course of life after injury and a third evaluates the pain as "severe", with a significant impact on quality of life, due to limitations in daily activities and autonomy. Persistent pain can be of different origin and may be nociceptive, neuropathic or mixed. However, it is often poorly responsive to pharmacological therapy. For some years, attention has been paid to the use of non-pharmacological therapies and interventional techniques in treating pain, and acupuncture has been the treatment most used and appreciated for its effectiveness. Only two studies on the use of acupuncture in SCI patients were included in the only Cochrane review available, dated 2014. Such studies, focusing on the painful shoulder syndrome and, therefore, on skeletal muscle pain, show a "non-superiority" of acupuncture compared to sham acupuncture treatment or Trager approach. However, the review does not come to any clear conclusions on the effectiveness of intervention because of the small number of cases and high risk of bias.

A more recent primary, randomized, controlled trial on SCI patients, although focusing on chronic pain and on a single acupuncture technique, uses a questionable study design (cross-over) to demonstrate treatment efficacy.

The present randomized, comparative trial aims to clarify the efficacy of traditional acupuncture vs. aspecific needle skin stimulation in treating persistent pain in subjects with spinal cord injury, by overcoming the biases reported in previous studies. Because of the intrinsic effects of sham acupuncture and, generally, of skin stimulation, a statistically significant change in the Numerical Rating Scale (NRS) measurements is expected even in the comparison group. To minimize this bias, which cannot be avoided, and to maintain the blindness of the patient as much as possible, the comparison group is treated by the insertion of needles in skin areas outside the metamer(s) affected by pain.

Primary objective:

- To evaluate the efficacy of traditional acupuncture vs. aspecific needle skin stimulation for persistent pain in subjects with spinal cord injury, at the end of treatment and at the 3 week follow-up.

Secondary objectives:

• Reduction of drug intake, at the end of treatment and at the subsequent follow-up;
• Reduction of anxiety/depression, at the end of treatment and at the subsequent follow-up;
• Improvement of quality of life, at the end of treatment and at the subsequent follow-up;
• Persistence of the effect of acupuncture 9 weeks after treatment.

Data concerning any adverse events, related to both experimental treatments of the trial, will also be collected.

Inclusion Criteria:

• Persistent pain: NRS score >2 in at least 5 assessments in 5 consecutive days, despite usual antalgic management;
• Spinal cord injury due to any etiology (both traumatic and non-traumatic);
• Spinal cord injury of any neurological level, complete or incomplete, classifiable as Asia Impairment Score (AIS) A, B, C or D;
• Stable medical conditions;
• At least 1 month away from the spinal cord injury event.

Exclusion Criteria:

• Sporadic pain;
• Mechanical ventilation;
• Pregnancy;
• Disorders of consciousness;
• Incapacity to give informed consent in person.

The statistician in charge for data analysis will be blind with respect to the identity of the assignment Groups (that will be coded so as not to be recognized) and will not be involved in filling data in the database to be analyzed.