Persistent postural-perceptual dizziness: A functional neuro-otologic disorder

Persistent postural-perceptual dizziness (PPPD) is a functional neuro-otologic disorder that is the most frequent cause of chronic vestibular syndrome. The core vestibular symptoms include dizziness, unsteadiness, and non-spinning vertigo, which are exacerbated by an upright posture or walking, active or passive motion, and exposure to moving or complex visual stimuli. PPPD is mostly precipitated by acute or episodic vestibular diseases; however, its symptoms cannot be accounted for by its precipitants. PPPD is not a diagnosis of exclusion, but may coexist with other structural diseases. Thus, when diagnosing PPPD, the patient's symptoms must be explained by PPPD alone or by PPPD in combination with a structural illness. PPPD is most frequently observed at approximately 50 years of age, with a female predominance. Conventional vestibular tests do not reveal any specific signs of PPPD. However, the head roll-tilt subjective visual vertical test and gaze stability test after exposure to moving visual stimuli may detect the characteristic features of PPPD, that is, somatosensory- and visually-dependent spatial orientation, respectively. Therefore, these tests could be used as diagnostic tools for PPPD. Regarding the pathophysiology of PPPD, neuroimaging studies suggest shifts in interactions among visuo-vestibular, sensorimotor, and emotional networks, where visual inputs dominate over vestibular inputs. Postural control also shifts, leading to the stiffening of the lower body. To treat PPPD, selective serotonin reuptake inhibitors/serotonin noradrenaline reuptake inhibitors, vestibular rehabilitation, and cognitive behavioral therapy are used alone or in combination.