Prospective, blind study of the triple stimulation technique in the diagnosis of ALS.
OBJECTIVE
To evaluate the diagnostic yield of magnetic cortical stimulation with the triple stimulation technique (TST) to identify upper motor neuron (UMN) involvement in patients suspected of having ALS.


METHODS
Fifty-nine patients were recruited to undergo TST in addition to the standard work-up for suspected motor neuron disease. TST combines transcranial magnetic stimulation of the motor cortex with collision studies, which results in a higher sensitivity in detecting UMN involvement. Primary outcome was the number of abnormal TST results in patients with possible ALS. The positivity rate was converted to the number needed to test with TST (NN-TST) for one extra diagnosis of ALS.


RESULTS
Fifty patients underwent TST. In the total group (n=59), 18 patients had a motor neuron disorder but did not fulfil criteria for 'probable' or 'definite' ALS. In four of these patients TST was abnormal (NN-TST, 4.5). One TST was erroneously interpreted as abnormal. TST findings were normal in inclusion body myositis and peripheral nerve disorders.


CONCLUSIONS
This prospective and blind study confirms open studies of TST in the evaluation of ALS. We suggest that TST can be used to arrive at a diagnosis of 'probable' or 'definite' ALS in patients lacking UMN signs in the upper extremities.
Kleine
Bert U
BU
Radboud University Nijmegen Medical Centre, Donders Institute for Brain, Cognition and Behaviour, Department of Clinical Neurophysiology, Nijmegen, The Netherlands. b.kleine@neuro.umcn.nl <b.kleine@neuro.umcn.nl>
Schelhaas
Helenius J
HJ
van Elswijk
Gijs
G
de Rijk
Maarten C
MC
Stegeman
Dick F
DF
Zwarts
Machiel J
MJ
D000200:Action Potentials; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000503:physiopathology*; D016477:Artifacts; D001917:Brachial Plexus / Q000502:physiology; D003937:Diagnosis, Differential; D004311:Double-Blind Method; D004576:Electromyography / Q000379:methods*; D006801:Humans; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D009046:Motor Neurons / Q000502:physiology; D018979:Myositis, Inclusion Body / Q000175:diagnosis / Q000503:physiopathology; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis / Q000503:physiopathology; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D014459:Ulnar Nerve / Q000502:physiology; D055815:Young Adult