Background: In 1987, Weiskrantz and Zhang described a stroke patient with severe somatosensory loss who nevertheless demonstrated impressive residual sensory performance when required to touch the affected limb with her ipsilesional hand (self touch; ST). The current study set out to ascertain the prevalence and characteristics of self touch enhancement (STE) in patients with unilateral stroke and hemihypaesthesia.
Methods: Thirty nine stroke patients with hemihypaesthesia referred fulfilled the criteria. STE was defined where a patient showed statistically significant increase (p<0.05) in performance for (i) detection, (ii) localization and /or (iii) perceived intensity during touch with their ipsilesional hand, compared to standard experimeter elicited sensory performance.
Results: Group comparisons between the conventional touch vs. ST conditions revealed significant differences for detection (p<.01), intensity estimation (p<.01) and localization (p<.001). using ST. Twenty-two of the 39 patients (56.4%) showed STE in at least one assessment mode. In detection, sixteen (41%) patients showed STE; for localization twelve patients (31%) showed STE and for intensity, seventeen patients (44%) showed STE. Out of the 22 patients with STE, seventeen had right hemisphere lesions.
Conclusion: In summary, over half of the stroke patients showed reliable and significant improvements in somatosensory performance when using their unaffected hand as the source of tactile stimulation. This striking phenomenon suggests that the threshold for the impaired hand is affected by active involvement of the contralateral (ipsilesional) limb when delivering the stimulus contact. Possible mechanisms to explain these findings are discussed.
- sensory loss