How vestibular dysfunction transforms into symptoms of depersonalization and derealization

Depersonalization and Derealization (DPDR) is a psychiatric disorder characterized by a sense of unreality and detachment from one’s surroundings, body, emotions, and self. The physical processes vary and include problems with sensory function that alter one’s perception of reality. Vestibular (inner ear) sensory dysfunction contributes to DPDR symptoms, as it interferes with a person’s perception of their posture and surroundings, and movement of themselves in relation to their surroundings.

The inner ear contains two divisions: 1) the peripheral vestibular system, which consists of the hearing and vestibular organs in the ear, and 2) the central vestibular system, which consists of the brain and brainstem, and is involved in processing and integrating information from the peripheral vestibular system.  Peripheral vestibular dysfunction may bring about DPDR disorder. However, there is a lack of information on DPDR symptoms in disorders that include central (nervous system) vestibular dysfunction. This paper investigates whether DPDR may develop due to central vestibular hypofunction, such as in Machado Joseph Disease (MJD), and how vestibular dysfunction may develop into DPDR disorder.

The paper creates a concept of the “Three-Stage Model of DPDR”:

1. In the 1st stage, patients develop peripheral vestibulopathy.
2. In the 2nd stage, vestibulopathy leads to spatial disorientation and panic anxiety:
   1. Spatial disorientation results from changes to the hippocampus and temporal-parietal junction of the cortex, which provides information about self-motion, self-location, and self-relation to objects in space.
   2. Panic anxiety may be related to an abnormal autonomic state and reactivity in response to vestibular dysfunction.
3. In the 3rd stage, DPDR symptoms develop in response to the combined effect of spatial disorientation and panic anxiety:
   1. Panic anxiety increases the attention to abnormal spatial perception and bodily sensations, interpreted as symptoms of DPDR.

The vestibular system consists of two main components: the semi-circular canals and the otolith organs.  The semi-circular canals are a series of tubes that sense rotational movement.  The otolith organs consist of sacs that sense gravity and change in linear (backwards and forwards) motion.  Patients with chronic (ongoing) peripheral vestibulopathy demonstrated reduced function of all six semi-circular canals (SCCs) of the inner ear, as well as spatial disorientation, anxiety, and other DPDR symptoms.  Spatial disorientation and anxiety together can lead vestibulopathy to develop into DPDR symptoms.  On the other hand, although patients with MJD demonstrated impaired function of all 6 SCCs and spatial disorientation, they showed normal otolith function and no anxiety or DPDR symptoms. These findings indicate that spatial disorientation and anxiety are prerequisites (required) for developing DPDR symptoms. Therefore, in the absence of panic anxiety, MJD central vestibulopathy is not necessarily converted into DPDR symptoms.

Studies of DPDR in vestibular patients have typically focused on SCCs functioning. This study tested both the SSCs and otoliths to evaluate their relative contribution to the beginning of DPDR symptoms, and their findings suggest that otolith dysfunction can generate DPDR symptoms. Otolith dysfunction creates spatial disorientation and anxiety by unsettling the activity of the hippocampus and TPJ. As the otoliths are the primary direct sensors of gravitational forces (gravity) and contribute to a person’s perception of being upright, dysfunction distorts this perception, causing anxiety and contributing to DPDR symptoms.

In conclusion, peripheral (inner ear), but not central (nervous system), vestibulopathy leads to DPDR symptoms. Specifically, otolith dysfunction, either with or without SSCs dysfunction, promotes DPDR symptoms. Finally, this paper proposes a three-step model for the development of DPDR in peripheral vestibulopathy: 

1. Patients develop peripheral vestibulopathy.
2. Vestibulopathy leads to spatial disorientation and panic anxiety;
3. DPDR symptoms develop in response to the combined effect of spatial disorientation and panic anxiety.

Source: Elyoseph, Z., Geisinger, D., Zaltzman, R., Gordon, C. R., & Mintz, M. (2023). How vestibular dysfunction transforms into symptoms of depersonalization and derealization? Journal of the Neurological Sciences, 444, 120530. https://doi.org/10.1016/j.jns.2022.120530

Summary by Sonia Vovan, PT, BHSc, MScPT