Pattern of cortical excitability in patients with geriatric depression and subcortical ischemic vascular disease: A TMS study

Introduction. It is stated that cognitive, behavior and mood abnormalities, mainly geriatric depression, may derive from lesions of the prefrontal-subcortical circuits [1]. Indeed, subcortical ischemic vascular disease may be commonly associated not only with cognitive impairment, even without dementia, but also with geriatric depression [2]. Previous studies using Transcranial Magnetic Stimulation (TMS) have demonstrated an hyperexcitability of motor cortex and a dysfunction of subcortical inhibitory circuits in patients affected by subcortical ischemic vascular dementia [3]. Conversely, no studies have investigated cortical excitability in patients with vascular depression. Objective. To investigate the pattern of cortical excitability among patients with geriatric depression and subcortical ischemic vascular disease. Materials and methods. We enrolled 14 right-handed patients aged 48-78 (mean ± SD: 64.71 ± 10.31 years old): seven with subcortical ischemic vascular disease and depressive symptoms (VD), four with depression without vascular disease (NVD) and three with subcortical ischemic vascular disease without depression (VND). All patients were required to have a score ≥24 on the Mini Mental State Examination and the diagnosis of depression was established by the Structured Clinical Interview for DSM-IV Axis I Disorders diagnostic criteria. Depression was rating by the 17-items Hamilton Depression Rating Scale. Magnetic Resonance Imaging of the brain was performed to all patients and WMLs were graded according to the visual scale of Fazekas. Motor evoked potentials and resting Motor threshold (rMT) were obtained by single-pulse TMS recording from the first dorsal interosseous muscle of right hand. Short intracortical inhibition (SICI) and intracortical facilitation (ICF) were examined with paired-pulse TMS at interstimulus intervals (ISIs) of 1, 3, 5, 7, 10 ms at the hot spot for the left primary motor cortex. References: 1. Tekin S, Cummigs JL. Frontal-subcortical neuronal circuits and clinical neuropsycjiatry. An update. J. of Psycosomatic Research. 2002;53:647-654. 2. De Groot JC et al. Cerebral white matter lesions and depressive symptoms in elderly adults. Arch of General Psychiatry. 2000;57:1071-1076. 3. Alagona et al.Motor cortex excitabilityt in Alzheimer’s disease and in subcortical ischemic vascular dememntia. Neurosci Lett. 2004;362:95-98. Results. The mean rMT was similar for all groups (mean ± SD: 45.79 ±6.29%). Statistical evaluation included a design with a twoway repeated measures analysis of variance (ANOVA), consisting in a “between” main factor “Group”, with three levels (VD patients vs. VND patients vs. NVD Patients) and in a “within” main factor “ISI” with five levels. p-Value <0.05 was taken as the significant threshold for all tests. A significant main effect of Group [F = 58.12, p < 0.001] and of ISI [F = 5.8, p < 0.001] were observed. Conclusion: Our results support the “vascular depression” hypothesis as a different syndrome than depression in patients without vascular disease and the relevance of subcortical ischemic vascular disease in the development of depression in elders.