Unilateral vestibular disorder. The UVD is a common cause of dizziness and disequilibrium associated with head movement. The most common etiology is VN (Baloh, 2003; Xxx et al., 2022) which accounts for 7% of visits to vertigo clinics (Xxxxxx and Xxxxxx, 2009). Other etiologies include blast trauma (Xxxxxxx et al., 2011), neoplasms (Xxxxxxxxx et al., 2003), iatrogenic causes, and cholesteatoma. People with an acute UVD may present with various symptoms including vertigo, nausea and/or vomiting, postural and gait abnormalities, ocular torsion, and a spontaneous horizontal nystagmus. The severity of the symptoms very much depends on the condition. For example, if VN or VL is caused as a viral infection or surgical accident, people may experience sudden severe symptoms (Bae et al., 2022). However, there are other conditions such as acoustic neuromas which involve slow progression of vestibular nerve pathology, thus, may cause less severe symptoms. In most cases with acute UVD, initially the vertigo may be constant, and people tend to lean their head and trunk towards the side of the lesion (Curthoys and Xxxxxxxx, 1995). The spontaneous nystagmus is often towards the affected side. For the first weeks, people experience severe unsteadiness in situations which require vestibular input for orientation. Clinically, the Xxxxxxx test may result in fall and past pointing towards the side of the lesion (Xxxxxx and Xxxxxx, 1980; Xxxxxx, 2000). People will often feel confused about the direction of their imbalance. In terms of their eye-head co- ordination, this is usually disturbed both during active and passive head movements such as in voluntary head turns and HIT during clinical examination, respectively. These intense symptoms experienced by people following an acute episode of VN or VL, usually resolve spontaneously within a short period of time in most cases (Black et al., 1989; Xxx et al., 2022) and most people will be able to compensate well within 6-8 weeks. However, even in people who compensated well, a slightly increased ocular torsion and spontaneous nystagmus in the dark may be seen (Xxxxx et al., 1997). People often recover faster and better in their static than dynamic balance. Xxxxx and Xxxxx (2003) showed that people regained quicker the control of their trunk in static tasks such as standing with feet together or on one leg, compared to dynamic gait tasks including climbing stairs and tandem (heel-toe) walking which were abnormal even after three months. A percentage of people aft...
