Cortical excitability and age-related volumetric MRI changes.
OBJECTIVE
Normative data on transcranial magnetic stimulation (TMS)-derived measures of cortical excitability in the elderly is sparse. Nevertheless, elderly subjects are included as controls in studies utilizing TMS to investigate disease states. Age-associated increased ventricular cerebrospinal fluid CSF (vCSF) and white matter hyperintensity (WMH) MRI volumes have uncertain significance in non-demented elderly. Information regarding cortical excitability in neurologically intact elderly would augment our understanding of the pathophysiology of aging and assist in the interpretation of TMS studies involving elderly subjects.


METHODS
Twenty-four healthy elderly subjects underwent TMS testing to determine outcomes of resting motor threshold (RMT) cortical silent period (cSP) and central motor conduction time for examination in relation to WMH, vCSF, and CNS volumes.


RESULTS
Increased vCSF and WMH volumes were associated with decreased right and left hemisphere RMT. Smaller CNS volumes were associated with decreased right hemisphere RMT and shorted cSP.


CONCLUSIONS
Commonly observed age-associated MRI changes are associated with findings consistent with increased cortical excitability.


CONCLUSIONS
Age-related MRI findings likely reflect changes at a cellular level, and may influence cognitive and motor integrity in the elderly. Future TMS studies investigating cortical excitability may wish to consider neuroimaging markers of neurodegeneration prior to enrolling elderly subjects as controls.
Department of Neurology, Layton Aging and Alzheimer's Disease Center, Oregon Health and Science University, Portland, OR 97201, USA. silbertl@ohsu.edu
L C
LC
Silbert
C
C
Nelson
S
S
Holman
R
R
Eaton
B S
BS
Oken
J S
JS
Lou
J A
JA
Kaye
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000134:cerebrospinal fluid* / Q000502:physiology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D002560:Cerebrovascular Circulation; D004056:Differential Threshold; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D016192:Resting Phase, Cell Cycle; D012680:Sensitivity and Specificity; D050781:Transcranial Magnetic Stimulation / Q000379:methods