1/24. Unilateral sensorineural hearing loss and its aetiology in childhood: the contribution of computerised tomography in aetiological diagnosis and management.OBJECTIVES: The objective of this study was to identify factors correlated with the CT outcome and to examine the contribution of the CT scan in the aetiological diagnosis and management of unilateral sensorineural hearing loss in childhood. methods: The records of 35 consecutively investigated patients by the audiology Department of Great Ormond Street Hospital between January 1996 and June 1998 were reviewed. The CT results, population sample characteristics, initiation of further investigations after the CT results and management decisions based on the CT results were tabulated and analysed. RESULTS: In a series of 35 consecutively investigated children with unilateral sensorineural hearing loss, 11 CT scans were identified as abnormal. The CT findings were: labyrinthitis ossificans (3), unilaterally dilated vestibular aqueduct (2), bilaterally dilated vestibular aqueduct (2), unilateral deformity of the cochlea ('Mondini') (1), unilateral severe labyrinthine dysplasia (1), unilateral markedly narrow internal acoustic meatus (1), bilaterally dilated lateral semicircular canals (1). The presence of progressive hearing loss was a significant predictor of abnormal CT outcome, while the severity of hearing loss was not. The CT scans offered valuable information regarding the aetiological diagnosis in all cases and, in addition, prompted the appropriate vestibular rehabilitation in three cases, further investigations in four (with dilated vestibular aqueduct) and hearing preservation counselling in two (bilateral DVA) (seven out of 35 = 20%). CONCLUSION: All children with unilateral sensorineural hearing loss should have a CT scan of the petrous pyramids/IAMs performed at some stage, as not only aetiology but also prognosis and management of these cases may be significantly influenced by the CT outcome.- - - - - - - - - - ranking = 1keywords = canal (Clic here for more details about this article) |
2/24. Superior canal dehiscence syndrome.OBJECTIVE: To present the symptoms, signs, and findings on diagnostic tests of patients with the superior canal dehiscence syndrome and to describe the surgical procedures used to treat the dehiscence in five patients. DESIGN AND SETTING: Prospective study of a series of patients identified as having this syndrome at a tertiary care referral center. patients AND RESULTS: Seventeen patients with vertigo, oscillopsia, or both evoked by intense sounds or stimuli that caused changes in middle ear and/or intracranial pressure were identified over a 4-year period. The evoked eye movements had vertical and torsional components, with the direction corresponding to the effect of the stimuli in causing excitation (Valsalva against pinched nostrils, tragal compression, sounds) or inhibition (Valsalva against a closed glottis or jugular venous compression) of the affected superior semicircular canal. Thirteen (76%) of these patients also experienced chronic dysequilibrium that was often the most debilitating symptom. Dehiscence of bone overlying the superior semicircular canal on the affected side was confirmed with computed tomographic scans in each case. Surgical procedures through the middle fossa approach to plug or resurface the superior canal were performed in five patients (canal plugging in three cases and resurfacing of the dehiscence without plugging in two). The debilitating symptoms resolved or improved after the procedures. Signs of vestibular hypofunction, without loss of hearing, were noted in one patient after plugging of the superior canal and in one other patient after resurfacing of the canal. CONCLUSIONS: The superior canal dehiscence syndrome is identified based on characteristic symptoms, signs, and computed tomographic findings. The clinical presentation and findings can be understood in terms of the effect of the dehiscence on the physiology of the labyrinth. The syndrome is a treatable cause of vestibular disturbance.- - - - - - - - - - ranking = 12keywords = canal (Clic here for more details about this article) |
3/24. Vestibular hypersensitivity to sound (Tullio phenomenon): structural and functional assessment.OBJECTIVES: To establish the role of high-resolution CT imaging and tests of vestibulocollic reflexes in diagnosing and understanding the pathogenesis of the Tullio phenomenon. BACKGROUND: The Tullio phenomenon is a syndrome in which acoustic stimulation produces symptoms and signs of vestibular activation. It has previously been associated with an abnormally low threshold for click-evoked vestibulocollic responses and also with dehiscence of the roof of the anterior (superior) semicircular canal on high-resolution CT scans of the temporal bones. methods: High-resolution CT scans of the temporal bones and vestibulocollic responses in sternocleidomastoid to both clicks and transmastoid galvanic stimulation (3 mA/2 msec) were studied in four patients with the Tullio phenomenon (one bilateral). RESULTS: Click-evoked thresholds were low for all affected ears (four at 65 dB nHL, one at 55 dB nHL) and normal (>70 dB nHL) for the three unaffected ears. In contrast, galvanic-evoked vestibulocollic responses were symmetric and of normal size in all patients. The bony roof of the anterior (superior) semicircular canal was thin, possibly absent, on CT of all affected ears and also in two out of three unaffected ears. CONCLUSIONS: The normal galvanic vestibulocollic responses indicate that sound sensitivity in patients with the Tullio phenomenon is likely to occur distal to the vestibular nerve, probably at the level of the receptors. Both click hypersensitivity and dehiscence of the anterior (superior) semicircular canal are associated with the Tullio phenomenon but as the CT scan abnormality can occur in clinically unaffected ears, click testing is important for specific diagnosis. Abnormal sound sensitivity, as demonstrated by click responses, confirms that the radiologic abnormality is function significant.- - - - - - - - - - ranking = 3keywords = canal (Clic here for more details about this article) |
4/24. Inferior vestibular neuritis.Sudden, spontaneous, unilateral loss of vestibular function without simultaneous hearing loss or brain stem signs is generally attributed to a viral infection involving the vestibular nerve and is called acute vestibular neuritis. The clinical hallmarks of acute vestibular neuritis are vertigo, spontaneous nystagmus, and unilateral loss of lateral semicircular function as shown by impulsive and caloric testing. In some patients with vestibular neuritis the process appears to involve only anterior and lateral semicircular function, and these patients are considered to have selective superior vestibular neuritis. Here we report on two patients with acute vertigo, normal lateral semicircular canal function as shown by both impulsive and caloric testing, but selective loss of posterior semicircular canal function as shown by impulsive testing and of saccular function as shown by vestibular evoked myogenic potential testing. We suggest that these patients had selective inferior vestibular neuritis and that contrary to conventional teaching, in a patient with acute spontaneous vertigo, unilateral loss of lateral semicircular canal function is not essential for a diagnosis of acute vestibular neuritis.- - - - - - - - - - ranking = 3keywords = canal (Clic here for more details about this article) |
5/24. Acute peripheral vestibular deficits after whiplash injuries.We report 3 patients who had acute peripheral vestibular dysfunction minutes to hours after a car collision with whiplash injury without head trauma. The accident was a frontal collision in 1 case, a rear impact in the second, and lateral in the third. All patients complained immediately of cervicalgia, headache, acute vertigo with a sensation of erroneous body movements, and slipping of image with head movements. A sudden sensation of tilting of the environment when driving, tinnitus, and hyperacusis were also described. The otoneurologic findings showed bilateral canalolithiasis in 1 patient and an acute peripheral vestibular deficit in 2 patients. Tilt of the subjective visual vertical was measured in all patients. Cerebral magnetic resonance imaging yielded normal findings. As angular and linear accelerometers, the vestibular organs are directly exposed to high forces generated by whiplash mechanisms. vertigo generated by peripheral vestibular lesions is probably underestimated in whiplash injuries and may often be incorrectly attributed to cervical or cerebral lesions.- - - - - - - - - - ranking = 1keywords = canal (Clic here for more details about this article) |
6/24. Anterior canal failure: ocular torsion without perceptual tilt due to preserved otolith function.A patient with anterior semicircular canal dehiscence syndrome underwent surgical patching that caused an isolated dysfunction of the left anterior semicircular canal postoperatively. He exhibited significant ocular torsion toward the side of the affected labyrinth (17 degrees excyclotropia of the ipsilateral eye), but no displacement of the subjective visual vertical. This dissociation suggests that an isolated ocular torsion may occur after an anterior semicircular canal lesion. A combined ocular torsion and subjective visual vertical tilt, which is usually seen with vestibular lesions, requires an associated otolith dysfunction.- - - - - - - - - - ranking = 7keywords = canal (Clic here for more details about this article) |
7/24. Familial early-onset progressive vestibulopathy without hearing impairment.A family with early-onset vestibulopathy is presented. The 34-year-old father had experienced brief attacks of vertigo and currently suffers from unsteadiness and oscillopsia during head movements. His two young sons also experience brief attacks of spontaneous vertigo. In vestibular testing all three subjects showed reduced caloric responses. However, only the father showed reduced otolith function (as reflected by the vestibular-evoked myogenic potentials). Further, all three subjects had walked before the age of 1 year and none of them had had any auditory symptoms. It is suggested that they have familial early-onset progressive vestibulopathy affecting the canals before the otoliths but sparing cochlear function.- - - - - - - - - - ranking = 1keywords = canal (Clic here for more details about this article) |
8/24. Vestibular-evoked myogenic potentials in three patients with large vestibular aqueduct.An enlarged vestibular aqueduct (LVA) is a common congenital inner ear anomaly responsible for some unusual vestibular and audiological symptoms. Most of the cases show bilateral early onset and progressive hearing loss in children. The gross appearance on CT scan of the inner ear is generally normal. However, precise measurements of the inner ear components reveal abnormal dimensions, which may account for the accompanying auditory and vestibular dysfunction. Despite extensive studies on hearing and the vestibular apparatus, saccular function is not studied. To our knowledge this is the first report of saccular malfunction in three patients with LVA by means of vestibular evoked myogenic potentials. Conventional audiograms revealed bilateral severe sensorineural hearing loss in two patients and mixed type hearing loss in one patient. Two of the patients complained about vertigo and dizziness but vestibular assessments of the patients showed normal results. The diagnosis had been made by high-resolution CT scans and MR images of the skull that showed LVA in the absence of other anomalies. The VEMP threshold measured from the ear with LVA in two patients with unilateral enlargement of the vestibular aqueduct was 75-80 dB nHL whereas the threshold from normal ears was 95 dB nHL. The third patient with mixed type hearing loss and bilateral LVA had VEMP responses despite a big air-bone gap in the low frequency range. The VEMP in this patient was greater in amplitude and lower in threshold in the operated ear (the patient had a tympanoplasty which did not improve her hearing). These findings and results of other patients with Tullio phenomenon and superior semicircular canal dehiscence, who also showed lower VEMP threshold, confirmed the theory of a 'third window' that allows volume and pressure displacements, and thus larger deflection of the vestibular sensors, which would cause the vestibular organ to be more responsive to sound and pressure changes.- - - - - - - - - - ranking = 1keywords = canal (Clic here for more details about this article) |
9/24. Patient and normal three-dimensional eye-movement responses to maintained (DC) surface galvanic vestibular stimulation.HYPOTHESIS: That disease or dysfunction of vestibular end organs in human patients will reduce or eliminate the contribution of the affected end organs to the total eye-movement response to DC surface galvanic vestibular stimulation (GVS). BACKGROUND: It was assumed that DC GVS (at current of 5 mA) stimulates all vestibular end organs, an assumption that is strongly supported by physiological evidence, including the activation of primary vestibular afferent neurons by galvanic stimulation. Previous studies also have described the oculomotor responses to vestibular activation. Stimulation of individual semicircular canals results in eye movements parallel to the plane of the stimulated canal, and stimulation of the utricular macula produces changes in ocular torsional position. It was also assumed that the total three-dimensional eye-movement response to GVS is the sum of the contributions of the oculomotor drive of all the vestibular end organs. If a particular vestibular end organ were to be diseased or dysfunctional, it was reasoned that its contribution to the GVS-induced oculomotor response would be reduced or absent and that patients thus affected would have a systematic difference in their GVS-induced oculomotor response compared with the response of normal healthy individuals. methods: Three-dimensional video eye-movement recording was carried out in complete darkness on normal healthy subjects and patients with various types of vestibular dysfunction, as diagnosed by independent vestibular clinical tests. The eye-movement response to long-duration bilateral and unilateral surface GVS was measured. RESULTS: The pattern of horizontal, vertical, and torsional eye velocity and eye position during GVS of patients independently diagnosed with bilateral vestibular dysfunction, unilateral vestibular dysfunction, charge syndrome (semicircular canal hypoplasia), semicircular canal occlusion, or inferior vestibular neuritis differed systematically from the responses of normal healthy subjects in ways that corresponded to the expectations from the conceptual approach of the study. CONCLUSION: The study reports the first data on the differences between the normal response to GVS and those of patients with a number of clinical vestibular conditions including unilateral vestibular loss, canal block, and vestibular neuritis. The GVS-induced eye-movement patterns of patients with vestibular dysfunction are consistent with the reduction or absence of oculomotor contribution from the end organs implicated in their particular disease condition.- - - - - - - - - - ranking = 5keywords = canal (Clic here for more details about this article) |
10/24. Drop attacks secondary to superior canal dehiscence syndrome.Two patients with unprovoked drop attacks were found to have dehiscence of the superior semicircular canal on CT of the temporal bone. Both had conductive hearing loss, preservation of stapedius reflex, and abnormal vestibular evoked myogenic potentials. Neither had sound- or pressure-induced nystagmus. Repair of the dehiscence in one case stopped the drop attacks, supporting a causal relationship between the dehiscence and the drop attacks.- - - - - - - - - - ranking = 5keywords = canal (Clic here for more details about this article) |
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