The Role of Intraoperative MRI in Excision of Clival Chordoma

Introduction: Chordoma is a rare aggressive bone cancer that originates from the remnants of notochord and accounts for 1–4% of all bone malignancies. The basisphenoidal region constitutes 35–40% of all chordoma sites mainly the clival region.[1] Clival chordomas are slowly growing tumors, but due to their location adjacent to important skull base structures, invasive nature and recurrence rate, they are considered to be malignant. The use of Intraoperative MRI (iMRI) provides high accuracy and precision specially when dealing with skull base tumors. The impact of iMRI in clival chordoma surgeries are not well studied as in pituitary surgeries.

The main objective is to evaluate the effect of iMRI in chordoma surgeries.

Method: A retrospective cohort study conducted at King Fahad Medical City (KFMC), Riyadh, Saudi Arabia which compares two groups of clival chordoma patients:

• Group A: Surgical resection with the use of iMRI.

• Group B: Surgical resection without the use of iMRI.

In terms of the Degree of surgical resection; using preoperative and postoperative volume assessment, hospital stay and functional status; using modified Ranking Scale (mRS)[2] at last follow-up. All operated clival chordoma cases from January 2008 to July 2018 were included, chordomas not involving skull base & redo surgeries were excluded.

Results: A total of 24 patients were included. Group A were 9 patients (37.5%) and Group B were 15 (62.5%). 58% of the sample were males. Headache and visual disturbance were the most presenting symptoms.

Mean preoperative tumor volume in both groups was 49.1mm3, in group A the mean preoperative tumor volume was 41mm3whereas in group B it was 53.9mm3.

The mean degree of resection in group A was 64.58% while in group B it was 58.63% with a p-value of 0.65. Hospital stay mean was 53 days in group A, in group B it was 97 days with a p-value of 0.12.

Most of the patients (88.8%) in group A were scaled 0 in mRS at their last follow-up while only (46.7%) of group B were scaled 0.

Discussion: Group A had a better degree of surgical resection (Fig. 1) and far shorter hospital stay compared with group B (Fig. 2). Although it was not statistically significant, it can be attributed to the small sample size. Patients’ long-term functional status was much better in group A as most of the patients were scaled 0 which supports the safety of the resection aided by iMRI guidance.

Conclusion: iMRI has a great potential in clival chordoma. However, further studies and more data are needed to confirm its utility.

Fig. 1 Mean degree of resection.

Fig. 2 Mean hospital stay.

• References

• Gay E, Sekhar LN, Rubinstein E, et al. Chordomas and chondrosarcomas of the cranial base: results and follow-up of 60 patients. Neurosurgery 1995; 36 (05) 887-896 , discussion 896–897
• Banks JL, Marotta CA. Outcomes validity and reliability of the modified Rankin scale: implications for stroke clinical trials: a literature review and synthesis. Stroke 2007; 38 (03) 1091-1096