Acute mastoiditis may be primary or secondary. Primary mastoiditis is rarely encountered and is generally due to tuberculosis, syphilis or trauma. According to Kerrison,1 the mastoid process seems to be immune from acute diseases.
The mastoiditis seen in daily practice is usually secondary to a diseased middle ear. It is natural for middle ear affections to involve the mastoid, since the mastoid always contains an antrum and at least a few cells lined by mucous membrane continuous from the middle ear; it is an accessory sinus to the middle ear which, in turn, is accessory to the nasopharynx. Primary mastoiditis of unknown origin has been reported from time to time, and a survey of the literature reveals about fifty-five cases reported. In none of these is it definitely proved that the middle ear was not involved, yet the cases are unusual because there was no discharge or inflammation