Glyn Lloyd

Juvenile angiofibroma: the lessons of 20 years of modern imaging

Seventy-two patients with juvenile angiofibroma have been investigated by computerized tomography (CT) and/or magnetic resonance imaging (MRI) over a period of 20 years. The evidence from these studies indicates that angiofibroma takes origin in the pterygo-palatine fossa at the aperture of the pterygoid (vidian) canal. An important extension of the tumour is posteriorly along the pterygoid canal with invasion of the cancellous bone of the pterygoid base, and greater wing of the sphenoid (60 per cent of patients). Distinctive features of angiofibroma are the high recurrence rate, and the rapidity with which many tumours recur. It is postulated that the principal determinant of recurrence is a high tumour growth rate at the time of surgery coupled with incomplete surgical excision. The inability to remove the tumour in toto is principally due to deep invasion of the sphenoid, as described above. In this series 93 per cent of recurrences occurred with this type of tumour extension. A contributory cause in these patients is the use of pre-operative embolization. The treatment implications of these findings are examined.

Recurrence and Its Avoidance in Juvenile Angiofibroma

Objective Angiofibroma is a highly vascular lesion for which a wide range of surgical approaches has been recommended. Irrespective of the approach, a significant and often rapid recurrence rate is reported in all major series.

Imaging for juvenile angiofibroma

Juvenile angiofibroma presents characteristic imaging signs, may of which allow diagnosis and accurate estimation of extent without recourse to the dangers of biopsy. The diagnosis by computed tomography (CT) is based upon the site of origin of the lesion in the pterygopalatine fossa. There are two constant features: (1) a mass in the posterior nasal cavity and pterygopalatine fossa; (2) erosion of bone behind the sphenopalatine foramen with extension to the upper medial pterygoid plate. Good bone imaging on CT is essential to show invasion of the cancellous bone of the sphenoid. This is the main predictor of recurrence: the deeper the extension, the larger the potential tumour remnant likely to be left following surgery. The characteristic features on magnetic resonance imaging (MRI) are due to the high vascularity of the tumour causing signal voids and strong post-contrast enhancement. MRI shows the pre-operative soft tissue extent of angiofibroma optimally, but its more important application is to provide post-operative surveillance: to show any residual or recurrent tumour, record tumour growth or natural involution and monitor the effects of radiotherapy.

Optimum imaging for mucoceles

A mucocele is an epithelial lined mucus-containing sac completely filling a paranasal sinus and capable of expansion. They are relatively unusual, occurring most frequently in the fronto-ethmoidal region. The imaging features on plain X-ray, computerized tomography and magnetic resonance imaging are relatively characteristic allowing distinction of the lesion from other pathologies in this area although the mucoceles may occur in association with other pathologies such as nasal polyposis and neoplasia.

Optimum imaging and diagnosis of cerebrospinal fluid rhinorrhoea.

Imaging is an important component in the investigation of unilateral watery rhinorrhoea suspicious of cerebrospinal fluid (CSF). Whilst the demonstration of the presence of beta 2 transferrin confirms that CSF is present it may prove difficult to demonstrate the exact site of origin. Fine detail coronal computed tomography (CT) with sections of 1-2 mm thickness through the anterior skull base may show small dehiscences and fractures. The commonest site for congenital dehiscences is the cribriform niche adjacent to the vertical attachment of the middle turbinate anteriorly and the superior and lateral walls of the sphenoid posteriorly. In the presence of frequent or constant CSF rhinorrhoea a CT cisternogram can be helpful in defining the exact site of the leak. Magnetic resonance imaging (MRI) is reserved for defining the nature of soft tissue i.e. inflammatory tissue, meningoencephalocele or tumour. Finally, per-operative intrathecal fluorescein is helpful when imaging does not prove positive. A management algorithm for CSF rhinorrhoea is presented.

Magnetic resonance imaging in the evaluation of nose and paranasal sinus disease.

Fifty patients with a wide range of sinus disease have been examined by magnetic resonance. These included congenital conditions, inflammatory and allergic sinus disease, fungus infection, and both necrotising and non-necrotising granulomas. A variety of benign and malignant tumours have been investigated, including eight examples of juvenile angiofibroma and 19 malignant sinus tumours. This experience of magnetic resonance scanning has shown that it is superior to computed tomography in showing the extent of malignant disease and, provided the correct pulse sequences are employed, it is always possible to distinguish tumour from retained secretion or inflamed mucosa. The extent of intracranial invasion can also be optimally demonstrated. One of the advantages of the method is the direct three-plane imaging and multislice technique, which gives total coverage of the head and neck for the assessment of malignant disease. Tissue diagnosis in the paranasal sinuses is less important than the demonstration of tumour extent and distribution. Only one tumour (juvenile angiofibroma) showed diagnostic spin-sequence characteristics, and no differentiation was observed between malignant tumours of epithelial and mesenchymal origin. The major drawback of magnetic resonance is the poor demonstration of bone and calcification in the sinuses, so that in some patients the scans need to be augmented by computed tomography studies.

Optimum imaging for sinonasal malignancy

A combination of computed tomography (CT) and magnetic resonance imaging (MRI) is now established as the optimum assessment of sinonasal malignancy. CT and MRI are of particular value in assessing the skull base, orbit and pteryo-palatine and infratemporal fossae. Although MRI offers better differentiation of tumour from surrounding tissue and fluid, coronal CT is still required for the demonstration of bone erosion particularly in the region of the cribriform plate. Thus the extent of local tumour spread may be determined with a degree of accuracy in excess of 98 per cent. However, the final determinant of penetration of the dura and orbital periosteum requires per-operative frozen section assessment. A knowledge of the tissue characteristics and site of origin can be of value in distinguishing some of the commoner sinonasal malignancies such as squamous cell carcinoma, adenocarcinoma, adenoid cystic carcinoma, olfactory neuroblastoma and chondrosarcoma. Imaging, particularly MRI also plays an important role in the post-therapeutic follow-up of patients, indicating areas of residual or recurrent disease, defining suspicious areas for biopsy. Post-operative surveillance is best achieved with three planar T1-weighted MRI, with, and without, gadolinium and axial T2-weighted sequences. The subtraction of the T1 pre- and post gadolinium T1 sequences can be of particular value in delineating recurrence.

Optimum imaging for inverted papilloma

Inverted papilloma is the most common benign tumour of the nose and paranasal sinuses, and usually arises in the lateral wall of the nasal cavity and the middle meatus. The diagnosis is suggested on computed tomography (CT) when there is a mass continuous from the middle meatus into the adjacent maxillary antrum, through an expanded maxillary ostium. The mass may contain areas of high density or calcification, and there may be sclerosis of the wall of the affected sinus. The main advantage of magnetic resonance imaging (MRI) is in defining the extent of the tumour, and in differentiating it from adjacent inflammatory tissue, but there are no certain signal intensity or enhancement characteristics to help differentiate inverted papilloma from sinus malignancy. In the differential diagnosis, antro-choanal polyp, malignant sinus tumours and chronic rhinosinusitis and fungal disease need to be excluded. The combination of bone deformity and sclerosis with the typical antro-meatal mass suggests a slow-growing tumour such as inverted papilloma.

Rhinologic changes in Wegener’s granulomatosis

Twenty-eight patients with a clinical diagnosis of sinonasal Wegeners granulomatosis were referred for imaging during the period 1990-2001. Of these, 10 had clinical symptoms and signs confined to the nose and sinuses and 18 had classical systemic Wegeners. The computed tomography (CT) and magnetic resonance (MRI) scans of the series were reviewed by a panel of one otolaryngologist and two radiologists. From the total of 28 patients, 85.7 per cent showed non-specific mucosal thickening in the nasal cavity or paranasal sinuses, 75 per cent showed evidence of bone destruction, and 50 per cent new bone formation in the walls of the sinus cavities. In addition the orbit was affected in 30 per cent of patients. The diagnosis of systemic Wegeners granulomatosis is made clinically but the condition may present characteristic features on imaging by CT and MRI. In a patient without a history of previous sinonasal surgery, a combination of bone destruction and new bone formation on CT is virtually diagnostic of Wegeners especially when accompanied on MRI by a fat signal from the sclerotic sinus wall. These changes are important diagnostically in localized sinonasal Wegeners granulomatosis where the clinical diagnosis may be uncertain and the cANCA test can be negative.

Radiological changes associated with inverted papilloma of the nose and paranasal sinuses

Inverted papilloma is an uncommon benign tumour of the nose and paranasal sinuses which has a characteristic histological pattern, high recurrence rate after surgery and may undergo malignant change. The X-ray features are reviewed in 60 patients with histologically confirmed tumours. Plain X-ray appearances were negative or non-specific in nearly half the patients. The changes shown on hypocycloidal tomography and on CT scan are more specific. A mass in the middle meatus of the nasal cavity extending into the adjacent maxillary antrum is highly suggestive of the tumour. Other features not hitherto reported are the presence of calcified areas within the tumour mass demonstrated by CT, and sclerosis and deformity of the walls of the sinuses involved by tumour.