Cochlear hydrops (or cochlear Meniere's or cochlear endolymphatic hydrops) is a condition of the

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

involving a pathological increase of fluid affecting the

cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus. A core component of the cochlea is the Organ of Corti, the sensory org ...

. This results in swelling that can lead to hearing loss or changes in hearing perception. It is a form of

endolymphatic hydrops Endolymphatic hydrops is a disorder of the inner ear. It consists of an excessive build-up of the endolymph fluid, which fills the hearing and balance structures of the inner ear. Endolymph fluid, which is partly regulated by the endolymph sac, ...

and related to

Ménière's disease Ménière's disease (MD) is a disease of the inner ear that is characterized by potentially severe and incapacitating episodes of vertigo, tinnitus, hearing loss, and a feeling of fullness in the ear. Typically, only one ear is affected initial ...

. Cochlear hydrops refers to a case of inner-ear hydrops that only involves auditory symptoms and does not cause vestibular issues.

Cause and behavior

Cochlear hydrops refers to an increase in endolymphatic fluid in the inner ear. This build-up is either due to an overproduction or insufficient drainage of

endolymph Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. I ...

in the constant regulation of fluid in the inner ear. Usually, only one ear is affected. The root cause of the process is unclear and may vary from patient to patient, but can have auto-immune, viral, and/or allergic triggers, among others. The build-up of endolymph creates pressure in the

scala media Scala or SCALA may refer to: Automobiles * Renault Scala, multiple automobile models * Škoda Scala, a Czech compact hatchback Music * Scala (band), an English electronic music group * Escala (group), an electronic string quartet formerly known ...

. This causes its diameter to increase, and the

vestibular membrane The vestibular membrane, vestibular wall or Reissner's membrane, is a diaphragm (acoustics), membrane inside the cochlea of the inner ear. It separates the cochlear duct from the vestibular duct. It helps to transmit vibrations from fluid in the ...

to curve outwards in the direction of the vestibule. The changes to the membrane can result in changes to either the hearing perception or hearing threshold of a patient.Salt AN, Plontke SK (2010). "Endolymphatic hydrops: pathophysiology and experimental models". Otolaryngologic Clinics of North America. 43 (5): 971–83. doi:10.1016/j.otc.2010.05.007. PMC 2923478. PMID 20713237. Episodes are usually cyclical and symptoms fluctuate through time. Patients may be symptom-free between episodes, which themselves may progressively worsen, improve, or remain constant in severity or duration. For some, permanent damage occurs, and they may be left with long-term hearing loss, hearing distortion,

tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...

, and/or a feeling of fullness in the affected ear(s). A study looking at

spiral ganglion The spiral (cochlear) ganglion is a group of neuron cell bodies in the modiolus, the conical central axis of the cochlea. These bipolar neurons innervate the hair cells of the organ of Corti. They project their axons to the ventral and dorsal co ...

cell counts compared to hair cell counts in the inner ear of patients who had Meniere's disease found that they maintained more hair cells than spiral ganglion cells. Thus, it could be possible that hydrops affects auditory nerves more than hair cells. In contrast, a 2021 article by Richard Gacek posits that the hearing loss is actually caused by toxic nucleic acids that are released to the outer hair cells: "Since the outer hair cells (OHC) are freely surrounded by perilymph, their walls and nerve terminals are also bathed in this fluid. The few type-II spiral ganglion cells in contact with the OHC are unlikely to play a significant role in hearing loss because of their low numbers and the lack of a known connection to the central auditory pathway."

Symptoms

Cochlear hydrops preferentially affects the apex of the

where low-frequency sounds are interpreted. Due to the fluid imbalance in this area, parts of the cochlea are stretched or under more tension than usual, which can lead to distortions of sound, changes in pitch perception, or hearing loss, all usually in the low frequencies. Common symptoms include: * Low-frequency sensorineural hearing loss. * A feeling of fullness in the ear. *

Tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...

(ringing in the ear). *

Diplacusis Diplacusis, also known as diplacusis binauralis, binauralis disharmonica or interaural pitch difference (IPD), is a hearing disorder whereby a single auditory stimulus is perceived as different pitches between ears. It is typically experienced ...

(the perception of sound being a different pitch in one ear). *

Hyperacusis Hyperacusis is the increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it can refer to normal noises being perceived as: loud, annoying, painful, fear-inducing, or a combina ...

(an intolerance to loud sounds). * Depression or

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

that the condition will worsen or progress to Meniere's disease. As with Meniere's disease, atypical, early, or mild cases may only present some symptoms.

Diagnosis

Diagnosis is based on symptoms and a hearing test that documents a loss in the low and mid frequencies, usually only in one ear. For patients with mild or atypical hydrops, the hearing thresholds may be normal, but they may experience a subjective, unilateral distortion of sounds in lower frequencies, such as diplacusis or that voices are sounding "robotic". Patients may also mention a feeling of pressure or fullness in the ear. It is also possible to reveal the presence of hydrops with an MRI. If

vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...

is experienced, the diagnosis progresses to Meniere's disease. This occurs if the fluid increase leads to a leak or rupture of the membranes in the inner ear, causing a mixture of perilymph and endolymph.

Treatment

Treatment for cochlear hydrops is the same as for Meniere's disease. Currently, no cure exists for either. If a patient has undergone sudden sensorineural hearing loss, a course of

steroids A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

is often prescribed in an attempt to recover the hearing. Steroids may be injected directly through the eardrum. Like Meniere's Disease, a low salt diet is recommended as a preventative measure. A

diuretic A diuretic () is any substance that promotes diuresis, the increased production of urine. This includes forced diuresis. A diuretic tablet is sometimes colloquially called a water tablet. There are several categories of diuretics. All diuretics in ...

may be prescribed to help lower salt content.

Betahistine Betahistine, sold under the brand name Serc among others, is an anti-vertigo medication. It is commonly prescribed for balance disorders or to alleviate vertigo symptoms. It was first registered in Europe in 1970 for the treatment of Ménière' ...

is the most widely prescribed medication for the treatment of Meniere's disease. The drug is thought to increase blood flow to the inner ear and to prevent the frequency and intensity of episodes. While Betahistine is considered safe, there is insufficient evidence that it is an effective treatment. It is not

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...

approved in the United States, yet has still been clinically observed to benefit patients, and is considered safer and more effective than diuretics. Betahistine at high doses (such as 144 mg/day) can yield similar vertigo control as intratympanic dexamethasone.

Antivirals Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do no ...

have been proven effective for those who suspect a viral cause for their cochlear Hydrops. For some, surgery may be effective, such as an

endolymphatic sac From the posterior wall of the saccule a canal, the endolymphatic duct, is given off; this duct is joined by the utriculosaccular duct, and then passes along the vestibular aqueduct and ends in a blind pouch, the endolymphatic sac, on the posteri ...

decompression. Surgery is often reserved for cases where other measures have proven ineffective and/or when vestibular issues are the main complaint, as it runs the risk of causing hearing or other nerve damage.

Prognosis

The symptoms of cochlear hydrops fluctuate, and the condition may stabilize or go away on its own after several years. However, because the

organ of Corti The organ of Corti, or spiral organ, is the receptor organ for hearing and is located in the mammalian cochlea. This highly varied strip of epithelial cells allows for transduction of auditory signals into nerve impulses' action potential. Transd ...

undergoes stress during the hydrops episodes, long-term hearing loss, tinnitus, or hyperacusis is possible. It is considered by some that cochlear hydrops is an early form of Meniere's disease. However, while all people with Meniere's disease have some form of hydrops, the majority of cochlear hydrops patients do not go on to develop Meniere's disease. It takes an average of one year from the onset of symptoms for someone to develop full Meniere's disease, if at all.

Relationship to Meniere's disease

The data on how often progression to Meniere's disease occurs is mixed, but the majority of recent studies suggest a low likelihood. A 1984 study from Japan looked at patients with Meniere's disease and classified them into subcategories based on their first symptoms. The study found that the majority of patients with Meniere's disease (104 out of 163, or 63.80%) presented vertigo with their first symptoms, and only 59 out of 163 (36.19%) of patients presented with cochlear symptoms first, such as "tinnitus or deafness." However, the study found that 59 out of 74 (79.72%) patients who started out with a cochlear hydrops diagnosis progressed to Meniere's disease, and concluded that "cochlear Meniere's disease frequently develops into Meniere's disease." Conversely, A 2006 study from doctors at the

House Ear Institute The House Institute Foundation (HIF), formerly the House Ear Institute, is a non-profit 501(c)(3) organization, based in Los Angeles, California, and dedicated to advancing hearing science through research, education, and global hearing health to ...

found that “conversion from cochlear hydrops to Meniere's disease occurred in 33%” of diagnosed patients in a study including 46 subjects. A 2009 study from Japan found that only about 10% of their diagnosed patients with sudden low-frequency hearing loss (SLFHL) went on to develop full Meniere's disease, and about 18% with recurring SLFHL developed Meniere's disease. From this study, about 70% of patients who did not develop Meniere's disease maintained their hearing in the end. 30% went on to have lasting hearing difficulty, reported from a ten-year follow-up. A 2018 study from Korea found the chance of progression to Meniere's disease of all participants with SLFHL to be 9.38% with an average progression time of 1.7±1.4 years, but when limited to patients with recurring symptoms "it was confirmed that about half (46.88%) of them progressed to Meniere's disease." However, the study was said to have limitations as "hearing fluctuations and the possibility of transitioning to Meniere's disease in the non-relapse group could not be completely ruled out."Kim Ji Hyung, Kwak Sang Hyun, Bae Seong Hoon, Kim Sung Hunh, Nam Gi-Sung. Prognosis of Sudden Low Frequency Hearing Loss During Long-Term Follow-Up, res Vestib Sci

References

{{reflist Hearing loss Lymphatic pathology