Skull Base

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Anterior skull base

Extracranial lesions - Nasal, paranasal sinus malignant tumors

Orbital plates, frontal bones, cribriform plate, planum sphenoidale

Occur in up to 30% of anterior skull base cases. Carcinomas represent 98% of adult nasopharyngeal tumors

• Squamous cell carcinomas (80%), adenocarcinomas (18%)

• Rhabdomyosarcoma (the most common soft tissue sarcoma in children—up to 35 % of these lesions occur here

• Esthesioneuroblastoma, or olfactory neuroblastoma (arises from the bipolar sensory cells and is histologically similar to adrenal or sympathetic gan-glionic neuroblastomas or retinoblastomas

Osteopetrosis Paranasal Sinus

- Bacterial or fungal sinusitis

- Sarcoidosis

- Lymphoma

- Granulomatoses Cocaine abuse, Wegener's

Intrinsic lesions

- Fibrous dysplasia

- Paget's disease

- Osteopetrosis

Intracranial lesions

- Meningioma Planum sphenoidale and olfactory groove menin giomas account for 10 -15% of all meningiomas

- Nasoethmoidal The most common anterior skull base lesion that orig-encephalocele inates from the brain; 15% of basal encephaloceles occur here

- Dermoid sinuses

- Cerebral heterotopias

- Primary brain neo- Rare lesions; may cause dural invasion or calvarial de-plasms struction

• Ganglioglioma

• Anaplastic glioma or glioblastoma multiforme

Central skull base Upper clivus, sella turcica, cavernous sinuses, sphenoid alae

Metastases Arise from regional extension of head and neck malig nancies or hematogenous spread from extracranial sites, e.g., prostate, lung, and breast carcinomas

^ Fig. 12 Skull base lesions

1. Fibrous dysplasia. Axial proton density MRI with thickening of the right sphenoid bone and reduction of the size of the orbit and associated exophthalmos.

2. Meningioma of the right cavernous sinus. Coronal T1 WI shows expansion of the right cavernous sinus and a very high signal intensity following contrast enhancement.

3. Metastasis. Axial CT demontrating an osteolytic lesion of the sphenoid tip of the petrous bone.

4. Chordoma. Axial CT with a high-density space-occupying lesion of the left temporal fossa and the parasellar region. The mass is eroding the apex of the petrous bone and is extending to the cerebellopontine angle of the same side.

5. Paraganglioma or glomus jugulare. Axial CT shows a space-occupying lesion of the right CP angle that occupies the right jugular foramen and demonstrates intense, heterogeneous postcontrast enhancement.

6. Paget's disease. Axial CT shows a marked thickening of all bones of the skull base with reduction of the size of the posterior fossa.

Immunocompromised states, diabetes, chronic mastoiditis, paranasal sinus infection, trauma or necrotizing otitis externa

From ethmoid or sphenoid sinuses, or intracranially via emissary veins and the cavernous sinus, resulting in cerebral infarction, meningitis, subdural empyema, and brain abscess

Candidiasis, aspergillosis, histoplasmosis, rhinomu-cormycosis, resulting in multiple cranial nerve palsies, internal carotid artery thrombosis, cavernous sinus thrombosis, cerebral infarction, and brain abscess in immunocompromised patients

• Wegener's granuloma

• Sarcoidosis

• Rhinoscleroma

• Cocaine abuse granulomatosis

• Lethal midline granuloma (variant of T-cell lymphoma)

• Eosinophilic granuloma

Primary benign neoplasms

- Pituitary adenoma May extend superiorly through the diaphragma sellae and laterally into the cavernous sinus

- Meningioma Located alongside the sphenoid wing, diaphragma sellae, clivus, and cavernous sinus

- Nerve sheath tumors

• Plexiform neurofi-bromas

• Schwannomas

- Juvenile angiofibroma

- Chordoma

- Enchondroma

- Epidermoid tumors

- Lipomas

- Cavernous hemangi-omas

Infection and inflammatory disease - Osteomyelitis

- Bacterial sinusitis

- Fungal sinusitis

- Nonfungal granulomas

Diffusely infiltrating masses originating primarily along the ophthalmic and the maxillary and mandibular divisions of the trigeminal nerve Cause one-third of primary trigeminal nerve and Meckel's cavity tumors. Neurinomas of the third, fourth and sixth cranial nerves are rare The most common benign nasopharyngeal tumor; highly vascular

The most common benign osteocartilaginous tumor in this area

Primary malignant neoplasms

- Nasopharyngeal carcinoma

- Rhabdomyosarcoma

- Multiple myeloma The most common primary bone tumor originating in the central skull base

- Solitary plasmacy-toma

- Osteosarcoma

- Chondrosarcomas

Posterior skull base, clivus

The second most common primary bone tumor after multiple myeloma

Includes the clivus below the spheno-occipital syn-chondrosis, the petrous temporal bone, the pars lat-eralis and squamae of the occipital bones, and surrounds the foramen magnum

Lesions in the temporal bone

Lesions in the foramen magnum

Clival and paraclival lesions

- Chordoma Chordomas or chondrosarcomas usually originate from the sacrococcygeal region, the spheno-occipital region (40%), or the vertebrae. Both these tumors represent 6-7% of primitive skull base lesions, and they are very rare, representing only 0.2 % of intracranial tumors. Differential diagnosis of intracranial chordomas vs. invasive and calcified tumors includes:

• Chromophobe adenoma

• Mucinous adenocarcinoma

• Meningioma

• Craniopharyngioma

• Schwannoma

• Nasopharyngeal carcinoma

• Salivary gland tumors

- Chondrosarcomas

- Metastasis

• Regional extension

• Hematogenous extracranial sites

- Meningioma

- Osteomyelitis

- Multiple myeloma

- Plasmacytoma

- Histiocytosis

Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme All rights reserved. Usage subject to terms and conditions of license.

E.g., nasopharyngeal squamous-cell carcinoma E.g., lung, prostate, breast

Including Gradenigo's syndrome thalamus claustrum diaphragm of sella anterior —

clinoid process





caudate nucleus head corpus callosum caudate nucleus head corpus callosum

Gradenigo Syndrome

venous spaces of cavernous sinus pituitary gland venous spaces of cavernous sinus pituitary gland internal capsule putamen

-3rd ventricle globus pallidus mamillary body

-optic chiasm infundibular stalk temporal lobe internal carotid artery

Fig. 13 Suprasellar and parasellar lesions. Diagram of the cavernous sinus and its contents; the sellar, suprasellar, and parasellar structures

Jugular foramen lesions - Neoplastic masses • Paragangliomas


• Nerve sheath tumors

Epidermoid tumor Chondroid, chordoma lesions

• Meningioma

Chemodectomas or glomus tumors; parasympathetic paraganglia located in the jugular bulb adventitia and in various sites of the head and neck, especially the carotid body, glomus jugulare, and glomus tympani-cum

- Regional extension (e.g., nasopharyngeal carcinoma, lymph node metastatic disease)

- Hematogenous extracranial sites (e.g., lung, prostate, breast)

Uncommon location

- Schwannomas of cranial nerves IX and XI

- Neurofibromas

Nonneoplastic masses

- Prominent jugular "Pseudomass"—normal variant bulb

- Jugular vein thrombosis

- Osteomyelitis Diffuse skull base le-

Neoplastic masses

- Metastases

- Multiple myeloma, plasmacytoma

- Meningioma

- Lymphoma

Nonneoplastic masses - Fibrous dysplasia

Paget's disease Eosinophilic granulo-

Primary or secondary; uncommon, but increasing in incidence, causing leptomeningeal disease and multiple cranial nerve palsies

The most common benign skeletal disorder in adolescents and young adults. In the most common monos-totic type, 25% of skull and facial bones are involved, compared with 40-60% in the polyostotic type, causing facial deformities and cranial nerve palsies

Cavernous sinus lesions


- Schwannoma

- Meningioma

- Metastasis

- Vascular lesions






Cranial nerves III, IV, V, and VI

These tend to follow the lateral margin of the cavernous sinus, and may extend posteriorly along the tentorial margin, with a dovetail appearance on MRI.

May encase or distort the cavernous portion of the

E.g., adenoid cystic carcinoma, basal-cell carcinoma, lymphoma, mucoepidermoid carcinoma, melanoma, and schwannoma, showing perineural spread through the basal skull foramen and into the brain E.g., ectatic carotids, caroticocavernous fistula, cavernous carotid aneurysm, cavernous hemangioma, and cavernous sinus thrombosis

E.g., actinomycosis, Lyme disease, and herpes zoster can also demonstrate perineural involvement ma

- Idiopathic inflammatory disease


- Extensive and aggressive pituitary adenoma

- Meningioma

- Metastases

- Thrombosis of the cavernous sinus

Tolosa-Hunt syndrome: characterized by recurrent attacks of retro-orbital pain, defects in cranial nerves III, IV, Va, and VI, with spontaneous remission and prompt response to steroid therapy

May occur as part of a septic process associated with spontaneous dural malformations, or may result from an interventional or surgical procedure

ICA: internal carotid artery; MRI: magnetic resonance imaging.

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