Altered Neurovascular Coupling in Unilateral Pulsatile Tinnitus

Altered neurovascular coupling in migraine without aura

Neurovascular coupling (NVC) provides new insights into migraine, a neurological disorder impacting over one billion people worldwide. This study compared NVC and cerebral blood flow (CBF) in patients with migraine without aura (MwoA) and healthy controls. About 55 MwoA patients in the interictal phase and 40 age- and sex-matched healthy controls underwent resting-state functional magnetic resonance imaging and arterial spin-labeling perfusion imaging scans. The CBF and resting-state neuronal activity indicators, including the amplitudes of low-frequency fluctuation (ALFF), regional homogeneity (ReHo), and degree centrality (DC), were calculated for each participant. The global and regional NVCs were assessed using cross-voxel CBF-neuronal activity correlations and CBF/neuronal activity ratios. Patients with MwoA showed increased CBF/ALFF ratios in the left media, superior and inferior frontal gyri, and anterior cingulate gyrus, increased CBF/DC ratios in the left middle and inferior frontal gyri, and increased CBF/ReHo ratios in the right corpus callosum and right posterior cingulate gyrus. Lower CBF/ALFF ratios in the right rectal gyrus, the left orbital gyrus, the right inferior frontal gyrus, and the right superior temporal gyrus were also found in the MwoA patients. Furthermore, the CBF/ALFF ratios in the inferior frontal and superior temporal gyri were positively correlated with the Headache Impact Test scores and Hamilton anxiety scale scores in the MwoA patients. These findings provide evidence for the theory that abnormal NVC contributes to MwoA.

Lateralization of cerebral blood flow in the auditory cortex of patients with idiopathic tinnitus and healthy controls: An arterial spin labeling study

Objectives

To assess the lateralization of cerebral blood flow (CBF) in the auditory cortex of idiopathic tinnitus patients and healthy controls (HCs) using 3D pseudocontinuous arterial spin labeling (pcASL).

Methods

Thirty-six patients with idiopathic tinnitus and 43 sex- and age-matched HCs underwent 3D-pcASL scanning using a 3.0 T MRI system. For both groups, region of interest analysis was performed on the primary auditory cortex (PAC), auditory associative cortex (AAC), and secondary auditory cortex (SAC). The clinical data of all subjects were analyzed.

Results

In both tinnitus patients and HCs, CBF of the left PAC was significantly higher than that of the right (HCs: P = 0.02; patients: P = 0.043), but CBF of the right AAC and SAC was significantly higher than that of the left (AAC: HCs, P < 0.001; patients: P < 0.001. SAC: HCs, P < 0.001; patients: P = 0.001). Compared with HCs, tinnitus patients exhibited significantly higher CBF in the bilateral PAC (right: P = 0.008; left: P = 0.022). CBF in the left PAC was positively correlated with tinnitus severity (r = 0.399, P = 0.016).

Conclusion

This study confirms the asymmetry of the auditory cortex and investigates the underlying neuropathology of idiopathic tinnitus in terms of CBF.