Tumors of the cerebellopontine angle (CPA) are frequent; acoustic neuromas and meningiomas represent the great majority of such tumors. However, a large variety of unusual lesions can also be encountered in the CPA. The site of origin is the main factor in making a preoperative diagnosis for an unusual lesion of the CPA. In addition, it is essential to analyze attenuation at computed tomography (CT), signal intensity at magnetic resonance (MR) imaging, enhancement, shape and margins, extent, mass effect, and adjacent bone reaction. CPA masses can primarily arise from the cerebellopontine cistern and other CPA structures (arachnoid cyst, nonacoustic schwannoma, aneurysm, melanoma, miscellaneous meningeal lesions) or from embryologic remnants (epidermoid cyst, dermoid cyst, lipoma). Tumors can also invade the CPA by extension from the petrous bone or skull base (cholesterol granuloma, paraganglioma, chondromatous tumors, chordoma, endolymphatic sac tumor, pituitary adenoma, apex petrositis). Finally, CPA lesions can be secondary to an exophytic brainstem or ventricular tumor (glioma, choroid plexus papilloma, lymphoma, hemangioblastoma, ependymoma, medulloblastoma, dysembryoplastic neuroepithelial tumor). A close association between CT and MR imaging findings is very helpful in establishing the preoperative diagnosis for unusual lesions of the CPA.

T1 signal hyperintensity is a common finding at magnetic resonance imaging of the sellar region. However, this signal intensity pattern has different sources, and its significance depends on the clinical context. Normal variations in sellar T1 signal hyperintensity are related to vasopressin storage in the neurohypophysis, the presence of bone marrow in normal and variant anatomic structures, hyperactive hormone secretion in the anterior pituitary lobe (eg, in newborns and pregnant or lactating women), and flow artifacts and magnetic susceptibility effects. Pathologic variations in T1 signal hyperintensity may be related to clotting of blood (in hemorrhagic pituitary adenoma, pituitary apoplexy, Sheehan syndrome, or thrombosed aneurysm) or the presence of a high concentration of protein (Rathke cleft cyst, craniopharyngioma, or mucocele), fat (lipoma, dermoid cyst, lipomatous meningioma), calcification (craniopharyngioma, chondroma, chordoma), or a paramagnetic substance (manganese, melanin). After treatment, T1 signal hyperintensity may result from the presence of materials used for surgical packing (gelatin sponge, fat); from compression of the cavernous sinus and reduction of the venous flow, caused by overpacking of the operative bed; or from hormone hypersecretion by a remnant of normal tissue in the anterior lobe of the pituitary gland.

Von Hippel-Lindau disease (VHL) is a hereditary cancer syndrome caused by germline mutations of the VHL tumor suppressor gene. Major progress has been made in the last decade in both clinical and fundamental aspects of VHL. The VHL gene product, pVHL, has major and multiple functions: pVHL regulates not only first angiogenesis but also extracellular matrix formation and the cell cycle. A molecular diagnosis of VHL is now available, leading to a transformation in clinical management of patients and their families. Diagnosis of VHL has to be suspected in patients with a VHL-related tumor without familial history and especially in case of hemangioblastoma or endolymphatic sac tumors. Such patients should be systematically investigated for clinical and molecular evidence of VHL disease. Treatment of symptomatic hemangioblastomas remains mainly neurosurgical, often in emergency, but stereotactic radiosurgery is emerging as an alternative therapeutic procedure. In the future, antiangiogenic drugs could represent a potential medical treatment of CNS hemangioblastomas in view of their highly vascular structure. Lastly, visceral manifestations of VHL disease are also of critical importance and require early detection for effective treatment.

Wegener's granulomatosis (WG) is a severe and potentially lethal granulomatosis. Even though no specific radiological criteria exist, CT may suggest the correct diagnosis at an early stage. Recent improvement in the prognosis is related to earlier diagnosis, allowing the initiation of efficient and specific treatment before any severe complications occur. We reviewed a series of WG cases in order to establish the CT diagnostic criteria.

We report here two cases of diffuse axonal injury (DAI) studied by MR diffusion tensor imaging (DTI) and fibre tracking (FT) focused on the corpus callosum. In one case, DTI and FT pattern matched the diagnosis of broken white matter tracts. In the other case there was a discrepancy between DTI and FT data that showed unaltered white matter tracts with the presence of intra-cellular oedema. These data suggested that DTI and FT are able to differentiate between traumatic cytotoxic oedema and broken fibres in the case of DAI.

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Head and neck lesions are encountered in more than 40-50% in patients with immunosuppression (HIV-infected individuals, diabetes mellitus, transplant recipients, patients treated with immunosuppressive drugs or post-radiotherapy). The organs affected are the salivary glands, the lymph nodes, the sinonasal tract, the orbits, the temporal bones, and the pharyngo-laryngeal mucosa. They are mainly involved by granulation tissue, perivascular and perineural inflammation, and neoplasms. In the pediatric population the temporal bone is the most frequent target organ. The most common clinical manifestation of salivary gland involvement is non-specific bilateral painless enlargement of the parotid gland and xerostomia. Lymphoepithelial cyst, sialosis, and lymphoma may be present. The high rate of salivary gland involvement is probably related to the presence of the human immunodeficiency virus within the saliva. Surgery, sclerotherapy by doxycycline, or low-dose radiotherapy may prevent further growth of tumoral lesions. Sinonasal diseases are the most frequent lesions which manifest in immunosuppressed adult patients (66%). They are associated with a trend of decreased survival rate. Invasive aspergillosis is defined by hyphae in the submucosa, and tumor necrosis without host inflammatory response; it may be lethal in 50-80%, especially when the skull base is involved. Computed tomography shows erosion of bone and extrasinonasal extension. The hypointensity of the lesion on T2-weighted images may suggest the diagnosis. Fungal sinus disease can affect 1-10% of transplant recipients and should be suspected when organ rejection is considered. The temporal bone is the most frequent target organ in the immunosuppressed pediatric population due to Eustachian,tube dysfunction. Otomastoïditis, necrotizing external otitis, and otosyphilis are reported. Prompt treatment may avoid lateral sinus thrombosis. Epithelial neoplasms, lymphomas, and Kaposi's sarcoma may also be considered. Kaposi's sarcoma, the most common neoplasm encountered in patients with AIDS, is an indicator of the progression of human immunodeficiency virus infection to AIDS. The lesions are often multifocal at presentation and may affect the skin, the mucosa, and visceral organs. The pathogenesis is unclear, but cytokines and growth factors may play a role. In conclusion, immunosuppressed patients are likely to develop virulent infection with vascular complications.

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