An Experimental Animal Model of Spinal Cord Stimulation for Pain

Abstract

In spite of the routine usage of spinal cord stimulation (SCS) as treatment of chronic pain, there is an insufficient understanding of the mechanisms underlying its effect. The method was originally developed as a spin-off from experiments demonstrating the inhibitory control of nociceptive signals by the activation of large afferent fibers, and on the basis of these findings the gate-control theory was advanced. Later experiments showed that stimulation of the dorsal columns can inhibit the relay of nociceptive impulses to second-order neurons in the dorsal horn. It should be emphasized that all these experiments were performed with acute noxious stimuli; it is now universally recognized that SCS in patients is preferentially, or exclusively, effective for chronic neuropathic types of pain. For these and other reasons the mode of action of SCS in clinical pain cannot be inferred from these early animal experiments. In ongoing studies we have used animal models of mononeuropathy (rat) in which we have applied SCS acutely or chronically with stimulation parameters similar to those used in patients. In these animals the first component of the flexor reflex appears with a lower stimulus threshold in the nerve lesioned than in the intact, sham-operated leg. SCS was applied at the approximate level of Th-XII during 10–20 min and produced a marked augmentation of the stimulus threshold. This abnormally high threshold was not normalized until 30–60 min after the end of SCS. In awake animals SCS was applied via an implanted spinal electrode and the effect on behavior changes associated with mononeuropathy was studied. There are several behavioral and neurological features of animal models of mononeuropathy resembling those associated with pain due to peripheral nerve injury in patients. Therefore, this model is particularly suitable for studies aiming at the exploration of mechanisms involved in SCS as treatment of chronic pain.

Spinal Cord Stimulation in a Mouse Chronic Neuropathic Pain Model

“…In Seltzer-injured rats, the onset of the tactile allodynia is rapid (one to three days) and persists for several weeks (3). With respect to experimental SCS in treatment of chronic neuropathic pain mainly the Seltzer type, or partial sciatic nerve injury, is used (4,5). In Seltzer-injured rats, SCS results in a robust and fast increase of the von Frey withdrawal threshold of the injured limb that is still noticeable 30 min after SCS cessation (6).…”

Effects of Posture on Stimulation Parameters in Spinal Cord Stimulation

“…Although the exact mechanism is still unclear, spinal cord stimulation (SCS) has proven to be an effective therapy in the reduction of chronic pain(2–4). Clinical experience has shown SCS to be most effective in relieving neuropathic pain(5, 6), but reports have also indicated that SCS also may affect nociceptive components(7) and ischemic pain(8). Advances in technology have increased the use of SCS, which once was plagued with difficulties related to lead breakage, inadequate surgical techniques, and unreliable pulse generators(9).…”

Effectiveness of spinal cord stimulation for painful camptocormia with Pisa syndrome in Parkinson’s disease: a case report

“…Blockage of pain at the spinal dorsal horn and the spinothalamic tract occurs by retrograde impulse conduction, which activates inhibitory neurons, increases GABA release, and reduces excitatory glutamic acid level. Other mechanisms have also been reported: activation of the descending pain suppression pathway and direct stimulation of the thalamus by SCS ascending impulses, leading to pain relief and improvement of failed sensory modulation action in the basal ganglia [4,[13][14][15][16][17][18][19].…”