Agraphesthesia. A disorder of directional cutaneous kinesthesia or a disorientation in cutaneous space

Tests for graphesthesia and for directional cutaneous kinesthesia (DCK) were performed on a large series of neurological patients and normal subjects, in addition to the standard tests for discriminative sensation. Defects in graphesthesia and DCK were found with lesions at all levels of the nervous system. Graphesthesia was more often and more severely affected than DCK. These functions when impaired were always associated with other sensory defects (directional joint kinesthesia, two-point discrimination, etc.) in different combinations. It appears DCK is probably the basis for graphesthesia. Recent experimental studies have provided an anatomic and physiologic basis for DCK and for graphesthesia. These studies have also discredited wide-held beliefs on the transmission of discriminative sensation through the spinal cord. In this light, the history of ideas about sensation and its mediation is reviewed, and it is concluded that DCK alone deserves to be called a "posterior column function". Graphesthesia and DCK are discussed as kinesthetic functions implying orientation in cutaneous sensory space. These are compared to stereognosis and braille reading, which are complex derived functions depending also on motion, but directed towards recognition in external haptic space. Graphesthesia and DCK should both be considered as distinct forms of somatic sensibility which are valuable adjuncts to the clinical sensory examination. in both systems, surpassed only by powerful, sudden, spatially summated stimuli. Doubtless the similarities have something important to teach us about how the nervous system transforms patterns of sensory inputs rapidly changing in space and time into coherent percepts.