Polyneuropathy

Definition

Polyneuropathy affects peripheral nerves that do not belong to the central nervous system.

These lesions have multiple causes, such as diabetes, side effects of toxic substances in chemotherapy, drug and alcohol abuse, as well as AIDS. In about one third of the patients, the cause of polyneuropathy remains unclear. It is known, however, that a primary lesion of the nerve fibres may lead to secondary lesions in the myelin sheath, ultimately resulting in the destruction of both long and short nerve fibres. Polyneuropathy can simultaneously affect sensory, motor and vasomotor fibres. The condition is chronic and its evolution is slow. Early symptoms are usually a tingling sensation in the legs, loss of feeling or hypersensitivity to touch.

Initial pain symptoms in polyneuropathy are usually located in the toes and feet and can spread later to calves and then to knees. In some patients, the disease remains confined to the lower limbs (feet and legs), while in others the hands can be affected as well. Walking difficulties may also develop: some patients have to install night lights in their bedroom and bathroom in order to avoid falling over in the dark. Burning pain is most manifest at night. In time, polyneuropathy can also affect the autonomous nervous system, which controls a variety of processes such as blood pressure, heart beat, salivation, digestion and bladder emptying.

Treatment

The treating physician’s task can be very complex because of the many different possible causes of polyneuropathy. Finding and – if possible – addressing the true cause of the disease is the top priority. Prescription medicine can play an important role in treatment but should only be used in urgent situations.

The treatment of pain in polyneuropathy remains a challenge because some patients fail to respond to pharmacological treatment while others experience overly adverse side effects. Alternative approaches have thus been tested. One such alternative, medullary electrostimulation, should only be considered for patients who fail to respond to conventional therapies. Medullary electrostimulation is an effective technique in about 50% of patients who cannot be treated by classical means. In contrast, other physical medical techniques such as Transcutaneous Electric NeuroStimulation (TENS) and high frequency muscular stimulation only yield marginally interesting results. Taken altogether, the different types of treatment currently available fall short of satisfying patients’ needs. New therapeutic options must therefore be discovered.

The technique, developed and implemented by Prof. Possover, consists in direct electrical stimulation of the nerves which innervate the affected region. This is an anatomical approach which is entirely different from the techniques described above. The efficiency of neurostimulation depends on the extent of the nerve lesion and on the actual site where neurostimulation takes place. In medullary stimulation, the electrodes are placed on one or maximum two sacral nerve roots. However, one cannot be certain that the electrodes are effectively in direct contact with all the nerves. Since the sciatic nerve is formed by the fusion of four or five different sacral nerve roots, the pain signal may travel to the central nervous system through some, or perhaps all sacral roots. If so, maximal therapy requires that electrostimulation be applied to all sacral roots. In the LION technique, in contrast to medullary electrostimulation, the electrodes are positioned exactly at the desired location thanks to optimal magnification of the endoscope. The electrodes can be made to contact the sciatic nerve directly in a region where all sacral roots are already fused. This portion of the nerve may be easily located by laparoscopy near the posterior wall of the pelvic cavity. Extensive preparation is thus not necessary. This aspect is important because additional surgical interventions such as the removal of lymphatic ganglions may lead to strong adhesions of the connective tissue and a build-up of lymph which can interfere with the functioning of the electrodes. Lower limb pain may be partially (and sometimes completely) controlled by neuromodulation, depending on the degree of severity of the lesion. However, neuromodulation cannot restore motor and sensitivity functions. Electrical stimulation may well control the «sensation» signals, but it cannot re-establish them.