what is mastoidectomy?describe its various types..

A mastoidectomy is a surgical procedure designed to remove
infection or growths in the bone behind the ear (mastoid bone). Its purpose is to create
a "safe" ear and prevent further damage to the hearing
apparatus.

its types
are:

1.

closed cavity
mastoidectomy: the external auditory canal is left intact.

simple
(or cortical) mastoidectomy: the mastoid is only opened to a limited extent; this
procedure is no longer performed for chronic inflammatory
disease.
 
intact canal wall mastoidectomy, with removal of Koerners
septum, allowing inspection of the middle ear structures

2.  open cavity (radical) mastoidectomy: the external
auditory canal is removed, the mastoid cavity communicates freely with the middle ear;
the ossicles, apart from the href="http://www.medcyclopaedia.com/library/topics/volume_vi_2/s/stapes.aspx">stapes
if possible, are removed .If the ossicles are preserved, the procedure is called a
modified radical mastoidectomy.