Temporal bone histopathologic abnormalities associated with mitochondrial mutation T7511C

Area of Science:

• Genetics
• Otolaryngology
• Neuroscience

Background:

• A mitochondrial T7511C mutation in the tRNA gene was previously identified in a Japanese family with nonsyndromic hearing loss (HL).
• Temporal bone histopathology associated with this specific mutation remained unreported.
• This study aimed to elucidate the histopathologic features of the temporal bone in a patient with the T7511C mutation.

Observation:

• A single case study involved a temporal bone from a male subject with progressive HL since age 5.
• The temporal bone underwent light microscopic study after embedding, sectioning, and staining.
• Cochlear graphic reconstruction was performed to assess neurosensory elements and the stria vascularis.

Findings:

• Severe loss of spiral ganglion cells was observed throughout the cochlea.
• Significant loss of neuronal filaments in Rosenthal's canal was noted.
• The organ of Corti exhibited scattered hair cell loss, particularly in the basal turn, and partial stria vascularis atrophy was present.

Implications:

• The findings strongly suggest that profound spiral ganglion cell degeneration is the principal cause of sensorineural hearing loss associated with the T7511C mutation.
• This histopathologic data provides crucial insights into the mechanism of hearing impairment in individuals with this mitochondrial mutation.
• Understanding the link between the T7511C mutation and spiral ganglion cell loss can inform future research on targeted therapies for hereditary hearing loss.