This week I want to address a specific variant of a condition that I’ve been seeing a lot of lately – dizziness. Primary Care doctors in the U.S. see about six million patients a year with dizziness.
Dizziness means different things to different people and can be a symptom of many different medical conditions. People usually describe being dizzy when they feel faint or lightheaded or when they feel like their environment is spinning. This latter sensation is called vertigo, from the Latin vertere meaning “to turn.”
I want to touch on the most common cause of vertigo, known as benign paroxysmal positional vertigo or BPPV. Benign means the condition is not dangerous, paroxysmal indicates it occurs in a recurring pattern for short periods of time, and positional refers to the vertigo being brought on by changes in position.
I have to open the anatomy and physiology books to explain what causes BPPV. Hopefully some of you recall from junior high science the organ that allows us to maintain our balance is the vestibular apparatus found in the inner ear. This is a truly remarkable and complex organ. I’ve included a diagram to hopefully help you visualize what I’m describing.
We have a left and right vestibular apparatus that reside deep inside each ear. These organs (along with input from our eyes) are constantly monitoring the position of our heads in space in relation to motion and gravity. If one or both of them gives faulty or conflicting information to the brain, we can lose our sense of orientation in space.
The semicircular canals are a key part of the vestibular apparatus and are oriented at 90 degree angles to each other. They are filled with a fluid called endolymph. When we move our heads, the fluid shifts to varying degrees inside each of the three canals, allowing us to detect motion in three different planes. Movement of the endolymph vibrates a piece of tissue called the otolithic membrane that resides in the utricle and saccule.
The membrane sits on top of tiny hairs protruding from nerve cells that communicate with the brain. When the membrane moves, it wiggles the hair cells that in turn fire off nerve impulses, telling the brain that the head is moving, and in what direction.
Resting on top of the otolithic membrane are tiny crystals made of calcium called otoliths. These crystals provide some weight on top of the membrane allowing it to stimulate the nerve cells more easily.
Now that you’re an expert in some inner ear anatomy and physiology, what does any of that have to do with BPPV? The cause of BPPV is a problem with the otoliths – they get dislodged from their position on top of the otolithic membrane and move into the semicircular canals. The displaced crystals cause the fluid in the semicircular canals to move at the wrong time and gives faulty information to the brain, resulting in the sensation of vertigo. Tilting the head, rolling over in bed, looking up or down, or sudden head motion can all cause vertigo associated with BPPV.
A good patient history may suggest BPPV. There is also a simple movement test called the Dix-Hallpike maneuver that a physician can perform in the office to determine if, and which vestibular apparatus is at fault. You can see a video demonstration here:
Most cases of BPPV resolve on their own when the otoliths move out of the semicircular canal. Sometimes medications like meclizine (Antivert®) or scopolamine are given to dull the severity of the vertigo.
For those cases of BPPV that don’t resolve on their own, most can be treated in the office by undergoing either the Epley, Lempert or deep head-hanging maneuver. These involve putting the patient through a series of movements that attempt to move the otolith(s) out of the semicircular canals. Surgery is performed on rare occasions for severe and refractory cases of BPPV.