Altered response to rTMS in patients with Alzheimer's disease.
OBJECTIVE
In this study, we tested the excitability of cortical motor areas in patients with Alzheimer's disease. Because repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability, possibly by inducing a short-term increase in synaptic efficacy, we used rTMS to investigate motor cortex excitability in patients with Alzheimer's disease.


METHODS
We tested the changes in the size and threshold of motor evoked potential (MEP) and cortical silent period (CSP) duration evoked by focal rTMS delivered in 10 trains of 10 stimuli at 5Hz frequency and 120% rMth intensity in a group of patients with Alzheimer's disease, and age-matched controls. In a further session, rTMS was also delivered at 1Hz frequency (trains of 10 stimuli, 120% rMth).


RESULTS
Whereas in control subjects, 5Hz-rTMS elicited normal MEPs that progressively increased in size during the train, in patients, it elicited MEPs that decreased in size. The increase in the duration of the CSP was similar in patients and healthy controls. One hertz rTMS left the MEP amplitude unchanged in patients and healthy controls.


CONCLUSIONS
The lack of MEP facilitation reflects an altered response to 5Hz-rTMS in patients with Alzheimer's disease.


CONCLUSIONS
Our rTMS findings strongly suggest an altered cortical plasticity in excitatory circuits within motor cortex in patients with Alzheimer's disease.
Inghilleri
M
M
Department of Neurological Sciences, University of Rome La Sapienza, Viale dell'Università, 30, 00185 Rome, Italy. maurizio.inghilleri@uniroma1.it
Conte
A
A
Frasca
V
V
Scaldaferri
N
N
Gilio
F
F
Santini
M
M
Fabbrini
G
G
Prencipe
M
M
Berardelli
A
A
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D000704:Analysis of Variance; D016022:Case-Control Studies; D004056:Differential Threshold / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology / Q000528:radiation effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology / Q000528:radiation effects*; D010507:Periodicity; D050781:Transcranial Magnetic Stimulation