Assessment of the upper motor neuron lesion in amyotrophic lateral sclerosis with the triple stimulation technique

Abstract

Objective To quantitatively estimate upper motor neuron (UMN) lesion with the triple stimulation technique (TST) in amyotrophic lateral sclerosis (ALS). Methods Fifty ALS patients and 22 normal controls were enrolled in the study. Patients were examined clinically with conventional transcranial magnetic stimulation (TMS) and TST at abductor digiti minimi. Central motor conduction time (CMCT),motor evoked potential ( MEP), resting motor threshold ( RMT), compound muscle action potential ( CMAP), modified ashworth scale ( MAS), Medical Research Council scale and modified ALS scale were assessed and their correlation to disease progress was analyzed. Results The TST amplitude ratio was significantly decreased in ALS patients with UMN signs(28 cases 62. 0% (40. 7%, 75.9% ) ), compared with controls ( 96. 9% ± 2. 6% ) and ALS patients without UMN signs ( 22 cases 95.6% ( 85.4%,100. 0% ) ;Z = -4. 827, -5.435, both P =0. 000). The abnormal rates of the TST amplitude in ALS with UMN signs, ALS without UMN signs and controls were 89. 3%, 27.3% ,9. 1% respectively. The abnormal rates of the TST amplitude, the latency of MEP, CMCT, RMT in detecting UMN lesions were 89. 3%,64. 3%, 53.6%, 64. 3% , 78. 6%, respectively. The TST amplitude was significantly correlated to tendon reflex in right arm ( r = 0. 690, P = 0. 000), with modified ashworth scale ( MAS, r = - 0. 772,P = 0. 000),with diagnostic degree ( r = 0. 483, P = 0. 000), with RMT ( r = - 0. 774,P = 0. 000), the latency of MEP (r = - 0. 444, P = 0. 005 ), motor evoked potential/compound muscle action potential of erb' s ( MEP/ CMAPerb, r = 0. 685, P = 0. 000 ), MEP/CMAPerb in facilitation ( r = 0. 770, P = 0. 000). Conclusions TST appears to be a more accurate and sensitive measure of detecting and quantifying UMN abnormality in ALS patients than the other parameters. TST may reveal the subclinical UMN impairment in ALS and provide an accurate diagnosis assessment for UMN loss in ALS and an objective scale for monitoring the progression of disease. Key words: Amyotrophic lateral sclerosis;  Transcranial magnetic stimulation;  Motor neurons