At the spinal level, the PNS and CNS are bilaterally symmetrical. And studies have shown that the two sides of the spinal cord are not independent due to the findings that unilateral peripheral nociception results in contralateral responses (Koltzeburg, 1999). The contralateral pain was perceived at a lesser magnitude and has a delayed response. This contralateral pain phenomenon can be attributed to a similar pathway as central sensitization leading to secondary hyperalgesia. Primary hyperalgesia is seen at the site of the injury as a resultant of a noxious stimuli. Secondary hyperalgesia, on the other hand, develops on non-stimulated skin adjacent to the injured site and is caused by central neuronal sensitization
In Shenker’s study with
In Shenker’s study with