Ectopic sensory discharges and paresthesiae in patients with disorders of peripheral nerves, dorsal roots and dorsal columns

Abstract

Ectopically generated and antidromically conducted nerve impulses were recorded in 5 patients with tungsten microelectrodes inserted into skin nerve fascicles. All patients had mainly positive sensory symptoms and reported paresthesiae which could be provoked by different maneuvers which suggested increased mechanosensitivity of the primary sensory neurons at different anatomic levels. Ectopic multiunit nerve activity correlating in intensity and time course to the positive sensory symptoms was recorded: when Tinel's sign was elicited in a patient with entrapment of the ulnar nerve at the elbow, when paresthesiae were provoked by elevation of the arm in a patient with symptoms consistent with a thoracic outlet syndrome, when paresthesiae were evoked by straining during chin-chest maneuver in a patient with an S1 syndrome due to a herniated lumbar disc, when a painful Lasegue's sign occurred during the straight-leg raising test in a patient with an S1 syndrome due to root fibrosis, and when Lhermitte's sign was elicited by neck flexion in a patient with multiple sclerosis. The sites for the ectopic impulse generation in these cases are suggested to be peripheral nerve, brachial plexus, dorsal root or dorsal root ganglion and dorsal columns. The paresthesiae were non-painful except in the patient with Lasegue's sign and the ectopic impulses were probably recorded from large myelinated afferent fibers.

Opposing effects of spinal nerve ligation on calcium-activated potassium currents in axotomized and adjacent mammalian primary afferent neurons

“…spontaneous pain and hyperalgesia. Aberrant firing of injured peripheral nerves definitely contributes to the manifestations of neuropathic pain [25,68], while excitability changes secondary to alterations of K (Ca) currents have already been implicated in the pathogenesis of this ectopic spontaneous firing on injured primary afferent neurons [3,100]. Inhibition of K (Ca) channels by norepinephrine has been also implicated in the membrane hyper-excitability and hyperalgesia after chronic constriction sciatic nerve injury [37].…”

Time Course and Nerve Growth Factor Dependence of Inflammation-Induced Alterations in Electrophysiological Membrane Properties in Nociceptive Primary Afferent Neurons

“…Spontaneous activit y. Spontaneous activity is thought to contribute to abnormal pain behavior in animals and neuropathic pain in humans by sensitizing spinal cord neurons (Nordin et al, 1984). In addition, spontaneous firing of nociceptive neurons is likely to cause spontaneous pain directly.…”

Downregulation of Tetrodotoxin-Resistant Sodium Currents and Upregulation of a Rapidly Repriming Tetrodotoxin-Sensitive Sodium Current in Small Spinal Sensory Neurons after Nerve Injury

“…One possibility is that nociceptive spinal sensory neurons generate inappropriate activity after injury. Spinal sensory neurons become hyperexcitable and generate spontaneous impulses after injury in experimental animals (Wall and Gutnick, 1974;Lisney and Devor, 1987;Matzner and Devor, 1994) and humans (Nystrom and Hagbarth, 1981;Nordin et al, 1984). Interestingly, anticonvulsants and local anesthetics have been used at concentrations known to act on sodium channels to manage chronic pain in humans (Boas et al, 1982;Chabal et al, 1989a;Chabal et al, 1992;Galer et al, 1993;Appelgren et al, 1996).…”