The mastoid infection which erodes through the outer coex of bone result in?

Epidural abscess Epidural abscess is a collection of pus between the outer covering of the brain and spinal cord and the bone of the skull and spine. Subperiosteal abscess Pus is collected outside the bone under the periosteum. A subperiosteal abscess from ethmoids form on the medial wall of the orbit and displaces the eyeball forward, downward and laterally; from the frontal sinus, the abscess is situated just above and behind the medial canthus and displaces the eyeball downward and laterally; from the maxillary sinus, abscess forms in the floor of the orbit and displaces the eyeball upwards and downwards. Perichondritis It results from infection secondary to lacerations, hematoma or surgical incisions. It can also result from an extension of infection from diffuse otitis externa or a furuncle of the meatus. Lateral sinus thrombophlebitis It is inflammation of the inner wall of the lateral venous sinus with the formation of an intrasinus thrombus. (Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 225)