Cerebral Hemodynamics After Transcranial Direct Current Stimulation (tDCS) in Patients with Consequences of Traumatic Brain Injury.

In recent years, hopes for better treatment of traumatic brain injury (TBI) have focused on non-pharmacologic transcranial electrical brain stimulation; however, studies of perfusion changes after stimulation are few and contradictory. Therefore, the aim of this study was to assess cerebral perfusion after high-definition transcranial direct current stimulation (HD-tDCS) in patients with posttraumatic encephalopathy (PTE). METHODS: Twenty patients with PTE (16 men and 4 women, aged 35.5 ± 14.8 years) underwent perfusion computed tomography (PCT), followed by anodal HD-tDCS and post-stimulation tomography at 21 days after TBI. The Westermark perfusion maps were constructed and quantitative perfusion parameters calculated. Significance was preset to P < 0.05. RESULTS: Qualitative analysis revealed that all patients had areas with reduced cerebral blood flow (CBF) and increased average mean transit time (MTT). HD-tDCS was accompanied by a significant decrease in the number of zones of both hypoperfusion and ischemia (p < 0.05). Quantitative analysis showed that, in all patients, HD-tDCS caused a significant increase in CBF (p < 0.001), cerebral blood volume (CBV) (p < 0.01) and MTT shortening (p < 0.05) in the frontotemporal region on the anode side. In the basal ganglia, a significant increase in CBF was found only in the five patients in whom this was initially reduced (p < 0.01) and only with an anode placed on the same side. CONCLUSIONS: In patients with complications due to PTE TBI, HD-tDCS causes a significant increase in CBV, CBF and a decrease in the average MTT, suggesting better oxygen delivery to tissue.

Comparison of Two Algorithms for Analysis of Perfusion Computed Tomography Data for Evaluation of Cerebral Microcirculation in Chronic Subdural Hematoma.

The aim of this work was comparison of two algorithms of perfusion computed tomography (PCT) data analysis for evaluation of cerebral microcirculation in the perifocal zone of chronic subdural hematoma (CSDH). Twenty patients with CSDH after polytrauma were included in the study. The same PCT data were assessed quantitatively in cortical brain region beneath the CSDH (zone 1), and in the corresponding contralateral brain hemisphere (zone 2) without and with the use of perfusion calculation mode excluding vascular pixel 'Remote Vessels' (RV); 1st and 2nd analysis method, respectively. Comparison with normal values for perfusion indices in the zone 1 in the 1st analysis method showed a significant (p < 0.01) increase in CBV and CBF, and no significant increase in MTT and TTP. Use of the RV mode (2nd analysis method) showed no statistically reliable change of perfusion parameters in the microcirculatory blood flow of the 2nd zone. Maintenance of microcirculatory blood flow perfusion reflects the preservation of cerebral blood flow autoregulation in patients with CSDH.

Intrahospital Transfer of Patients with Traumatic Brain Injury: Increase in Intracranial Pressure.

AIM: To assess the dynamic of intracranial pressure (ICP), cerebral perfusion pressure (CPP), and dynamic pressure reactivity index (PRx) during intrahospital transport. MATERIALS AND METHODS: There were 33 comatose patients with severe traumatic brain injury (TBI). The mean age was 36.3 ± 4.8 years (range 19-45 years), and there were 17 men and 16 women. The median Glasgow Coma Scale score at admission was 6.2 ± 0.7. Computed tomography (CT) included native CT, perfusion CT, and CT angiography. RESULTS: The mean CPPs before and after the CT scans were 95.9 ± 10.7 and 81.5 ± 12.5 mmHg respectively. The mean ICP before transport was 19.98 ± 5.3 mmHg (minimum 11.7; maximum 51.7). It was statistically significantly lower (p < 0.001) than during the transfer (26.1 ± 13.5 mmHg). During the period described all patients had increased ICP, especially during vertical movement in an elevator. During horizontal movement on the floor ICP remained higher (p < 0.05). The mean dynamic PRx before and after intrahospital transport was 0.23 ± 0.14 and 0.52 ± 0.04, respectively (p < 0.001). Average duration of the transfer and CT study was 15.3 ± 3.4 min. CONCLUSION: Intrahospital transport of patients with TBI may lead to a significant increase in ICP, dynamic PRx, and decreased CPP. The results suppose that the decision to perform brain CT in comatose patients with TBI should be carefully considered by clinicians.

Comparison of Cerebral Oxygen Saturation and Cerebral Perfusion Computed Tomography in Cerebral Blood Flow in Patients with Brain Injury.

The purpose of this study was to determine the relationship between cerebral tissue oxygen saturation and cerebral blood volume in patients with traumatic brain injury. Perfusion computed tomography of the brain was performed in 25 patients with traumatic brain injury together with simultaneous SctO2 level measurement using cerebral near-infrared oxymetry. The mean age of the injured persons was 34.5±15.6 years (range 15-65); 14 men, 11 women. The Injury Severity Score (ISS) values were 44.4±9.7 (range 25-81). The Glasgow Coma Score (GCS) mean value before the study was 10.6±2.1 (range 5-13). SctO2 ranged from 51 to 89%, mean 62±8.2%. Cerebral blood volume (CBV) values were 2.1±0.67 ml/100 g (min 1.1; max 4.3 ml/100 g). Cerebral blood flow (CBF) was 31.99±13.6 ml/100 g×min. Mean transit time (MTT) values were 5.7±4.5 s (min 2.8; max 34.3 s). The time to peak (TTP) was 22.2±3.1 s. A statistically significant correlation was found between SctO2 level and cerebral blood volume (CBV) level (R=0.9; p<0.000001). No other significant correlations were found between brain tissue oxygenation and other parameters of brain perfusion.

Cerebrovascular Time Constant in Patients with Head Injury.

The cerebrovascular time constant (τ) theoretically estimates how fast the cerebral arterial bed is filled by blood volume after a sudden change in arterial blood pressure during one cardiac cycle. The aim of this study was to assess the time constant of the cerebral arterial bed in patients with traumatic brain injury (TBI) with and without intracranial hematomas (IH). We examined 116 patients with severe TBI (mean 35 ± 15 years, 61 men, 55 women). The first group included 58 patients without IH and the second group included 58 patients with epidural (7), subdural (48), and multiple (3) hematomas. Perfusion computed tomography (PCT) was performed 1-12 days after TBI in the first group and 2-8 days after surgical evacuation of the hematoma in the second group. Arteriovenous amplitude of regional cerebral blood volume oscillation was calculated as the difference between arterial and venous blood volume in the "region of interest" of 1 cm(2). Mean arterial pressure was measured and the flow rate of the middle cerebral artery was recorded with transcranial Doppler ultrasound after PCT. The time constant was calculated by the formula modified by Kasprowicz. The τ was shorter (p = 0.05) in both groups 1 and 2 in comparison with normal data. The time constant in group 2 was shorter than in group 1, both on the side of the former hematoma (р = 0.012) and on the contralateral side (р = 0.044). The results indicate failure of autoregulation of cerebral capillary blood flow in severe TBI, which increases in patients with polytrauma and traumatic IH.