FREQUENTLY ASKED QUESTIONS

Persons receiving intravenous, (IV), gentamicin are often very sick otherwise, or are bed-bound, so some of the symptoms of gentamicin poisoning may be incorrectly attributed to their general condition, or the effects of being in bed for a long period. The most common symptoms of gentamicin poisoning are:

• Ringing or hissing in the ears (tinnitus)
• Bouncing vision (oscillopsia)
• Difficulty with balance or walking
• A sensation that the room is spinning (vertigo)
• Nausea
• A sense of confusion

Individuals receiving gentamicin should be aware of these potential symptoms, so that they may report them to their healthcare providers immediately.

Physicians and nurses often dismiss complaints of “feeling dizzy” in gentamicin patients who are bed-bound to a condition known as orthostatic hypotension. Orthostatic hypotension is feeling faint when getting up from a lying position. It is due to blood pooling in the legs. Feeling faint, or being close to losing consciousness, is different than feeling dizzy, where the room spins, or where it is hard to keep balance when walking.

MANY HEALTHCARE PROVIDERS ARE TOTALLY IGNORANT OF THE FACT THAT GENTAMICIN CAN CAUSE SYMPTOMS OF BOUNCING VISION OR IMBALANCE. MANY BELIEVE THAT SYMPTOMS ARE TRANSITORY, AND WILL RESOLVE AFTER GENTAMICIN IS DISCONTINUED. IF YOU ARE CURRENTLY TAKING GENTAMICIN, AND EXPERIENCE ANY OF THESE SYMPTOMS, DO NOT LET YOUR DOCTOR DISMISS THESE SYMPTOMS. DEMAND AN IMMEDIATE INFECTIOUS DISEASE OR OTOLARYNGOLOGY CONSULT TO RULE OUT GENTAMICIN OTOTOXICITY.

Thousands of persons receive gentamicin by IV every year, and complete their course of treatment without any noticeable signs of toxicity. However, a significant percentage of persons do suffer some ill effects. Although the development of serious symptoms is best correlated with total exposure to gentamicin (dose times days of therapy). There is no way to predict exactly when a person becomes ototoxic. This is why it is necessary to provide close monitoring of kidney function, gentamicin blood levels, and if practical, audiometric hearing tests to determine the early onset of conditions that can lead to ototoxicity.

An extremely small percentage of the population is extremely sensitive (or genetically predisposed to become sensitive) to gentamicin and other aminoglycosides. A specialized laboratory test may demonstrate this sensitivity, and could potentially be used to screen persons at extreme risk. These persons usually develop ototoxicity after one or a very few doses.

For the vast majority of the population, however, symptoms typically appear (if they appear at all) over 15 days after moderate dose administration without renal failure or compromise, or after 7 days of high or excessive dosing. (I know of one instance where a patient received over 9,000 mg of gentamicin in one dose due to a miscalculation by the nurse preparing the infusion, and the symptoms appeared within hours.)

If symptoms do appear, it is not uncommon for them to appear days or even two to three weeks after the discontinuance of gentamicin. This is due to the fact that the fluid in the inner ear acts as a sort of sponge and holds the gentamicin in the inner ear next to the vulnerable hair cells long after the gentamicin blood level drops to zero. If the hair cells are already weakened, it is hypothesized that the remaining gentamicin in the inner ear is enough to further injure the hair cells to the point of death.

WHEN SYMPTOMS OF GENTAMICIN OTOTOXICITY APPEAR BEFORE THE DRUG HAS BEEN DISCONTINUED, IT IS CRITICAL THAT THE DRUG BE STOPPED UNLESS THE SITUATION IS SO SERIOUS THAT THERE IS NO OTHER RATIONAL ALTERNATIVE TREATMENT TO CONTINUED GENTAMICIN THERAPY. IMMEDIATELY STOPPING THE GENTAMICIN ADMINISTRATION CAN PROVIDE A BETTER CHANCE OF SOME HAIR CELLS ESCAPING DESTRUCTION, LEAVING THE PATIENT WITH A PARTIAL RATHER THAN TOTAL VESTIBULAR LOSS.

Your sense of balance is controlled by:

• Vision - being able to see what is up and what is down
• Proprioception - the feeling of pressure on the bottoms of your feet, or feeling how far your joints and muscles are flexed, all of which help provide a sense of your body’s position spatially, and
• Vestibular input - signals to the brain from the inner ear, or vestibular system

Gentamicin poisoning damaged your vestibular system’s ability to send signals to the brain. The gentamicin attacked and killed “hair cells” in the inner ear that sense even very small movements of the head. If enough of these cells are destroyed, there is no vestibular input to the brain, so the brain has to rely only on vision and proprioception to determine what is up or down, or where the body is positioned in three-dimensional space. In order for our eyes to remain stable when our head is moving, vestibular input is necessary. This “vestibular-ocular reflex” or VOR, acts as a kind of gyroscope to stabilize the eyes. This is why you are experiencing balance problems and bouncing vision.

Gentamicin can kill the “hair cells” of the inner ear that sense motion, sense gravity, and provide input to the nerves connecting the inner ear to the brain. Without these hair cells, the body has no internal “gyroscope” to keep the body in balance. If you have been the victim of gentamicin poisoning, your body’s vestibular system has been damaged and you must rely on vision and proprioception, (feeling the ground with the soles of your feet, or feeling a chair underneath you to know which is up and down), to keep balanced upright.

This is why it is usually easier to balance and navigate on a bright, sunny day where there are few distractions. Plenty of light makes it easier to see and to judge variations in walking surfaces. The less visual distractions there are about you, the easier it is to use the eyes to get important visual information about what is up and down and to appreciate small variations in the area on which you are walking.

When a person with an intact inner ear looks at a spot on the wall and rotates his or her head from side to side, the “vestibular-ocular reflex,” or “VOR,” keeps the eyes focused on that spot. When that person moves their head 10 degrees to the right, the movement is sensed by the vestibular system, and a signal is sent to the eye muscles to rotate the eyes 10 degrees to the left. Likewise, when that person moves their head up 10 degrees, the eyes automatically compensate via the VOR and move 10 degrees down. Within limits, the head can freely move about, while the eyes can keep focused on a distant object.

If you have been the victim of gentamicin poisoning, your vestibular system may be damaged to a degree that there is no input to the VOR to keep the eyes steady. Any time the head moves at all, even while walking or riding in a car, the eyes move also. The result is bouncing vision, or oscillopsia.

Unfortunately, there is little published scientific literature that specifically addresses the impact of gentamicin poisoning on concentration or memory, although a very common complaint of gentamicin poisoning victims is a frustrating lack of concentration and ability to plan and carry out complex tasks, coupled with short-term memory loss.

The most simplistic explanation for lack of concentration and short-term memory loss is that the brain of a person suffering from gentamicin poisoning is totally overloaded with keeping the body upright and functioning in 3 dimensional space. Dr. Timothy Hain, a neurologist who has had extensive experience treating victims of gentamicin ototoxicity and other balance disorders, has stated:

"Many people with bilateral vestibulopathy complain of a mild confusion or 'brain fog', which is attributed to the increased attention needed to maintain balance and good vision, due to loss of vestibular input. Others call it 'inability to multi-task'. It is thought that in persons with bilateral vestibular loss, the ongoing extra effort needed to keep ones balance reduces the amount of attention that is available for other thinking tasks.

As of now, there is no known cure for gentamicin poisoning. Most victims, however, have a great capacity to accommodate certain aspects of their disability. Accommodation is the process whereby people train themselves to rely on other senses (vision, proprioception) to partially make up for the loss of vestibular input. Just as a person who is blinded develops keen hearing, a person with no vestibular function can learn to use visual and proprioceptive clues to a greater extent. While a gentamicin poisoning victim’s ability to walk will gradually improve, no amount of accommodation can replace the vestibular system. In the dark, visual accommodation is useless.

There is some hope for victims who participate in Vestibular Rehabilitation, which is a sub-specialty of Physical Therapy. Vestibular Rehabilitation involves exercises and maneuvers designed to stimulate a partially damaged vestibular system, and training for people with no vestibular systems to best accommodate their losses. The earlier Vestibular Rehabilitation therapy is begun, the better the usual outcome.

Early diagnosis of gentamicin poisoning, coupled with sufficient vestibular testing by a qualified neurotologist, (also referred to as a neuro-otologist or neurootologist) and a referral to a competent vestibular rehabilitation specialist can provide the best course of vestibular rehabilitation.

In representing over 70 persons who have suffered gentamicin poisoning, I have found that those persons who can maintain a positive attitude, force themselves to exercise daily, try to find some part time occupation or avocation, and who focus on what they can rather than cannot do, seem to manage the best. Having said this, it is admittedly difficult to "be positive" when you can't go to the bathroom at night unless the hall is well lit, have to have someone drive you wherever you want to go, and can't seem to remember anything. However, in virtually all of the cases I have seen, things usually get better over time.

A healthcare provider should be able to make an early diagnosis of gentamicin poisoning based on a thorough physical examination and a careful medical history. By performing a Romberg test, (having the patient stand upright with the feet close together and the eyes closed, and the examiner pushing slightly on the shoulders to cause imbalance), and watching the patient walk; by having the patient read text while the examiner rotates the head up and down and side to side; and by testing the patient for high frequency hearing loss, the healthcare provider should be able to determine whether damage to the vestibular system has occurred.

If you think you may have gentamicin poisoning, but your doctor who prescribed the gentamicin or a doctor to whom he or she referred you is blaming your symptoms on something else, or taking the position that your symptoms will eventually go away and to not worry, you probably should go for examination by a doctor not associated in any way with the doctor who prescribed or administered the gentamicin.

In order to determine the extent of gentamicin poisoning, and to rule out other causes of vestibular dysfunction, comprehensive vestibular testing should be ordered and interpreted by an ear specialist who is familiar with vestibular testing. These physicians are referred to generally as ear, nose and throat specialists (ENT, or EENT). An otologist further specializes in just the function of the ear. A neurotologist specializes even further in the nerve function of the ear, and how the ear interacts with the brain. Neurologists may also sub-specialize in otology or balance disorders. If available, (and competent), a neurotologist or someone well versed in both neurology and otology is probably the best physician to evaluate the nature and extent of gentamicin poisoning.

Vestibular testing is performed in a laboratory containing specialized equipment for measuring the nature and extent of vestibular damage. A more detailed explanation of the tests used to determine vestibular function is located on the Vestibular Testing page of this website, on Dr. Timothy Hain's site page of the Vestibular Disorder Association’s, (VEDA’s) website. The Vestibular Disorders Association also has an excellent web page that lists professionals who evaluate and treat vestibular disorders.

MANY HEALTHCARE PROVIDERS ARE TOTALLY IGNORANT OF THE FACT THAT GENTAMICIN CAN CAUSE SYMPTOMS OF BOUNCING VISION OR IMBALANCE. MANY BELIEVE THAT SYMPTOMS ARE TRANSITORY, AND WILL RESOLVE AFTER GENTAMICIN IS DISCONTINUED. IF YOU ARE CURRENTLY TAKING GENTAMICIN, AND EXPERIENCE ANY OF THESE SYMPTOMS, DO NOT LET YOUR DOCTOR DISMISS THESE SYMPTOMS. DEMAND AN IMMEDIATE INFECTIOUS DISEASE OR OTOLARYNGOLOGY CONSULT TO RULE OUT GENTAMICIN OTOTOXICITY.

If you are taking gentamicin, have symptoms of dizziness, bouncing or jerky vision, difficulty walking in a straight line, ringing or hissing in your hear, and have reported these to your physician, and they do not immediately stop the drug to have you further evaluated, PRINT THE PAGE OF THIS WEBSITE "FOR PHYSICIANS AND PHARMACISTS" AND FAX OR GIVE TO YOUR PHYSICIAN IMMEDIATELY. Be blunt and forceful with your Doctor. "Doctor, do you realize that continuing gentamicin could cause permanent and irreversible damage to my inner ear?"

There is no surgery that can replace the damaged inner ear. Research is underway to try and find ways of regenerating lost hair cells, but there has been no proven regeneration of human hair cells to date. An experimental mechanical device, an artificial balance sensor fitted on the tongue, is being developed at the University of Wisconsin-Madison. A description of the device from the web publication Sensory Substitution for Vestibular Function Deficit, May 2001 states:

Research is currently being performed at the University of Wisconsin-Madison and related institutions to develop a substitute vestibular information (SVI) system for persons with bilateral vestibular dysfunction. The focus of this work is to demonstrate the possibility of replicating the function of the vestibular system to develop “vestibulo”-ocular reflexes that would reduce or eliminate postural instability and oscillopsia in persons affected by this syndrome. This replication would be done by developing a wholly self-contained, intraoral device to present artificially sensed accelerations analogous to those sensed by the vestibular system. By presenting this information as tactile patterns on the tongue, the SVI system could be used to train users to moderate lateral and anterior/ posterior sway, resulting in improved postural stability.

The current status of this research is unknown.

• Medicine Net.com –Vestibular Disorders

A physician written informational page with a comprehensive discussion of vestibular disorders.

• American Academy of Otolaryngology

A professional organization that credentials specialists in otolaryngology, or ears, nose and throat.