Published by the Students of Johns Hopkins since 1896
July 2, 2022

MRI side-effects uncover vertigo diagnostic

By MARU JAIME GARZA | April 3, 2014

Magnetism is the attractive force between positive and negative charges. In our everyday lives, we see it as what makes souvenirs stick on refrigerators and compasses magically point north or south. In reality, the effects of magnetism go much further. The natural magnetism created by our planet’s iron core protects the Earth from charged particles released from the sun.

The magnetic diversion of these particles keeps vital components of our atmosphere, such as the ozone layer, intact. Additionally, magnetism has proven to be an extremely useful tool for medical technologies.

A few years ago, scientists working with MRI machines noticed that the imaging procedure sometimes led to vertigo and odd eye movements. In 2011, these symptoms were linked to the MRI magnetic field.

Apparently, the magnetic field could affect ionic currents in bodily fluids, such as the endolymph in the human ear. By changing the pressure exerted by the endolymph on the inner ear, the magnetic field caused the sensation of vertigo and led to vertigo-induced eye movements.

Researchers concluded that Lorentz forces, the forces experienced by charged particle within a magnetic field, were responsible for the magnetic field’s effect on the body. Various other studies reaffirmed this theory. This past month, two intriguing discoveries have further elucidated the effect magnetic forces have on human health.

The first study was led by Bryan Ward, a resident at the Hopkins School of Medicine. Ward’s team wanted to compare magnetic field effects on patients with balance problems to those on healthy individuals. The team worked off published studies that demonstrated the back and forth movement of healthy participant’s eyes under a magnetic field of seven Tesla.

The balance problems of the patients in the study were caused by issues with their semi-lunar canals. These canals are fluid-filled spaces inside human ears that have small hairs called cilia that act as motion sensors. The movement of these cilia is responsible for the human perception of balance.

By observing the patient’s eyes under the influence of a magnetic field, researchers found differences in the semicircular canals. With great precision, the eye movements reflected which ear manifested the abnormality in each patient. This correlation, if developed further, could lead to less invasive diagnostic methods and treatments for people with vestibular problems.

A second study was published a couple of days later with analogous results. Ward and his team decided to test their previous observation on a much simpler organism, Danio reiro, also known as zebrafish. These organisms are often used in genetic studies because of their similarities to human systems. Because zebrafish use hair cells to hear, they were an ideal model organism for testing magnetic effects on larger populations.

Thirty different zebrafish were placed in very strong 11.7 Tesla magnetic fields in two-minute intervals. The results were immediately apparent. The fish reacted similarly to humans experiencing imbalance and vertigo. Inside the tanks the fish would swim faster than usual, looping and rolling. The fish even developed a preferential roll direction depending on the field.

Visibility and the zebrafish’s ability to sense movement and vibration also could have affected the fish’s swimming patterns. To assure it wasn’t the visibility factor, the lighting of the fish tank was changed drastically in different runs. The results were the same regardless of lighting levels.

Similarly, the Zebrafish movement and vibration sense was cancelled out by immersing the fish in the antibiotic Gentamicin. This drug destroys cells that allow functionality of organ called the Lateral line in fish. The lateral line, present in many aquatic species, is responsible for the detection of movement and vibration. This did not change the experimental results, leading researches to attribute the fish’s reactions to the magnetic field.

A current running through an ion rich fluid, such as the endolymph of the inner ear, generates a force on the fluid. When this current is exposed to a strong magnetic field, a new force is created that is proportional to the strength of the magnetic field, the height of the column of fluid, and the current density.

Ward’s team showed that in a magnetic field of at least 1.5T, this new force could deflect the sensing mechanism of the inner ear. This means that the magnetic field might produce enough hydrodynamic force to move the endolymph overlying the cilia of the fish’s and potentially human’s ears causing the vertigo and lack of balance observed. Although preliminary, these experiments could one day lead to a different method of treatment for ear, balance, and vertigo problems.

There are around 69 million Americans, 35% of adults over the age of 40, suffering from some type of vestibular dysfunction in the United States according to the National Institute of Deafness and other Communication Disorders. Magnetism might just lead to new safe and easy diagnosis technologies and treatment methods for these patients.

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