Assessment of corticospinal excitability after traumatic spinal cord injury using MEP recruitment curves: a preliminary TMS study.

STUDY DESIGN: Transcranial magnetic stimulation study. OBJECTIVES: To further investigate the corticospinal excitability changes after spinal cord injury (SCI), as assessed by means of transcranial magnetic stimulation (TMS). SETTING: Merano (Italy) and Salzburg (Austria). METHODS: We studied resting motor threshold (RMT), motor evoked potential (MEP) amplitude and recruitment curve in five subjects with good recovery after traumatic incomplete cervical SCI. RESULTS: RMT did not differ significantly between patients and controls, whereas the slope of MEP recruitment curve was significantly increased in the patients. CONCLUSION: This abnormal finding may represent an adaptive response after SCI. The impaired ability of the motor cortex to generate proper voluntary movement may be compensated by increasing spinal excitability. The easily performed measurement of MEP recruitment curve may provide a useful additional tool to improve the assessment and monitoring of motor cortical function in subjects with SCI. Increasing our knowledge of the corticospinal excitability changes in the functional recovery after SCI may also support the development of effective therapeutic strategies.

rTMS modulates reciprocal inhibition in patients with traumatic spinal cord injury.

STUDY DESIGN: Randomized, double-blind, crossover, sham-controlled trial. OBJECTIVES: Repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) leads to a significant reduction of spasticity in subjects with spinal cord injury (SCI), but the physiological basis of this effect is still not well understood. The purpose of this study was to evaluate the disynaptic reciprocal Ia inhibition of soleus motoneurons in SCI patients. SETTING: Department of Neurology, Merano, Italy and TMS Laboratory, Paracelsus Medical University, Salzburg, Austria. METHODS: Nine subjects with incomplete cervical or thoracic SCI received 5 days of daily sessions of real or sham rTMS applied over the contralateral M1. We compared the reciprocal inhibition, the Modified Ashworth Scale and the Spinal Cord Injury Assessment Tool for Spasticity at baseline, after the last session and 1 week later in the real rTMS and sham stimulation groups. RESULTS: We found that real rTMS significantly reduced lower limb spasticity and restored the impaired excitability in the disynaptic reciprocal inhibitory pathway. CONCLUSIONS: In a small proof-of-concept study, rTMS strengthened descending projections between the motor cortex and inhibitory spinal interneuronal circuits. This reversed a defect in reciprocal inhibition after SCI, and reduced leg spasticity.

Central motor conduction studies in patients with spinal cord disorders: a review.

STUDY DESIGN: Topical review of the literature. OBJECTIVES: The evaluation of patients with myelopathies requires radiological investigations; however, for the correct interpretation of the neuroimaging findings, the functional assessment of corticospinal conduction is helpful or even mandatory in many conditions. The objective of this review article was to assess the utility of the motor evoked potentials (MEPs) in diagnosis and management of the most frequent spinal cord disorders. SETTING: Salzburg (Austria) and Merano (Italy). METHODS: A MEDLINE search was performed using following terms: 'motor evoked potentials', 'transcranial magnetic stimulation', 'central motor conduction', 'compressive myelopathy', 'spinal cord infarction', 'spinal cord injury', 'syringomyelia', 'myelitis', 'hereditary spastic paraparesis', 'subacute combined degeneration' and 'hepatic myelopathy'. RESULTS: Central motor conduction abnormalities can be detected also in the absence of neuroradiological abnormalities-for example, in patients with subacute combined degeneration or hepatic myelopathy. In the most frequent patients with compressive myelopathies, MEPs were found to be very helpful in determining the functional significance of neuroimaging findings. MEP recording can supplement clinical examination and neuroimaging findings also in the assessment of the spinal cord injury level. In patients with spinal cord infarction, the MEP study can demonstrate spinal involvement even when radiological evidence for spinal cord damage is absent or equivocal, thus allowing an important early diagnosis. CONCLUSION: MEPs represent a highly sensitive and accurate diagnostic tool in many different spinal cord disorders. MEPs can also be useful in follow-up evaluation of motor function during treatment and rehabilitation.