Endoscopic Approach for Resection of Esthesioneuroblastoma
At the Skull Base Institute (SBI), we have modified our endoscopic minimally invasive techniques to tackle esthesioneuroblastomas (ENBs), we have routinely over the past several years used our transnasal endoscopic approach and our supraorbital endoscopic approach to treat patients with ENBs. This has obviated the need for large disfiguring transcranial and transfacial approaches without sacrificing outcomes and with reduced complications.
Esthesioneuroblastoma, also called olfactory neuroblastoma, is a rare cancer that occurs in the upper cribriform region of the nasal cavity. The disease is believed to arise from the cribriform region of the olfactory nerves that carry the sensation of smell from the nose to the brain.
ENB can develop in all age groups. It accounts for 3-5% of all nasal neoplasms. Although it mainly affects Caucasians, but has been reported in all races. The tumor has a bimodal age distribution occurring most commonly in teenagers and in the sixth decade of life; ENB is 1.6 times more common in females than in males.
Most patients with ENB present with symptoms of nasal obstruction causing inability to breath through the involved nostril, nose bleeding or both. These tumors can spread to the regional lymph nodes of the head and neck and less commonly may metastasize to other areas of the body.
The cause of ENB is unknown and its exact cell of origin is controversial, proposed sources of origin include the autonomic ganglia in the nasal mucosa, the sphenopalatine ganglion, the ectodermal olfactory placode, and the olfactory epithelium, the latter being the most anticipated site of origin. Smokers are thought to be at increased risk for ENB.
ENB is generally a slow growing tumor, but some ENBs behave aggressively. The initial symptoms are usually subtle in nature and the average delay between the appearance of the first symptom and the diagnosis is approximately six months. The most frequent symptoms of ENB are unilateral nasal obstruction, followed by epistaxis.
In general, the symptoms caused by ENB are non-specific and can be shared by other common nasal diseases, including long-term rhinosinusitis or allergic polypoid sinus disease as well as many other nasal and paranasal neoplasms. However, the unilateral nature of symptoms should always raise the suspicion of a possible neoplasm. The symptoms of ENB can be classified into:
Nasal - Obstruction, epistaxis, discharge, unilateral polyp, and anosmia
Neurological - Headache and nausea
Oral - Loose teeth, non-healing following tooth extraction and oral ulcers
Facial - Swelling, pain, anesthesia, and trismus (lockjaw)
Cervical - Mass, due to neck metastasis
Further growth of the tumor can be directed laterally within the orbit resulting in symptoms such as proptosis, extraocular movement paralysis, and blindness or superiorly toward the base of the skull producing intracranial symptoms and complications. Nasal and neurological symptoms are the most common while facial and oral symptoms are rare initial presentations.
Early referral for an intranasal biopsy is key to early diagnosis. A patient with a unilateral nasal obstruction and/or a recurrent epistaxis lasting longer than 1-2 months should be suspected and should undergo a thorough nasal evaluation.
Standard X-ray films do not have a role in the evaluation of ENB and a coronal thin-cut computed tomography (CT) scan is usually the initial radiological study of choice. Although ENB does not have a specific radiological appearance and typically appears as a homogeneous soft-tissue, CT images are essential for correct staging of ENB and should be evaluated carefully for erosion of the cribriform plate, and bone of the skull base.
Magnetic resonance imaging (MRI) is often necessary to better delineate sinonasal, intraorbital or intracranial extension of ENB. Because the details of bony erosion are better demonstrated by CT images, while soft tissue structures are better seen in MRI, both studies usually are required in the majority of patients.
The optic nerves, due to their close proximity to the olfactory nerves, are at risk of being invaded by the tumor as well as being injured during either radical surgery or radiation. Therefore, a preoperative ophthalmological evaluation is always required to obtain a "baseline" for vision and evaluate any possible existing visual deficits.
The role of an accurate histopathological diagnosis before initiating treatment for ENB is of critical importance. Treatment depends on the tumor stage; the classic treatment strategies for ENB are surgery or radiotherapy or a combination of both. More recently, chemotherapy has been introduced in the therapeutic armamentarium. The optimal treatment sequence varies in each individual case.
Surgery to remove ENBs is usually performed by skull base surgeons working together with head and neck surgeons. Traditionally combined cranio-facial resection is required especially with larger advanced tumors. In this procedure, a skull base surgeon operates through the skull via a craniotomy, while a head and neck surgeon makes the transfacial approach via an incision along the side of the nose (lateral rhinotomy). At the Skull Base Institute, endoscopic minimally invasive techniques have replaced these traditional open approaches.
ENBs are not as aggressive as other undifferentiated nasal and paranasal sinus carcinomas; however, if not treated early,they can spreads rapidly and may be fatal. Prognosis depends on the tumor stage and early tumors are often well controlled with the variety of available treatment modalities.