Abnormal parameters of magnetically evoked motor-evoked potentials in patients with cervical spondylotic myelopathy

Department of Physiology, University of Peradeniya, Sri Lanka.
The Spine Journal (Impact Factor: 2.43). 07/2008; 8(4):645-9. DOI: 10.1016/j.spinee.2006.11.010
Source: PubMed


Magnetic stimulation (MS), which is used to evaluate motor pathways, is helpful in evaluating cervical spinal cord compression (cervical myelopathy [CM]). Previous studies have shown that the central motor conduction time (CMCT), which is the time taken for the nerve impulses to reach the cervical spinal roots after the stimulation of the motor cortex, is prolonged in CM. However, the duration of motor-evoked potentials (MEPs) in CM has not been studied in detail.
To compare the duration, CMCT and amplitude of MEPs by MS between patients with clinical and magnetic resonance imaging (MRI) features of CM and a control group.
A cross-sectional study done at Teaching Hospital, Peradeniya, Sri Lanka.
Consecutive patients with clinical features of cervical spondylotic myelopathy, without coexisting neurological abnormality.
Transcranial and cervical spinal magnetic stimulation were performed on 21 patients with clinical and MRI features of spondylotic CM (mean age, 43.5years; range, 36-63 years; 9 men) and 17 healthy volunteers (mean age, 39.05 years; range, 23-54yrs; 6 males) using a circular coil with a Magstim 200 stimulator. MEPs were recorded over abductor digiti minimi muscle on both hands.
Seventeen patients had upper motor neuron (UMN) features in all four limbs; in the others, both lower limbs and one upper limb were affected. The upper limbs with UMN features had shorter duration MEPs compared with the control group. The CMCT and the total motor conduction time were also delayed in the CM group. All three differences were very highly significant (t=5.75, -3.76, 5.27; p<.001). The amplitudes showed no significant difference between the two groups (t=1.27, p=.208).
This study shows that in addition to the CMCT, the duration of MEPs is also useful in evaluating patients with CM using MS.

6 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: The authors set out to study the role of transcranial magnetic stimulation (TMS) in the pre-surgical assessment of patients with cervical spondylotic myelopathy. Central motor conduction time (CMCT) was calculated in 50 patients and 50 controls by recording muscle evoked potentials from upper limb muscles. The level of spinal cord compression was determined according to the pattern of CMCT prolongation and compared with the level disclosed by MRI. Direct comparison of the TMS and MRI results was possible in 42 cases and agreement was noted in 25 (59.5%). In the 23 patients in whom the two methods did not give convergent findings, post-operative data were used in order to determine the actual level of compression. This level was correctly indicated by TMS in 87.5% of cases and by MRI in 12.5%. TMS is a neurophysiological tool that can complement existing methods for determining the level of cervical spinal cord compression.
    No preview · Article · Apr 2009 · Functional neurology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Based on reports published so far, organophosphorus (OP) compounds do remarkable harm to human health. In 1995 there was an outbreak of organophosphorus-ester induced delayed neuropathy (OPIDN) due to tri-ortho-cresyl phosphate (TOCP) poisoning in northern suburbs of Xi'an in China. The 74 affected patients were treated and followed up after definite diagnosis. 13 years later, all the epidemiological data obtained from 61 survivors were evaluated, and 15 patients underwent clinical, laboratory, neuroimaging and electrophysiological examinations. In addition, a review of the literature about the possible mechanism of OPIDN was made. According to our investigation, of 61 survivors, 35 patients almost regained normal function of limbs and work outside; 23 patients walked with bilateral support and could perform housework; and 3 patients could not self-care. The patients undergoing examinations presented spasticity and minor lower leg muscle atrophy without sensory impairment. Laboratory investigations and brain and spinal cord magnetic resonance imaging examinations were normal. Neurophysiological investigations also showed normal electroencephalogram and visual, brainstem auditory and somatosensory evoked potentials. Motor evoked potential (MEP) obtained from the upper limbs had normal central motor conduction time (CMCT). However, the CMCT of MEP response recorded from the bilateral lower limbs was delayed, or showed even no MEP responses. Motor and sensory nerve conduction velocity and electromyography studies were normal except for two severely affected patients. TOCP showed long-term effects on the nervous system and influenced the quality of life. OP compounds should be strictly regulated to prevent similar occurrences.
    No preview · Article · Aug 2009 · NeuroToxicology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Magnetic stimulation is a non-invasive and painless technique for studying the motor pathways in medical neurology. A time-varying magnetic field induces an electrical field in conducting objects, such as nervous tissue. The technique can be applied to nerve roots and peripheral nerves or to the motor cortex of the brain in human and veterinary medicine. In this review, the basic principles, applications and risk factors of peripheral nerve and motor cortex stimulation in human and veterinary medicine are discussed.
    No preview · Article · Feb 2011 · The Veterinary Journal
Show more