Overview

A perilymphatic fistula happens when some of the fluid in your inner ear, called perilymph, leaks into the middle ear. This usually occurs through a small tear or defect in the membranes of the round window or oval window, which are the thin barriers separating the inner ear from the middle ear. Because of this leak, you may experience problems with your hearing or balance, since the inner ear is responsible for both.¹

Perilymphatic fistulae are considered uncommon, but doctors cannot say exactly how rare they are because reliable numbers are not available. 

You can be born with a perilymphatic fistula (this is called congenital), or it can happen later in life. Known causes include head injuries, sudden pressure changes such as from diving or flying, and occasionally as a result of ear surgery. In some cases, though, no cause can be identified which are referred to as idiopathic fistula.

This article aims to explain what a perilymphatic fistula is by going over its definition, common causes, symptoms, how it is diagnosed, and the treatments that may be offered.

Importance of the inner ear structure

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Your inner ear plays a vital role in both hearing and balance. It has two main parts: the cochlea, which helps you hear, and the vestibular system, which helps you stay balanced. The vestibular system includes the vestibule and three semicircular canals. 

When sound enters your ear, it first passes through the outer ear and then the middle ear, where tiny bones amplify the vibrations. These vibrations then travel into the cochlea, which converts them into electrical signals that are sent to your brain so you can understand what you are hearing. Meanwhile, the vestibule and semicircular canals sense movement and changes in head position. They send signals to your brain to help you keep your balance.

Due to these important functions, problems in the inner ear can cause hearing loss, dizziness, or difficulties with balance.

Congenital vs acquired fistulas

Congenital fistula

Congenital fistula refers to the conditions that are present since birth. Sometimes, it is associated with clinical symptoms and abnormalities of the temporal bone that can be detected with radiology technology. However, some may not show symptoms or detectable abnormalities. Instead, they are found to have small malformations of the middle ear during surgery.²

Acquired fistula

Acquired fistula refers to people in which perilymphatic fistula is caused later in life either by an identifiable cause, like head trauma, or an unidentifiable cause, like sneezing.²

Common causes

Head trauma

Severe head injuries, such as those sustained in accidents or falls, can cause sudden changes in pressure, leading to the formation of a fistula. Perilymphatic fistulas resulting from head trauma often occur due to a sudden increase in intracranial pressure. Impact injuries, falls, or accidents can lead to a forceful transmission of pressure to the inner ear, causing a rupture or tear in the delicate membranes.^1,3

Barotrauma

Exposure to rapid changes in atmospheric pressure, as seen in scuba diving or air travel, can also contribute to the development of acquired fistulas. Barotrauma-induced fistulas are associated with exposure to rapid changes in pressure, such as those experienced during scuba diving, airplane travel, or activities involving significant altitude variations. The pressure differentials can force the perilymphatic fluid through the oval or round window, leading to the formation of a fistula.^1,3

Ear infections

Chronic or severe ear infections, particularly those affecting the middle ear, may weaken the membranes, creating a pathway for perilymphatic fluid to escape. Prolonged inflammation or fluid accumulation in the middle ear can exert pressure on the membranes, potentially resulting in the development of a fistula.^1,3

Surgical complications

Certain ear surgeries, especially those involving the delicate structures of the inner ear, carry a risk of accidentally creating a fistula. Ear surgeries, especially those involving procedures on the inner ear, carry a risk of unintentional damage to the membranes. While surgical intervention is sometimes necessary for various ear conditions, careful consideration and precise techniques are essential to minimise the risk of postoperative perilymphatic fistulas.^1,3

Symptoms

Dizziness and vertigo

The hallmark symptom of a perilymphatic fistula is vertigo, a sensation of spinning or rotational movement. Vertigo can be triggered or worsened by changes in head position, sudden movements, or activities that alter intracranial pressure. The intensity of vertigo can vary, ranging from mild episodes of imbalance to severe, incapacitating sensations.^1,3,4

Imbalance and coordination issues

Postural instability

Individuals with perilymphatic fistulas often experience challenges in maintaining a steady posture, especially when standing or walking. A persistent sense of unsteadiness may accompany simple movements, contributing to a feeling of imbalance.^1,3,4

Coordination challenges

The disruption in the balance of fluids within the inner ear can affect spatial orientation, leading to difficulties in coordinating movements. Some people report increased clumsiness or a feeling of uncoordinated movements during everyday activities.^1,3,4

Hearing loss

Gradual-onset hearing loss

Perilymphatic fistulas can result in sensorineural hearing loss, affecting the ability to hear sounds clearly. Hearing loss may develop gradually, making it challenging for individuals to recognise changes in their auditory capabilities.^1,3,4

Fluctuating hearing loss

Hearing abilities may fluctuate, with periods of relative improvement and deterioration. The severity of hearing loss may correlate with the presence and intensity of other symptoms, such as vertigo.^1,3,4

Sensation of ear fullness or pressure

Ear fullness

Individuals with perilymphatic fistulas often describe a persistent sensation of fullness or pressure in the affected ear. This sensation can be accompanied by discomfort or a feeling of 'blockage' within the ear.^1,3,4

Pressure changes

Changes in atmospheric pressure or activities that affect intracranial pressure may exacerbate the feeling of ear fullness. Some individuals may find that rest and avoiding triggering activities provide temporary relief from the sensation of pressure.^1,3,4

Tinnitus 

While not a universal symptom, some individuals with perilymphatic fistulas may experience tinnitus, a perception of ringing, buzzing, or other sounds in the affected ear. Tinnitus associated with perilymphatic fistulas may be intermittent and may vary in intensity.^1,3,4

Diagnosis

Medical history and symptom assessment

Usually, the first symptoms of a perilymphatic fistula are an acute onset of hearing-related (audiological) problems and balance-related (vestibular) problems. Sometimes, people with a perilymphatic fistula show only one type of symptom, either hearing-related or balance-related, but in other cases, both types occur together. These may include sudden hearing loss in one ear, tinnitus, vertigo, a feeling of fullness in the ear (aural fullness), and imbalance (disequilibrium).^1,5

Proposed diagnostic criteria for perilymphatic fistula

These are the criteria doctors use to decide if someone has a perilymphatic fistula.

Definite perilymphatic fistula

Fluctuating or non-fluctuating hearing loss, tinnitus, aural fullness, and/or vestibular symptoms immediately preceded by one of the following events:^1,5

• Barotrauma caused by external events, such as head trauma, underwater diving
• Barotrauma caused by internal events, such as sneezing, heavy lifting
• Direct trauma to the inner ear, such as cotton buds injury

Meanwhile, it also has to fulfil one of the criteria below:^1,5

• A laboratory test shows a perilymph biomarker with high sensitivity and specificity
• There is proven leakage of perilymph into the middle ear, and symptoms improve after treatment - either with an intratympanic blood patch (a small amount of your own blood placed in the middle ear to seal the leak) or with surgery to close the leak.

Possible perilymphatic fistula

A person may have a possible perilymphatic fistula if they develop hearing loss that may come and go or stay the same, tinnitus, aural fullness, and/or balance problems, but without any history of barotrauma or a direct injury to the ear. In these cases, doctors may find what are called third window abnormalities (extra openings in the inner ear that should not be there). 

The possibility of perilymphatic fistula is also suspected when the symptoms don’t improve with migraine-related lifestyle changes, diet changes, or preventive medicines. However, if symptoms get better after an intratympanic blood patch or after surgery to close the leak, this supports the diagnosis.^1,5

Imaging

With the advanced technology in imaging, computed tomography (CT) and magnetic resonance imaging (MRI) can be used to diagnose perilymphatic fistula.

Pneumolabyrinth is usually considered a sign of perilymphatic fistula. It refers to gas or air in the cochlea, vestibule, and/or semicircular canals. High resolution of CT scans can be used to visualise it. 

Another sign of perilymphatic fistula is fluid in the round and oval window that can also be visualised by high resolution CT scans. A combination of CT and MRI can diagnose almost all cases of perilymphatic fistula.^1,5

Treatment options

Conservative approaches

Conservative approaches are often taken when there is no known cause of perilymphatic fistula to avoid further damaging the inner ear. However, if conservative management fails, undertaking surgery is recommended.^1,5

• Rest: It is shown that in some cases, perilymphatic fistula can heal on its own without other intervention as long as there are no activities that would trigger high intracranial pressure like straining
• Avoidance of triggering activities: Activities that would stress the inner ear should be avoided as these activities may further damage the inner ear

Surgical intervention

Repair of the fistula

The main aim of surgery is to seal the fistula (close the leak of inner ear fluid). Research shows this is usually effective at reducing symptoms. People generally notice a greater improvement in balance problems (vestibular symptoms) than in hearing problems (auditory symptoms).^1,5

Minimally invasive (endoscopic) surgery

In some cases, doctors use a tiny endoscope (a slim tube with a camera) inserted through the ear canal. This allows them to see small tears or defects clearly and seal them without making a larger surgical opening. This approach is particularly helpful for idiopathic cases (where no clear cause has been found).^1,5,6

Some specialists believe surgery should be carried out as soon as possible after symptoms begin, while others suggest that immediate treatment is not always necessary, since hearing often shows only small improvement after surgery. The best timing for treatment varies between people, depending on the cause and location of the perilymphatic fistula.^1,5.7

Intratympanic blood patch

This is a non-surgical treatment where a small amount of your own blood is placed in the middle ear. The blood naturally clots and forms a patch that can seal the fistula. Studies show this can relieve symptoms in many individuals and is less invasive than surgery.⁸

Summary

Perilymphatic fistula is a very rare condition. However, it is treatable. Individuals with perilymphatic fistula can experience hearing loss, tinnitus, difficulty balancing and vertigo. Some may even experience a mixture of these symptoms. It can often be diagnosed with a combination of CT and MRI scans. Sometimes, it may go away over time or it can be treated with surgical interventions. However, it is always important to seek professional medical advice if you find yourself or people around you experiencing these symptoms so that the best treatment for the condition can be given.