Research indicates link between persistent dizziness and anxiety

Functional magnetic resonance imaging of patients suffering from treatment-refractory dizziness suggests exacerbated activity of brain pathways related to anxiety and fear.

By Karina Toledo

Agência FAPESP – Balance, which enables humans to walk on dry land or skim the waves on a surfboard, depends on tiny structures in the inner ear known as the vestibular system. The cochlea, which is dedicated to hearing, and the vestibular system together comprise the labyrinth.

A number of ailments that impair the functioning of the labyrinth, some of which are commonly known as labyrinthitis, may interfere with balance and cause symptoms such as dizziness, which are usually resolved by appropriate treatment lasting between one and three months.

In some patients, however, dizziness persists even after recovery from the underlying disorder of the inner ear and without any other apparent cause. New research carried out at the University of São Paulo’s Medical School (FMUSP) suggests the explanation for these cases may be the anxiety- and fear-related overexcitement of parts of the central nervous system.

“Functional magnetic resonance imaging [fMRI] points to a physiological difference in the brains of these patients. Although their brain structures are identical to those of the control group, the pathways related to anxiety and fear become more active than normal when subjected to certain stimuli,” said Roseli Saraiva Moreira Bittar, a member of the Medical School’s academic staff and coordinator of the ongoing research project, which is supported by FAPESP.

According to Bittar, in these cases – currently classified as persistent postural-perceptual dizziness (PPPD) – labyrinthic disease triggers a balance disorder that cannot be diagnosed and treated by conventional methods.

“Once this trigger is fired, the disease goes into perpetual motion. Any motor, emotional or situational stimulus can activate the anxiety and fear pathways and cause dizziness. These patients feel dizzy when standing, sitting or lying down. They feel as if they were floating or about to fall over. They never feel well and do not get better without specific psychiatric treatment,” Bittar said.

Unlocking the brain’s secrets

The study is in progress at the Medical School’s teaching hospital, Hospital das Clínicas, with the participation of neuroradiologist Edson Amaro Junior and graduate student Eliane Von Sohsten. Dr. Jeffrey Staab, a psychiatrist and member of the Mayo Clinic (USA), is a collaborator.

The scientists are currently engaged in more detailed comparisons between the fMRI scans of patients with PPPD and those of the control group, which is composed of patients whose dizziness resolved after treatment, to discover exactly what works differently in their brain.

The sample includes 16 women aged 18-60 years in each group. According to Bittar, only right-handed women were selected so that the brain functions of all the volunteers can be more easily compared.

Individuals suffering from other diseases that can affect the functionality of the labyrinth, such as diabetes, high blood pressure and thyroid disorders, were excluded. Volunteers were also excluded if their fMRI scans showed alterations in brain structure.

The volunteers were subjected to a number of examinations to prove that the underlying inner ear ailment was in fact controlled, as well as to tests for assessing balance profiles and psychiatric questionnaires used in diagnosing anxiety and depression disorders.

One of the completed studies, involving a sample of 81 male and female volunteers and published in Brazilian Journal of Otorhinolaryngology, showed that patients suffering from PPPD display a profile considered borderline for anxiety and depression.

“Although they cannot be considered mentally ill, they’re far more sensitive than patients in the control group,” Bittar said. “Their questionnaire scores are as much as six times higher.”

Another study in collaboration with Staab, due to be published shortly, showed that patients with PPPD have a different balance profile from that of the control group. According to Bittar, even in ordinary everyday situations, the women displayed an exaggeratedly high level of muscular tension.

“They walk on a normal floor as if they were wearing high heels and teetering on a narrow beam, although they react just like the control group in a situation that presents a real danger of falling,” Bittar said.

Although the research findings are preliminary, they are already leading to significant changes in the treatment of PPPD.

“The great merit of this research is fostering the integration of otoneurology and psychiatry. Previously, neither specialty knew for certain how to proceed with these cases. Patients were often treated with anti-depressants, but only half responded. Today, I can say that more than 90% of my patients are well,” Bittar said.