Vestibular evoked myogenic potentials in patients with the mitochondrial A1555G mutation

Mechanisms and Impact of Aminoglycoside-Induced Vestibular Deficits

PURPOSE

Acquired vestibulotoxicity from hospital-prescribed medications such as aminoglycoside antibiotics affects as many as 40,000 people each year in North America. However, there are no current federally approved drugs to prevent or treat the debilitating and permanent loss of vestibular function caused by bactericidal aminoglycoside antibiotics. This review will cover our current understanding of the impact of, and mechanisms underlying, aminoglycoside-induced vestibulotoxicity and highlight the gaps in our knowledge that remain.

CONCLUSIONS

Aminoglycoside-induced vestibular deficits have long-term impacts on patients across the lifespan. Additionally, the prevalence of aminoglycoside-induced vestibulotoxicity appears to be greater than cochleotoxicity. Thus, monitoring for vestibulotoxicity should be independent of auditory monitoring and encompass patients of all ages from young children to older adults before, during, and after aminoglycoside therapy.

Progression of Peripheral Vestibular Dysfunctions in Patients With a Mitochondrial A3243G Mutation

OBJECTIVE

To evaluate the progression of peripheral vestibular dysfunction in patients with an A-to-G point mutation at nucleotide pair 3243 in mitochondrial DNA (A3243G mutation).

STUDY DESIGN

Retrospective patient series.

SETTING

Tertiary referral center.

PATIENTS

Six unrelated patients with an A3243G mutation (four mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes; and two maternally inherited diabetes and deafness; five females and one male; average age 41 ± 11.3 yr old), who underwent repeated vestibular examinations, were included (average interval between the first and second examinations: 5.7 ± 2.1 yr).

INTERVENTION

Diagnostic.

MAIN OUTCOME MEASURE

Results of caloric testing and cervical vestibular evoked myogenic potential testing in response to air-conducted sound were analyzed.

RESULTS

All the patients except one, who was already completely deaf in both ears at the first examination, showed progression of hearing loss (average 4.0 ± 6.3 dB per year). Five of the six patients had vestibular symptoms at the first examination. The other patient developed dizziness later. Caloric responses were abnormal in four patients at the first examination and in five patients at the second examination. Cervical vestibular evoked myogenic potential responses were bilaterally absent in three patients at the first examination and in five patients at the second examination.

CONCLUSIONS

The A3243G mutation causes progression of peripheral vestibular dysfunction as well as that of hearing loss.

Bilateral Vestibulopathy Aggravates Balance and Gait Disturbances in Sensory Ataxic Neuropathy, Dysarthria, and Ophthalmoparesis: A Case Report

In patients with a triad of sensory ataxic neuropathy, dysarthria, and ophthalmoparesis (SANDO), the presenting features are mainly ataxia or ptosis. SANDO patients often have impaired balance and gait, which is not surprising considering the combination of sensory ataxic neuropathy, and additional symptoms like cerebellar ataxia and limb girdle weakness. We describe a SANDO patient who noticed an increasingly impaired balance and gait, without any dizziness. Neurological investigation revealed an external ophthalmeplegia and a cerebellar ataxia; the head impulse test was not reliable because of eye movement disorders. The caloric reflex tests showed lack of responses on both sides, compatible with severe bilateral vestibulopathy. Making the diagnosis of bilateral vestibulopathy in SANDO patients may have implications for the management of the patient, because specific vestibular rehabilitation can improve gaze and postural stability.

[Vestibular examination of children with alterations in balance (II): results by pathologies]

We review the findings of vestibular examinations in children according to disease. Just as in adults, the dizziness can be classified following a physiopathological scheme.

Novel ATP6V1B1 mutations in distal renal tubular acidosis and hearing loss

CONCLUSION

Novel ATP6V1B1 mutations were found in a patient with distal renal tubular acidosis (dRTA), hearing loss (HL), and enlargement of the vestibular aqueduct (EVA). The deterioration of HL and vertiginous attacks may be associated with the disruption of the endolymph pH homeostasis.

OBJECTIVES

To study the audiovestibular functions and to identify the causative gene.

METHODS

This study enrolled a Japanese family, where the proband showed type 1 dRTA, early onset HL, and bilateral EVA. A deterioration of HL occurred several times in both ears. Vertiginous attacks were always associated with a deterioration of HL. Audiovestibular examinations included distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABRs), caloric testing, and vestibular evoked myogenic potentials (VEMPs). Direct sequencing was utilized to screen for ATP6V1B1, SLC26A4, and GJB2 mutations.

RESULTS

The findings of DPOAEs and ABRs indicated cochlear HL. The vestibular function was thought to be mildly impaired according to the caloric responses and VEMP findings. Two novel ATP6V1B1 mutations of a heterozygous 15 base-pair deletion (c.756_770del) in exon 7 and a heterozygous 1 base-pair insertion (c.1242_1243insC) in exon 12 were detected in a compound heterozygous state. No mutation was identified in either SLC26A4 or GJB2.