PMC8321740_01
Magnetic resonance imaging. (a) T1-weighted image on coronal section. (b) T2-weighted image on coronal section.
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T1 and high intense on T2 and showed no thickening of the left dura mater or invasion of the middle cranial fossa (shown in Figures 1(a) and 1(b)). The left frontal sinus was filled with secondary mucus, and no tumour component was observed.
Computed tomography of the frontal sinus. (a) Axial section. The anteroposterior (AP) diameter of the right frontal sinus is 9.6 mm and that of the left frontal sinus is 5.9 mm. (b, c) Sagittal section of the right and left frontal sinuses. The skull base-frontal sinus angle (SBA) on the right frontal sinus is 126  and that of the left frontal sinus is 107 .
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However, both sides of the frontal sinuses were hypoplastic, with thickening of the septum of the frontal sinus and a difference in the anteroposterior (AP) diameter of the frontal sinus between the right and left sides (shown in Figure 2(a)). The AP diameter was 9.6 mm on the right and 5.9 mm on the left, and the skull base-frontal sinus angle (SBA) was 126  on the right and 107  on the left (shown in Figures 2(b) and 2(c)).
Surgical image presentation. (a) The endoscopic modified Lothrop procedure (EMLP) on the right side. The first olfactory fibre was identified (white arrow), and the right frontal beak was drilled out (white dotted line). (b) The posterior wall of the right frontal sinus was identified, the floor of the frontal sinus (white dotted line) was drilled out, and the left frontal sinus was approached. The first olfactory fibre is visible (white arrow). (c) After drilling out the floor of the frontal sinus. The first olfactory fibre on the left side (tumour side) is identified (yellow arrow), and a space was observed (white triangle) on the left side at the same depth as the right frontal sinus. (d) The space was drilled out to open by 4 mm (white triangle); leakage of cerebrospinal fluid was observed. The first olfactory fibre (white and yellow arrow). (e): The EMLP was finished. Bilateral frontal sinuses were observed; it was confirmed that the posterior wall of the left frontal sinus was damaged (white triangle). The first olfactory fibre (white and yellow arrow). (f) After anterior cranial resection of an olfactory neuroblastoma. The injured area of the skull base overlapped with the resected area of the tumour. (g) The skull base was reconstructed to be water-tight by suturing the dura mater to the fascia. (h) Multilayer reconstruction using fascia and cartilage. (i) Finally, the wound was covered with a nasoseptal flap.
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First, the first olfactory fibre was identified on the right side (non-tumour side) (shown in Figure 3), and the depths of the right frontal sinus and the right anterior skull base were confirmed by Draf 2B (Figure 3). Subsequently, Draf 2D was used to approach the left frontal sinus from the right frontal sinus via the septum of the frontal sinus (shown in Figure 3). After opening the space by 4 mm, CSF leakage was observed, and the skull base was judged to be damaged (shown in Figure 3). Figure 3). Fortunately, the injured area of the skull base overlapped with the resected area of the tumour (shown in Figure 3), and the skull base was reconstructed to be water-tight by suturing the dura mater to the fascia with 11 stitches of 6-0 proline (shown in Figure 3). Figure 3). Finally, the nasoseptal flap was over-layed to complete the operation (shown in Figure 3).