Morphometric evaluation of the delayed cerebral arteries response to acetazolamide test in patients with chronic carotid artery stenosis using computed tomography angiography

Background: The evidence accumulates that the response to acetazolamide test is delayed on the ipsilateral side to stenosis. However, the effect of acetazolamide beyond 30 min after acetazolamide administration remains unknown. The aim of this study was to assess the diameters of anterior cerebral arteries (ACAs), middle cerebral arteries (MCAs) and posterior cerebral arteries (PCAs) before and 60 min after the acetazolamide test. Materials and methods: Seventeen patients with carotid artery stenosis ≥ 90% on the ipsilateral side and ≤ 50% on the contralateral side were enrolled into the study. Diagnosis was based on ultrasonography examination and was confirmed using digital subtractive angiography. In all patients, two computed tomography angiography examinations were carried out; the first was performed before the acetazolamide administration, while the second one was carried out 60 min after injections. Results: In response to the acetazolamide test: PCA diameter diminished in both ipsi- and contra-lateral side to stenosis (from 1.31 to 1.24 mm and from 1.23 to 1.15 mm, respectively), ACA and MCA decreased in the contralateral side to the stenosis (from 1.33 to 1.26 mm and from 2.75 to 2.66 mm, respectively), ACA and MCA increased in the ipsilateral side to the stenosis (from 1.29 to 1.46 mm and from 2.77 to 2.96 mm, respectively). All changes were statistically significant. Conclusions: There were significant differences in reactivity to acetazolamide challenge between the internal carotid artery (ICA) and vertebrobasilar circulation in patients suffering from chronic carotid artery stenosis. Within the ICA territory, ACA and MCA responses vary in the affected and not affected side.

Subarachnoid Space: New Tricks by an Old Dog

PURPOSE: The purpose of the study was to: (1) evaluate the subarachnoid space (SAS) width and pial artery pulsation in both hemispheres, and (2) directly compare magnetic resonance imaging (MRI) to near-infrared transillumination/backscattering sounding (NIR-T/BSS) measurements of SAS width changes in healthy volunteers. METHODS: The study was performed on three separate groups of volunteers, consisting in total of 62 subjects (33 women and 29 men) aged from 16 to 39 years. SAS width was assessed by MRI and NIR-T/BSS, and pial artery pulsation by NIR-T/BSS. RESULTS: In NIR-T/BSS, the right frontal SAS was 9.1% wider than the left (p<0.01). The SAS was wider in men (p<0.01), while the pial artery pulsation was higher in women (p<0.01). Correlation and regression analysis of SAS width changes between the back- and abdominal-lying positions measured with MRI and NIRT-B/SS demonstrated high interdependence between both methods (r = 0.81, p<0.001). CONCLUSIONS: NIR-T/BSS and MRI were comparable and gave equivalent modalities for the SAS width change measurements. The SAS width and pial artery pulsation results obtained with NIR-T/BSS are consistent with the MRI data in the literature related to sexual dimorphism and morphological asymmetries between the hemispheres. NIR-T/BSS is a potentially cheap and easy-to-use method for early screening in patients with brain tumours, increased intracranial pressures and other abnormalities. Further studies in patients with intracranial pathologies are warranted

Coupling between blood pressure and subarachnoid space width oscillations during slow breathing

The precise mechanisms connecting the cardiovascular system and the cerebrospinal fluid (CSF) are not well understood in detail. This paper investigates the couplings between the cardiac and respiratory components, as extracted from blood pressure (BP) signals and oscillations of the subarachnoid space width (SAS), collected during slow ventilation and ventilation against inspiration resistance. The experiment was performed on a group of 20 healthy volunteers (12 females and 8 males; BMI= 22.1 ± 3.2 kg/m2; age 25.3 ± 7.9 years). We analysed the recorded signals with a wavelet transform. For the first time, a method based on dynamical Bayesian inference was used to detect the effective phase connectivity and the underlying coupling functions between the SAS and BP signals. There are several new findings. Slow breathing with or without resistance increases the strength of the coupling between the respiratory and cardiac components of both measured signals. We also observed increases in the strength of the coupling between the respiratory component of the BP and the cardiac component of the SAS and vice versa. Slow breathing synchronises the SAS oscillations, between the brain hemispheres. It also diminishes the similarity of the coupling between all analysed pairs of oscillators, while inspiratory resistance partially reverses this phenomenon. BP-SAS and SAS-BP interactions may reflect changes in the overall biomechanical characteristics of the brain