Approximately 9 million to 15 million people in the U.S. suffer from recurrent bouts of dizziness and 3 million experience symptoms of dizziness nearly every day. According to a paper that appears in the February issue of Archives of Otolaryngology - Head & Neck Surgery, researchers at the University of Pennsylvania School of Medicine found that chronic subjective dizziness (CSD) may have several common causes, including anxiety disorders, migraine, mild traumatic brain injuries, and neurally mediated dysautonomias - disorders in the autonomic nervous system, which controls involuntary actions.

Among the various forms of dizziness, clinicians have found CSD to be particularly vexing. "Patients with CSD experience persistent dizziness not related to vertigo, imbalance, and hypersensitivity to motion, which is heightened in highly visual settings, such as walking in a busy store or driving in the rain," says Jeffrey P. Staab, MD, MS, Assistant Professor, Departments of Psychiatry and Otorhinolaryngology at Penn, and coauthor of the paper.

Staab and coauthor, Michael J. Ruckenstein, MD, Associate Professor Department of Otorhinolaryngology at Penn, studied 345 men and women age 15 to 89 (average age 43.5) who had dizziness for three months or longer due to unknown causes. From 1998 to 2004, the patients were tracked from their referral to Penn's balance center through multiple specialty examinations until they were given a diagnosis.

"All but six patients were diagnosed as having psychiatric or neurologic conditions, including primary or secondary anxiety disorders, migraine, traumatic brain injury and neurally mediated dysautonomias," said Ruckenstein. Most patients (59.7%) had CSD with anxiety, 38.6% had CSD and illnesses of the central nervous system (migraine, traumatic brain injuries, or dysautonomias), and 1.7% had CSD and irregular heartbeats.

Two-thirds of patients had medical conditions associated with the onset of dizziness, whereas one-third had anxiety disorders as the initial cause. Therefore, CSD may be triggered by either neurotologic or psychiatric conditions.

Key diagnostic features were identified in the clinical history for each illness. For example, those with migraines often had nausea or vomiting, anxiety disorders were associated with fear and worry, and those with dysautonomias tended to become dizzy when they exerted themselves. "Careful inquiry about these key features during exams may lead to better diagnoses and more specific treatment recommendations for the many patients with chronic dizziness who have not found a cause for their symptoms and those who have been given diagnoses that have not brought them relief," says Staab.