Dysphagia is an impairment in the process of transferring food boluses or liquids from the oral cavity to the stomach (Wilkins et al., 2007), which can present as difficulty in swallowing, coughing, choking, or aspiration. It is one of the debilitating symptoms in demyelinating diseases such as neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) (Wilkins et al., 2007; Panebianco et al., 2020; Carnero Contentti and Correale, 2021). Involvement of the brain, especially brainstem structures such as medulla oblongata (MO) can manifest as dysphagia in these disorders (Panebianco et al., 2020).

While dysphagia has been well studied in MS patients, there is limited research on dysphagia in NMOSD patients, and previous studies on dysphagia in NMOSD patients have mostly been case reports. (Alshurafa and Alkhateeb, 2020; Li et al., 2016; Pan et al., 2022; Wang et al., 2014; Jarius et al., 2016; Milewska et al., 2020; He et al., 2022; Chan et al., 2011; Kremer et al., 2014). Most of them emphasized the presence of dysphagia due to brain involvement (Wang et al., 2014; Jarius et al., 2016; Chan et al., 2011; Kremer et al., 2014; Pawlitzki et al., 2021; Turkoglu et al., 2012). Wang et al. reported that 29.5 % of NMOSD patients with MO lesions experienced dysphagia, compared to 1.6 % of NMOSD patients without MO lesions. These patients also experienced higher disability scores (Wang et al., 2014). Although there was an association between dysphagia and other clinical presentations of brain involvement such as nausea, vomiting, vertigo, hiccups, or dysarthria (Chan et al., 2011), no association was seen with concordant MRI findings (Pawlitzki et al., 2021). It was also found that dysphagia can rarely be seen as an isolated symptom (Turkoglu et al., 2012). Patients with either positive or negative results for aquaporin-4 antibody (AQP4-Ab) can have dysphagia. Jarius et al. reported that 3 out of 15 cases of AQP4-Ab-negative patients with brainstem involvement experienced dysphagia (Jarius et al., 2016). In another report by Milewska et al., dysphagia was present in half (4/8) of the NMOSD patients (Milewska et al., 2020). However, the prevalence of dysphagia and the related risk factors have been evaluated in small samples of NMOSD patients so far. In MS patients, the prevalence of dysphagia was estimated to be 43.33 %. Moreover, this prevalence was 37.21 % and 58.47 %, using subjective and objective methods, respectively (Aghaz et al., 2018). Mirmossayeb et al. also reviewed recent studies, achieving almost similar results (44.8 %, 95 %CI: [40.4 %−49.2 %]) (Mirmosayyeb et al., 2023).

Dysphagia can have serious consequences, such as reduced quality of life (QoL) (Opara et al., 2010). Quality of Life (QoL) is a multidimensional construct of physical, mental, and social domains. Dysphagia can affect the physical, psychological, and social aspects of QoL and the pleasure of eating. The effect of swallowing impairment on QoL in MS patients was evaluated in limited studies. The swallowing-related QoL in MS patients is reduced the presence of dysphagia according to the Alali et al. study (Alali et al., 2018). Approximately 60 % of dysphagic MS patients found this symptom a major distraction in their lives, and 50 % of them declared that dysphagia has affected their mental health. The change in QoL in NMOSD patients in the presence of dysphagia has not been evaluated yet.

This study aimed to compare the frequency of dysphagia as well as its effect on health- and swallowing-related QoL between patients with moderate to severe NMOSD and MS and control group. In addition, the relationship between dysphagia and different clinical characteristics such as disease type, disease duration, and disability status was also assessed.