The aim of the study was to compare the longterm
efficacy of high versus low frequency repetitive
transcranial magnetic stimulation (rTMS), applied bilaterally
over the dorsolateral prefrontal cortex (DLPFC), on
cognitive function and cortical excitability of patients with
Alzheimer’s disease (AD). Forty-five AD patients were
randomly classified into three groups. The first two groups
received real rTMS over the DLPFC (20 and 1 Hz,
respectively) while the third group received sham stimulation.
All patients received one session daily for five
consecutive days. In each session, rTMS was applied first
over the right DLPFC, immediately followed by rTMS
over the left DLPFC. Mini Mental State Examination
(MMSE), Instrumental Daily Living Activity (IADL) scale
and the Geriatric Depression Scale (GDS) were assessed
before, after the last (fifth) session, and then followed up at
1 and 3 months. Neurophysiological evaluations included
resting and active motor threshold (rMT and aMT), and the
duration of transcallosal inhibition (TI) before and after the
end of the treatment sessions. At base line assessment there
were no significant differences between groups in any of
the rating scales. The high frequency rTMS group
improved significantly more than the low frequency and
sham groups in all rating scales (MMSE, IADL, and GDS)
and at all time points after treatment. Measures of cortical
excitability immediately after the last treatment session showed that treatment with 20 Hz rTMS reduced TI
duration. These results confirm that five daily sessions of
high frequency rTMS over the left and then the right
DLPFC improves cognitive function in patients with mild
to moderate degree of AD. This improvement was maintained
for 3 months. High frequency rTMS may be a useful
addition to therapy for the treatment of AD.