During the development of the temporal bone, the best site for qi transformation is the mastoid, while the petrous bone has poorer qi transformation, with only 30% of petrous bones developing well, allowing air cells to reach the petrous apex. In chronic otitis media, inflammation can only spread to the petrous apex through small cell infection, resulting in a very low clinical incidence of petrous apicitis. The air cells of the petrous bone are divided into two groups: the posterior-superior group surrounds the tympanic antrum, tympanic cavity, and semicircular canals, while the to-be-decocted-later group surrounds the hypotympanum, Eustachian tube, and cochlea. If acute otomastoiditis is improperly treated and progresses to masked mastoiditis, it can gradually lead to the fusion and necrosis of petrous air cells, invading the petrous apex and forming an abscess. It may also be caused by bone destruction due to sebaceous cysts in chronic otitis media, developing slowly. Some patients only begin to show symptoms 1–2 weeks after undergoing a simple mastoidectomy.

bubble_chart Clinical Manifestations

After necrosis of the petrous apex involves the dura mater anteriorly and posteriorly, it causes meningeal irritation symptoms, leading to paralysis of the first branch of the trigeminal nerve and the abducens nerve. This results in severe frontal and retro-orbital pain, inability to abduct the eye, diplopia, and increased ear discharge. In 1904, Gradenigo first described this syndrome, hence it is called Gradenigo's triad (ear discharge, paralysis of the lateral rectus muscle, and severe retro-orbital pain on the same side). Sometimes there may not necessarily be retro-orbital pain, but there is always paralysis of the lateral rectus muscle.

The presence of Gradenigo's sign in suppurative otomastoiditis, or a sudden increase in pus discharge after simple mastoidectomy, along with severe retrobulbar pain and diplopia, confirms the diagnosis. Mastoid X-rays and CT petrous bone scans reveal bone destruction in the petrous bone.

bubble_chart Treatment Measures

In addition to high-dose broad-spectrum antibiotic therapy, a radical mastoidectomy should be performed. Use a curette to remove the posterior group of air cells via the posterior and superior semicircular canals, and the anterior group of air cells via the hypotympanum and eustachian tube inward. Excise diseased granulation tissue and sequestra, and expand drainage until reaching the normal tissue at the petrous apex. Take care to avoid injuring the internal carotid artery, jugular vein, superior petrosal sinus, and facial nerve. For those skilled in otoneurosurgical techniques, a middle cranial fossa approach via the temporal region can be used. Separate the dura mater from the skull base to expose the petrous apex, then use an electric drill under direct vision to remove diseased air cells medial to the internal auditory canal, eradicate the lesion, and establish drainage.