Cervical spondylotic myelopathy in elderly people: a high incidence of conduction block at C3–4 or C4–5
- aDepartment of Orthopaedic Surgery, Kochi Medical School, Japan, bDepartment of Neurology, Faculty of Medicine, Kyoto University, Japan
- Dr T Tani, Department of Orthopaedic Surgery, Kochi Medical School, Kohasu Oko-cho, Nankoku City, Kochi 783, Japan. Telephone 0081 888 80 2387; fax 0081 888 80 2388; email tanit{at}kochi-ms.ac.jp
- Received 5 May 1998
- Revised 28 August 1998
- Accepted 14 October 1998
Abstract
OBJECTIVES To precisely localise the site of conduction block in elderly patients with cervical spondylotic myelopathy in the presence of multilevel compression shown by MRI.
METHODS A total of 44 patients aged 65 and older underwent serial intervertebral recording of spinal somatosensory evoked potentials (SSEPs) from either the intervertebral disc or the ligamentum flavum after epidural stimulation. The site of conduction block identified by abrupt reduction in size of the negative peak was designated as the 0 level with the other levels numbered in order of distance assigning a minus sign caudally.
RESULTS A single site of focal conduction block was disclosed in 42 patients, 23 (55%) at C3–4, 17 (40%) at C4–5, and two (5%) at C5–6. At these levels (0), the amplitude of the negative component was reduced (p<0.0001) to 29% and the area to 22%, with a concomitant increase (p<0.0001) of the initial positive component to 150% in amplitude and 293% in area as compared to the−2 level which was taken as the baseline (100%).
CONCLUSIONS A high incidence (95%) of focal conduction block at C3–4 or C4–5 with normal conduction at C5–6 and C6–7 characterises cervical spondylotic myelopathy in elderly people. Incremental SSEP studies documenting the site of conduction block will help exclude clinically silent cord compression, directing the surgical intervention to the appropriate level of concern.
- spinal somatosensory evoked potential
- conduction block
- cervical spondylotic myelopathy
- elderly people
