## 4 Discussion  
The present investigation is one of the first to evaluate the pressure pain threshold (muscle pressure pain sensitivity) of the masticatory muscles and the prevalence of TMD in a group of patients affected by NT1 compared to healthy controls. The groups proved to be homogeneous for age and gender with the expected differences in sleep architecture. The main outcome of this study is represented by the absence of significant differences in the PPTs between the two groups for all the muscles evaluated (Table 2). It is important to underline that no differences were found even in the PPTs of the thenar muscle, which does not belong to the area of the head and neck muscles, thus indicating the absence of central pain sensitization in the sample recruited. No differences emerged for the prevalence of TMD between the two groups either. [PERSON] and coworkers in 2011 investigated chronic pain in patients affected by narcolepsy with cataplexy (NT1) by means of questionnaires and interviews [32]. Subjective pain assessment showed more frequent pain complaints in NT1 patients compared to the controls, a finding unrelated to medication use and significantly related to lower quality of life and depression [32]. The outcomes do not allow a symptomatic cause of pain in NT1 to be formally ruled out, but it is important to consider that depressive symptoms and sleep quantity emerged as significant determinants of the presence of pain. In 2015, [PERSON] evaluated the pain perception in 13 people with NT1 and matched healthy controls using standardized quantitative sensory testing [33], that consists of the assessment of the mechanical detection threshold, vibration detection threshold, warm detection threshold, cold detection threshold, cold pain threshold, heat pain threshold, mechanical pain threshold, and PPT. None of the parameters regarding perception of sensory or painful stimuli differed significantly between the groups, and the authors indicated that the increased pain referred by NT1 patients does not result from an altered perception of sensory or nociceptive stimuli. The outcomes of this study support the presence of a psychological component in NT1 patients' pain reporting. In fact, the N group showed a significant difference in PHQ-9 score, a questionnaire evaluating the depressive state of the subject, indicating a higher prevalence of depressive symptoms in NT1 patients (\(p=0.006\)), which has already been described in studies with a larger sample size [28; 56]. However, the absence of significant differences in the PPTs of head and neck muscles between the two groups does not meet the assumption of a possible modification in NT1 patients' pain thresholds formulated by [PERSON]. These results sustain the findings of [PERSON] and coworkers, with a larger sample size, and support the hypothesis that hypocretin-1 deficiency in NT1 subjects does not lead to dysregulation in the nociception and that EDS does not impair to such an extent that modifies pain perception, although some studies speculate that pain sensitivity is altered in sleepy individuals [57; 58]. Concerning the prevalence of TMD, previous studies described an increased frequency of migraine and tension-type headache [30; 31; 59]. No significant differences emerged \begin{table}
\begin{tabular}{l l l l l} \hline
**Questionnaires** & **Group N (n = 39)** & **Group C (n = 39)** & **X\({}^{2}\)**=** & \(p\)**=** \\ \hline GCPS 2.0 Chronic & 23.1\% (n = 9) & 28.2\% (n = 11) & 0.269 & 0.604 \\ Orofacial Pain & & & & \\ \hline JFLS-20 & 23.1\% (n = 9) & 7.7\% (n = 3) & 4.754 & 0.093 \\ \hline PHQ-9 & 74.4\% (n = 33) & 56.4\% (n = 22) & 20.844 & 0.006 * \\ \hline PHQ-15 & 69.2\% (n = 27) & 66.7\% (n = 26) & 0.059 & 0.808 \\ \hline GAD-7 & 56.4\% (n = 22) & 43.6\% (n = 17) & 1.282 & 0.258 \\ \hline OBC & 56.4\% (n = 22) & 52.6\% (n = 20) & 1.040 & 0.594 \\ \hline \end{tabular}
\end{table} 
Table 4: Comparison of prevalence of over cut-off scores of the Axis II DC/TMD questionnaires between the two groups (X\({}^{2}\) test).