Temporal bone rule 9 : Pearls of cholesteatoma

Pathognomonic signs of cholesteatoma:

1-Non dependent mass:

If the mass is dependent, so it is fluid (otitis media).

2-Non enhanced mass:

If it is enhanced, it will be glomus tympanicum and not a cholesteatoma.

3-In diffusion weighted image, cholesteatoma will appears as a hyper intense lesion while in case of otitis media, it will appear as a hypo intense lesion, this is very important in case of severely affected middle ear, in such a case the surgeon needs an accurate diagnosis.

4-Congenital cholesteatoma can occur any where in the middle ear

    ( commonly near Eustachian tube and stapes ).

5-Acquired type occurs in two places:

    *Prussak's space (95%).

    *Sinus tympani (5%).

6-Look for erosion in tegmen tympani which could cause dural vein thrombosis or brain abscess.

7-Look for erosion in the lateral semi circular canal which may cause Labyrinthine fistula which means abnormal connection between middle and inner ear.

8-This fistula leads to infection of the inner ear causing labyrinthitis which is diagnosed only by MRI with contrast showing Labyrinthine enhancement.

9-Erosion of facial nerve at facial recess.

Non dependent, non enhanced mass seen in the middle ear cavity eroding lateral tympanic wall

Black arrow pointed to oval window while white arrow is pointing to labyrinthine fistula connecting middle ear cavity to the inner ear.