Link
between coil-cortex distance and antidepressant
effect of repetitive transcranial magnetic
stimulation in the elderly
Antidepressant
effects of repetitive transcranial magnetic
stimulation (rTMS) have been shown to be smaller
in older depressed patients than in young
people. A reduction in orbitofrontal cortex
volume has been demonstrated in geriatric
depressed patients. A recent study set out to
investigate whether a prefrontal atrophy could
be related to the antidepressant response to
rTMS.
The distance between the stimulating coil and
the cerebral cortex (coil-cortex distance index
or CCDI) and the Hamilton Depression (HAMD)
rating scale were determined in 13 outpatients
with a mean age of 56.4 years with
treatment-resistant major depression undergoing
a standard rTMS. Computed tomography was used to
obtain CCDI.
HAMD rating was improved in the patients by
a mean reduction of 21.2%, and a negative
correlation was found between the CCDI and the
percentage decrease of the HAMD rating after
treatment, indicating the importance of the
distance between the prefrontal and motor cortex
coil-cortex for antidepressant response.
This study shows that the process of prefrontal
atrophy can occur more rapidly than motor cortex
atrophy in chronically depressed middle-aged
patients. These findings may lead to a better
understanding of the neurobiology of depression
in older patients and allow specific designs for
future studies of rTMS treatment in this
population. Arch
Gen Psychiatry 59: 560-561, 2002