57.1 Introduction

Tonal tinnitus is the phantom perception of sound when no external generating stimulus is present. In the general U.S. population, 15% of adults experience tinnitus.s. Literatur ^,​ s. Literatur However, with vestibular schwannoma (VS), it can be a presenting symptom in up to 70 to 80% of patients.s. Literatur For some, subjective tinnitus is merely a fleeting annoyance; however, a significant subset of individuals experience audiological, neurological, and/or cognitive impairment resulting in poor attention, increased distractibility, anxiety, sleep deprivation, depression, and even suicide.s. Literatur It appears that factors beyond tinnitus pitch, loudness, and quality of noise influence tinnitus handicap, as some patients appear greatly distressed by what they describe as relatively quiet or intermittent noise, while other seem to tolerate constant loud ringing. Unfortunately, most publications in the VS literature detail whether tinnitus was simply present or absent without attempting to ascertain the perceived severity or impact on the patient’s well-being. Furthermore, it still remains unclear whether one treatment strategy demonstrates a clear benefit over another with mitigating or preventing severe tinnitus.

57.2 Mechanism of Tinnitus

The primary mechanisms underlying the development and persistence of tinnitus remain largely unknown. However, one can imagine any of the following as potential underlying causes: ephaptic coupling of cochlear nerve fibers by compression, cochlear dysfunction by ischemia or by biochemical degradation (protein or ionic changes), and cortical reorganization following hearing loss or surgical deafferentation. A leading hypothesis holds that tinnitus occurs as a result of detrimental cortical reorganization following an injury to the peripheral auditory pathway that disrupts the equilibrium between afferent and efferent signaling.s. Literatur The theory of cochlear deafferentation as a cause for tinnitus parallels phantom limb pain, where cortical maladaptation develops in response to loss of sensory input.

Curiously, some patients with VS present with normal hearing by all objective criteria and still report tinnitus, thus making ephaptic transmission (i.e., abnormal cochlear nerve firing) a possible origin of tinnitus in these patients.s. Literatur In other cases, tinnitus may worsen following surgical tumor resection including division of the cochleovestibular nerve, suggesting that in these cases cortical reorganization after deafferentation may be causative. Lastly, vascular compression as a source of tinnitus is perhaps the most understudied possibility. Paralleling this hypothesis, a limited population of patients with VS present with trigeminal neuralgia, in which circumstance the authors will commonly recommend surgical removal with formal microvascular decompression (MVD) for relief. In the general neurosurgical literature, there is evidence that MVD may be effective for some forms of tinnitus.s. Literatur While only speculative, it may be possible that formal MVD of the eighth cranial nerve at the root exit zone following hearing preservation microsurgical resection provides an advantage for tinnitus outcome in a select population over simple tumor resection alone. This topic is explored further later in the chapter.

57.3 Outcome of Tinnitus after Vestibular Schwannoma Treatment

There are a number of validated self-report inventories for tinnitus assessment that VS surgeons should be aware of (Table 57‑1 ). Symptom-specific and disease-specific instruments are critical in characterizing outcomes in diseases such as VS, since other generic measures such as the SF36 lack the sensitivity required to detect longitudinal changes within an individual or between treatment strategies. In addition, the absolute scores help ascertain the degree to which the symptom is affecting patient well-being.

A summary of published studies with reported tinnitus outcomes in VS is presented in Table 57‑2 . In 2014, Kohno et al reported that of 290 patients with preoperative tinnitus who were treated with retrosigmoid craniotomy for VS resection, tinnitus resolved in 20%, improved in 22%, was unchanged in 35%, and worsened in 14%. In addition, among 77 patients without preoperative tinnitus, 22% developed new-onset tinnitus following the operation.s. Literatur Therefore, this study found that among subjects with preoperative tinnitus, microsurgical treatment was associated with improvement in just over 40% of cases.s. Literatur Interestingly, it was found that younger age, better preoperative hearing, and smaller tumor size demonstrated worse tinnitus outcomes postoperatively.s. Literatur Furthermore, the prognosis of tinnitus was significantly worse in the group of patients left with an anatomically preserved cochlear nerve without useful hearing compared to the group with a surgically divided cochlear nerve. In a more recent study, Bell et al found that among 53 patients who underwent microsurgical resection of VS, 17% reported that their tinnitus resolved, 9% reported improvement, 23% reported no change, 43% reported worsening, and 8% were unsure. Sex, tumor size, surgical approach, hearing preservation, and cochlear nerve status did not correlate with the prognosis of tinnitus after surgery. However, the prognosis of tinnitus was worse for younger respondents, those with serviceable hearing preoperatively, and those with residual tumor postoperatively.s. Literatur Henrich and colleagues published their experience with 160 VS cases treated by translabyrinthine approach between 1980 and 1991. Data regarding the presence and severity of tinnitus after treatment were obtained via telephone correspondence. Overall, among patients with tinnitus preoperatively, the condition was absent postoperatively in 45%, lessened in 17%, was unchanged in 30%, and worsened in 8%.s. Literatur These results appear to be similar to the retrosigmoid cohort reviewed earlier.

Currently, there is a paucity of published data reporting tinnitus outcomes in the stereotactic radiosurgery (SRS) literature for VS. In 2009, Kano et al reported tinnitus improvement in only approximately 10% of patients. Although this appears poor, the SRS literature focuses less on this symptom. One prospective study comparing SRS to a smaller number of microsurgical patients reported stable to worsening tinnitus in the patients treated with stereotactic radiation and a reduction in tinnitus in those treated with microsurgery.s. Literatur

Van Gompel et al previously explored the symptom of tinnitus and its relationship with treatment utilizing the Acoustic Neuroma Association (ANA) 2007–2008 annual survey which included 2,004 respondents.s. Literatur In this survey, tinnitus severity was recorded as a continuous variable, asking respondents at initial presentation and presently to grade their tinnitus on a 10-point scale, from 1 (least severe/mild) to 10 (most severe/disabling).s. Literatur Overall, there were 1,138 patients who received treatment and 289 patients who received no treatment or observation in this study.s. Literatur Overall, the average presentation score and most recent tinnitus score were 4.3 ± 0.1 and 3.8 ± 0.1, respectively (p < 0.001).s. Literatur Tinnitus scores worsened over time among patients who did not receive active intervention (3.7 ± 0.1 to 4.1 ± 0.2; p = 0.018).s. Literatur When evaluating tinnitus improvement by microsurgical approach, the cohort of patients who underwent translabyrinthine and retrosigmoid craniotomy both demonstrated an improvement in score. However, the middle fossa approach did not appear to impact tinnitus.s. Literatur SRS was performed in 221 patients as primary treatment and further appeared to improve postoperative tinnitus at last follow-up.s. Literatur The authors conclude that those undergoing observation have a greater risk of experiencing worsening tinnitus, while intervention (microsurgery or radiation) has a higher likelihood of tinnitus stabilization or improvement.s. Literatur Future studies will be necessary to examine tinnitus outcomes according to treatment modality. As with hearing preservation, tinnitus outcomes will require very long-term follow-up as delayed audiovestibular symptoms are common.

Related posts:

50 Reporting of Hearing Outcome Data for Vestibular Schwannoma 52 Hearing and Vestibular Function Loss After Radiation Treatment of Sporadic Vestibular Schwannoma 51 Natural History of Hearing and Vestibular Function in Untreated Sporadic Vestibular Schwannoma 54 Reporting of Facial Nerve Outcome Data for Vestibular Schwannoma 59 Epidemiology and Pathogenesis of Headache in Patients with Vestibular Schwannoma 58 Dizziness in Sporadic Vestibular Schwannoma

Stay updated, free articles. Join our Telegram channel

Join