Absent Caloric Responses Research Articles

Chronic Unilateral Vestibular Hypofunction: Insights into Etiologies, Clinical Subtypes, Diagnostics and Quality of Life.

Background/Objectives: Chronic unilateral vestibular hypofunction (UVH) can lead to disabling vestibular symptoms and a decrease in quality of life. The aim of this study was to investigate etiologies, clinical subtypes, symptoms, and quality of life (QoL) in patients with chronic UVH. Methods: A retrospective study was performed on 251 UVH patients in a tertiary referral center. Inclusion criteria comprised reduced or absent caloric responses, with a caloric asymmetry ratio ≥25%. Patients with central vestibular pathology, symptom duration <3 months, and incomplete responses to questionnaires were excluded. Patient records were assessed for etiologies, secondary vestibular diagnoses, clinical subtypes, and questionnaires related to QoL. Additionally, multiple linear regression analysis was performed to evaluate factors influencing QoL. Results: Thirteen different etiologies were identified, with Menière's Disease as the most prevalent (31%, n = 79). The most frequently reported secondary vestibular diagnoses were benign paroxysmal positional vertigo (BPPV) (21%, n = 54) and persistent postural perceptual dizziness (PPPD) (19%, n = 47). Five distinct clinical subtypes were identified: recurrent vertigo with UVH (47%), rapidly progressive UVH (25%), idiopathic/unknown UVH (18%), slowly progressive UVH (8%), and congenital UVH (2%). Over 80% of UVH patients experienced moderate-to-severe handicap, as indicated by the Dizziness Handicap Inventory. Approximately 20-25% of UVH patients exhibited moderate-to-severe depression and anxiety, based on the Hospital Anxiety and Depression Scale. Multiple linear regression analyses demonstrated that the presence of PPPD significantly reduced QoL in chronic UVH patients. Conclusions: Chronic UVH is a heterogeneous disorder. Secondary vestibular diagnoses like BPPV and PPPD often co-exist and can significantly impact QoL. A structured diagnostic approach and tailored interventions are crucial to address the diverse needs of UVH patients.

Acute vestibulopathy with simultaneous bilateral involvement of the vestibulo-ocular reflex limited to the low-frequency range

We report a novel type of idiopathic bilateral vestibulopathy with acute simultaneous involvement of the vestibulo-ocular reflex limited to the low-frequency range. A 64-year-old female presented with dizziness, oscillopsia, and difficulty walking. She did not experience rotatory vertigo and did not show any nystagmus. Vestibular function tests showed absent caloric responses in both ears, while vestibulo-ocular reflex (VOR) gains in the video head impulse test (vHIT) were preserved in all six semicircular canals. Cervical and ocular vestibular evoked myogenic potentials in response to air-conducted sound were absent on both sides. Since the caloric test and vHIT measures low-frequency and high-frequency VOR, respectively, we diagnosed the patient as having a bilateral VOR deficit limited to the low-frequency range. During a 1-year follow-up with vestibular rehabilitation, the subjective symptom of dizziness gradually recovered while recovery of vestibular function was minimal.

Chapter 17 - Bilateral vestibulopathy

The leading symptoms of bilateral vestibulopathy (BVP) are postural imbalance and unsteadiness of gait that worsens in darkness and on uneven ground. There are typically no symptoms while sitting or lying under static conditions. A minority of patients also have movement-induced oscillopsia, in particular while walking. The diagnosis of BVP is based on a bilaterally reduced or absent function of the vestibulo-ocular reflex (VOR). This deficit is diagnosed for the high-frequency range of the angular VOR by a bilaterally pathologic bedside head impulse test (HIT) and for the low-frequency range by a bilaterally reduced or absent caloric response. If the results of the bedside HIT are unclear, angular VOR function should be quantified by a video-oculography system (vHIT). An additional test supporting the diagnosis is dynamic visual acuity. Cervical and ocular vestibular-evoked myogenic potentials (c/oVEMP) may also be reduced or absent, indicating impaired otolith function. There are different subtypes of BVP depending on the affected anatomic structure and frequency range of the VOR deficit: impaired canal function in the low- and/or high-frequency VOR range only and/or otolith function only; the latter is very rare. The etiology of BVP remains unclear in more than 50% of patients: in these cases neurodegeneration is assumed. Frequent known causes are ototoxicity mainly due to gentamicin, bilateral Menière's disease, autoimmune diseases, meningitis and bilateral vestibular schwannoma, as well as an association with cerebellar degeneration (cerebellar ataxia, neuropathy, vestibular areflexia syndrome=CANVAS). In general, in the long term there is no improvement of vestibular function. There are four treatment options: first, detailed patient counseling to explain the cause, etiology, and consequences, as well as the course of the disease; second, daily vestibular exercises and balance training; third, if possible, treatment of the underlying cause, as in bilateral Menière's disease, meningitis, or autoimmune diseases; fourth, if possible, prevention, i.e., being very restrictive with the use of ototoxic substances, such as aminoglycosides. In the future vestibular implants may also be an option.

両側前庭機能高度低下例の検討

Bilateral vestibular failure causes movement-dependent postural vertigo, unsteadiness of gait, and in serious cases patients complain of blurred vision while walking (known as the jumbling phenomenon). This condition is defined as bilateral vestibulopathy and its diagnostic criteria have been cited in various professional publications. These criteria include, symptoms, bedside evaluation (e.g., Head Impulse Test), laboratory tests (e.g., caloric tests) and other causes excluded. On the other hand, in Japan, the Peripheral Vestibular Disorder Research Committee has proposed a set of diagnostic criteria for bilateral vestibular losses, which is based solely on the result of an ice-water caloric test, regardless of whether the patient has the characteristic symptoms or not. The purpose of this retrospective study was to clarify the relationship between the vestibular failure tested by both the caloric test and video Head Impulse Test (vHIT), and the presence of symptoms characteristic of bilateral vestibulopathy. A total of 210 patients were screened during the study period. Eight patients were included in this study who showed bilateral absent caloric responses to the ice-water caloric test due to peripheral vertigo. Among these 8 patients, only 3 patients complained of the jumbling phenomenon and vHIT showed a bilateral profound vestibular deficit. vHIT did not show any bilateral profound vestibular deficit in the other 5 patients. These results show that the abnormal caloric responses may not have clinical significance in some cases. The authors believe that bilateral vestibulopathy should be considered first with patients who have characteristic symptoms. Furthermore, they should be tested by a combination of 2 test batteries (the ice-water caloric test and vHIT) to make a proper diagnosis.

P.1.g.077 Effects of clozapine on the prepulse inhibition of rats submitted to the model of schizophrenia induced by neonatal immune challenge

The aim of this study was to establish an animal model of acoustically evoked vestibulo-collic reflex using guinea pigs. A special clamp was applied to restrain the head and body of the guinea pigs, but leaving its four legs free. Each animal underwent vestibular evoked myogenic potential (VEMP) and caloric tests using clip electrode method without general anesthesia or decerebrate surgery. The response rates for the myogenic potentials on the neck of guinea pigs using 100, 90, 80 and 70 dB monaural acoustic stimulation with unilateral recording were 100%, 62%, 50% and 0%, respectively. The mean latencies of the positive and negative peaks for the myogenic potentials were 7.24 ± 0.49 and 9.15 ± 0.47 ms, 7.09 ± 0.43 and 9.28 ± 0.42 ms, as well as 7.03 ± 0.59 and 9.14 ± 0.56 ms, when elicited by 100, 90 and 80 dB acoustic stimulation, respectively. The median (minimum–maximum) peak-to-peak amplitudes were 11.93 (6.14–16.86), 10.99 (5.28–19.40), and 11.17 (5.02–20.72) μV, when elicited by 100, 90 and 80 dB acoustic stimulation, respectively. We found no significant relationship between the stimulus intensity and the mean latencies or peak-to-peak amplitude of the myogenic potentials in guinea pigs. For those treated with gentamicin unilaterally, all guinea pigs showed absent caloric responses on the lesion side, and absent myogenic potentials on the neck when using ipsi-lesional acoustic stimulation, while the hearing was preserved. Hence, the use of gentamicin-treated animals, along with normal controls and auditory brainstem responses, results in convincing results that the recorded myogenic potentials are in fact of vestibular origin.

Sudden vertigo in a 49-year-old man

The diffusion-weighted MRI (DWI) showed a small, subacute right middle cerebellar peduncle infarct in the territory of the anterior inferior cerebellar artery (AICA) without brainstem infarction (Fig. 1). Audiometry showed a total right hearing loss with normal hearing on the left; caloric testing showed absent responses from the right. CT angiography revealed only right vertebral artery hypoplasia. He was given anti-hypertensive treatment and aspirin. One year later he still had a total right hearing loss, positive rightward Head Impulse Test, a positive Romberg test standing on foam and absent caloric responses from the right. Sudden unilateral vestibular loss (SVL) produces a stereotyped syndrome of vertigo, vomiting, nystagmus beating away from the affected side, ipsiversive lateropulsion and ocular tilt reaction. The Head Impulse Test is invariably positive towards the affected side. Whereas the SVL syndrome invariably resolves within 1 week, the Head Impulse Test will, if the ear does not recover, remain positive forever. When the SVL is spontaneous and isolated, the cause is usually presumed to be due to herpes simplex virus infection and since the cochlea is spared, it is called ‘‘acute vestibular neuritis’’. When there is simultaneous sudden unilateral hearing loss (SHL) the cause is presumed to be herpes zoster virus infection – ‘‘herpes zoster oticus’’ or the ‘‘Ramsay Hunt syndrome’’, affecting the labyrinth as well as in the vestibulo-cochlear nerve, and such cases are called ‘‘acute viral labyrinthitis’’ or ‘‘neuro-labyrinthitis’’. However, labyrinthine infarction can also cause combined SVL+SHL, although this diagnosis is as hard to verify as that of viral labyrinthitis, since MRI of the inner ear is usually normal in both. The internal auditory artery, usually a branch of the AICA, supplies the inner ear. With AICA occlusion there can be infarction in the cerebellum or the brainstem, or both, as well as the inner ear. The hearing loss with AICA infarction is mostly cochlear and can improve in time, as can the canal paresis. A cerebellar or even brainstem component of an AICA territory infarct, evident on DWI, can be clinically asymptomatic so that the patient will present with isolated SHL+SVL and if a DWI is not requested (in time), the patient will be assumed to have viral

Sudden vertigo in a 49-year-old man

The diffusion-weighted MRI (DWI) showed a small, subacute right middle cerebellar peduncle infarct in the territory of the anterior inferior cerebellar artery (AICA) without brainstem infarction (Fig. 1). Audiometry showed a total right hearing loss with normal hearing on the left; caloric testing showed absent responses from the right. CT angiography revealed only right vertebral artery hypoplasia. He was given anti-hypertensive treatment and aspirin. One year later he still had a total right hearing loss, positive rightward Head Impulse Test, a positive Romberg test standing on foam and absent caloric responses from the right.

Assessment of Postural Stability Using Foam Posturography at the Chronic Stage After Acute Unilateral Peripheral Vestibular Dysfunction

To investigate the utility of foam posturography for assessing equilibrium at the chronic stage after acute unilateral peripheral vestibulopathy. Thirty-four consecutive patients (16 patients at the chronic stage) with acute unilateral peripheral vestibulopathy and absent caloric responses unilaterally were recruited, along with 66 healthy control subjects. Two-legged stance tasks were performed in 4 conditions: with eyes open or closed, with or without using foam rubber. We adopted 6 parameters: the movement velocity of the center of pressure, the envelopment area traced by the movement of the center of pressure with eyes closed/foam rubber, Romberg's ratios of velocity and area with foam rubber, and the foam ratios (the ratio of a parameter measured with and without foam rubber) of velocity and area with eyes closed. All 6 parameters were significantly higher in the patients in the acute/subacute stage (<3 mo) than in the control subjects (p < 0.0001). Five parameters, excluding the foam ratio of the area with eyes closed, were still significantly higher in the patients at the chronic stage (>3 mo) than in the control subjects (p < 0.01). Foam posturography is useful for assessing equilibrium even at the chronic stage after acute unilateral peripheral vestibulopathy.

Pre-operative vestibular pattern and balance compensation after vestibular schwannoma surgery

This longitudinal study aimed to assess the sensorimotor balance strategies before and after vestibular schwannoma (VS) surgery according to the degree of pre-operative vestibular lesion. Thirty-eight VS patients were split in three groups according to caloric vestibular test results before surgery; nine had a symmetrical vestibular response (vestibular normoreflexy), 19 with a decreased response of more than 20% of the affected side (vestibular hyporeflexy) and 10 with an absent caloric response on the side of the affected labyrinth (vestibular areflexy). They underwent pendular rotary vestibular testing (RVT), allowing to evaluate gain and directional preponderance of the vestibulo-ocular reflex, and a sensory organisation test (SOT), evaluating balance control in six conditions (C1 to C6). These tests were performed shortly before, and 8 and 90 days after surgery. Directional preponderance performances of patients with vestibular normoreflexy or hyporeflexy followed a classical time-course with a huge asymmetry just after surgery and a recovery to pre-operative performances at 90 days; patients with vestibular areflexy were relatively stable in time. Variation in SOT performances of patients with vestibular normoreflexy, especially in the more complex C4 to C6, followed a classical time-course with an important postural degradation just after surgery and a recovery to pre-operative performances at 90 days. Patients with vestibular areflexy showed no balance degradation just after surgery and a marked increase in performances at 90 days after surgery, especially in C5 and C6. Performances of patients with vestibular hyporeflexy were intermediate, close to performances of patients with vestibular normoreflexy before surgery and close to performances of patients with vestibular areflexy at 8 and 90 days after surgery. Pre-operative vestibular function alteration triggers an adaptive process, characterized by a restoration of the symmetry of the vestibular nuclei activity and by sensory substitution and new behavioural strategies, allowing the anticipation of unilateral vestibular deafferentation effects.

POC08 A case of central and peripheral vestibular vestibular failure

A 63-year old male presented with a 3-year history of worsening mobility due to difficulty maintaining balance and deterioration in his hearing. He had a past medical history of ankylosing...

Prodromal dizziness in vestibular neuritis: frequency and clinical implication

Although vestibular neuritis (VN) usually includes a single attack of prolonged vertigo (lasting more than 1 day), we have previously observed several patients with VN who experienced paroxysmal dizziness prior...

Abnormal Deviation of Subjective Visual Horizontal in Patients with Vestibular Schwannoma

This study was aimed to examine the correlation between the results of subjective visual horizontal (SVH) and other vestibular function tests in patients with untreated unilateral vestibular schwannoma (VS). The subjects comprised 40 consecutive patients (17 men, 23 women) with VS who underwent vestibular function tests before surgery and had surgically and histopathologically confirmed unilateral VS. The vestibular function tests included SVH, caloric, and vestibular evoked myogenic potential (VEMP) tests. Of the 40 patients, 31 (77.5%) showed deviation of the SVH toward the affected side down. Especially in 8 patients (20.0%), abnormal deviation (more than 2.2 degrees) toward the affected side down was seen. None of the patients showed abnormal deviation toward the unaffected side down. On the caloric test, the proportion of absent caloric responses and the percent canal paresis in patients with an abnormal SVH was significantly higher than those in patients with a normal SVH. The proportion of abnormal VEMP responses was higher and the percent VEMP asymmetry was smaller in patients with an abnormal SVH than in patients with a normal SVH; however, the differences were not significant. Abnormal results on the caloric test and/or VEMP test were more frequently seen in VS patients with abnormal deviation of the SVH.

Correlating the cochleovestibular deficits with tumor size of acoustic neuroma

Conclusion. The tumor size of acoustic neuroma correlates with cochleovestibular deficits. Those tumors with global frequency hearing loss, bilateral gaze nystagmus, or absent caloric and VEMP responses may indicate a tumor size >2.5 cm. Objective. This study aimed to investigate the correlation between cochleovestibular deficits and the size of acoustic neuroma. Patients and methods. A total of 44 patients with acoustic neuroma were enrolled in this study. Pure tone audiometry, electronystagmography, caloric test, vestibular evoked myogenic potential (VEMP) test, and MRI were conducted. Results. There is a trend of correlation between tumor size and audiographic configuration, with small-sized tumor in normal and rising types, medium-sized tumor in mid- and high-frequency hearing loss, and large-sized tumor in flat and deafness types. Five patients with bilateral gaze nystagmus had significantly larger tumor size than those without nystagmus. When 1 and 0 are used to represent abnormal and normal responses, respectively, the relationship between tumor size and vestibular function can be expressed as: tumor size (cm)=1.43 (caloric response)+1.35 (VEMP response), indicating that the estimated tumor size for those with abnormal caloric or VEMP responses increased by 1.43 or 1.35 cm, respectively.

Long-Term Vertigo Control in Patients After Intratympanic Gentamicin Instillation for Méni;ère's Disease

To assess long-term vertigo symptom control in patients after intratympanic gentamicin instillation for incapacitating unilateral Ménière's disease. To analyze whether an absent caloric response, as analyzed using electronystagmography after gentamicin treatment, is a good predicator of long-term symptom control. Finally, to quantify the patient's perception of long-term posttreatment handicap. A retrospective study from a single institution. All patients underwent a similar fixed-dose and duration protocol of drug instillation. Patients were enrolled in this study, and initial outcomes were assessed according to the American Academy of Otolaryngology-Head and Neck Surgery Committee on Hearing and Equilibrium Guidelines for Reporting Treatment Results in Ménière's Disease (1985 and 1995). In this study, only those patients treated more than 5 years previous were considered. One hundred thirty-two patients were eligible for inclusion. All patients underwent hearing testing and electronystagmography, including caloric testing before and after treatment. Posttreatment handicap and long-term vertigo control were assessed using the Dizziness Handicap Index questionnaire expanded with 5 questions specific for Ménière's disease. Analysis of results is based on the 63 patients who responded. Forty-four were vertigo-free, whereas 14 continued to experience some degree of vertigo. On average, they described 5 episodes in the immediate 24 months before the study. Of the 44 patients who were asymptomatic, 35 had an absent caloric response. Of the 14 patients who realized some vertigo, 12 had an absent caloric response posttreatment. Of the 63 responders, 44 filled in the Dizziness Handicap Index. Of the 19 who did not, 17 reported that they were vertigo-free. Our current protocol achieves complete or substantial vertigo control in most patients. A significant caloric response reduction has been a consequence in almost all patients, although an absent caloric response is not invariably a predictor of long-term symptom control. Finally, patient-perceived handicap in this long-term follow-up is consistent with that of others followed for a much shorter duration in that those who were vertigo-free volunteered a significantly lower score.

Ipsilateral and contralateral vestibular schwannomas in unilateral long-term deaf ears

In the past decade, we have encountered two patients with unilateral long-term deaf ear having vestibular schwannoma. One was on the deaf ear in a 53 years' woman and the other was on the contralateral hearing ear in a 62 years' woman. These two patients had total deafness on the right ear since childhood, associated with absent auditory brainstem response (ABR) and caloric responses, whereas normal ABR and caloric responses were shown on the left ear. Although similar physiological findings were disclosed on the deaf ears, MRI scan demonstrated vestibular schwannoma on the different side, that is, one in deaf ear and the other in hearing ear. For the former, absent ABR and caloric results indicate that the tumor originates from the superior vestibular nerve. In contrast with the latter, normal ABR and caloric responses, but absent vestibular-evoked myogenic potentials on the hearing ear imply that the tumor originates from the inferior vestibular nerve. The ipsilateral tumor on the deaf ear underwent intracranial surgical excision, followed by radiosurgery due to tumor recurrence 10 years later, while the contralateral one on the only hearing ear received radiosurgery only. Both patients were rather well, 3 years after last treatment.

Click-evoked myogenic potentials recorded on alert guinea pigs

The aim of this study was to establish an animal model of acoustically evoked vestibulo-collic reflex using guinea pigs. A special clamp was applied to restrain the head and body of the guinea pigs, but leaving its four legs free. Each animal underwent vestibular evoked myogenic potential (VEMP) and caloric tests using clip electrode method without general anesthesia or decerebrate surgery. The response rates for the myogenic potentials on the neck of guinea pigs using 100, 90, 80 and 70 dB monaural acoustic stimulation with unilateral recording were 100%, 62%, 50% and 0%, respectively. The mean latencies of the positive and negative peaks for the myogenic potentials were 7.24 ± 0.49 and 9.15 ± 0.47 ms, 7.09 ± 0.43 and 9.28 ± 0.42 ms, as well as 7.03 ± 0.59 and 9.14 ± 0.56 ms, when elicited by 100, 90 and 80 dB acoustic stimulation, respectively. The median (minimum–maximum) peak-to-peak amplitudes were 11.93 (6.14–16.86), 10.99 (5.28–19.40), and 11.17 (5.02–20.72) μV, when elicited by 100, 90 and 80 dB acoustic stimulation, respectively. We found no significant relationship between the stimulus intensity and the mean latencies or peak-to-peak amplitude of the myogenic potentials in guinea pigs. For those treated with gentamicin unilaterally, all guinea pigs showed absent caloric responses on the lesion side, and absent myogenic potentials on the neck when using ipsi-lesional acoustic stimulation, while the hearing was preserved. Hence, the use of gentamicin-treated animals, along with normal controls and auditory brainstem responses, results in convincing results that the recorded myogenic potentials are in fact of vestibular origin.

Vestibular evoked myogenic potentials in basilar artery migraine.

Because the sacculocollic reflex is a descending pathway passing through the territory of basilar artery, the aim of the study was to investigate whether hypoperfusion affects this pathway by applying vestibular evoked myogenic potential (VEMP) testing in patients with basilar artery migraine. A prospective study from May 2000 to April 2002. Twenty patients were diagnosed as having basilar artery migraine according to the criteria of the International Headache Society and literature. Eight were male and 12 were female patients, and their ages ranged from 9 to 48 years (mean age, 40 y). Each patient underwent a battery of audio-vestibular tests. Electronystagmography disclosed abnormal eye tracking test in six patients (30%), and there were abnormal optokinetic nystagmus test results in nine patients (45%). Caloric test revealed canal paresis in seven patients, directional preponderance in four patients, and normal responses in nine patients (45%). Vestibular evoked myogenic potential testing disclosed absent vestibular evoked myogenic potentials in seven patients and delayed vestibular evoked myogenic potentials in two patients, with one patient showing absent vestibular evoked myogenic potentials on one side and delayed vestibular evoked myogenic potentials on the other side. The remaining 10 patients (50%) had bilateral normal vestibular evoked myogenic potentials. Five patients had preserved both caloric and VEMP test responses, six patients displayed absent caloric and VEMP test responses, and the remaining nine patients had either abnormal caloric test responses or abnormal vestibular evoked myogenic potentials, exhibiting a nonsignificant relationship between caloric test responses and vestibular evoked myogenic potentials. Relief of headache and vertigo was achieved after 3 months of medication. Ten asymptomatic patients with either absent or delayed vestibular evoked myogenic potentials before treatment underwent follow-up VEMP test, and nine patients (90%) displayed normal vestibular evoked myogenic potentials bilaterally. Vestibular evoked myogenic potential testing evaluates the sacculocollic reflex, which descends through the lower brainstem. Some patients with basilar artery migraine have absent or delayed vestibular evoked myogenic potentials, presumably because the descending pathway from the saccule through the brainstem to cranial nerve XI is interrupted, which is attributed to hypoperfusion in the territory of the basilar artery. After 3 months of medication, recovery of normal vestibular evoked myogenic potentials in an asymptomatic patient indicates reversible ischemia in the territory of the basilar artery.

Postirradiation vertigo in nasopharyngeal carcinoma survivors.

Vertigo rarely manifested as an initial symptom of nasopharyngeal carcinoma or an early symptom after irradiation; however, increasing numbers of long-term nasopharyngeal carcinoma survivors experienced it. The purpose of this study was to investigate the causes of vertigo in irradiated nasopharyngeal carcinoma survivors. University hospital. From January 1992 to December 2001, a total of 113 nasopharyngeal carcinoma patients (67 men and 46 women) with postirradiation vertigo consecutively visited our vertigo clinic. The mean interval from completion of irradiation to the occurrence of vertigo was 10 years. Each patient underwent otoscopic examination and a battery of audiovestibular function tests. Then, correlation between the vertigo and the radiation effect was explored. Postirradiation vertigo was mainly attributable to peripheral labyrinthine disorder (69%), followed by central vestibular lesions (31%). The vertiginous and associated symptoms including severity, nausea/vomiting, oscillopsia, or imbalance in cases of peripheral labyrinthine disorder were milder than those in central vestibular lesion. Meanwhile, the former had less life impact and better response to therapy compared with the latter. The mean radiation dosage in both groups was 73 +/- 6 Gy and 74 +/- 5 Gy, respectively, without a significant difference. Of these 113 patients, 85 patients (75%) had radiation otitis media in one or both ears, and 28 patients disclosed bilateral intact eardrums. The prevalence of radiation otitis media in patients with postirradiated vertigo was 53% versus 73% for those with radiation dosage less than or more than 71 Gy, respectively, exhibiting a significant difference. However, the prevalence of radiation otitis media is unrelated to radiation interval. In comparison with absent caloric responses in radiation otitis media ears, 32% versus 57% in those of less than or more than 71 Gy, respectively, indicates a significant difference. Vertigo is a late complication in irradiated nasopharyngeal carcinoma survivors, which is mainly caused by the sequela of radiation otitis media. Because the latter is correlated with the radiation dosage, 70 Gy is recommended as the maximum dosage for nasopharyngeal carcinoma. Eradicating radiation otitis media in nasopharyngeal carcinoma survivors may subsequently prevent the postirradiation vertigo.

Vertigo from herpes zoster oticus: superior or inferior vestibular nerve origin?

This study aims to analyze which division of vestibular nerve in the internal auditory canal is responsible for inducing vertigo in patients with herpes zoster oticus (HZO). Eight patients (three men and five women) suffered from auricular vesicles, otalgia, and facial palsy, and five of them also had vertigo. Each patient received a battery of tests, including neurological examination, blood examination, audiometry, caloric test, electronystagmography, and vestibular evoked myogenic potential (VEMP) test. All five HZO patients with vertigo had facial palsy on the lesioned side and spontaneous nystagmus beating toward the healthy side. Absent VEMPs were noted in five patients, absent caloric response was noted in four, and sensorineural HL was noted in three. Compared to another three HZO patients without vertigo, all revealed normal responses in both the caloric test and the VEMP test. On MRI scan, two out of four had abnormal gadolinium enhancement along the nerve segments within the internal auditory canal. Six months after treatment, a follow-up caloric test and VEMP test in these eight patients did not alter the results compared with before treatment. The nerve trunks within the internal auditory canal are widely affected in HZO patients with vertigo. Both superior division and inferior division of the vestibular nerve attribute to the vertiginous attack. Further, large numbers of HZO patients undergoing caloric testing and VEMP testing are required to support this tentative conclusion.

Vestibular evoked myogenic potentials in delayed endolymphatic hydrops.

Vestibular evoked myogenic potential (VEMP) has become an established test to explore the sacculo-collic reflex. The study aims to investigate the VEMPs in cases of delayed endolymphatic hydrops because greatly dilated saccule was observed in histopathological specimens of delayed endolymphatic hydrops. Prospective study. Twenty patients with delayed endolymphatic hydrops were subjected to pure-tone audiometry, caloric testing, and VEMP test. Delayed VEMP was defined as the latency of peak I exceeding 22.6 milliseconds or of peak II exceeding 33.1 milliseconds. Interaural amplitude difference over the sum of amplitudes of both ears was measured, and when the ratio exceeded 0.36, it was identified as augmented VEMP or depressed VEMP depending on whether the amplitude of the lesioned side was greater or less than the opposite side. The VEMP test revealed that 9 patients (45%) were normal, 6 (30%) exhibited absent VEMPs, and 5 (25%) displayed abnormal VEMPs, including delayed VEMPs in 2, depressed VEMPs in 2, and augmented VEMPs in 1. The caloric test indicated that 9 (47%) of the 19 ears exhibited normal caloric response, whereas 10 ears displayed abnormal caloric responses including canal paresis in 8 and absent caloric response in 2. Six ears had preserved both the caloric response and the VEMPs, whereas no ear demonstrated both absent caloric response and absent VEMPs. The residual caloric as well as saccular functions after ear insult may determine whether delayed endolymphatic hydrops will occur. These findings suggest that patients with sudden deafness or juvenile unilateral total deafness should undergo caloric testing and VEMP test to predict the occurrence of delayed endolymphatic hydrops in the future.