Diagnosis

The diagnosis of PLF can be established only at tympanotomy. Although imperfect, the clinical gold standard for PLF diagnosis remains visual inspection for perilymph leakage into the middle ear at tympanotomy. Unfortunately, this method is subjective, and two competent surgeons inspecting the same visual field may come to two different conclusions regarding the absence or presence of a perilymph leak. This is especially true if one of the surgeons is viewing the field from a monocular side arm or with any other monocular instrument such as an endoscope.

Even if a clinical fistula test69-72 is positive, the results are not diagnostic of PLF because any anatomic or pathologic condition permitting transfer of middle inner ear or intracranial pressure changes to stimulate vestibular receptors will result in a positive fistula test based on external canal pressure changes as the stimulus. Examples include otic capsule softening from lues, Paget's disease, or labyrinthine fibrosis.73 Conversely, a negative PLF test does not rule out a PLF because external auditory canal pressures may not be transmitted to the inner ear receptors (e.g., with ossicular discontinuities). It is also possible that persons with a loss or absence of vestibular hair cell function in the affected ear will yield negative responses (objective and subjective) to conventional fistula tests. Reduced ability of the vestibular hair cells to respond to stimulation must be considered (established) when interpreting negative fistula test results. Although the only generally accepted way that a PLF can be confirmed is identification of perilymphatic leakage at tympanotomy, failure to observe a PLF leak at tympanotomy does not rule out a PLF because otic capsule integrity can be compromised without perilymph fluid leak.

Standard tests of vestibular and auditory function are normal in patients with uncomplicated PLFs because PLFs do not directly cause loss of auditory and vestibular hair cell function. It is only when complications of persistent PLFs damage receptors that hearing loss and vestibular function deficits occur. Electronystagmography (ENG) may or may not show a positional nystagmus in PLF patients, and caloric and rotation (vestibulo-ocular reflex, or VOR) testing are normal in virtually all uncomplicated PLF patients. Computed dynamic pos-turography (CDP) often shows abnormal results on sensory organization testing (SOTs); these findings are neither specific for, nor diagnostic of, PLFs. However, the auditory and vestibular functional status of PLF patients should be established by objective tests as early as possible in order to establish a baseline and in order to plan treatment and rehabilitation based on quantitative data.

Hearing loss complicating PLFs does not present a specific pure-tone threshold pattern or configuration, but most are sensorineural in type. Some clinicians have used electrocochleog-raphy (ECoG) to assist in the diagnosis of PLFs;74'75 we have not found ECoGs to be useful for diagnosis of PLFs, although we do employ ECoG to help identify a secondary endolymphatic hydrops, which is probably the most frequent comorbid (complicating) condition accompanying PLFs.

Strohm5 was among the first to observe that PLFs may arise many years after the initial traumatic event. Strohm reported a case of a PLF that became symptomatic more than 30 years later in the second ear of a patient with a traumatic PLF. The clinical dictums regarding the close temporal relationship between the traumatic event and onset of symptoms must therefore be regarded with circumspection in patients with traumatic PLF.

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