Postcentral Topectomy Optimization by Selective Ablations of the Primary Somatosensory Cortex

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  • March 21, 2019
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  • Challener, Timothy
    • Affiliation: School of Medicine, UNC/NCSU Joint Department of Biomedical Engineering
Abstract
  • Postcentral topectomy is a neurosurgical procedure, practiced in the mid-20th century, in which surgical ablations of the primary somatosensory cortex (SI) were used as a therapeutic means of treating patients suffering from intractable chronic pain. While successful in treating many cases, the procedure was poorly understood and eventually became displaced by methods that more consistently stopped patient complaints of pain, such as opiates and frontal lobotomies. SI contains nociresponsive neurons in two regions: one region in cytoarchitectonic area 1, with properties resembling sharp, discriminative, first pain; and the other in the anterior part of area 3a, with properties resembling burning, affective, second pain. To test the hypothesis that permanent pain loss in postcentral topectomy was achieved when the nociresponsive part of area 3a was removed, we trained unrestrained squirrel monkeys to obtain a juice reward by pulling a noxiously heated metal rod. Pull duration shows high sensitivity to rod temperature and was used as a measure of each animal’s pain sensibility. After training, all monkeys gave consistent baseline pull durations for each trial in a series of chosen neutral (control) and noxious temperatures. Next, we made small electrolytic cortical lesions in 2 monkeys, targeting the hand region of nociresponsive area 3a. These lesions significantly elevated pull durations for at least 4 months (at which time the animals were euthanized), thus indicating permanently reduced pain sensibility. In contrast, ablation of motor cortex anterior to area 3a in the 3rd monkey significantly reduced pull durations, indicating permanently elevated pain sensibility. The current opioid crisis makes these results particularly relevant to clinical medicine. Although the precise location of area 3a in the central sulcus varies extensively among humans, its nociresponsive region can be accurately localized in any given patient by using high-resolution fMRI. Once localized, the area 3a nociresponsive region can be targeted for reversible or permanent inactivation. Such precisely targeted inactivation might greatly improve the success rate of the postcentral topectomy in amelioration of pathological pain, making it a highly attractive means of treating otherwise intractable chronic pain.
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  • In Copyright
Advisor
  • Dennis, Robert
  • Macdonald, Jeffrey
  • Cartee, Lianne
  • Tommerdahl, Mark
  • Favorov, Oleg
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2018
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