An increase in certain chemicals in the brain may be causing movement problems in some people, according to a study published in the journal Neurology.

Experts call these movement problems functional motor symptoms. These include tremors, muscle contractions and difficulty walking. These symptoms are primarily considered a psychological issue although their precise cause is still unknown. The study, on the other hand, provides a new perspective on the nature of functional motor symptoms.

“These findings suggest that these abnormal chemical changes in the brain could play a key role in functional motor symptoms, ultimately leading to the abnormal movements,” said Alberto Priori, one of the authors of the study.

Priori also said that treatments targeting these chemical changes can be developed to help manage functional motor symptoms.

What are functional motor symptoms?

Functional motor symptoms are associated with neurological (nervous system-related) disorders. Unlike conditions like stroke, these disorders are not linked to structural damage but have to do with functional issues in the brain. Their exact cause remains unknown, although experts posit that they might be triggered by a reaction to stress or psychological or physical trauma.

Previously, functional motor symptoms were thought to be psychogenic, or caused by psychological reasons. However, many patients display these symptoms in the absence of emotional stressors, so experts have abandoned this notion. It is now clear that a person can be affected by neurological disorders without being depressed, anxious or traumatized.

However, diagnosing and treating patients with neurological disorders can be difficult. Brain scans, for example, often show that a person with functional motor symptoms has a structurally normal brain. Moreover, the lack of clear neurologic conditions, such as a seizure disorder, stroke or Parkinson’s disease, compels neurologists to think they have nothing to treat in a patient.

“These are challenging patients to interview,” said Dr. David L. Perez, the director of the Functional Neurology Research Group at Massachusetts General Hospital. “They require more time than many other neurological problems and patients often have high rates of psychiatric [comorbidities].”

Chemical changes in the brain cause movement problems

For their study, Priori and his team compared the brain scans of 10 patients with functional motor symptoms with those of 10 healthy people. But instead of the usual imaging technique, they used magnetic resonance spectroscopy, which measures the concentrations of various compounds in the brain.

The researchers also asked the participants to take tests for depression, anxiety, quality of life and alexithymia, a condition characterized by a failure to identify and describe emotions experienced by oneself.

The researchers found that people with functional motor symptoms had four times the levels of glutamate and glutamine in the limbic areas of their brains than healthy people. They also noticed that this was specific only to the limbic areas; glutamate and glutamine levels remained normal in other brain regions.

Upon analyzing the results of the psychological tests, the researchers found that people with functional motor symptoms had high scores for depression, anxiety and alexithymia, and low scores for quality of life. Those with high neurochemical abnormalities in the brain suffered from worse motor, anxiety and alexithymia symptoms.

These findings suggest that the abnormal increase in glutamate and glutamine in limbic areas of the brain plays a crucial role in the development of functional motor symptoms. As such, controlling the levels of these brain chemicals may be a promising strategy for treating functional motor symptoms.