Different patterns of I-waves summation in ALS patients according to the central conduction time.
OBJECTIVE
To study facilitatory I-waves interaction, using two near threshold stimuli, to test both excitability and conductivity changes related to cortico-motoneuronal involvement in amyotrophic lateral sclerosis (ALS) patients in different stages of the disease.


METHODS
Pairs of threshold magnetic stimuli were applied over the motor cortex at inter-stimulus intervals (ISI) ranging from 1-1.5 to 2.5-3 ms and from 4 to 4.5ms. The electromyogram responses were recorded from relaxed first dorsal interosseus (FDI).


RESULTS
The data of I-waves summation were distributed according to the central conduction time (CCT) and all 3 peaks of facilitation were considered for statistical analysis. Patients with normal CCT showed a normal I-waves summation for the first peak, whilst patients with abnormal CCT had a significant reduction in facilitation (P<0.02). Six out of 11 patients with normal CCT had facilitation in the first peak, which exceeded 2 SD of normal values.


CONCLUSIONS
In conclusion ALS patients showed two different and opposite patterns of I-waves summation which could be related to different stages of the disease.
Quartarone
A
A
Department of Neuroscience, Psychiatric and Anaesthesiological Sciences University of Messina, Italy. angelo.quartarone@unime.it
Battaglia
F
F
Majorana
G
G
Rizzo
V
V
Bagnato
S
S
Messina
C
C
Girlanda
P
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology*; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D004576:Electromyography; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D009431:Neural Conduction