Blog Archives

The mitochondrial A3243G mutation involves the peripheral vestibule as well as the cochlea

Conclusions:
The A3243G mutation is associated with vestibular dysfunction involving both the superior and inferior vestibular nerve systems. Furthermore, our results from galvanic-VEMP testing suggests that a labyrinthine lesion is primarily responsible for the symptoms of vestibular dysfunction

from The Laryngoscope

Progressive mitochondrial myopathy, deafness, and sporadic seizures associated with a novel mutation in the mitochondrial tRNASer(AGY) gene

We sequenced the mitochondrial genome from a patient with progressive mitochondrial myopathy associated with deafness, sporadic seizures, and histological and biochemical features of mitochondrial respiratory chain dysfunction. Direct sequencing showed a heteroplasmic mutation at nucleotide 12262 in the tRNASer(AGY) gene. RFLP analysis confirmed that 63% of muscle mtDNA harboured the mutation, while it was absent in all the other tissues. The mutation is predicted to influence the functional behaviour of the aminoacyl acceptor stem of the tRNA. Several point mutations on mitochondrial tRNA genes have been reported in patients affected by encephalomyopathies, but between them only four were reported for tRNASer(AGY).

from the Journal of the Neurological Sciences

Vestibular evoked myogenic potentials in patients with the mitochondrial A1555G mutation

Results:
Four of the five patients suffered from repetitive vestibular symptoms. Positioning, positional, and spontaneous nystagmus were not observed except in one patient. Three of the five patients had normal caloric responses, but all the patients had abnormal VEMPs. The interpeak amplitudes in the mutation group were significantly lower at the intensities of 95 and 105 dB normal hearing level (nHL) in comparison to the healthy volunteer group. In addition, the amplitudes in the mutation group were significantly lower at the intensity of 95 dB nHL in comparison to the sudden SNHL groups.

Conclusions:
These results indicated that the A1555G mutation can cause vestibular dysfunction, especially saccular dysfunction and cochlear dysfunction. Further studies are necessary to elucidate the pathophysiological nature of the inner ear dysfunction in patients with the A1555G mutation. Laryngoscope, 2009

from The Laryngoscope

Vestibular evoked myogenic potentials in patients with the mitochondrial A1555G mutation

Results:
Four of the five patients suffered from repetitive vestibular symptoms. Positioning, positional, and spontaneous nystagmus were not observed except in one patient. Three of the five patients had normal caloric responses, but all the patients had abnormal VEMPs. The interpeak amplitudes in the mutation group were significantly lower at the intensities of 95 and 105 dB normal hearing level (nHL) in comparison to the healthy volunteer group. In addition, the amplitudes in the mutation group were significantly lower at the intensity of 95 dB nHL in comparison to the sudden SNHL groups.

Conclusions:
These results indicated that the A1555G mutation can cause vestibular dysfunction, especially saccular dysfunction and cochlear dysfunction. Further studies are necessary to elucidate the pathophysiological nature of the inner ear dysfunction in patients with the A1555G mutation. Laryngoscope, 2009

from The Laryngoscope

Technical report: Laser microdissection of cochlear structures from celloidin embedded human temporal bone tissues and detection of the mitochondrial DNA common deletion using real time PCR

from Hearing Research

Laser microdissection (LMD) has been used to isolate groups of cells and single cells from numerous tissues. In this study, we describe a technique for isolating cochlear structures and individual spiral ganglion cells from archival celloidin embedded human temporal bone sections. The specimens isolated are suitable for quantifying the mitochondrial DNA (mtDNA) common deletion (CD) within these tissues using a real time polymerase chain reaction (PCR) assay. The results presented in this manuscript demonstrate the feasibility of using this LMD technique to study the accumulation of mtDNA deletions in diseases of the ear. To our knowledge, this approach to analyzing archival human temporal bone tissues has not been previously reported.