The TOMAX-procedure

Abstract

Most patients with a low spinal lesion (LSL) have intact erectile function but no penile sensation, which can lead to frustration. To tackle this problem, we designed TOMAX, TOMAXimize sensation, sexuality and quality of life, a surgical procedure in which a functional "groin” nerve is connected to the non-functional “penile” nerve on one side to bypass the LSL. Our goal was to increase LSL patients’ sexual health by restoring penile sensation: we show that TOMAX can achieve dramatic improvements for such patients.

We operated on 30 patients with spina bifida or a spinal cord injury, who had no penis- but normal groin sensation. This resulted in unilateral glans-penis sensation, experienced as ‘groin’ or as ‘glans’, in 80% of them. Patients reported more satisfaction with their erections, masturbated more frequently, and had more pleasurable sensations and sometimes orgasms. Five patients masturbated for the first time ever, while three patients experienced their first orgasm. This led to more frequent and more satisfying sexual activities, and a more meaningful sexual relationship. The new sensation significantly enhanced their quality of life and sexual satisfaction.

Because the TOMAX procedure restores genital sensation unilaterally, we investigated if a bilateral procedure could be performed safely with a chance of full glans sensation. This would entail cutting both penile-nerves, risking patients’ ability to have erections. We determined whether penile nerve function (intact Bulbocavernosus-reflex (BCR) and ability to have reflex erections (RE)) was still present in 30 LSL patients: we found that seven patients had RE ability, of which four had an intact BCR, and of nine patients with an intact BCR, four had RE. This shows that LSL patients can have remaining penile-nerve function, so that cutting both penile-nerves in a bilateral TOMAX procedure might be risky. We therefore developed a new protocol using both RE and BCR parameters to select patients; we operated on three bilaterally, resulting in full glans sensation for two of them.

Large numbers of LSL patients could benefit from the TOMAX procedure. Our technique has been described and a video made to extend this information to peripheral nerve surgeons worldwide. Strategies for providing realistic patient information are given. We have also analysed our experience with an expanded series of 43 nerve transfers. We found that no matter what the origin, all patients with no penile- but good groin sensation are eligible for the procedure, as long as their groin nerve has not been damaged by earlier surgery or is absent due to anatomical variations.

The brain-plasticity that remaps groin sensation to penis sensation takes at least one year and these sensations are often experienced as pleasant and/or erotic. To study this remapping we scanned three post-TOMAX patients using functional MRI, while penis, groin and finger were lightly stimulated. Our observations suggest that changing the origin of the groin nerve receptive field from groin to penis recruits a higher-order somatosensory pMCC-OIC network (middle cingulate cortex - right parietal operculum and insula), which presumably encodes enhanced meaning/salience, or a remapped body scheme, or both.