Attentional Deficits In Medication Overuse Headache:Neurophysiological And Behavioral Evidence

BackgroundMedication overuse headache (MOH) is a chronic secondary headache and a common problem in clinics. Its exact pathogenesis is still unkown. There are many studies aiming at the pathogenesis of MOH from different perspectives including molecular genetics, biochemistry, functional imaging and psychology. While attention is crucial in the process of pain perception, and tightly correlated with substance use disorders, there is no study in attention of patients with MOH. In addition, most previous studies in primary headaches suggested a deficit in voluntary attention. The study in substance use disorders might suggest a deficit of visuospatial attention in patients with MOH. Taken together, we might hypothesize that patients with MOH have a deficit in attention. However, previous researchers attached little importance to the involuntary attention. Most of them focused on one but neglected another part of attention. There was no overall research in attention. Furthermore, they ignored the influence of anxiety, depression on attention. Therefore, we would like to evaluate the involuntary attention and visuospatial attention in MOH. We hoped to determine whether there was a deficit of attention in MOH by a combined design of local and global, time and space assessment of attention. Aims1. To explore the preattentive processing of patients with MOH.2. To explore visuospatial attention of patients with MOH.3. By comparing with the attention function of chronic tension-type headache (CTTH) patients and evaluating the levels of anxiety and depression of all patients and healthy volunteers, we would like to look for possible deficit in attention of MOH patients.Methods1. Auditory frequency deviance elicited mismatch negativity was recorded from22patients with CTTH,26with MOH from underlying CTTH and41healthy volunteers as controls. Their depression and anxiety scores were also noted. Two-way ANOVA was used to analyze the latencies and amplitudes of Nl to standard and deviant tones, and of MMN at the three midline electrodes (Fz, Cz, and Pz), and to analyze the gender effects on these parameters. Whenever a significant main effect was found, a post-hoc LSD test was performed to evaluate between-group differences for the corresponding parameter.2. We administered the line bisection test and measured anxiety and depression levels in21patients with MOH,26patients with CTTH and in22healthy volunteers. The mean Index and Net in the three groups were submitted to one-way ANOVA. Whenever a significant main effect was found, a post-hoc LSD test was performed to evaluate between-group differences for the corresponding parameter.3. One-way ANOVA was used to analyze the levels of anxiety and depression. We used the Spearman rank order correlation to search for possible relationships between MMN latency/amplitude and age, education level, anxiety, depression, and headache history. Regarding MMN latency/amplitude, only the correlations which were significant at all three midline electrodes, were considered stable and meaningful. The Spearman rank order correlation was also used to search for possible relationships between the Index/Net and age, education, anxiety, depression level, or headache duration (in months).Results1. In MMN test, there were no significant differences in the Nl latency or amplitude to both standard and deviant stimuli for different groups. However, the latency and amplitude of MMN were significantly shortened and reduced at Fz, Cz, and Pz in MOH as compared to CTTH and healthy volunteers.2. In line bisection test, MOH patients significantly bisected leftward when referring to both frequency and magnitude, whereas the healthy volunteers and CTTH patients bisected slightly rightward.3. Anxiety level and depression levels were elevated in MOH patients compared to healthy controls but they were neither correlated with MMN latency or amplitude, nor correlated with Index or Net.Conclusions1. In patients with MOH, the shortened MMN latency indicates quicker involuntary preattention switching to auditory change, while its reduced amplitude indicates decreased neuronal resources assigned per se.2. Through line bisection test, we found a pronounced right hemineglect in MOH. It might indicate a relatively hyperactive right or hypoactive left hemisphere, or both in MOH, suggesting its neuropsychological mechanism might overlap with that of drug dependence.3. The findings demonstrated a high comorbidity of both anxiety and depression in MOH. However, neither latency/amplitude of MMN, nor Index/Net were correlated with anxiety and depression levels, headache pain, headache duration, suggested our findings in MOH be specific. They also indirectly suggested that MOH might share a common neuropsychological mechanism with the substance use disorder.