Risk of sensorineural hearing loss in patients with vitiligo.

OBJECTIVE: The purpose of this study was to determine the prevalence of hearing loss and vestibular symptoms among Israeli vitiligo patients as compared with healthy controls. METHODS: 16 vitiligo patients and 16 healthy controls were enrolled in this prospective study. Vitiligo patients had undergone dermatologic evaluation and complete ENT evaluation. RESULTS: Vitiligo patients demonstrated a significantly higher prevalence of sensorineural hearing loss (SNHL) (p = 0.001). A 'notch'-shaped audiogram was the most frequent type of audiogram found among vitiligo patients (p = 0.021). Patients with mucosal involvement as the primary site of onset had a significantly more normal hearing level (p = 0.004). CONCLUSIONS: Due to the high prevalence of SNHL amongst vitiligo patients, it is recommended that these patients undergo a complete hearing evaluation, avoiding ototoxic hazards if possible.

Image guided navigation system-a new technology for complex endoscopic endonasal surgery.

PURPOSE: Endoscopic endonasal surgery (EES) has become the standard practice in sinonasal and anterior skull base surgery. The purpose of this manuscript is to describe experience using a new technology-the image guided navigation system (IGNS)-in complex cases undergoing EES. The advantages and disadvantages of computer aided surgery are discussed. PATIENTS AND METHODS: A total of 165 endoscopic endonasal procedures were performed between April 2001 and January 2003. IGNS was used in 34 patients in whom it was assumed that the ability to identify surgical sites accurately could be compromised by previous surgery, massive recurrent polyposis, or abnormal anatomy, or when biopsies had to be taken from specific anatomic locations (for example, clivus, wall of sphenoid sinus, orbital apex). The precision of the navigation system, total operating room time, surgeon's satisfaction and confidence, and intraoperative and postoperative complications were recorded. RESULTS: In 33 out of 34 patients the surgical procedure was uneventful. One patient with an atelectatic maxillary sinus developed a minor complication of preseptal orbital haematoma. In 94% the IGNS provided accurate anatomical localisation with less than 2 mm localisation error (1.1-2.0 mm, mean 1.6 mm). In all cases the surgical team felt that the system increased the intraoperative safety factor for the patient. The overall operating room time at the end of the study was 15 minutes longer than when regular EES was used. CONCLUSIONS: IGNS enables a new level of efficiency and safety in EES. Nevertheless, it is not advised for surgeons who are not familiar with regular EES. For the experienced endoscopist, however, IGNS is a valuable new tool in complex procedures.

Objective method for differentiating between drug-induced vestibulotoxicity and cochleotoxicity.

HYPOTHESIS: An objective direct method is proposed to differentiate between drug-induced functional vestibulotoxicity and cochleotoxicity. BACKGROUND: Many substances are ototoxic. Although there are objective methods to directly evaluate functional cochlear toxicity (auditory nerve brainstem responses [ABR]), it is more difficult to assess direct functional ototoxicity to the various vestibular end organs. METHODS: Short-latency vestibular evoked potentials (VsEP) from different vestibular end organs and ABR, were used to assess functional impairment of the vestibular and cochlear end organs caused by daily injections of the aminoglycoside amikacin (known to be preferentially cochleotoxic) in guinea pigs. RESULTS: There was no significant change in the various VsEPs. whereas ABR thresholds were elevated, confirming the selective functional cochleotoxicity previously reported, as evaluated by other (mainly nondirect) methods. CONCLUSION: This study demonstrates the feasibility in general of using short-latency evoked potentials to evaluate functional cochleotoxicity and vestibulotoxicity of ototoxic drugs and to differentiate between them.

Use of evoked potentials to objectively differentiate between selective vulnerability of cochlear and vestibular end organ function.

Auditory nerve brainstem evoked responses (ABR) have been used for several decades to investigate cochlear function. Recently techniques have been developed to elicit similar recordings from the vestibular end organs - short latency vestibular evoked potentials (VsEPs). Both ABR and VsEP reflect appropriate end organ function and may therefore be used to investigate the vulnerability of these end organs to various experimental insults, such as noise exposure and ototoxic drugs.

Assessment of vestibular ototoxicity of ear drops by recording of vestibular evoked potentials to acceleration impulses.

INTRODUCTION: The cochlear ototoxicity of several ear drops is well documented in the literature, but very few studies exist on the vestibular ototoxicity of these topical drugs. GOAL OF STUDY: To develop an animal model for the assessment of the vestibular ototoxicity of ear drops. MATERIALS AND METHODS: Two animal groups, consisting of five fat sand rats (FSRs) each, underwent unilateral labyrinthectomy. Normal saline was topically applied into the middle ear cavity of rats in the first group for 7 days (control group). Rats in the second group were treated in the same way by topical gentamicin solution. Cochlear function was assessed by the recording of auditory evoked potential (ABPs) thresholds, and vestibular function was assessed by the recording of vestibular evoked potentials (VsEPs) to angular accelerations. RESULTS: In the control group, except for the amplitude of the first wave, there was no significant difference in the VsEPs recorded before and after topical application. In the gentamicin group, VsEPs could not be recorded after 7 days, and ABPs were recorded in one case only, with a threshold of 100 dB sound pressure level (SPL). CONCLUSION: VsEPs seem to be a reliable measure for evaluating the vestibular ototoxicity of topical ear drops.

Spontaneous vertebral artery dissection mimicking acute vertigo. Case report.

A patient with acute vertigo, and normal findings on neurologic examination, was found to have vertebral artery dissection (VAD). This case shows that the clinical picture of VAD can mimic vertigo of labyrinthine (i.e, peripheral) origin.

Development of short latency vestibular evoked potentials in the neonatal rat.

The development of short latency vestibular evoked potentials (VsEPs) was investigated in the neonatal rat. Using the appropriate stimulus (linear or angular acceleration impulses) and head orientation, responses elicited in various vestibular end-organs (utricle: x-VsEP; saccule: z-VsEP; lateral semi-circular canal: a-VsEP) were measured in rat pups at various ages between post-natal days (PND) 5 and 30, and compared to those recorded from adult animals. It was found that the VsEPs initially appeared on PND 6 (x-VsEPs and z-VsEPs) or 7 (a-VsEPs), and that by PND 8 the three responses could be recorded in all animals. The first wave of the responses, generated in the primary sensory nerve and reflecting end-organ activity, reached adult latencies and amplitudes by PND 10, showing rapid maturity of the responses. Auditory responses, on the other hand, develop at a later stage (from PND 11). The possible mechanisms involved in this differential maturation between vestibular and auditory activity are discussed.

The effect of head orientation on the vestibular evoked potentials to linear acceleration impulses in rats.

OBJECTIVE: To investigate the influence of linear acceleration impulses delivered when the head is held in different static head orientations, on the first wave of the short latency vestibular evoked potential (VsEP). The first wave is the compound action potential of the primary vestibular neurons synchronously activated. BACKGROUND: It has been shown previously that the VsEP elicited in response to linear acceleration is initiated mainly in the otolith organs. These organs are responsive to both dynamic and static linear forces, including gravity. METHODS: VsEPs to linear acceleration stimuli (4g) were recorded when the rats head was oriented so that a) the plane of the utricular macula was aligned with the plane of the stimulus, b) in supine position and c) with the head pitched up and down in various angles with respect to gravity (stimulus-head spatial relation remained constant) as compared to a reference position. RESULTS: With the stimulus aligned with the plane of the utricular macula, the amplitude of the first wave of the L-VsEPs was significantly larger than in the reference position. In the supine position, the amplitude of the first wave was significantly larger and the latency was significantly shorter. The amplitude of the first VsEP wave tended to be larger in the "head up" orientations as compared to the "head down" orientations (not statistically significant). CONCLUSIONS: These results demonstrate the influence of head position and gravity on the VsEPs to linear acceleration impulses, which is in accordance with their otolithic origin.

Surgical anatomy of the ear of the fat sand rat.

OBJECTIVE: This study was conducted to investigate and describe the anatomical details of the ear of the fat sand rat (Psammomys obesus). METHODS: Thirty ears (15 in dry skull and 15 in live animals) were dissected with the aid of an operating microscope and microsurgical techniques. Photographs were taken through an operating microscope. RESULTS: The temporal bone of the fat sand rat consists mainly of an unusually large bulla. Three distinct auditory ossicles were visualized and the manubrium of the malleus is relatively long in relation to the size of the ear. Most parts of the inner ear bulge into the bulla cavity and are easily accessible. The cochlea consists of 3.25 turns. The tympanic membrane, facial nerve, stapedial artery, and eustachian tube are described in detail. The large size of the bulla is probably related to the high sensitivity, particularly at low frequencies of the animals ear. CONCLUSION: The fat sand rat was found to be an excellent experimental animal for the investigation of middle and inner ear physiology.

Effect of white noise "masking" on vestibular evoked potentials recorded using different stimulus modalities.

Short latency vestibular evoked potentials (VsEPs) to linear acceleration impulses (L-VsEPs) are initiated in the otolith organs (saccule and utricle). Some of the saccule afferents have been reported to respond not only to linear acceleration, but also to high intensity acoustic stimuli. If so, the L-VsEP recorded from the saccule (elicited with the stimulus orientated relative to the head so as to optimally activate the saccule, i.e. stimulus in the vertical plane, Z-VsEP) should be reduced during high intensity broad band noise (BBN) "masking". Conversely, the utricular afferents have been reported to be less auditory-sensitive. Therefore, an L-VsEP which is mainly utricular in origin (stimulus in the horizontal plane, X-VsEP) should be less affected by this noise "masking". This was investigated in rats by recording X-VsEPs and Z-VsEPs and angular VsEPs (A-VsEPs), originating in the lateral semi-circular canals, before, during and after exposure to short duration, high intensity (113 dB SPL) BBN. This intensity completely masked auditory nerve evoked responses. The Z-VsEP did appear to be slightly more affected by the noise "masking" than the X-VsEP, implying the presence of more auditory-sensitive elements in the saccule. The A-VsEP was also affected by the BBN. The overall effect was relatively small (on average, 10-25% depression of the first wave of the different VsEPs). The responses showed recovery 5 min later.

Origins of the short latency vestibular evoked potentials (VsEPs) to linear acceleration impulses.

OBJECTIVE: To verify the vestibular origin of the short latency (t < 12.5 msec) vestibular evoked potentials (VsEPs) in response to linear acceleration impulses (L-VsEPs) and to differentiate between the contributions of the otolith organs and the semi-circular canals (SCCs) to their initiation. DESIGN AND METHODS: L-VsEPs (stimulus intensity, 3 g; rise time, 1.0 to 1.5 msec) were recorded in fat sand rats (Psammomys obesus) before and after unilateral labyrinthectomy, plugging of the SCCs in the remaining ear, and bilateral labyrinthectomy. Auditory nerve brainstem evoked responses (ABRs) and VsEPs to angular acceleration impulses (A-VsEPs) were also recorded. Wave amplitudes and latencies were statistically analyzed (MANOVA, repeated t-tests). RESULTS: In the intact animal, the linear VsEPs consisted of 5 to 6 waves, several mV in amplitude, with short latencies. The latency of the first wave was 2.0 msec. These waves were abolished after bilateral labyrinthectomy. Before and after plugging of the SCCs, linear acceleration VsEP wave latencies did not change, although amplitudes were slightly reduced. Similar results were obtained with respect to ABRs recorded from the same ear. Angular acceleration VsEPs were abolished after SCC plugging. CONCLUSIONS: These and other results confirm that the linear VsEPs are compound action potentials of the vestibular pathway, the first wave is the response of the vestibular nerve, and they are initiated mainly in the otolith organs.

Differential effect of the loop diuretic furosemide on short latency auditory and vestibular-evoked potentials.

OBJECTIVE: This study aimed to investigate the differential effect of the loop diuretic furosemide on the auditory and vestibular (otolith) end organs in the same animals simultaneously. DESIGN AND METHODS: Auditory nerve-brain stem-evoked responses (ABR-generated in the cochlea) and short latency vestibular-evoked responses to linear acceleration impulses (L-VsEP-generated in the otolith organs) were recorded from albino Sabra rats both before and at minute intervals after intravenous injections of the loop diuretic furosemide. In some animals, an equal volume of saline was injected to control for the effect of the injection itself. In most animals, more than one injection of saline or furosemide was possible (furosemide, N = 17 injections in 10 rats; saline, N = 18 injections in 9 rats). Peak-to-peak amplitude and peak latency changes in the first wave in each recording (representing end-organ activity) as a function of postinjection time were compared between the two evoked potentials using analysis of variance and repeated t-tests. RESULTS: Saline injections caused only minor changes in the amplitude of the ABR and the L-VsEP. After administration of furosemide, the amplitude of the L-VsEP hardly changed. However, there was a noticeable decrease in the amplitude of the ABR. CONCLUSIONS: Although furosemide has a major depressant effect on cochlear function, vestibular end-organ activity is hardly altered.

Effect of noise on the vestibular system - Vestibular evoked potential studies in rats.

Studies have shown that in order for sound to affect the vestibular end organs in the inner ear, very high intensities are required. Furthermore, in patients with noise induced hearing loss, vestibular signs, if present, are subclinical. In order to study possible auditory-vestibular interactions in a more controlled fashion, using physiological sound intensities, the present study used short latency vestibular evoked potentials (VsEPs) to impulses of angular (15,000 degrees /sec(2), risetime 1.5 msec) and linear (3-5 g, risetime 1.5 msec) acceleration were used to study the possible effects of sound on peripheral vestibular function in rats. Four different paradigms were used: a - an intense (135 dB pe SPL) click stimulus was presented 5 msec before the linear acceleration impulse and the VsEP to 128 stimuli were recorded with and without this click stimulus. There was no effect of the preceding intense click on the first wave (reflecting end organ activity) of the linear VsEP. b - 113 dB SPL white noise "masking" was presented while the VsEPs were elicited. A 10-20% reduction in the amplitude of the first VsEP wave was seen during the noise exposure, but 5 minutes after this exposure, there was almost complete recovery to pre-exposure amplitude. c - 113 dB SPL noise was presented for one hour and VsEPs were recorded within 15 minutes of cessation of the noise. The auditory nerve-brainstem-evoked response showed a temporary threshold shift while there was no effect on the VsEP. d - 113 dB SPL white noise was presented for 12 hours per day for 21 consecutive days. Auditory nerve-brainstem-evoked responses and vestibular (VsEPs) function were studied one week after the conclusion of the noise exposure. Auditory function was severely permanently depressed (40 dB threshold elevation and clear histological damage) while the amplitude of wave 1 of the VsEP was not affected. It seems therefore that even though intense noise clearly affects the cochlea and may have a "masking" effect on the vestibular end organs, the intensities used in this study (113 dB SPL) are not able to produce a long-term noise induced vestibular disorder in the initially normal ear. These differences between the response of the cochlear and vestibular end organs to noise may be due to dissimilarities in their acoustic impedances and/or their electrical resting potential.