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Clival chordoma is a rare disease with high recurrence rates even after a combination of surgical resection and radiotherapy. Apparent diffusion coefficient (ADC) has been used to evaluate aggressive features of chordoma, but its utility for clival chordoma has not been explored specifically. In this study, the utility of preoperative ADC values was analyzed for predicting tumor progression and recurrence in patients with clival chordoma. Between 2012 and 2019, a total of 30 operated cases were analyzed with available preoperative ADC data. Receiver operating characteristic (ROC) analysis was used to obtain ADC cutoff values for predicting tumor aggressiveness. The mean and minimum ADC values were significantly lower in the aggressive tumor group than in the stable tumor group (both P < 0.001). ROC analysis showed that a mean cutoff ADC value of 1198 × 10 -6 mm 2 /s and minimum ADC value of 895.5 × 10 -6 mm 2 /s could be used to predict aggressive features of clival chordoma. Subtotal resection, partial resection, and mean and minimum ADC values that were lower than cutoff values were negative predictors of overall survival and progression-free survival. In conclusion, mean and minimum ADC values could be useful in predicting aggressiveness of clival chordoma.

Clival chordoma with occipito-cervical (OC) joint invasion can result in preoperative and postoperative instability. The authors investigate the appropriate timing of OC fusion to prevent instability-, fusion-, and surgery time-related morbidity. Twenty-two consecutive patients underwent surgery for clival chordoma from December 2008 to September 2014. OC fusion was performed for patients with OC joint invasion and instability due to preoperative destruction of the occipital condyle or extensive postoperative condylectomy. The data in relation to OC joint instability, fusion, and surgery time were analyzed retrospectively and compared between OC fusion before and after tumor resection. Of the 22 patients, 8 with tumor invasion of the OC joint underwent OC fusion. OC fusion was performed after tumor resection in one-stage for four patients and before tumor resection in two-stage for four patients. There was OC joint instability from tumor destruction of the occipital condyle in seven patients (87.5%). Patients with OC fusion after tumor resection encountered complications such as surgery site wound dehiscence, encephalitis, and cardiac arrest with consequent mortality in one patient. These complications were avoided in subsequent patients where OC fusion was performed before tumor resection. There were no differences in the extent of tumor resection between OC fusion before and after tumor resection. Two-stage OC fusion before tumor resection can reduce instability-, fusion-, and surgery time-related morbidity and achieve feasible tumor resection when OC joint instability is expected. The extent of tumor invasion and brain stem compression should be considered when fusion precedes tumor resection.

Ecchordosis physaliphora (EP) is a distinct clinical entity defined as a notochordal remnant found on the dorsal surface of the clivus, occurring in about 2 % of autopsies. The aim of this study is to introduce typical and atypical imaging features of EP, which can be confused with those of clival chordoma. Forty-one patients with clinical suspicion for clival chordoma visited the outpatient clinic from June 2007 to August 2015. A retrospective review was performed with magnetic resonance imaging (MRI) and computed tomography (CT) studies to revise the diagnosis to EP. Eight of 41 patients (19.5 %) manifested lesions on the dorsal surface of the clivus that were well circumscribed and homogenous, with no septations or osteolysis. The lesions were all hypointense on T1, hyperintense on T2-weighted MRI, and had no enhancement with gadolinium. A distinct T2-hypointense pedicle, which is the hallmark of EP, was seen in five patients (62.5 %) and defined as typical EP. A characteristic T2-hypointense rim was observed in three patients and defined as atypical EP (37.5 %). The mean largest diameter of the lesions was 1.1 cm (0.6-1.8 cm). Lesion size did not change in all the patients who were followed for a mean of 3.6 years (1.4-8.2 years) by separate MRI scans performed every 6 months to 1 year. EP and clival chordoma represent different spectra of the same pathology. As the two lesions have completely different prognoses, precise knowledge of the imaging features of EP is very important. Accurate diagnosis is essential for proper treatment planning.