Vertigo is a phantasm of movement, mostly that of whirling motion, though patients may describe it as a feeling of linear movement or tilt [1]. Peripheral vestibular vertigo is induced by abnormalities of the peripheral vestibular system, semicircular canals, and vestibular nerves. It is mostly caused by dislodging otoconia, endolymphatic hydrops, inner ear viral infection, or trauma of the bony labyrinth or the oval and round window. Vertigo can present as a collection of symptoms consisting of dizziness, nausea, vomiting, nystagmus and unsteadiness.
Complaints of vertigo affect about 20–30% of the general population, and is more likely to affect females [2]. Vertigo is more frequent in the elderly relative to younger age groups and is the most common complaint in people over 75 years [3]. About 80% of people who experience vertigo report that the complaint interferes with their daily activities, as it impedes with the ability to work, and results in an increased risk of falling and the high use of health services with downstream impact on economic costs [4].
The severity index of vertigo is often measured by the intensity and frequency of the vertigo attacks. However, severity is a multidimensional concept that may not be fully explained solely by the intensity and frequency of symptoms. Emotional, functional and physical disturbances caused by vertigo can be assessed by the Dizziness Handicap Inventory (DHI) score [5]. In 2004, Whitney et al. conducted a study on the degree of dizziness using the DHI questionnaire and classified it as mild (0–30), moderate (31–60), severe (61–100) in relation to performance in people with vestibular disorders [6]. The authors concluded that patients perceiving high handicap scores show greater functional impairment than patients with low handicap scores. In addition, another study reported an association between balance function and DHI in people with peripheral vestibular disorders, in which a high DHI score correlated with a high risk of falls [7]. The DHI itself is a widely used self-reporting questionnaire that has been utilized to evaluate dizziness, and has been translated into several languages with excellent psychometric validity, reliability and internal consistency in all translations [8,9,10]. In BPPV assessment specifically, the DHI showed 75% sensitivity and 92% negative predictive value (NPV) in reference to Dix–Hallpike tests [11].
Several studies have reported the correlation between vertigo, stress, and inflammation. In 2014, Gucluturk et al. [8] reported a link between inflammation and vertigo, in which they found increased pre-inflammatory mediators in patients with benign paroxysmal positional vertigo (BPPV) [12]. Other studies have also reported relationships between stress-related inflammation with the mechanism of peripheral vertigo [13, 14]. In a study on patients with vestibular neuritis, it was observed that the inflammatory process induced an increase in peripheral blood mononuclear cells that play a role in thrombotic processes in the tubular microvascular circulation, resulting in impaired vestibular function and manifesting as vertigo [14].
Several markers of inflammation have been evaluated in vertigo. The immune response to inflammation often has characteristic features, including an increase in the number of neutrophils and a decrease in the number of lymphocytes. A decrease in lymphocyte levels (lymphocytopenia) is a marker of a decline in the immune system, and occurs due to the redistribution of lymphocyte cells into the lymphatic system and accelerated apoptosis [15]. An example of early investigations into the dynamics of increasing neutrophil values and decreasing lymphocyte values reported that the severity of clinical status and clinical outcomes in 90 ICU oncology patients correlated with the neutrophil to lymphocyte ratio (NLR), the intensity of neutrophilia, and lymphocytopenia [16]. The NLR is a frequently assessed marker in non-infectious inflammatory diseases, and is obtained by dividing the absolute or relative number of neutrophils by the absolute or relative number of lymphocytes. Although some variations exist, the normal range of NLR in a healthy adult population has been reported to be between 0.78 and 3.53 [17].
A study conducted by Ozbay et al. in 2014 reported an increase in the mean NLR value in peripheral vertigo patients compared to healthy controls [13]. In another study, it was reported that there was a two-fold increase in the mean NLR value in patients with vestibular neuritis (3.31 ± 2.02) relative to controls (1.60 ± 0.71), indicating that NLR values may reflect an inflammatory process and could be considered as a simple, reliable parameter to assess the severity of vestibular neuritis [14]. This was supported by another study, which concluded that increased levels of the NLR support the role of inflammation in patients with vestibular neuritis, although these inflammatory markers are not specific to support the diagnosis of vestibular neuritis [12].
The mechanisms behind NLR increase in peripheral vestibular disorders may be related to the physical and psychological stress that lead to increased expression of corticotropin releasing hormone (CRH). CRH overexpression stimulates sympathetic activity in the locus coeruleus of the brain stem by the release of catecholamines, and may result in symptoms such as pale, cold skin and vertigo [18, 19]. Subsequent increase of parasympathetic activity then arises as a reciprocal inhibitory mechanism, which causes symptoms of nausea and vomiting. CRH overexpression also causes the release of cortisol through the hypothalamus-pituitary-adrenocortical axis (HPA axis), leading to an increase in neutrophil activation [20], a decrease in lymphocyte levels, and eventually resulting in higher NLR levels [21].
Although many studies have assessed the levels of NLR in peripheral vestibular vertigo, it is still unclear whether or not the NLR parameter is related to vertigo severity. Hence, this study aimed to assess the differences in the NLR levels of patients with peripheral vestibular vertigo of various DHI severity categories.
