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July2007 Vol.44 Issue:        2        Table of Contents
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Motor Evoked Potential in Presymptomatic Spondylotic Cervical Cord Compression

Inas Shaheen1, Walid Al Saadany2, Ghada A. Osman3

Departments of Physical Medicine, Rheumatology and Rehabilitation1,

Neurosurgery2, Neurology3, Alexandria University


Background: Cervical spondylotic myelopathy (CSM) is the most severe consequence of degenerative disease of cervical spine as it is usually a chronic and progressive disease. Despite advances in diagnosis and surgical treatment, many patients still have severe permanent neurologic deficits caused by this condition. An early measure (s) is highly needed to detect preclinical manifestations of such condition. Aim: is to investigate whether electrophysiological parameters of Motor Evoked potential (MEP) could detect clinically asymptomatic (preclinical) spondylotic cervical cord compression before progression to symptomatic myelopathy and to compare between MEP and Somatosensory Evoked Potential (SEP) in this regard. Subjects: Twenty patients with clinical and radiological (plain X-ray and MRI) features of spondylotic cervical root compression, but without clinical or radiological evidence of cervical myelopathy were included in the study. Fifteen healthy subjects, matching in age and sex were included as a control group. Methods: A modification of the Japanese Orthopedic Association Scale (mJOA) was used to confirm the functional status of the patients. The following procedures were carried out bilaterally for patients and unilaterally for control subjects. Percutaneous transcranial magnetic stimulation (TMS) was carried over the corresponding motor cortices of the upper and lower limbs  to elicit MEP. SEP of both median and posterior tibial nerves was recorded  as well. Results: The mean age of patients was 52.7±6.2 years; the majority of them were males (60%). The mean duration of illness was 3.36±1.5 years. There were 6 patients (30 %) with mJOA score of 17 and 14 patients (70 %) with mJOA score of 18. The mean score of mJOA scale was 17.73±0.45. The mean age of control subjects was 48.8±4.5 years. Both plain X- ray and MRI revealed cervical spondylotic changes from C4 to C7 in the form of intervertebral disc degeneration and osteophytosis of vertebral bodies. Indentations of the dural sac on MRI were observed at C5/6, C6/7 and C4/ 5 intervertebral levels in order of incidence. However, the cord was reportedly normal. Central motor conduction time (CMCT) was prolonged in 6 patients. Three of those patients had bilaterally prolonged CMCT. In the other 3 patients CMCT was unilaterally prolonged. MEP amplitude didn't show significant abnormality among patients. There was no significant difference in patients' SEP latencies or amplitudes when compared to control subjects. Conclusion: MEP provides an objective and quantitative approach to assess the motor functional integrity of the corticospinal pathways. Measurement of CMCT could serve as a detector of subclinical spondylotic cervical cord involvement before progression to symptomatic mylopathy even earlier than SEP can do.

(Egypt J. Neurol. Psychiat. Neurosurg., 2007, 44(2): 713-721)


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