Discussion

Up to 85 per cent of children will have at least one episode of acute otitis media in their lives.^{Reference Goldenberg and Goldstein5} Complications of acute otitis media can be defined as the spread of infection beyond the confines of temporal bone air space and residing mucosa.^{Reference Neely, Brackmann, Shelton and Arriaga6} One of the most feared complications is petrous apicitis, which occurs in the presence of a pneumatised petrous apex. The prevalence of pneumatisation in the general population is 30 per cent.^{Reference Goldenberg and Goldstein5,Reference Kazemi7} Because of its rarity, the incidence of petrous apicitis is unknown in the adult population, but the incidence in children is 2 per 100 000 cases of acute otitis media.^{Reference Goldstein, Casselbrant, Bluestone and Kurs-Lasky4} One study showed a mortality rate of 2.3 per cent of cases, but older reports have estimated rates as high as 18 per cent.^{Reference Gadre and Chole3,Reference Sears8} Contemporary guidelines for management of acute otitis media have recommended a period of watchful waiting rather than aggressive initial antibiotic therapy, which has raised concern for an increased risk of complications such as petrous apicitis. Despite decreasing rates of antibiotic use in children with acute otitis media, there is a lack of evidence in the literature of a concordant rise in the incidence of complications.^{Reference Meissner9}

Although petrous apicitis can present with many combinations of symptoms, the most well-known presentation is Gradenigo's syndrome consisting of deep retro-orbital pain, ipsilateral abducens palsy and purulent otorrhoea.^{Reference Kitsko, Dedhia, Myers and Snyderman1} In addition to the classic triad, other symptoms include otalgia (79 per cent), otorrhoea (59 per cent), fever (22 per cent), coma, and paralysis of cranial nerves V, VII, VIII and X.^{Reference Chole, Flint, Haughey, Lund, Niparko, Robbins, Thomas and Lesperance2} We present a classic case of Gradenigo's syndrome, but one must be familiar with the variety of manifestations of petrous apicitis to not overlook this diagnosis.

The pathophysiology of neuropraxia associated with Gradenigo's syndrome can be explained by inflammation of Dorello's canal and Meckel's cave combined with neural oedema compressing the abducens and trigeminal nerves.^{Reference Janjua, Bajalan, Potter, Whitney and Sipaul10} The abducens nerve contacts the apex of the petrous part of the temporal bone as it runs under the petroclinoid ligament and through Dorello's canal. The trigeminal nerve and ganglion lie within the petrous apex. In addition, the facial and vestibulocochlear nerves pass through the temporal bone and may be damaged from local inflammatory factors.

Differential diagnosis of petrous apicitis includes inflammatory pseudotumor, sarcoidosis, tuberculosis, intracranial abscess, lateral sinus thrombosis, Tolosa–Hunt syndrome and malignancy.^{Reference Gadre and Chole3,Reference Janjua, Bajalan, Potter, Whitney and Sipaul10} Malignancy is less likely in the presence of an elevated erythrocyte sedimentation rate or C-reactive protein. Tolosa–Hunt syndrome is an extremely rare condition defined by chronic granulation tissue of the cavernous sinus, and it may present as Gradenigo's syndrome with ocular neuropraxia without petrositis or mastoiditis.^{Reference Neely, Brackmann, Shelton and Arriaga6} Diagnosis of petrous apicitis is typically confirmed by high-resolution CT scan or MRI.^{Reference Gadre and Chole3,Reference Goldenberg and Goldstein5}

Management of petrous apicitis depends on control of the infection.^{Reference Chole, Flint, Haughey, Lund, Niparko, Robbins, Thomas and Lesperance2,Reference Gadre and Chole3} Antibiotics should cover the most commonly seen organisms, including Streptococcus pneumoniae, staphylococcus spp., beta-haemolytic streptococci, Haemophilus influenza, pseudomonas spp., Moraxella catarrhalis and various anaerobes.^{Reference Gadre and Chole3} Cases that do not respond to traditional therapy should raise the suspicion for uncommon organisms such as aspergillus spp. and non-tuberculosis mycobacteria.^{Reference Kazemi7} Most authors advocate for the use of a cephalosporin antibiotic along with metronidazole with or without the addition of dexamethasone and vancomycin.^{Reference Gadre and Chole3,Reference Janjua, Bajalan, Potter, Whitney and Sipaul10} Although controversial, the anti-inflammatory and analgesic properties of corticosteroids can alleviate neural pathology such as ocular palsies and headache. In our case, ceftriaxone and vancomycin were chosen pre-operatively for empiric broad-spectrum coverage. The patient was discharged on six weeks of ceftriaxone administered by peripherally inserted central catheter line based on culture results.

The ideal treatment for petrous apicitis is controversial and typically depends on the severity of the disease. Some authors agree that antibiotic therapy combined with modified or radical mastoidectomy and tympanostomy tube placement may be sufficient to allow drainage of the petrous apex air cell tracts.^{Reference Goldstein, Casselbrant, Bluestone and Kurs-Lasky4} However, more recently authors have advocated for non-surgical intervention with intravenous antibiotic therapy. Petrous apicitis management is challenging because the petrous apex is the most surgically inaccessible portion of the temporal bone.^{Reference Chole, Flint, Haughey, Lund, Niparko, Robbins, Thomas and Lesperance2} Indications for surgical intervention include abscess formation, osteonecrosis and failure of medical therapy. The choice of surgical approach depends on the patient's pre-operative hearing status, individual temporal bone anatomy and the surgeon's experience. In non-hearing ears, translabyrinthine and transcochlear approaches provide the most direct access but result in destruction of the cochlea. Approaches that preserve hearing include infracochlear, infralabyrinthine, retrolabyrinthine, middle fossa and subarcuate approaches. In the case presented, our neurosurgical colleagues were available if a middle cranial fossa approach was deemed necessary or if the patient failed treatment with mastoidectomy, myringotomy and antibiotics.

Risks of surgical intervention on the petrous apex cannot be overlooked and include facial nerve damage, intracranial infections and thrombosis.^{Reference Janjua, Bajalan, Potter, Whitney and Sipaul10} Although there may not be one ideal therapy for all cases of petrous apicitis, favourable outcomes are associated with a high index of suspicion, early diagnosis with appropriate imaging studies and prompt intervention (either medical or surgical).^{Reference Gadre and Chole3} Post-operative management may include intensive care unit monitoring.^{Reference Kitsko, Dedhia, Myers and Snyderman1} In this period, it is critical to monitor the patient for signs of cerebrospinal fluid leak, cerebral oedema, increased intracranial pressure, pneumocephalus and seizures. Infectious disease and neurosurgery consultations are recommended, and many patients require long-term antibiotic therapy.