Cerebral Hemodynamics With rTMS in Alcohol Dependence

Alcohol abuse is a worldwide problem causing serious physical, psychological, social and economic consequences. Chronic alcohol intake has been found to increased blood viscosity, erythrocyte deformability or dehydration resulting in alterations of cerebral blood flow measures. Transcranial Doppler (TCD) sonography is a non-invasive radiological tool used for assessing the hemodynamics of the basal cerebral arteries, which can thus indirectly reflect the relative changes in regional cerebral blood flow velocity (CBFV) and vascular wall resistance. It has been used to evaluate the relative cerebral blood flow velocity changes in various psychiatric disorders like depression, schizophrenia, panic disorder, and substance use disorders including alcohol and marijuana. TCD also gives a real time assessment of the abrupt or short and long lasting effects of any external mechanical manipulation or functional stimulation of the intracranial circulation.

The Mean flow velocity (MV) is the average of the edge frequency over a cardiac cycle; the edge frequency being the envelope of instantaneous peak velocities throughout the course of a cardiac cycle. Pulsatility index (PI) represents an estimate of downstream vascular resistance; low resistance vascular beds have higher diastolic flow velocities than high resistance vascular beds, hence they have low PI, and vice versa. Similarly, Resistance index (RI) is another presumptive measure of downstream vascular resistance.

TCD sonography studies in alcoholism have revealed reduced mean blood flow velocities in basal cerebral arteries in chronic alcohol dependence, [1] as well as in acute stage of intoxication, but an increase after resolution of withdrawal state. [12] However, ethanol in low concentration has been found to increase the systolic, diastolic and mean blood flow velocity in middle cerebral arteries (MCA), anterior cerebral arteries (ACA) and decrease the resistance indices by reducing the cerebrovascular resistance in healthy individuals. Studies have reported that alcohol related hepatic dysfunction results in increased blood viscosity and reduced velocity in the cerebral arteries, which can be a risk factor for ischemic brain diseases. So, normalization of hemodynamic parameters is important in the prevention of possible ischemic brain diseases due to alcohol dependence.

Studies evaluating cerebral hemodynamic response to rTMS application have been limited to healthy individuals, with high frequency rTMS application found to increase the cerebral blood flow velocities in both anterior and posterior basal cerebral arteries, and low frequency rTMS to temporarily decrease the blood flow velocity in ipsilateral MCA followed by an increase in the contralateral MCA. With this background, the present study was conducted to measure the cerebral hemodynamic indices of alcohol dependent patients and observe the relative changes in these parameters with rTMS application.