The skull base: tumoral lesions

Abstract

Many lesions occur in the anterior, central and posterior skull base. In order to detect and characterise them, one has to apply the best imaging technique. Today MR is the preferred technique, and the use of CT is more and more restricted to evaluate the presence of calcifications and involvement of thin bony walls, foramina and fissures. However, MR is only superior when the right sequences and imaging planes are used. Many lesions can be characterised by their specific signal intensity on different sequences and by their location. Nevertheless some lesions can only be characterised after biopsy. The purpose of imaging in skull base tumours remains in the first place the evaluation of the exact tumour extent, and this is again best achieved with MR. In this paper the imaging technique and the most frequent skull base tumours are discussed.

Ectopic growth hormone-secreting pituitary adenoma involving the clivus treated with octreotide: role of magnetic resonance imaging in the diagnosis and clinical follow-up

“…It has been suggested that EPAs could arise along the cranial migration route of Rathke's pouch toward the hypothalamus, after its development as an invagination of the primitive oral cavity during the third week of gestation; remnants of this pharyngopituitary canal in bone areas, for example, could explain EPAs in the clivus or sphenoid bone 4,5 . Surgical resection of the adenoma causing acromegaly has been the traditional approach, although normalization of IGF-1 and GH levels is observed in only 40-70% of patients 1 …”

Imaging of skull base tumours

“…Chordomas present as expansile clival tumours, often exhibiting an aggressive pattern of bone destruction with replacement of the clivus bone marrow and erosion of its cortical margins. 29 On MRI, they are typically T1 isointense to hypointense and T2 isointense to hyperintense lobulated masses (Fig. 12) showing heterogenous Gadolinium enhancement.…”

Kafa Kaidesi Tumörleri

“…MR görüntüleme, lezyonun yumuşak doku bileşenini ve çevre yapılar ile ilişkisini değerlendirmek için tercih edilen inceleme yöntemi olup, tümörün intrakraniyal uzanımını (dural, leptomeningeal, beyin parankimi invazyonunu), perinöral ve perivasküler yayılımını ve kemik iliğini tutulumunu göster-mede doğruluğu en yüksek modalitedir [2,6]. BT ise kafa tabanının kemik anatomisini gös-termede tercih edilen görüntüleme tekniğidir.…”

“…Kemikte ekspansiyona yol açar, nöral foramen ve fissür-lerde daralma veya yer değiştirmeye neden olabilir. Ancak, lezyon kemiğin genel şeklini ve konturlarını takip eder (Resim 4) [6]. MR'de aktif fibröz displazi lezyonları, T2A'da yük-sek sinyalli kistik alanlar içerebilir ve yoğun kontrastlanabilirler.…”