No patient had a history of neurologic disease, tumors in the IAC or CPA, or temporal bone trauma. During the same period, 8 control subjects (4 men and 4 women age range, 47–74 years mean age, 60.5 years) who did not have tinnitus but underwent MR imaging for dizziness were also included in our study (16 sides, group 3). Because all patients presented with unilateral tinnitus except for 1 patient who had bilateral tinnitus, 2 groups were included in the analysis as follows: group 1, symptomatic sides ( n = 16), and group 2, asymptomatic sides ( n = 14). and B.S.C, with 7 and 17 years of experience, respectively) evaluated both the IACs and CPAs of all patients separately. Of the 25 subjects, 15 (5 men and 10 women age range, 27–84 years mean age, 54.1 years) underwent MR imaging of the IAC and CPA thus, these 15 subjects were finally enrolled in the current study. After a 3-week trial, all 25 patients reported complete resolution or marked improvement of tinnitus.Īt the initial visit, MR imaging of the internal acoustic canal (IAC) and the cerebellopontine angle (CPA) was recommended for all patients with typewriter tinnitus. Of the 27 subjects, 2 were lost to follow-up and were excluded from further analysis. After we excluded other possible pathologic causes of tinnitus by taking a thorough history and performing neuro-otologic examinations, the patients were prescribed carbamazepine as an initial empiric treatment. The subjects visited the outpatient clinic of the otorhinolaryngology department with typical symptoms of typewriter tinnitus, which they described as “typewriter,” “machine gun,” or “crackling” sounds. From January 2014 to April 2016, 27 patients were initially diagnosed with typewriter tinnitus at our institution. This retrospective study was approved by the institutional review board of the Clinical Research Institute of Seoul National Bundang Hospital (B-1608–360-101). In other words, the purpose of the current study was to examine whether radiologic evidence of cochlear nerve compression is pathognomonic in subjects with typewriter tinnitus. Thus, in this study, we aimed to evaluate MR imaging findings of subjects with typewriter tinnitus with regard to the presence of radiologic evidence of cochlear nerve compression by performing a 3D T2-weighted volume isotropic turbo spin-echo acquisition (T2-VISTA Phillips Healthcare, Best, the Netherlands) sequence on 3T MR imaging to effectively visualize neurovascular compression. 6, 10 Moreover, signs of neurovascular compression have frequently been detected on MR imaging in asymptomatic patients, which raises questions about the role of MR imaging in the diagnosis of typewriter tinnitus. A few previous studies investigating subjects with typewriter tinnitus with carbamazepine responsiveness showed evidence of NVC-C on T2-weighted CISS images however, the sample sizes were relatively small (4 and 5 subjects, respectively), and no control subjects without tinnitus were included. However, because typewriter tinnitus is a relatively rare condition and was only recently described, few studies have been performed investigating the relationship between radiologic evidence of cochlear nerve compression on MR imaging and the presence of typewriter tinnitus, to our knowledge. 6 – 8, 10, 11 Complete suppression of tinnitus with carbamazepine treatment, in addition to its paroxysmal character, has led to the hypothesis that typewriter tinnitus results from neurovascular compression of the cochlear nerve (NVC-C), for which microvascular compression would be an effective treatment. 9 As in other vascular compression syndromes such as trigeminal neuralgia, typewriter tinnitus is highly responsive to carbamazepine. 6 – 8 Typewriter tinnitus is considered the result of dysmyelination and demyelination of the contact point between the arterial loop and the cochlear nerve that transmits an abnormal signal to the auditory cortex. It is either spontaneous or precipitated by positioning or sounds and occurs with staccato sounds described as “Morse code,” “machine gun,” “coins in a can,” “crackling,” or “typewriter” sounds. 1 – 4 Among these clinical symptoms, typewriter tinnitus, which was first described by a pediatric cardiologist as “ear-clicking tinnitus responding to carbamazepine,” 5 is characterized by paroxysmal attacks. Arterial compression of the cochleovestibular nerve complex has been suggested as a potential cause of hearing deficit, typewriter tinnitus, and equilibrium disturbance or vertigo.
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