[Usefulness of neuroendoscopy and a neuronavigator for removal of clival chordoma]

We report a case of large clival chordoma. The patient was a 56-year-old male who was admitted to our hospital with left eye ptosis and diplopia of 2 months duration. On admission, neurological examinations revealed oculomotor nerve palsy of the left eye. Skull radiographs with polytomographs demonstrated marked destruction of the clivus. A plain computed tomography (CT) scan revealed a large iso-attenuated mass in the clivus, extending anteriorly into the sphenoidal sinus, superiorly into the suprasellar cistern, bilaterally into the petrous apex, posteriorly into the prepontine cistern and caudally into the foramen magnum. An enhanced CT scan demonstrated a slightly enhanced tumor. A high-resolution bone-window CT scan revealed marked destruction of the clivus and bilateral petrous apex. Magnetic resonance imaging (MRI) scans disclosed a large enhanced mass extending superiorly into the suprasellar cistern, bilaterally into the petrous apex and inferiorly into the foramen magnum. The tumor extended so widely that we decided on a one-stage operation via a transsphenoidal sublabial transseptal approach and transoral transpalatal approach. At surgery, we employed a neuronavigator and Codman 4-mm rigid neuroendoscope with 0 degree, 30 degrees and 70 degrees angled lenses. The tumor was very soft and suckable, and could be easily removed by applying CUSA, a pituitary curette and suction. The neuronavigator was particularly useful because the surgeon had a real-time two-dimensional representation of the position of the tip of this device in the corresponding imaging space intraoperatively. The neuroendoscope also proved useful, since remnant tumor tissues that could not be seen under an operating microscope were frequently recognized near or around the entrance of the tumor cavity, cavernous sinus region and petroclival junction area. The surgeon was able to remove these remnants safely by checking on the neuroendoscope monitor. The tumor was excised completely. The dead space of the tumor cavity was reconstructed using a free rectus abdominis muscle flap. Postoperatively, cerebrospinal fluid leakage and meningitis were recognized, but improved following spinal drainage for one week and intrathecal injection of antibiotic. The oculomotor nerve palsy of the left eye also showed good recovery at one month after the operation. Recently, skull base surgery has undergone considerable developments. Neuroendoscopes and neuronavigators are very helpful for the neurosurgeon in performing skull base tumor surgery safely and with precision, although further instrument modifications are needed.