Learn · Module
Where the lead actually goes
Most explanations of spinal cord stimulation skip the anatomy, which is a mistake — almost every question patients ask has an anatomical answer. Why does the stimulation change when I stand up? Why can't it cover my foot? Why is the DRG different? Select any marker on the diagram to find out.
What You'll Learn
Approx. 8 min read- Where the epidural space is and why the lead goes there
- What the dorsal columns are and why they are the target
- Why cerebrospinal fluid causes positional variation
- How the dorsal root ganglion differs from the spinal cord
- Why lead position determines coverage
- What the lead does not touch
Interactive Diagram
A spinal segment, viewed from above
An original illustration of an axial cross-section — as if you were looking down through a slice of the spine. The front of the body is at the top, the back at the bottom. Select any marker to read what that structure does and why it matters for stimulation.
Structure
The stimulator lead
The electrode array delivering therapy from the posterior epidural space.
What it is
The lead is a thin, flexible insulated wire carrying a row of electrode contacts — 8, 16 or 32 depending on the system. Percutaneous leads are cylindrical and placed through a needle; paddle leads are flat, insulated on one side, and require a small laminotomy to place.
Why it matters in neuromodulation
Where this lead sits determines everything about coverage. It is positioned under live fluoroscopy during the procedure, and its position is confirmed in multiple views. Lead migration — the lead shifting from its programmed position — is the most common complication of the therapy, and it is why activity restrictions matter during healing.
The Key Relationship
Lead, fluid, cord — in that order
If you remember one thing from this module, make it the ordering. The lead sits in the posterior epidural space. Between the lead and the spinal cord there is a layer of cerebrospinal fluid. The dorsal columns — the fibres being targeted — sit on the posterior surface of the cord, closest to the lead.
That fluid layer is not a fixed thickness. It changes as you breathe, cough, bend and change position, because the cord moves within the canal. The same electrical output therefore reaches the cord differently depending on what you are doing.
Nearly every technical development in this field over the past decade traces back to that single fact. Paresthesia-free waveforms reduce how noticeable the variation is. Closed-loop systems measure the resulting neural activation and correct for it in real time. DRG stimulation sidesteps the problem entirely by targeting a structure with very little fluid around it.
A diagram is not your anatomy
This schematic is simplified for teaching. Real anatomy varies between individuals and between spinal levels, and scoliosis, prior surgery, epidural scarring and hardware all change the picture. Your own imaging is what guides your procedure.
Questions about your own anatomy and imaging?
Your clinician can review your actual MRI alongside your symptoms. This diagram is a starting point for that conversation, not an individual assessment.