BackgroundIntrathecal baclofen therapy can substantially improve symptoms in most patients with severe spasticity due to traumatic spinal cord injury, multiple sclerosis, or cerebral paresis. To the best of our knowledge, decompression surgeries at the intrathecal catheter insertion site in patients with a preexisting intrathecal pump for drug delivery have not been reported.Case presentationWe report the case of a 61-year-old Japanese man with lumbar spinal stenosis who underwent intrathecal baclofen therapy. We performed decompression for lumbar spinal stenosis at the intrathecal catheter insertion site during intrathecal baclofen therapy. The yellow ligament was removed by partial resection of the lamina under a microscope to avoid damage to the intrathecal catheter. The dura mater was distended. No obvious cerebrospinal fluid leakage was observed. Postoperatively, lumbar spinal stenosis symptoms improved, and spasticity remained well controlled with intrathecal baclofen therapy.ConclusionsThis is the first reported case of lumbar spinal stenosis decompression at an intrathecal catheter insertion site during intrathecal baclofen therapy. Preoperative preparation is necessary, as the intrathecal catheter may be replaced during surgery. We performed surgery without removing or replacing the intrathecal catheter, taking care not to damage the spinal cord by migrating the intrathecal catheter.