Efficacy
Seven out of 16 evaluable patients (44%) showed improvement of at least one AIS grade at 6 months postimplantation. Among these, two patients remained at AIS C through 24 months, while three improved to AIS C by 12 or 24 months. Additionally, four patients demonstrated improvement in motor score, with one patient showing consistent improvement across multiple assessments.
Changes in NLI and Sensory Scores
At 6 months postimplantation, 25% of patients showed improvement in motor score. Sensory scores also improved, with 63% of patients showing improvement in sensory pin prick scores and 63% in sensory light touch scores at the same time point.
Cyst Formation and Bowel/Bladder Function
Cysts were present in 8 of 12 patients with evaluable images at 24 months. Despite this, none of the events required surgical intervention. A post hoc analysis revealed that 57% of responders reported normal or indirect awareness of the need to defecate and empty the bladder at 1 month, increasing to 100% at 12 months.
Key Results and Interpretation
The study's 6-month AIS conversion rate exceeded historical benchmarks for patients with complete thoracic SCI. Three of seven responders had further improvement in neurological function to motor incomplete injury by 12 or 24 months postimplantation. The study also noted that 31% of INSPIRE patients had conversion to motor incomplete injury, which is higher than natural history rates.
Potential Benefits and Safety
The NSS may reduce cyst progression after SCI, as suggested by a rat contusion model. The study also highlighted the importance of bowel and bladder function for quality of life in SCI patients, with responders showing better awareness of these needs. Adverse events were consistent with routine care for SCI patients, with no serious or unanticipated adverse device effects related to the NSS or its implantation reported during the 24-month follow-up period.
