Age related shift in the primary sites of involvement in cervical spondylotic myelopathy from lower to upper levels.

Ascending axonal volleys were analysed after epidural stimulation at multiple sites along the cervical cord to localise the site of the lesion precisely in cervical spondylotic myelopathy. The intraoperative recordings uncovered a single site of focal conduction block in 129 of 136 affected patients who underwent surgical intervention because of evidence of multilevel compression obtained by magnetic resonance imaging. Statistical analyses showed a shift of abnormalities from lower to upper cervical levels with advancing age (p < 0.0001). In particular, 92% of the oldest group (aged over 70 years) had localised dysfunction at C3-4 or C4-5, while 68% of patients aged under 60 years had lesions at C5-6 or C6-7.