Possover’s Procedure – the LION Procedure for People With Spinal Cord Injury

1. What is the LION procedure?

The LION procedure (Laparoscopic Implantation Of Neuroprosthesis) is a minimally invasive operation that places stimulation electrodes directly on the pelvic nerves – mainly the sciatic, femoral, pudendal and sacral nerves – using laparoscopy.

These nerves are the “final common pathway” from the spinal cord to the leg muscles and pelvic organs. By stimulating them continuously with low-frequency electrical impulses and combining this with intensive rehabilitation, the procedure aims to:

• restore some voluntary control of leg movements and enable assisted standing and walking,

• improve bladder, bowel and sexual functions,

• and positively influence complications such as osteoporosis and pressure ulcers.

The electrodes are connected to an implanted pacemaker (neurostimulator). Patients control different stimulation programs with a handheld remote.

2. Historical background

• 2004 – First description - Possover M. Laparoscopic exposure and electrostimulation of the somatic and autonomous pelvic nerves: a new method for implantation of neuroprothesis in paralysed patients? Journal Gynecological Surgery – Endoscopy, Imaging, and Allied Techniques. 2004;1:87–90 . The first publications described laparoscopic exposure and electrostimulation of the somatic and autonomic pelvic nerves as a new way to implant neuroprostheses in paralyzed patients. This work showed that pelvic nerves can be safely visualized and stimulated laparoscopically, creating the anatomical and technical basis for the LANN (Laparoscopic Neuro-Navigation) and later the LION procedure. (Possover M, Rhiem K, Chiantera V. The “Laparoscopic Neuro-Navigation” (LANN): from a functional cartography of the pelvic autonomous nervous system to a new field of laparoscopic surgery. Minim Invasive Ther Allied Technol. 2004;13:362–7 - Possover M, Baekelandt J, Kaufmann A, Chianteras V (2007). Laparoscopic endopelvic sacral Implantation of a Brindley Controller for recovery of bladder functions in a paralyzed patient. Spinal Cord 45:334-337)

  
  

• 2009 – Sacral LION for pelvic organ functions. A first clinical series reported laparoscopic implantation of electrodes on sacral roots (S2–S4) in eight completely paraplegic patients after failure of a dorsal Finetech-Brindley device. Most patients recovered electrically induced urination and defecation, and some men recovered erections (Possover M. Laparoscopic implantation of neuroprosthesis on sacral nerve roots for recovery of pelvic visceral functions and locomotion in paraplegics. J Minim Invasive Gynecol. 2009;16:472–6.)

• 2010 – New strategies in paraplegics (Possover M, Schurch B, Henle KP. New strategies of neurostimulation for recovery of pelvic functions and locomotion in spinal cord injured patients (the LION procedure). Acta Neurochir Suppl. 2010;106:77–80). A further series in three complete paraplegics combined sacral, pudendal and sciatic stimulation. Continuous pelvic nerve stimulation controlled spasticity and reflex incontinence and enabled standing, cycling or short-distance locomotion with functional electrical stimulation (FES).

• 2014 – First report of neurological recovery. An observational case series of four chronic SCI patients showed, for the first time, progressive recovery of sensory function and supraspinal voluntary leg control after the LION procedure with continuous low-frequency stimulation plus FES-assisted training. Three patients became able to stand and walk a few meters without stimulation; one could walk about 900 m with electrically assisted gait (Possover M. Recovery of sensory and supraspinal control of leg movement in people with chronic paraplegia: a case series. Arch Phys Med Rehabil. 2014 Apr;95(4):610-4)

• Ten-year experience in 29 patients. A later prospective case series summarized a decade of experience in 29 chronic SCI patients of all types (paraplegic and tetraplegic, complete and incomplete lesions). (Possover M. The LION Procedure to the Pelvic Nerves for Recovery of Locomotion in 18 Spinal Cord Injured Peoples - A Case Series. Surg Technol Int. 2016 Oct 26;XXIX:19-25 - Possover M, Forman A. Recovery of supraspinal control of leg movement in a chronic complete flaccid paraplegic man after continuous low-frequency pelvic nerve stimulation and FES-assisted training. Nature - Spinal Cord Ser Cases. 2017 Apr 27;3:16034.  -  Possover M. 10-years experience with continuous low-frequency pelvic somatic nerves stimulation for recovery of voluntary walking in chronic spinal cord injured peoples: a prospective case series of 31 consecutive patients. In press Archives of Physical Medicine and rehabilitation 2021; 102(1):50-57)

• Independent confirmation. Two independant study, one a study from Aarhus/Dk and a second, a Brazilian prospective study of 30 patients with chronic SCI reproduced these results and showed improvements not only in gait but also in urinary, bowel and genital functions. (Love US, Elmgreen SB, Foramn A, Arsic I, Possover M, Jonsson AB, Kasch H. Surgical aspects of the Possover LION procedure: an Emerging procedure for recovery of visceral functions and locomotion in paraplegics. World J of Laparoscopic Surgery 2021; 14:75-80.

Up to today, in Zurich alone a little over 150 patients with chronic SCI have undergone the LION procedure. Initially the focus was mainly on complete paraplegics (AIS A); with growing experience, more tetraplegic patients with incomplete lesions (AIS B/C) are being operated, because in this group the functional recovery is often even more impressive.

3. How does the procedure work?

Using laparoscopy, the pelvic nerves are exposed by the LANN technique. One or more multi-polar electrodes are placed along:

• the sciatic and superior gluteal nerves (for hip and knee extension and gluteal muscles),

• the femoral nerve (for quadriceps and knee extension),

• the pudendal nerve (for pelvic floor, sphincters and genital sensitivity),

• and, in some cases, the sacral roots S2–S4.

The electrodes are connected to an implanted pacemaker programmed with several stimulation modes:

1. Continuous low-frequency stimulation (≈5–20 Hz). Runs 24/7 at low intensity to control spasticity, maintain muscle tone and – most importantly – provide continuous antidromic neuromodulation of the spinal networks.

2. Training programs. Higher-frequency trains for quadriceps and gluteal strengthening, used several times per day together with active attempts of the patient to extend knees and stand.

3. Standing and walking program. A stimulation pattern (initially high frequency, then decreasing) that supports standing and stepping while the patient uses parallel bars, walker or crutches.

Over time, this combination appears to trigger neuroplastic changes within the spinal cord and central nervous system, allowing residual pathways above and below the lesion to reconnect and regain some function. (Possover M. Does low-frequency pelvic nerves stimulation in people with spinal cord injury allow fort he formation of electrical pathways responsible for the recovery of  walking functions? Med Hypotheses 2021; 146:110376)

4. Clinical results in spinal cord injured patients

4.1 Locomotion and motor recovery

In the 10-year series of 29 chronic SCI patients (paraplegics and tetraplegics, complete and incomplete):

Posso:APMR

• All patients with incomplete SCI regained some voluntary control over muscles that were previously completely paralyzed.

• 26 of 28 evaluable patients (92.8 %) could stand up when the pacemaker was switched on.

• 20 patients (≈71 %) achieved electrically assisted voluntary knee extension.

• 19 patients (≈68 %) could walk more than 10 m at the bars;

  
  

  – 11 of them (≈40 %) could walk >10 m with crutches/walker without braces.

The early 4-patient case series already showed that some patients could eventually walk short distances even without electrical stimulation, indicating true recovery of supraspinal control.

Nerves-growth

The independent Brazilian study with 30 chronic SCI patients confirmed these findings: about 72 % of thoracic and 60 % of cervical patients established a walker-assisted gait at one year.

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Clinical experience over the last years suggests that tetraplegic patients with incomplete lesions (AIS B/C) often have even greater potential for functional gains than classic complete paraplegics, which is why they are now an important target group.

4.2 Bladder, bowel and sexual function

Several studies and case series have documented improvements in pelvic organ function:

• Bladder and bowel control. Sacral LION procedures on S2–S4 roots restored electrically induced micturition and defecation in most of eight paraplegic patients after failed dorsal Brindley implants. In the Brazilian cohort, nearly half of patients reported less urinary incontinence, bowel emptying time decreased, and fecal incontinence scores improved.

• Genital sensitivity and sexual function. Many patients report improved genital sensitivity after pudendal and sacral nerve stimulation; in the Brazilian series 71 % noticed improved genital sensitivity at 12 months.

• Autonomic effects via antidromic neuromodulation. A recent study in 10 SCI patients showed that continuous low-frequency pelvic nerve stimulation can acutely increase intestinal peristalsis and significantly slow resting heart rate, suggesting a modulatory effect on the autonomic nervous system (sympathetic–parasympathetic balance).

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5. Effects on osteoporosis, pressure ulcers and general health

Continuous stimulation and regular standing/walking have important systemic effects:

1. Bone density and osteoporosis.Long-term observations show restoration or stabilization of bone mineral density in stimulated patients – the opposite of what is typically seen after SCI, where sympathetic overactivity leads to progressive bone loss. (Possover M. Low Frequency Pelvic Nerves Stimulation: Cutaneous vasodulation and Restoration of Bone Density in chronic Speinal Cord INjured People. J Osteo Phys Act. 2022; 2: 1-6). By enabling weight-bearing standing and walking, the LION procedure further reduces osteoporosis and fracture risk.

2. Muscle mass and circulation. Thigh and gluteal circumference increase significantly over time, reflecting muscle hypertrophy. Skin perfusion of the legs improves, with visible vasodilation and warmer extremities.

3. Pressure ulcers (decubitus). A dedicated case series of five SCI patients with severe gluteal or heel pressure ulcers showed complete healing within three months under continuous low-frequency sciatic/femoral stimulation, combined with clonic contractions of the gluteal and calf muscles. Improved muscle bulk and blood flow relieved pressure and supported tissue repair. (Possover M. Continuous low-frequency pelvic nerve stimulation for therapy of intractable gluteal/heel pressure ulcers in persons with spinal cord injury. J Spinal Cord Med. 2025 Sep 15:1-5. doi: 10.1080/10790268.2024.2448045. Epub ahead of print. PMID: 40952749).These systemic effects are clinically very relevant: fewer pressure ulcers, fewer infections, better sitting tolerance, and a lower risk of life-threatening complications.

   
   

6. Who might benefit?

The procedure has been used mainly in:

• chronic spastic paraplegic or tetraplegic patients at least 12 months after trauma,

• with stable neurological status,

• who are medically fit for laparoscopy and intensive rehabilitation,

• and highly motivated to train.

In Zurich and collaborating centers worldwide, more than 150 patients have now been implanted. Experience suggests:

• Complete thoracic paraplegics (AIS A) can often achieve assisted standing and short-distance gait.

• Incomplete thoracic and cervical patients (AIS B/C) may reach even higher levels of functional recovery, sometimes with segments of walking that become partly or fully voluntary.

  
  

7. Outlook

Possover’s LION procedure has evolved from a bold idea in 2004 into a reproducible, minimally invasive therapy that:

• opens a new neuropelveological access to the lumbosacral nerves,

• combines neuroprosthetics, neuromodulation and classic rehabilitation,

• and addresses not only mobility, but also pelvic organ functions, bone health and skin integrity.

Ongoing work on continuous antidromic pelvic neuromodulation and possible interactions with spinal and vagal pathways may further enhance recovery after spinal cord injury and open the door to combined pelvic–vagal neuromodulation strategies in the future (Possover, M., & Abrao, H. M. (2025). Low-frequency antidromic pelvic neuromodulation as a potential enhancer of recovery after spinal cord injury: hypothetical promotion of spinal Renshaw cells and corticovagal plasticity. The Journal of Spinal Cord Medicine, 1–7. https://doi.org/10.1080/10790268.2024.2414146)