Eui-Cheol Nam

Tinnitus, Diminished Sound-Level Tolerance, and Elevated Auditory Activity in Humans With Clinically Normal Hearing Sensitivity

Phantom sensations and sensory hypersensitivity are disordered perceptions that characterize a variety of intractable conditions involving the somatosensory, visual, and auditory modalities. We report physiological correlates of two perceptual abnormalities in the auditory domain: tinnitus, the phantom perception of sound, and hyperacusis, a decreased tolerance of sound based on loudness. Here, subjects with and without tinnitus, all with clinically normal hearing thresholds, underwent 1) behavioral testing to assess sound-level tolerance and 2) functional MRI to measure sound-evoked activation of central auditory centers. Despite receiving identical sound stimulation levels, subjects with diminished sound-level tolerance (i.e., hyperacusis) showed elevated activation in the auditory midbrain, thalamus, and primary auditory cortex compared with subjects with normal tolerance. Primary auditory cortex, but not subcortical centers, showed elevated activation specifically related to tinnitus. The results directly link hyperacusis and tinnitus to hyperactivity within the central auditory system. We hypothesize that the tinnitus-related elevations in cortical activation may reflect undue attention drawn to the auditory domain, an interpretation consistent with the lack of tinnitus-related effects subcortically where activation is less potently modulated by attentional state. The data strengthen, at a mechanistic level, analogies drawn previously between tinnitus/hyperacusis and other, nonauditory disordered perceptions thought to arise from neural hyperactivity such as chronic neuropathic pain and photophobia.

Hippocampal Shape Deformation in Female Patients with Unremitting Major Depressive Disorder

Although the fact is that hippocampal atrophy occurs in patients with major depression, shape contractions also happen but have been found to be inconsistent. Here, the authors used shape analysis to study the hippocampi in 21 women with major depression and 21 control subjects. Both hippocampi were small in patients compared with controls. Regional shape contractions were found in the ambient gyrus, basal hippocampal head, posterior subiculum, and dorsal hippocampus of the left hemisphere. The right hippocampus showed a similar pattern but was less atrophic compared with the left hippocampus. The authors concluded that atrophy and regional shape contractions in the hippocampi of patients with major depression were more dominant on the left side. The causes of hippocampal damage could be hypersecretion of glucocorticoids contributing to neuronal death or the failure of adult neurogenesis in the dentate gyrus. BACKGROUND AND PURPOSE: The hippocampal atrophy of MDD has been known, but the region shape contractions of the hippocampus in MDD were inconsistent. Spheric harmonic shape analysis was applied to the hippocampus in female patients with unremitting MDD to evaluate morphometric changes of the hippocampus. MATERIALS AND METHODS: Shape analysis was performed by using T1-weighted MR imaging in 21 female patients with MDD and 21 age- and sex-matched healthy controls. Manually segmented hippocampi were parameterized, and the point-to-point–based group difference was compared by using the Hotelling T-squared test. The partial correlation analyses were tested between clinical variables and shape changes. RESULTS: Both hippocampal volumes were small in patients with MDD compared with healthy controls, and the right hippocampal volume was negatively correlated with the number of episodes at marginal significance. Regional shape contractions were found in the ambient gyrus, basal hippocampal head, posterior subiculum, and dorsal hippocampus of the left hemisphere. The right hippocampus showed a similar pattern but was less atrophic compared with the left hippocampus. A negative correlation was found between the HDRS and shape deformation in the CA3, ambient gyrus, posterior subiculum, and gyrus fasciolaris of the left hippocampus. CONCLUSIONS: We showed atrophy and regional shape contractions in the hippocampi of patients with MDD, which were more dominant on the left side. The causes of hippocampal damage could be the hypersecretion of glucocorticoids contributing to neuronal death or the failing of adult neurogenesis in the dentate gyrus.

Clonazepam quiets tinnitus: a randomised crossover study with Ginkgo biloba.

Objective To assess the effect of Ginkgo biloba and clonazepam, a γ-aminobutyric acid (GABA)-receptor agonist, upon tinnitus. Methods This was an open-label, randomised, crossover study. 27 men and 11 women (aged 16–80 (mean 58)) with tinnitus for more than 2 months were enrolled. Participants were randomised to either clonazepam or G biloba for the first 3 weeks. For the next 2 weeks of washout no medication was taken. For the final 3 weeks, subjects were given the other drug. The initial dose of clonazepam and G biloba was one tablet daily (clonazepam 0.5 mg; G biloba 40 mg). Subjects were instructed to increase the dose by one tablet every 3 days to a maximum of four tablets daily until they perceived a satisfactory decrease in tinnitus loudness or intolerable side effects. Tinnitus was assessed with pitch and loudness matching, tinnitus handicap inventory, and visual analogue scales of loudness, duration and annoyance. Results Comparing before and after each drug, clonazepam significantly improved tinnitus loudness (74% of subjects), duration (63%), annoyance (79%), and tinnitus handicap inventory score (61%), whereas the G biloba showed no significant differences on any of these measures. Conclusion Clonazepam is effective in treating tinnitus; G biloba is ineffective.

Is it necessary to differentiate tinnitus from auditory hallucination in schizophrenic patients

Although the definitions of subjective tinnitus and auditory hallucination are very similar, the origins and underlying causes of each symptom clearly differ. This study examined whether the differentiation of tinnitus from auditory hallucination is necessary for the proper management of these symptoms in schizophrenic patients. We investigated the characteristics of auditory hallucinations in 15 schizophrenic patients, and measured their pure-tone hearing levels and auditory brainstem responses (ABR). The average hearing level was 20.6 +/- 16.2 dB, with a mild decrease at high frequencies. We classified the patients into three groups: pure hallucination, tinnitus, and hallucination plus tinnitus. Eight patients (53.3 per cent) complained of pure hallucination and only one of them had a mild hearing loss. Hearing deficits were observed in six of seven tinnitus patients. Abnormal findings of ABR were found only in the pure hallucination group. The results suggest that tinnitus should be differentiated from auditory hallucination in the evaluation of schizophrenic patients.

Somatosensory Pulsatile Tinnitus Syndrome: Somatic Testing Identifies a Pulsatile Tinnitus Subtype That Implicates the Somatosensory System

A new tinnitus syndrome is described: high-pitched, cardiac-synchronous tinnitus, whose pulsations are suppressed by strong contractions or compressions of the neck and jaw muscles (somatic testing). 14 cases, 6 non-lateralized and 8 unilateral, are reported. In the non-lateralized cases, onset was bilateral. In the one intermittent case, while her tinnitus was absent her pulsatile tinnitus could be induced by somatic testing. No etiology was found from physical examination, imaging, or ancillary testing. Because these cases of pulsatile tinnitus can be both induced and suppressed by activation of the somatosensory system of the head or upper lateral neck, we propose that this syndrome is occurring from (a) cardiac synchronous somatosensory activation of the central auditory pathway or (b) failure of the somatosensory-auditory central nervous system interactions to suppress cardiac somatosounds.

Optimization of Transcutaneous Vagus Nerve Stimulation Using Functional MRI.

Vagus nerve stimulation (VNS) is an established therapy for drug‐resistant epilepsy, depression, and a number of other disorders. Transcutaneous stimulation of the auricular branch of the vagus nerve (tVNS) has been considered as a non‐invasive alternative. Several functional magnetic resonance imaging (fMRI) studies on the effects of tVNS used different stimulation parameters and locations in the ear, which makes it difficult to determine the optimal tVNS methodology. The present study used fMRI to determine the most effective location for tVNS.

Prevalence and Factors Associated with Neck and Jaw Muscle Modulation of Tinnitus

Forceful contractions of neck and jaw muscles have consistently been shown to modulate tinnitus and can be used to screen patients who are responsive to somatic stimulation and, therefore, optimal candidates for somatosensory-based treatment. To identify the factors associated with somatic modulation of tinnitus, 163 patients underwent 19 neck and jaw maneuvers after an extensive physiological and audiological profile was compiled. Overall, tinnitus was modulated in 57.1% of ears tested. Unilateral tinnitus showed greater prevalence of modulation. Neck maneuvers generally decreased tinnitus loudness, whereas jaw maneuvers increased loudness. Female gender and buzzing tinnitus were associated with a high prevalence of modulation and a decrease in tinnitus loudness. Loud tinnitus and low-pitched tonal tinnitus were associated with exacerbation of the condition as a result of somatic testing. Use of these characteristics to select optimal candidates for somatosensory-based tinnitus therapies may be essential for the development of an effective approach for tinnitus treatment.

Carbamazepine responsive typewriter tinnitus from basilar invagination

Basilar invagination due to a congenital skeletal disorder kinked the brainstem at the ponto-medullary junction causing both auditory nerves to make an acute turn at the porus acousticus. The associated bilateral asynchronous clicking tinnitus responded to carbamazepine.

Electrocochleography is More Sensitive than Distortion-Product Otoacoustic Emission Test for Detecting Noise-Induced Temporary Threshold Shift

OBJECTIVE: We investigated and compared the usefulness of the electrocochleography and distortion product otoacoustic emission tests for detecting the earliest noise-induced damage by analyzing the sensitivity and specificity of the 2 tests. STUDY DESIGN: A prospective study. METHODS: After listening to music at 90.3 ± 4.2 dB in the same night-club for 2 hours continuously, 23 healthy normal ears experienced a temporary threshold shift exceeding 5 dB. Pure-tone audiometry, the distortion product otoacoustic emission test, and electrocochleography were performed before, immediately after, and 24 hours after the exposure. RESULTS: Before exposure, the measured distortion product/noise floor was 9.8 ± 10.4, 23.5 ± 6.4, 18.7 ± 6.4, and 19.1 ± 5.6 dB sound pressure level (SPL) at frequencies of 1, 2, 3, and 4 kHz, respectively. Immediately after exposure, it decreased significantly at 2, 3, and 4 kHz to 16.6 ± 7.6, 12.5 ± 6.8, and 14.8 ± 7.7 dB SPL, respectively. Marked increases in the amplitude of the summating potential and summating potential/action potential ratio were recorded from 0.15 ± 0.06 to 0.32 ± 0.11 and 0.23 ± 0.06 to 0.44 ± 0.08, respectively. The respective sensitivity and specificity of electrocochleography were 76.7% to 88.5% and 91.0% to 100%. Those of the distortion product otoacoustic emission test were 54.8% to 62.2% and 75.5% to 87.0%, respectively. CONCLUSION: Electrocochleography appears to provide more sensitive and specific information than the distortion product otoacoustic emission test for detecting a noise-induced temporary threshold shift.

Extratympanic electrocochleographic changes on noise-induced temporary threshold shift

OBJECTIVE: Electrocochleography (ECoG) is a sensitive evoked-response test for evaluating changes in cochlear function. We investigated the extratympanic ECoG in a noise-induced temporary threshold shift (TTS) to evaluate the usefulness of ECoG in the early detection of noise-induced hearing loss (NIHL). STUDY DESIGN AND METHODS: In a prospective analysis, 15 healthy ears were exposed to 90.3- to 105.0-dB noise for 3 hours in the same computer-game arcade. Pure-tone audiometry and ECoG were performed before, immediately after, and 24 hours after the exposure. RESULTS: Before the exposure, the average hearing level was 5.8 ± 2.7 dB, which increased significantly to 12.8 ± 2.8 dB immediately after exposure. A marked increment in the SP/AP (summating potential/action potential) ratio was observed with the TTS. The mean ratio was 0.22 ± 0.11 before the exposure, 0.46 ± 0.18 in the TTS phase, and 0.20 ± 0.11 after resolution. CONCLUSION: The results of this study suggest that the SP/AP ratio is useful for the early detection and monitoring of NIHL. (Otolaryngol Head Neck Surg 2004;130:437–42.)