Image: a lithograph plate from Gray's Anatomy
By the time Stephen came to my office complaining of painful spasms and ringing in both ears, he had already been to several physicians about his problem. He had been given an array of diagnoses; most doctors said he had acute outer or middle ear infections and prescribed oral antibiotics or ear drops. These measures had not helped, though. He was 21 years old and had suffered with this pain for nearly a year.
Like many people with ear or head sounds—which we lump into one word, tinnitus—Stephen was distraught. Knowing that there is no magic drug for ringing, I mentally prepared my usual sermonette: Avoid noise, aspirin, and methylxanthines (stimulants of the central nervous system, such as caffeine). And embrace the tried-and-true helper, sound substitution, or “masking.” This technique, in my experience, is a remedy for almost every patient with tinnitus.
Then Stephen delivered the bombshell. “I’ve been treated twice with extended courses of intravenous antibiotics for Lyme disease,” he told me. “In fact, I have an intravenous line in my arm right now and am just finishing an eight-week course of Rocephin [an antibiotic] for my second bout of Lyme. I’ve had to drop out of college because the pulses in my ears are so bad I can’t concentrate on anything. Could it be related to Lyme?” The spasms were occurring every few seconds in both of his ears throughout his entire waking day, he continued. The associated pain was so severe that his whole life revolved around dealing with it. Clearly this was not the typical case of tinnitus.
Stephen was first exposed to Lyme disease, a tickborne infection, as a child while playing in the woods near his home in Westchester County, New York. He was reinfected as a college student in 2007. Severe cases of Lyme disease can involve cardiac or neurological symptoms and are often treated with the intravenous antibiotic ceftriaxone. But I was unaware of any link between Lyme disease and pulsatile tinnitus. Otherwise, Stephen was in stable health with no other contributory medical or surgical problems.
I examined his right ear with a microscope and an ear speculum. There it was, apparent right away in an otherwise normal eardrum: The drum pulsed and appeared to go into spasm in an irregular way. I observed the exact same thing in the left ear. There was no mass behind either drum, and the middle ear clefts on each side were normal. My exam did find spasms of his soft palate (palatal myoclonus) and twitching around his eyes (blepharospasm), but these were not as bothersome to him as the pulsing. I had never before seen a patient like this.
It was time to put Stephen through some proper hearing tests to find out what was going on. The middle ear has two muscles, the tensor tympani and the stapedius. The stapedius and, to a lesser extent, the tensor tympani engage in the acoustic reflex (or the middle ear muscle reflex), a contraction in response to loud sounds. A reflex is an involuntary motor response, so it is present both while a person is awake and while unconscious. All reflexes follow a looping nerve response: an arc toward the central nervous system, called the afferent limb, and an arc away from the central nervous system to the end organ, termed the efferent limb. For the middle ear muscle reflex, the afferent limb is the auditory nerve; the efferent limb is the facial nerve for the stapedius muscle and the trigeminal nerve for the tensor tympani muscle. The reflex itself occurs in the brain stem, one of the deepest and most basic parts of the brain.
The stapedius responds by tightening the mobility of the stapes (or “stirrup”), and the tensor tympani tightens the eardrum and pulls the malleus (“hammer”). The stapes and malleus are tiny bones that transmit hearing through the inner ear. By restricting the motion of the stapes, the stapedius may be able to dampen loud sounds coming toward the ear, but that response does not happen quickly enough to prevent acoustic trauma from fast-acting sounds, such as a gun blast. The acoustic reflex is also thought to play a role in preventing us from hearing our own voices as we speak. Although we know that the reflex is present in healthy individuals and we evaluate it as part of every complete hearing test, its ultimate function is not entirely understood.
