Teaching Case

Exophthalmia, nasal congestion and headache.

The patient was admitted with exophthalmia, nasal congestion and headache.

A spiral CT (Philips Tomoscan AV) examination was performed in the axial plane with sagittal and coronal reformation. A soft-tissue mass was observed, filling the left nasal cavity and extending into the left ethmoid cells. The mass had eroded the ipsilateral upper, middle and lower turbinates. It had destroyed the inner wall of the left maxillary sinus and invaded the sinus cavity. It had also invaded the left frontal sinus and sphenoid sinus. It had eroded the lamina papyracea and extended into the left orbit where it displayed a mass effect on the median rectus muscle and caused exopthalmia. Through the cribriform plate the mass extended to the anterior cranial fossa and through the perpendicular plate it crossed the midline to the right ethmoid cells. Finally, inferiorly it extended to the epipharynx. After i.v. injection of contrast medium the mass displayed heterogeneous enhancement with areas of central necrosis.

MRI was not performed as it was not available. The tumour extension into the nasal vault made it accessible to intra-nasal biopsy.

The histopathological result of the intra-nasal biopsy was neuroblastoma of the olfactory epithelium.

Esthesioneuroblastoma (ENB, or olfactory neuroblastoma) is an uncommon, malignant, neuroendocrine tumour that arises from the bipolar receptory cells in the olfactory mucosa. These cells originate in the neural crest and differentiate into the olfactory sensory elements. ENBs are histologically similar to adrenal or sympathetic gaglionic neuroblastomas and retinoblastomas. They account for 1-5% of all intranasal tumours and show a bimodal distribution with a peak incidence in the second and fourth or fifth decades. ENBs are often confined to the nasal cavity, but may extend into the adjacent paranasal sinuses, orbit, or through the cribriform plate into the anterior cranial fossa, invading also the cavernous sinuses. CT studies demonstrate a high nasal vault soft tissue mass with focal bone destruction, but hyperostotic forms have also been reported. Intra-lesional calcifications may occur. The expansile tendency of ENB is characterised by remodelling of the sinus walls. The destructive aspect is manifested by tumour eroding the turbinates, septum and sinus walls with extension into contiguous areas. Metastatic involvement of the cervical lymph node chains, as well as more distant sites, like lungs and bones, often occurs. Central nervous system dissemination is sometimes observed.

Clinical presentation is non-specific and includes unilateral nasal obstruction, recurrent epistaxis, hyposmia and frontal headache.

The treatment of choice is radical surgery, which may require a combined craniofacial approach. A combination of radiation therapy and chemotherapy is advocated for unresectable tumours.

The prognosis of esthesioneuroblastoma is doubtful, as local recurrences and distant metastases often occur.

A combination of CT and MRI is now established as the optimum method of assessment of esthesioneuroblastomas and other sinonasal malignancies. CT and MRI are of particular value in assessing the skull base, orbit, pteryo-palatine and infratemporal fossae. Although MRI allows better differentiation of tumour spread into surrounding soft-tissue areas, such as the anterior cranial fossa and the retromaxillary space, coronal CT is still required for the demonstration of bone erosion, particularly in the region of the cribriform plate. Fat saturated T1-weighted spin-echo images with and without gadolinium enhancement are of particular value in differentiating enhancing tumour from post-obstructive mucous debris and in evaluating tumour extension to non-enhancing orbital fat. Esthesioneuroblastomas have variable signal intensity on MR imaging. Moderate but inhomogeneous enhancement following contrast administration is typical. Thus the extent of local tumour spread may be determined with a degree of accuracy in excess of 98%. However, the final determinant of penetration of the dura and orbital periosteum requires per-operative frozen section assessment.

CT provides the best information about the tumour and its local invasion especially into surrounding bony structures. MRI allows estimation of tumour spread into surrounding soft tissue areas and into the brain.

The differential diagnosis includes undifferentiated lymphoma, embryonal rhabdomyosarcoma, squamous cell carcinoma, extramedullary plasmacytoma and amelanotic melanoma. All of these neoplasms can occur in the nasal fossa, with spread to the paranasal sinuses and anterior cranial fossa. Other radiologically aggressive processes that occasionally cause anterior skull base lesions include bacterial or fungal sinusitis, sarcoidosis, lymphoma, cocaine granulomatosis and Wegener's granulomatosis.

The radiologist should be aware of this tumour entity, although definitive diagnosis is based on histopathology followed by immunohistochemical investigation. The possible extension to the skull base, brain and orbit should be investigated and reported because of the important clinical implications.

Unfortunately early diagnosis is still uncommon. A greater awareness of the tumour and earlier diagnosis seems the major focus for future research.