2.1 Clinical data:
10 patients with skull base ChSa were enrolled in this study. They were all treated by endoscopic endonasal resection from 2001 to 2017, including 6 males and 4 females, aged from from 18 to 47 years, with a median of 35.2 years. And the mean duration of follow-up was 43.8 months（range，24-108months）. Patient characteristics are reported in Table 1. Clinical symptoms of the patients: seven of ten patients were nose bleeding, runny, stuffy, four of ten patients were headache, two of ten patients diplopia, eye outreach limited, blurred vision, and one patient was even blindness. Clinical examination: tumor was gray or pink, easy bleeding, and occupying one side, bilateral nasal cavity and even the entire nasopharynx. Imaging examination: range of tumor invasion to the single or bilateral nasal cavity, anterior skull base, nasal septum, the entire nasopharyngeal cavity, maxillary sinus, ethmoid sinus, orbital paper plate, sphenoid sinus, anterior cranial fossa, bilateral eyes, bilateral optic canal, part of the ICA bone and slope area. In 3 of the 10 cases, tumor invaded anterior cranial base, and in the remaining 7 cases, tumor invaded middle cranial base. Besides, in 2 cases, tomor invaded ICA and optic nerve bone canal. No tumor invasion of cerebrum was observed during endoscopic surgery in all cases. Before operation, three of the patients were misdiagnosed of ossifying fibroma, fibrous dysplasia, fibrous vascular tumor, olfactory neuroblastoma and cartilage tumors in other hospitals’department of image and pathology.
2.2 Surgical methods
All cases with skull base ChSa were operated by endoscopic endonasal resection under general anesthesia.
First of all, we used the adrenalin gauzes to shrink nasal mucosa to reduce bleeding and used long gauze to push the tumor to the bottom of nasal cavity to check the situation of tumor. Then we cut all or part of the middle turbinate and inferior turbinate. Inserted nerve disseetor along the incision and separating it up and down while pushing the tumor towards to nasal cavity, used turbinate scissors to remove the upper and lower parts of the maxillary sinus wall, exposed the maxillary sinus internal angle, and used tissue forceps to trim the maxillary sinus medial wall. Besides we pulled the sliver back downwards to expose the front of the middle turbinate, used bipolar electrocoagulation to expose the bone at the front of the middle turbinate, and placing a wide white gauze in the incision of electrocoagulation. According to the differences among tumor tissue, normal soft tissue and bone texture, we used 5 mm suction as a nerve dissector, while sucking with a suction device and protected with a sliver, to peel the tumor back and down. We can also use tonsil dissector, while stopping the bleeding with electrocoagulation treatment, to peel the tumor back and down. The entire tumor, middle turbinate, and some normal ethmoidal tissues were dissected from the anterior skull base and sent to the posterior nostril, nasopharyngeal cavity, and even the oropharynx. Clear up soft tissue that adheres to normal skull base bone and papyraceous lamina. Examine the size of the anterior cranial bone destruction zone and the condition of the meninges carefully. High-speed drill was used to grind suspected invaded anterior skull base bone. Because the tumor growed expansively and the tumor boundaries are clear. When the base of skull bone was destructed, tumor is likely adhensive to endocranium. In order to reduce the meningeal hemorrhage when stripping off tumor, using bipolar electrocoagulation coagulate around the meninges which were adhere to the tumor. The tumor was dragged and spun off by vise and then removed. Tumors may invade other non-functional anatomy regions, such as papyraceous lamina, posterior part of nasal septum and the bottom of the junction between medial wall of maxillary sinus with the palate. We should removed the organizational structure as far as possible and removed tumor from the oropharynx, filling nasal cavity with iodine spinning.
If the tumor invade middle cranial fossa, such as the saddle area, clivus regions, ICA, optic canal and so on, in addition to the above-mentioned steps, we resected anterior wall of sphenoid sinus by drill or bone rongeur. The sphenoid sinus cavity and adjacent tumors were separated bluntly, such as twining the front part of the nerve dissector, peeling the tumor towards oropharynx and so on. We must pay attention to the direction of the ICA and the bony duct of the optic nerve, the anatomic site of the cavernous sinus, and the extent of bone erosion in the clivus, to avoid damage the important anatomical structure and major complications. When we were dealing with the invaded optic nerve or internal carotid arterial bone tube, because the tumor has a clear boundary with the normal tissue and the connection is loose, we can use medical gauze and nerve dissector separated them easily. Fragmented soft tissue strips could be slowly removed by an electric cutter. The direction of tumor separation should be consistent with the direction of nerves and arteries. When tumor has been detached and the optic nerve or ICA has been exposed, we could remove the surrounding tumor tissue with a small nerve dissector that wraps two to three layers of gauze on the head and then bited with the rongeur to remove the tumor gently. High-speed drilling was used to deal with parts of the suspected invaded bone were as far as possible to achieve contours or expanded contours, such as the optic nerve, ICA bone canal, clivus and pterygoid bone. After ICA bone canal was open, fascia was covered to protect artery. And then we must be careful not to damage the joint capsule of atlanto-cone when dealing with the bone of the lower clivus. Otherwise, it would affect the stability of the skull.
2.3 Typical case
A male patient, aged 38, hospitalized for “repeated headaches, left eye pain with blurred vision four week” in April 2007. Clinical examination: left eye vision 1.0, right eye visual 1.5, bilateral eyes move normally, no external nose deformities, the forward edge of bilateral choanal and the anterior wall of sphenoid sinus was ectasia and hyperemia. Bilateral middle and inferior turbinates were neither hypertrophy nor shrink. Magnetic resonance imaging (MRI) examination: an irregular regiment massive lump could be found in plain cross-section T1WI, T2WI, and in sagittal plane, T1WI. The lump signal is not uniform, the boundary is clear, the edges are irregular and slightly lobulated. Sign of the lump shows slightly long T1, and equal T2 signal. The inside of the lump showed irregular long T1, long T2 signal liquefaction and necrosis area. Adjacent to the mass, the ethmoid bone, the bilateral orbit, the slope, and the skull base are oppressed and absorbed. On both sides of the lump, medial rectus, optic chiasm, pituitary, ICA, top wall of nasopharynx, posterior turbinate and right maxillary sinus medial wall were under a little pressure. Enhanced scan shows non-uniform enhancement in heterogeneous lump, no enhancement in liquefaction necrosis. The tumor was about 3.6cm × 4.5cm × 3.8cm. No abnormal signal was found in the brain parenchyma. These MRI revealed: Tip 1.The tumor located in ethmoid and sphenoid sinus is most likely to be olfactory neuroblastoma. 2. Paranasal sinusitis. Operation range: right around the ethmoidal cellules, posterior nasal septum, sphenoid sinus, left orbital apex, the left optic bone pipe, clivus(Figure 1). Pathological diagnosis in other hospital was consistent with cartilage tumors. In February 2008, the patient was admitted to our hospital because of left eye vision and sharp decline in visual acuity for 10 days. His speciality examination showed that his left eye has no light perception, right eye vision is 0.2. White secretions can be observed in the left nasal cavity, with pale red neoplasia at the top of nasal cavity, upper septum, and nasopharyngeal top. Preoperative MRI T2WI scans showed a 5.2cm × 5.2cm × 6.3cm lobulated soft tissue lump in the anterior cranial fossa, ethmoid, sphenoid sinus and nasal cavity. The signal around the lump was high and the central signal was low. Bone had been destroyed in anterior cranial fossa, ethmoid, sphenoid sinus wall, nasal septum, bilateral orbital wall and upper middle turbinate. Normal tissue had been invaded in bilateral orbital and the right maxillary sinus (Figure 2). Range of operation: the former base of the skull, bilateral frontal mouth around the tip of bilateral orbital, maxillary sinus, clivus and bilateral optic bone tubes. During the operation, it was observed that the bone of the right ICA was partially destroyed, the defect of anterior skull base bone was about 3.0 cm × 2.5 cm, and the endocranium was not damaged. The tumors that could be seen with the naked eye during the operation were resected and there was no residue in the postoperative radiological examination. (Figure 3). The surface of the tumor was as smooth as jade, while texture was like cartilage(Figure 4).Pathology diagnosis: well-differentiated ChSa. Ater follow-up, recurrence was found in 32 months, and the patient has been living with tumor.(Figure 5).