The diagnosis of perilymph fistula continues to be elusive, spawning both extremes of overdiagnosis and underdiagnosis. In this situation, the otolaryngologist is confronted with the possibility of becoming either a charlatan for overdiag-nosing, and therefore overoperating on patients, or a therapeutic nihilist, and so failing to eliminate inner ear symptoms in one of the rare instances in which surgical intervention can remedy sensorineural impairment. The question of whether such a condition even exists has been raised by some investigators.1, 2 By contrast, Goodhill’s³ original descriptions of the pathophysiology of perilymphatic fistula and my personal experience with elimination of symptoms after surgical repair of obvious perilymph leaks would indicate that this condition does in fact exist. This chapter reviews my understanding of this entity and outlines my approach to arriving at the diagnosis and management of patients who present with the appropriate symptoms.

Pathophysiology

Perilymph fistula refers to a pathologic condition in which there is a persistent communication between the inner ear and the middle ear. Perilymph fistula implies that there is an egress of perilymph, either constantly or intermittently from the inner ear, and it is this loss of perilymph from the inner ear that produces symptoms. The precise effect of this change in the volume of perilymph is not understood. Temporary loss of perilymph occurs often in stapedectomy with little or no permanent effect on inner ear function. Chronic perilymphatic leak, as seen in fistulization of the labyrinth by cholesteatoma, can result in permanent auditory and vestibular dysfunction. Although not proved, the chronic loss of fluid from the perilymphatic space should lead to expansion of the endolymphatic spaces, producing a condition similar to endolymphatic hydrops. This most likely explains the reason that the symptoms of perilymph fistula and endolymphatic hydrops are at times indistinguishable.

The mechanisms for the development of perilymph fistula are credited to Goodhill.³ He described both implosive and explosive causes. Implosive fistulae occur when a force is exerted on the oval and round windows through the middle ear. This might involve severe excursion of the tympanic membrane or ossicular chain, such as in acoustic trauma, or by direct positive pressure on the oval and round windows due to severe change in middle ear pressure as in a sudden decompression syndrome (scuba diving). The explosive mechanism occurs by transmission of a sudden increase in intracranial pressure to the inner ear. This occurs primarily through the cochlear aqueduct, theoretically, when the aqueduct is abnormally patent, but it also can occur through the internal auditory canal in congenital anomalies such as Mondini dysplasias. This increase in intracranial pressure can occur as a result of head trauma, coughing, or any type of straining activity. The existence of microfissures or patent tracts in the fissula ante fenestra have been postulated as sources for the perilymph fistula by various investigators. The precise pathophysiologic mechanism has not been described, obviously lending concern to the actual existence of this disorder.

Perilymph fistulae are either traumatic, iatrogenic, idiopathic, or congenital. Trauma may be blunt, such as a head injury with a temporal bone fracture, barotrauma, increased intracranial pressure; acoustic, as occurs with a blast injury; or penetrating, as in ossicular fracture due to foreign body injury. Iatrogenic causes of perilymph fistula most commonly occur after stapedectomy but may occur in any case of inadvertent ossicular disruption. Idiopathic, or spontaneous, perilymph fistulae occur in cases in which no identifiable preceding condition can be recognized. Congenital malformations such as Mondini dysplasias carry a high risk of perilymph fistulae because of the more extensive communication with intracranial cerebrospinal (CSF) pressure due to the foreshortened patent internal auditory canals that often open directly into the otic capsule.

Signs and Symptoms

As with most disorders of the inner ear, hearing loss, tinnitus, fullness, and vestibular symptoms are all possible symptoms of perilymph fistula.⁴ Obtaining a careful history with attention to onset, duration, and frequency of symptoms, in addition to an understanding of events antecedent to the development of the symptoms and other associated symptoms, will lead in most instances to the appropriate diagnosis.

HEARING LOSS

The hearing loss associated with perilymph fistula varies according to the mechanism that produced the fistula. In the majority of cases the onset of hearing loss is sudden, and can be correlated with a particular event (e.g., head trauma, a sneeze, explosion, foreign body). Hearing loss may be complete, but it is usually partial. The sudden hearing loss is often associated with vertigo at the time of the incident. Tinnitus commonly occurs around the time of the hearing loss as well. There may be partial or complete recovery of hearing days after the inciting event. If the fistula becomes chronic, the hearing loss may fluctuate or progressively deteriorate over time. A positive diagnosis can be made if fluctuation or progressive deterioration can be correlated with activities that increase intracranial pressure.

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