Abstract
Measuring central motor conduction time (CMCT) is one of the useful methods to detect
an impaired level of the spinal segment in cervical myelopathy patients. We modified
a new technique to calculate the CMCT using tendon reflex latency (T-response) and
investigated its accuracy. Motor-evoked potentials (MEPs) following transcranial stimulation
were recorded in 19 patients with cervical myelopathy caused by a single level of
spinal cord compression. CMCT was measured by subtracting the peripheral conduction
time, which was calculated by using the T-response for the biceps brachii muscle (Biceps),
the compound muscle action potentials (CMAPs) and the F-wave of the abductor digiti
minimi muscle (ADM). In the control subjects, the mean value of CMCT of the Biceps
and ADM was 3.8 and 7.0 ms, respectively. The accuracy of the determination of the
CMCT for Biceps using T-response was investigated beforehand in the unilateral brachial
plexus palsy patients and thoracic spinal cord myelopathy patients. The calculated
CMCT (3.88±0.65 ms) for Biceps was close to the N2 latency (4.06±0.3 ms) of the evoked
spinal cord potentials which were recorded from the epidural space on the C3–4 vertebral
level following transcranial magnetic stimulation. The CMCT of both the Biceps and
ADM was delayed in all cases of C1–2 cord compression. In patients with cord compression
on the C3–4 level, two of four patients showed CMCT prolongation in Biceps. The prolongation
of CMCT was observed only in ADM in patients with C4–5 or C5–6 cord compression. Measurement
of the CMCT using T-responses was useful in proximal limb muscles. Comparison of the
CMCT in Biceps and ADM could allow us to better detect the functional level diagnosis
for compressive cervical myelopathy.
Keywords
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Article info
Publication history
Accepted:
April 15,
1998
Received in revised form:
April 14,
1998
Received:
October 9,
1997
Identification
Copyright
© 1998 Elsevier Science B.V. Published by Elsevier Inc. All rights reserved.
