Tactile asymbolia

J Clin Neurosci. 2016 Apr;26:164-5. doi: 10.1016/j.jocn.2015.10.021. Epub 2015 Nov 24.

Abstract

Agraphesthesia has been attributed to impairment of the ability to detect more rudimentary directionality of lines written on the skin (directional cutaneous kinesthesia). We examined a patient who had a dissociation between preserved perception of line directionality and the loss of graphesthesia for letters and numbers. A man with a metastatic right parietal lesion was tested for the ability to determine the directionality of lines drawn on the palms and forehead and then evaluated for recognition of letters and numbers in these regions. Our patient could identify the directions of lines, letters and numbers drawn on paper. The ability to detect the direction and shape of lines drawn on the skin of the palms and on the forehead was preserved but he had agraphesthesia for numbers and letters in these same locations. The finding of isolated agraphesthesia for letters and numbers may be assigned to damage in the right parietal lobe. It represents a deficit of somatosensory processing that is of a higher order than detection of line directionality. The term "tactile asymbolia" may capture the dissociation. These clinical findings suggest that tactile cortex in humans, like visual cortex, may be hierarchically organized, as has been demonstrated in primates.

Keywords: Clinical neurology; Graphesthesia; Neurological exam findings; Parietal cortex; Somatosensory processing.

Publication types

  • Case Reports

MeSH terms

  • Brain Neoplasms / complications*
  • Brain Neoplasms / pathology
  • Female
  • Humans
  • Male
  • Sensation Disorders / etiology*
  • Skin / innervation
  • Somatosensory Cortex / pathology*
  • Touch
  • Touch Perception / physiology