Transcranial magnetic stimulation in the diagnosis of cervical compressive myelopathy: comparison with spinal cord evoked potentials.

Abstract

STUDY DESIGN:

Single-center retrospective study.

OBJECTIVE:

To reveal the characteristic changes in central motor conduction time (CMCT) produced by transcranial magnetic stimulation among the responsible levels of cervical compressive myelopathy (CCM).

SUMMARY OF BACKGROUND DATA:

CMCT is a useful and noninvasive measure for evaluating the central motor pathway. However, a systematic correlation between CMCT findings and the responsible level of CCM has so far not been addressed in a large patient cohort.

METHOD:

We measured CMCT in 75 patients with CCM who were determined by intraoperative spinal cord evoked potentials to have a single site of conduction abnormality at the intervertebral level. Twenty-one healthy controls were also evaluated. Motor evoked potentials, compound muscle action potentials, and F wave were recorded from bilateral abductor digiti minimi (ADM) and abductor hallucis (AH) muscles. CMCT was calculated as follows: motor evoked potentials latency-(CMAPs latency+F latency-1)/2 (ms).

RESULT:

The mean values of ADM-CMCT and AH-CMCT at each responsible level were significantly longer than those of normal values (P<0.01). However, the mean value of ADM-CMCT at the C6-C7 level was markedly shorter than those at the other levels, whereas the mean values of AH-CMCT were not significantly different between each responsible level. We determined that an ADM-CMCT longer than 7.9 ms (mean+2.5 standard deviation) was abnormal. Using this definition, the sensitivity of ADM-CMCT for CCM was 92% for C3-C4 myelopathy, 95% for C4-C5, 58% for C5-C6, and 9% for C6-C7.

CONCLUSION:

ADM-CMCT is useful for the screening of CCM rostral to the C5-C6 level. Diagnosis of patients with C6-C7 myelopathy should include assessment of the AH-CMCT.

LEVEL OF EVIDENCE:

4.

• Authors: Masahiro Funaba, Tsukasa Kanchiku, Yasuaki Imajo, Hidenori Suzuki, Yuichiro Yoshida, Norihiro Nishida, Toshihiko Taguchi
• Journal: Spine (Spine (Phila Pa 1976)) Vol. 40 Issue 3 Pg. E161-7 (Feb 01 2015) ISSN: 1528-1159 [Electronic] United States
• PMID: 25384053 (Publication Type: Journal Article)

Topics

• Aged
• Electric Stimulation
• Electrodiagnosis
• Evoked Potentials, Motor (physiology)
• Female
• Humans
• Male
• Middle Aged
• Muscle, Skeletal
• Retrospective Studies
• Spinal Cord Compression (diagnosis, physiopathology)
• Transcranial Magnetic Stimulation