Correlation between tympanometry volume and three-dimensional computed tomography mastoid volumetry in tympanoplasty candidates

Abstract

Objective Ventilation of the middle ear and mastoid air cells is believed to play an important role in the pathogenesis of chronic ear disease. Traditionally, ventilation is assessed by computed tomography. However, this exposes patients to cumulative radiation injury. In cases with a perforation in the tympanic membrane, tympanometry potentially presents a non-invasive alternative to measure the ventilated middle-ear and mastoid air cell volume. This study hypothesised that total tympanometry volume correlates with ventilated middle-ear and mastoid air cell volume. Method Total tympanometry volume was compared with ventilated middle-ear and mastoid air cell volume on computed tomography scans in 20 tympanic membrane perforations. Results There was a high correlation between tympanometry and computed tomography volumes (r = 0.78; p < 0.001). A tympanometry volume more than 2 ml predicted good ventilation on computed tomography. Conclusion These results may help reduce the need for pre-operative computed tomography in uncomplicated cases with tympanic membrane perforations.

Could tympanometric volume be a useful tool to predict the success of type I tympanoplasty in simple chronic otitis media

“…This was also concluded in a study by Merenda et al about type I tympanoplasty with underlay autograft temporalis fascia in the pediatric population where tympanometry volume greater than 3 cm 3 had an 89 percent success rate compared with 34 percent for those who had a volume of less than 3 cm 3 . 6 On the other hand, Yegin et al concluded in their work with type 1 tympanoplasties with cartilage that mastoid pneumatization did not affect the success rate of surgery, which may be explained by the greater resistance that cartilage offers to pressure changes. 4 Performing mastoidectomy with tympanoplasty for tympanic membrane perforations in the absence of cholesteatoma remains controversial and not all results show that it improves the success of tympanoplasty.…”

“…1,4,8 Traditionally, this aeration could be evaluated through some measurements in a three-dimensional volume reconstruction CT scan. 6,9 Recent studies by Kim et al and Epprecht et al demonstrated that, when the mastoid antrum is patent, there is a good correlation between middle ear and mastoid cells volume measurements done with three-dimensional volume reconstructions CT scan or calculated with the interaural volume differences with tympanometry. 6,9 Since a good aeration of the middle ear is an important predictive factor for a successful tympanoplasty and tympanometry is a good tool to evaluate that, it was expected that a higher ear canal volume measurement in tympanometry would increase the chance of having a successful surgery.…”

“…This result reflects the state of middle ear ventilation and eustachian tube function. 3,6 A typical tympanometry report of a normal ear comprises the external ear canal volume and the compliance of the tympanic membrane. 3,6 Mathematically, the tympanometry curve is derived from the acoustic admittance which measures how easily the sound from the tympanometry probe is transmitted through the sound conducting system.…”

“…3,6 A typical tympanometry report of a normal ear comprises the external ear canal volume and the compliance of the tympanic membrane. 3,6 Mathematically, the tympanometry curve is derived from the acoustic admittance which measures how easily the sound from the tympanometry probe is transmitted through the sound conducting system. 7 Tympanometry also measures the volume of the sound conducting system, which in a normal ear measures the volume of the ear canal while in patients with simple chronic otitis media (COM) it measures the ear canal volume plus middle ear and possibly mastoid cells.…”

“…So, in a patient with unilateral simple COM, if we subtract the volume of the good ear to the total volume of the affected ear, we obtain the volume of the middle ear plus the mastoid cells, and it is usually greater than 2 ml. 6,7 This means, in theory, that a higher ear volume in tympanometry measure reflects a greater aerated middle ear in patients with COM without cholesteatoma. This theory was demonstrated in a work by Epprecht et al who studied the correlation between tympanometry volumes and the volume of mastoid air cells measured on CT scans and concluded that there is a high correlation between those two measures in patients with dry tympanic membrane perforations.…”