Imaging of skull base tumours

Abstract

The skull base is a highly complex and difficult to access anatomical region, which constitutes a relatively common site for neoplasms. Imaging plays a central role in establishing the differential diagnosis, to determine the anatomic tumour spread and for operative planning. All skull base imaging should be performed using thin-section multiplanar imaging, whereby CT and MRI can be considered complimentary. An interdisciplinary team approach is central to improve the outcome of these challenging tumours.

Keywords: Head and neck; Oncology; Skull base imaging; Skull base tumours.

Fig. 1

(a) and (b) Coronal and sagittal post Gadolinium T1 images demonstrating an olfactory groove meningioma with a dural tail (arrow). (c) Large right spheno-orbital mengioma in a different patient with proptosis, optic nerve compression and intracranial extension. Note the hyperostotic expansion of the adjacent sphenoid wing (arrow).

Fig. 2

Coronal post Gadolinium T1 images in two different patients demonstrating subtle enhancing tissue in the right olfactory groove (a, white arrow) and an extensive destructive lesion (b) involving the anterior skull base and paranasal sinuses with evidence of prior surgery. In both patients, the proven histological diagnosis was olfactory neuroblastoma. Patient (a) also has an incidental mucus retention cyst in the left maxillary antrum (black arrow) characterised by minimal rim enhancement.

Fig. 3

Not a tumour: Sagittal T2 image demonstrating a mass within an anterior skull base defect. This sincipital encephalocele could be mistaken for a tumour, unless the herniation of brain tissue (arrow) is appreciated. (Courtesy of Dr K. Mankad, Great Ormond Street Hospital, London.)

Fig. 4

Axial T1 image: Avidly enhancing juvenile angiofibroma presenting as a posterior nasal space mass with extension into the right pterygopalatine fossa, sphenoid sinus and masticator space.

Fig. 5

(a) and (b) Axial and coronal post Gadolinium T1 images showing a SCC centred on the left sided nasal space with invasion of the ethmoid air cells, orbit and secondary obstruction of the left maxillary antrum (non-enhancing secretions, arrow).

Fig. 6

(a) and (b) Axial CT and post Gadolinium coronal T1 images featuring a destructive frontoethmoidal tumour with a histological diagnosis of adenocarcinoma.

Fig. 7

(a) Axial CT featuring right sided nasal mucosal thickening with subtle erosion of the middle turbinate. (b) Axial post Gadolinium T1 image obtained 9 months later demonstrating a destructive lesion involving the nasal mucosa and both maxillary antra. The diagnosis in this case was sinonasal melanoma.

Fig. 8

(a) Coronal CT showing nasal lymphoma with bone destruction and (b) coronal post Gadolinium T1 image in a different patient demonstrating sinonasal lymphoma spreading to the central skull base.

Fig. 9

(a) Coronal post Gadolinium T1 image demonstrating a pituitary microadenoma (arrow). (b) Pituitary macroadenoma with suprasellar extension and encroachment on the optic chiasm. The lesion extends to the medial surface of the right cavernous ICA.

Fig. 10

(a) and (b) Sagittal pre and post Gadolinium T1 images demonstrating a cystic-solid craniopharyngioma with intrinsic T1 shortening and heterogeneous enhancement.

Fig. 11

Coronal post Gadolinium T1 image showing SCC perineural spread along the left mandibular nerve (V3) characterised by nerve thickening with avid perineural enhancement.

Fig. 12

(a) and (b) Axial T2-weighted and coronal T1-weighted image through Meckel's cave featuring a trigeminal Schwannoma.

Fig. 13

(a) and (b) Axial T2 and unenhanced sagittal T1 image demonstrating a well-defined clival chordoma.

Fig. 14

(a)–(c) Axial CT, axial T2 and sagittal post Gadolinium T1 image showing chondroid matrix, T2 hyperintensity and heterogenous enhancement within a chondrosarcoma.

Fig. 15

(a) Axial unenhanced T1 image demonstrating loss of the normal skull base bone marrow signal (arrows), which was subsequently proven to represent metastatic infiltration from breast cancer. (b) Normal appearances (N) for comparison.

Fig. 16

(a) Axial CT demonstrating a lytic-sclerotic osteosarcoma of the left maxilla (featuring clips relating to previous surgery) with diffuse infiltration of the ipsilateral sphenoid base and clivus. (b) Not a tumour: Expansile ground glass matrix (arrow) of fibrous dysplasia; note the absence of bone destruction.

Fig. 17

(a) and (b) Axial CT and post Gadolinium T1 image showing typical features of a small glomus tympanicum arising on the cochlear promontory (arrow).

Fig. 18

(a) Axial post Gadolinium T1 image demonstrating a left sided glomus jugulare. (b) Coronal T2 image in a different patient showing a right sided GJ with flow voids causing a “salt and pepper” appearance and (c) corresponding digital subtraction angiogram obtained during right external carotid artery injection showing marked hypervascularity of the lesion.

Fig. 19

Axial T2 image demonstrating a small endolymphatic sac tumour (arrow) in a patient with multiple cerebellar lesions representing haemangioblastomas (arrow heads) and an underlying diagnosis of von-Hippel Lindau syndrome.

Fig. 20

(a) and (b) Axial post Gadolinium T1 and T2 images demonstrating the typical “ice cream on a cone” appearance of VS.