Transcallosal inhibition in amyotrophic lateral sclerosis.
OBJECTIVE
Assessment of upper motor neuron (UMN) involvement is essential for the diagnosis of amyotrophic lateral sclerosis (ALS). In a number of ALS cases, mirror movements (MM) suggest an involvement of transcallosal fibre tracts in conjunction with UMN involvement. The present study analysed whether deficient transcallosal inhibition (TI) tested by TMS enables detection of cortical affection in ALS, even at early stages of the disease.


METHODS
In three patients with definite ALS and 12 patients with early ALS (aged 64.1+/-7.8 years) TMS investigation included analysis of contralateral (cMEP) and ipsilateral (iMEP) motor evoked potentials as well as measurement of TI (latency, duration) with recording from both first dorsal interosseus muscles.


RESULTS
Clinical UMN signs were present in four patients. 83.3% of patients showed a pathological TI (prolongation or loss of TI). Five out of eight ALS patients showing a pathological TI had no clinical UMN signs. Two of these patients showed MM. One patient displayed also pathological findings in TI investigation.


CONCLUSIONS
Our findings suggest a functional deficit of transcallosal fibre tracts even at early stages of the disease still lacking clinical UMN signs.


CONCLUSIONS
Measurement of TI tested by TMS can detect an involvement of the cortical output system in ALS and may be helpful in an early assessment of the diagnosis.
Wittstock
M
M
Laboratory of Human Cortical Physiology, Department of Neurology, University of Rostock, Germany. matthias.wittstock@med.uni-rostock.de
Wolters
A
A
Benecke
R
R
D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000503:physiopathology*; D003337:Corpus Callosum / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007395:Interneurons / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology; D016472:Motor Neuron Disease / Q000175:diagnosis* / Q000503:physiopathology*; D009046:Motor Neurons / Q000473:pathology; D009431:Neural Conduction / Q000502:physiology; D009433:Neural Inhibition; D011930:Reaction Time / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014855:Wallerian Degeneration / Q000503:physiopathology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D005680:gamma-Aminobutyric Acid