Petrous Apex Lesions
• The petrous apex may be affected by cystic and solid lesions. Cystic lesions are more common and are benign. Solid lesions are less common and may be benign or malignant.
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s Apex Lesions
Z Core Messages • The petrous apex may be affected by cystic
and solid lesions. Cystic lesions are more common and are benign. Solid lesions are less common and may be benign or malignant. • Clinical signs and symptoms of expanding lesions of the petrous apex include Eustachian tube compression, third and sixth nerve deficits, and headache. • Both magnetic resonance imaging and computerized tomography are recommended in the diagnosis and management of petrous apex lesions. • Surgical approaches to biopsy or fistulize petrous apex lesions include perilabyrinthine cell tracts, sphenoid sinus, middle cranial fossa, transcochlear.
The subtle clinical presentations of petrous apex lesions are related to the regional anatomy of the apical segment of the temporal bone (Fig. 5.1). Prior to 1975, the major lesion of the petrous apex described in the literature was infection, causing epidural abscess formation responsible for a classic triad of symptoms (Gradenigo’s syndrome). These were diplopia, deep pain, and facial hypoesthesia. Nearby structures in the petrous apex (fifth and sixth cranial nerves) provided logical explanation of the clinical findings in this potentially lethal sequela of middle ear infection. Radiologic techniques (plain x-rays, polytomography) were capable of demonstrating only the most advanced osteolytic lesions in this area [3, 7]. Using these methods, a series of solid and cystic lesions primary in the petrous apex were demonstrated and managed in a monograph publication [3, 7]. These lesions are a manifestation of the complex anatomical composition of the petrous apex, consisting of air cells, bone marrow, cartilage, nerves, and vascular structures (internal carotid artery, jugular bulb). This report of petrous apex cases and their management unlocked the many
pathologies located in this obscure region of the skull base. Sophisticated imaging techniques (CT, MRI) now permit early recognition of a petrous apex lesion. The usual presenting symptoms of an expanding lesion in the petrous apex are a conductive hearing loss from the serous effusion caused by Eustachian tube obstruction, headache from pressure on the dural covering, diplopia related to involvement of the third and sixth cranial nerves, facial hypoesthesia caused by compression of the fifth cranial nerve, and varying degrees of faintness or vertigo probably caused by changes in the labyrinthine blood supply. The pathologies involving the petrous apex may be divided into solid and cystic lesions (Table 5.1). . Table 5.1 Petrous apex pathologies categorized by lesion type Solid lesions Benign Neurofibroma or schwannoma Chondroma Meningioma Paraganglioma Malignant Chondrosarcoma Eosinophilic granuloma Lymphoma Metastatic malignancies (breast, lung, kidney, prostate) Cystic lesions Vascular Internal carotid aneurysm Venous lake Nonvascular Apicitis (abscess) Congenital epidermoid cyst Cholesterol granuloma (mucocele)
5.1
Diagnosis
The clinical suspicion of a progressive lesion in the petrous apex is based on recognitio
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