Bidirectional alterations in ALFF across slow-5 and slow-4 frequencies in the brains of postherpetic neuralgia patients

Purpose: Postherpetic neuralgia (PHN) detrimentally affects brain function. Recent studies have suggested that frequency-dependent changes in electroencephalography in chronic pain patients and blood oxygenation level dependent (BOLD) fluctuations can reflect neuronal activity in different frequencies. The current study aimed to investigate PUN-related brain oscillatory activity in a specific frequency band by using the amplitude of low-frequency fluctuation (ALFF) method. Materials and methods: AL FP changes were analyzed across different frequencies (slow-4 band: 0.027-0.073 Hz; slow-5 band: 0.01-0.027 Hz; and typical band: 0.01-0.08 Hz) in the brains of PHN patients and compared with those in the brains of healthy controls (HCs) during resting-state fMRI. Eighteen HCs and PHN patients underwent fMRI scanning. Results: In the typical band, compared with HCs, PHN patients showed prominently decreased ALFF in the right prefrontal cortex (Brodmann area 10/46) and increased ALFF in the bilateral brain stern/cerebellum anterior lobe (BS/CAL). In the slow-4 band, PHN patients exhibited significantly decreased ALFF in the bilateral cuneus/lingual gyrus and the right prefrontal cortex. In the slow-5 band, PHN patients presented significantly increased ALFF in the bilateral 13S/CAL and left parieto-occipital cortex. Moreover, the increased ALIT in the left parieto-occipital cortex in the slow-5 band was positively correlated with VAS scores (P=0.022), and the increased ALIT in the bilateral BS/CAL in the slow-5 band was positively correlated with disease duration (P=0.020). Conclusion: Our results suggested that the intrinsic brain activity of PUN patients was abnormal and frequency dependent, especially the bidirectional alteration in ALFF across the slow-4 and slow-5 frequencies in the brains of PHN patients.