The cerebral hemodynamics of repetitive transcranial magnetic stimulation

Abstract

Repetitive transcranial magnetic stimulation (rTMS) has been shown to be effective in the treatment of affective disorders. However, only little is known about hemodynamic physiological and safety aspects of this method. We studied the cerebral hemodynamics as measured by transcranial Doppler sonography in 20 healthy subjects during different rTMS procedures. Mean cerebral blood flow velocity (CBFV), pulsatility index (PI), and oxygen consumption were recorded continuously and averaged directly after the rTMS procedure. RTMS did not influence blood pressure, pulse rate, or blood oxygenation. There was a maximal increase of CBFV in the middle cererbal artery (MCA) of 3.6% and 5.6% during 10 Hz and 20 Hz stimulation, respectively. This increase was only seen on the stimulated left hemisphere. The PI remained unchanged during the whole procedure. It is likely that the increase of CBFV is due to dilatation of the small resistance vessels rather than due to vasoconstriction of the MCA. In terms of cerebral hemodynamics, rTMS is a safe and well-tolerated technique with a lower increase of CBFV than that seen in electroconvulsive therapy.

Differential Hemodynamic Response to Repetitive Transcranial Magnetic Stimulation in Acute Stroke Patients with Cortical versus Subcortical Infarcts

“…As in other studies using rTMS [17] and even hypercapnia [7,8,19], PI was also unchanged in the present study indicating that the observed changes were not the result of a direct vasoconstricting effect on the MCA. Although the exact dynamics of the effect of rTMS are incompletely understood, it is likely mediated by a change in small arteriolar diameter paralleling oxygen consumption as suggested by PET studies showing an increase in regional CBF following rTMS [23,24], and by an observed decrease in capacity for further reactivity to a CO 2 stimulus after rTMS [25].…”

“…As a stimulus, however, hypercapnia is not immediately comparable to rTMS since it acts globally and independently on each hemisphere. In healthy volunteers, Pecuch et al [17] demonstrated an increase in only the ipsilateral MCA CBFV with infrathreshold 10–20 Hz rTMS, whereas the increase was also seen in the contralateral MCA (albeit to a lesser extent) with suprathreshold stimulation – attributable to activation of interhemispheric pathways. This is consistent with our finding of a smaller percent change in the contralesional MCA CBFV in both groups, and it is conceivable that this is compounded by the presence of an infarct in the stimulated hemisphere further hampering interhemispheric transmission.…”

“…Previous studies have shown increases and decreases in ipsilateral MCA flow velocity in response to high-frequency (stimulatory) [12,17] and low-frequency (inhibitory) rTMS [13] respectively. This suggests that the vasomotor response is largely driven by the metabolic demand of the stimulated cerebral cortex.…”

“…A baseline TCD recording of the mean MCA CBFV and pulsatility index (PI) ipsilateral to the site of brain lesion and on the contralateral side was performed as described above. Three trains of 10-Hz rTMS stimuli for 5 s (1 train/min) were then applied [17] in accordance with published risk and safety guidelines [18]. CBFV and PI measurements were repeated after the third train of stimuli.…”

Effects of High-Frequency Repetitive Transcranial Magnetic Stimulation on Cerebral Hemodynamics in Patients with Disorders of Consciousness: A Sham-Controlled Study

“…In fact, the term 'neurovascular coupling' (NVC) is used to describe the close spatial and temporal relationships between neural activity and CBF [11] . For example, CBF velocity immediately increases after high-frequency rTMS in the stimulated area of healthy subjects [18,19] , and it is possible that this increase is induced by a transitory increase in neural activity in the stimulated cerebral region based on the NVC mechanism [20] . Thus, it can be speculated that the transient increase in neural cell function induced by excitatory rTMS may produce a transient increase in CBF in the stimulated area.…”