PMC9727165_01
Preoperative spine MRI showed a compression of the midbrain at the craniovertebral junction on the STIR sequence (A); an axial section contrastenhanced T1-weighted (C) depicted a low-enhancing lesion with extension from the clivus, left petroclival fissure, and left condyle up to the prevertebral plane of the fifth cervical vertebral body, determining an anterior dislocation of the oropharynx and an osteolysis of the left part of anterior C1 arch; the lesion showed an hyperintensity in T2-weighted images (B, D). Preoperative CT scan showed an osteolytic involvement of the left condyle and lateral mass (E-G) causing instability of the craniovertebral junction.
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F1
Contrast-enhanced magnetic resonance imaging (MRI) and computed tomography (CT) scans showed an extensive skull base tumor, located in the left paravertebral space, growing from the clivus and reaching the left anterior portion of C1 arch, the left occipital condyle compromising both C0-C1 and C1-C2 left joints (Figure 1).
An occipitocervical fusion was planned after endoscopic endonasal removal of the lesion. A preoperative planning of C2-C3 pedicle screws was reproduced. The 3D-printed guides were manufactured considering values of sagittal plane angle (SAL or SAR) and transverse plane angle (TAL or TAR) of screws, horizontal and vertical distances, screw directions and angulations and their entry points (A, C); C2 and C3 3D planning were shown (B, D).
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F2
Intraoperative view of the printed guide fitting on C3 lamina (A) and postoperative results. Transversal CT scan of screws' trajectories in C2 and C3, respectively (B, C). The result of anterior decompression was shown in (D) and an occipital plate and bicortical screws connected with precontoured rods completed the occipitocervical constructs. One month brain and spine MRI (E, F) confirms the decompression of the cervicomedullary junction and the optimal extent of resection.
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F3
Cancellous bone was laid on the midline between occiput and the C2 to promote fusion (Figure 3D). C1 posterior arch was removed along with the left lateral mass, through which was possible to reach the margin of anterior resection (Figure 3).