Changes in caloric responses after temporal bone surgery with posterior tympanotomy

Area of Science:

• Otolaryngology
• Neuroscience
• Vestibular System Research

Background:

• The caloric stimulation test is crucial for evaluating vestibular peripheral function.
• The role of the facial recess bony plate in thermal transmission during caloric testing is not fully understood.
• Posterior tympanotomy, used in procedures like facial nerve decompression (FND) and cochlear implantation (CI), involves altering the temporal bone structure.

Purpose of the Study:

• To investigate the influence of the facial recess bony plate on thermal transmission during caloric stimulation.
• To assess the impact of posterior tympanotomy, with and without inner ear damage, on vestibular responses.

Main Methods:

• Caloric stimulation tests (30°C cold and 44°C hot water) were performed before and 6 months after surgery in patients undergoing FND (n=19) and CI (n=34).
• Vestibular responses were measured using electronystagmography (ENG) to record maximum slow-phase eye velocity.
• FND served as a model for posterior tympanotomy without inner ear damage, while CI represented posterior tympanotomy with surgery-induced inner ear damage.

Main Results:

• FND group showed a significant decrease in 30°C cold water caloric responses (p=0.049) but no significant change in 44°C hot water responses (p=0.467).
• CI group exhibited significant changes in both 30°C (p<0.0001) and 44°C (p=0.011) caloric responses, indicating vestibular peripheral damage.
• These findings suggest that structural changes in the temporal bone affect thermal transmission.

Conclusions:

• Cochlear implantation can induce vestibular peripheral damage, reducing both hot and cold caloric responses.
• Posterior tympanotomy, as performed in FND, can decrease caloric responses, especially with cold stimulation.
• The structural changes in the temporal bone must be considered when interpreting vestibular peripheral function assessed by caloric stimulation tests.