Analysis of parameters for epidural spinal cord stimulation. 1. Perception and tolerance thresholds resulting from 1,100 combinations.

A computerized statistical analysis of 1,100 quadripolar electrode combinations used in epidural spinal cord stimulation therapy for the management of pain was carried out to investigate perception and tolerance thresholds. This analysis showed that the thresholds are higher at high-cervical, mid-cervical, mid-thoracic and low-thoracic spinal levels. It is also higher for the combinations with contacts located in the midline than those implanted laterally. As the contact separation increases, the perception and tolerance thresholds increase in bipolar combinations. Unipolar combinations have the lowest thresholds.

Analysis of parameters for epidural spinal cord stimulation. 2. Usage ranges resulting from 3,000 combinations.

A computerized statistical analysis of 3,000 implanted electrode (multi-contact, quadripolar) combinations for epidural spinal cord stimulation therapy for the management of pain was carried out in three groups: spinal levels (20 different levels, C2-L2), spinal placement (midline and lateral) and contact separation (unipolar, bipolar with a separation of 10, 20 and 30 mm) to investigate the clinically required usage ranges (difference between the perception threshold and tolerance threshold). The usage range is relatively higher at midthoracic levels (T4-T10), and for the combinations located in midline. As the contact separation increases, the usage range increases in bipolar combinations. The usage range of unipolar combinations is higher than that of bipolar combinations with 10 and 20 mm separation, and is less than that of bipolar combinations having a separation of 30 mm.

Analysis of parameters for epidural spinal cord stimulation. 3. Topographical distribution of paresthesiae--a preliminary analysis of 266 combinations with contacts implanted in the midcervical and midthoracic vertebral levels.

As a part of the systematic analysis of parameters involved in electrical epidural spinal cord stimulation therapy, distribution of paresthesiae in accordance with the position of contacts, as related to midline and vertebral level of contacts, was investigated. A preliminary analysis performed for 266 combinations having contacts implanted in the midcervical and low-thoracic vertebral levels showed that the topographical spread of the paresthesiae did not always cover the classical dermatomes. Significant paresthesiae spread was found as follows: C4-midline, unipolar combinations; the hand, forearm and upperarm, bipolar combinations; the hand, forearm; C4-lateral, unipolar combinations: the anterior shoulder, forearm, upper arm and hand, bipolar combinations: the hand, forearm and upper arm; T10-midline, unipolar combinations: the anterior and posterior of thigh, leg, knee, ankle and foot, bipolar combinations: the anterior and posterior thigh, leg, knee and foot; T10-lateral, unipolar combinations: the abdomen, anterior leg, knee and anterior thigh, bipolar combinations: the anterior thigh, anterior leg, knee and foot. This preliminary analysis suggests that more detailed studies would be worthwhile in the investigation of sensory responses to electrical stimulation of the spinal cord with epidural electrodes. Findings from such investigations could also be useful to extend our present anatomical knowledge of central and peripheral sensory neural structures.

Advances in electrical nerve stimulation techniques to manage chronic pain: an overview.

Pharmacologic treatments to manage chronic intractable pain have long been sought. Neuropathic pain is usually resistant to analgesics. At present, no analgesic drug totally relieves pain without producing significant unwanted side effects. Electrical stimulation can offer a degree of relief to some sufferers without risk. Transcutaneous electrical nerve stimulation (TENS) has a long clinical history. Stimulation parameters have been studied to improve the efficacy of this method. TENS is inadequate for extensive and bilateral pain, and epidural spinal cord stimulation is indicated. Dorsal column stimulation (DCS) initially was used to manage pain, but recent clinical reports show that it also can be effective in vascular disease and movement disorders. This review article reports on improvements in the electrical parameters used in neurostimulation and advances in research to overcome methodologic problems of DCS.