Middle ear risk index (MERI)
The term Middle ear risk index is used to predict the success rate of middle ear reconstruction procedures. For accurate prediction of the surgical results of middle ear ossiculoplasty the status of middle ear and its ossicles must be ascertained. Austine Kartush classification has been used as a method to define the pre reconstruction ossicular status.
Austine Kartush classification:
This classification uses middle ear osscicular status. Four different groups have been identified:
Group A - Malleus and stapes present (commonly seen status) because of precarious vascularity of incus
Group B - Malleus and foot plate of stapes present
Group C - Malleus absent and stapes present
Group D - Malleus and stapes suprastructure absent
Kartush added three more classes as a modification of this scheme in include ossicular fixity even when all three ossicles are present.
O - Intact ossicular chain
E - Ossicular head fixation
F - Stapes fixation
Middle ear risk index includes:
1. Austin Kartush classification of ossicular defects
2. Ear drum perforation
4. Belluci classification
Weightage is given to these 4 parameters to arrive at the middle ear risk index.
Belluci classification uses otorrohea as an index.
Perforation if present adds a value of 1 to the risk index
Cholesteatoma if present adds a value of 2 to the risk index
Austin Kartush classification
1. M+I+S += 0
3. M-S+ = 3
4. M-S- = 4
5. Ossicular head fixation = 2
6. Stapes fixation = 3
Presence of effusion / granulation in the middle ear adds 2 to the risk index
History of previous surgery adds 2 to the risk factor
History of smoking adds another 2 to the risk factor
Totalling all these factors adds to the middle ear risk index