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March 1994

Central Motor Conduction Time to Upper and Lower Limbs in Cervical Cord Lesions

Author Affiliations

From the Department of Neurology, University of Erlangen-Nürnberg, Erlangen, Germany.

Arch Neurol. 1994;51(3):245-249. doi:10.1001/archneur.1994.00540150039013

Objective:  Diagnostic value of central motor conduction time (CMCT) to upper and lower limbs in cervical cord lesions was investigated.

Design:  A series of patients underwent transcranial magnetic stimulation.

Setting:  Patients hospitalized in our department were investigated.

Patients:  Forty-seven consecutive patients with cervical spinal lesions (31 patients with myelopathy due to cervical spondylosis, eight with syringomyelia, eight with tumors) were tested.

Main Outcome Measures:  Compound muscle action potentials were recorded from the abductor digiti minimi (ADM) and the anterior tibial (TA) muscles bilaterally. The CMCT was calculated after transcranial magnetic and electrical nerve root stimulation. Correlation of abnormal CMCT to radiologically proved cord compression and to clinical signs of upper motor neuron involvement were tested.

Results:  Of 37 patients with extramedullary lesions, CMCT to the ADM was abnormal in 19 cases (51%) and to the TA in 26 cases (70%). In 10 patients with intramedullary lesions, abnormal CMCT to the ADM was observed in three cases (30%) and to the TA in three cases (30%) as well. Higher sensitivity of measurements to the TA in extramedullary disorders was not significant. Abnormal CMCT correlated to cord compression and to upper motor neuron involvement. In eight patients (42%), subclinical lesions were detected by an abnormal CMCT.

Conclusion:  In extramedullary lesions, measurement of CMCT to the TA is more sensitive. The procedure is valuable in detecting subclinical lesions. Abnormal CMCT correlates with cord compression and clinical signs of upper motor neuron involvement.

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