The Assessment and Treatment of Balance Impairment Using Virtual Reality (VR) in Panic Disorder Patients

Introduction

Anxiety disorders are a group of ailments, which are characterized by excessive and abnormal vague senses of apprehension followed by stress and restlessness (Berrios 1999). As a group, anxiety disorders were found to have the highest lifetime prevalence, i.e. they are the most commonly occurring class of mental disorders (Kessler et al. 2010) with 17.7% prevalence in a year (Kessler et al. 2005). This group of disorders consists of five main mental disorders: specific phobia, obsessive-compulsive, post-traumatic stress, generalized anxiety and panic disorder - which the investigators will be focusing on.

Panic disorder (PD) is a chronic ailment characterized by spontaneous, unexpected occurrence of panic attacks, i.e. periods of intense fear, which vary dramatically in the recurrence of panic attacks between patients and within a patient, ranging from a few per day to a few per year (American Psychiatric Association 2000). PD often occurs in conjunction with agoraphobia, i.e. the fear and avoidance from situations and settings they perceive they have little control on, such as public places and 'suffocating' surroundings (Kessler et al. 2005). PD can reach a lifetime prevalence of 5% (Kessler et al. 2010) and above (Serretti et al. 2011) and women are two to three times more likely to be affected than men (Schumacher et al. 2011). PD mostly develops in young adulthood (25y mean age), however this is not mandatory as onset during childhood or early adolescence most likely remains undiagnosed (Schumacher et al. 2011). Individuals suffering from PD are also said to have a deregulated autonomic nervous system at rest and during orthostatic challenge (i.e. tilt test), displayed by heightened heart rate and diastolic blood pressure compared to those of healthy controls (Martinez et al. 2010).

Many years of research have been invested in seek of an association between anxiety or PD and impaired physical balance (Perna et al. 2001; Sklare et al. 2001; Staab and Ruckenstein 2003; Staab 2006; Redfern et al. 2007). Many times the treatment of anxiety disorders in general, and PD among them, which target limbic areas, fail to succeed; thus it is recommended to treat the comorbid balance impairment, which its treatment alone can ameliorate anxiety (Shefer et al. 2010). Literature on the subject has indicated high prevalence of comorbid balance disorders and anxiety in general (Alvord 1991; Balaban and Jacob 2001; Kalueff et al. 2008) as well as anxiety disorders specific ranging from agoraphobia, panic attack and generalized anxiety (Alvord 1991; Balaban and Jacob 2001; Balaban and Thayer 2001; Jacob and Furman 2001). Anxiety in general and PDs are a common co-morbidity in acute and chronic vestibular disorders (Eagger et al. 1992; Matheson et al. 1999; Jacob and Furman 2001; Pollak et al. 2003), evolving from vestibular deficiency or sensorimotor disintegration. In spite of abundant literature supporting anxiety-imbalance relationship, it is still uncertain whether they are causality related.

Further investigation on the subject revealed that individuals who suffer from PD may also display altered cognitive patterns (Casey et al. 2004; Starcevic and Berle 2006). In addition, last decade research in the cognitive field has been dedicated to evaluating cerebellar involvement (Andreasen and Pierson 2008). Studies in animal models (Brodal et al. 1991; Dum and Strick 2003; Kelly and Strick 2003) have shown cerebellar connection to the frontal cortex through the pons and thalamus, suggesting its participation in neural circuits mediating higher cognitive functions. While cerebellar lesions in animals have indicated motor coordination and motor learning impairments (Thach 1996; Bastian et al. 1998), studies in humans have assigned the cerebellum a role in time intervals perception (Akshoomoff and Courchesne 1992), rhythm sequences imitation (Fiez et al. 1995) and associative learning (Attwell et al. 2002). Hence, the cerebellum seems to act as a modulator of cognitive processes performed by the cerebral cortex, which detects patterns and pattern changes as well as errors in both motor and cognitive functions and feedbacks the cerebrum (Andreasen and Pierson 2008).