Introduction: Incidental findings on cranial imaging comprise a significant proportion of neurosurgical referrals. Determining which incidentally found lesions necessitate surgical intervention, and which may safely be observed over time remains a challenge. Apart from metastasis, clival lesions most commonly originate from notochord remnants; they may be benign lesions such as ecchordosis physilaphora (EP) or locally aggressive tumors such as chordoma. Several groups have described features that suggest a lesion is more likely benign such as EP; for example, T1 hypointesity, T2 hyperintesity, and minimal or no enhancement. While these features may be reassuring, the mode of practice is to follow patients with surveillance imaging to detect changes. In this case series, we followed several patients with small lesions of the clivus who underwent surgical intervention. We review the imaging characteristics and histopathologic findings in these cases to develop a set of properties that assist in predicting which small clival lesions may be safely observed and which merit early intervention .

Methods: We performed a retrospective review of our institution’s experience with lesions of the clivus between 2006-2016. Cases were identified by ICD9/ICD10 codes and were reviewed for demographic information, imaging characteristics, symptoms at presentation, clinical course and histopathologic correlation where available. This case series was restricted to small lesions of the clivus, with minimal or no radiographic intradural extension as graded by a neuroradiologist, with histopathologic correlation.

Results: Six patients were identified who fit the above criteria. Three patients were found to have chordoma. The remaining three were diagnosed with benign fibrous tissue, chronic polypoid sinusitis, and lymphoid aggregate tissue, respectively. One patient with chordoma had surgery complicated by persistent CSF leak, requiring early reoperation. The imaging characteristics are summarized in Table 1. All patients remained neurologically intact.

Conclusions: Chordoma share some imaging characteristics with benign lesions, however dural involvement and even minimal enhancement may be worrisome for more aggressive pathology. Patients with these imaging characteristics should be followed closely and considered for early surgical intervention. Care must be taken not too extrapolate too broadly from this small case series.

Patient Care: The above work should assist clinicians in determining which clival lesions may be safely observed and which may merit closer observation and possible early intervention.

Learning Objectives: 1. To learn the differential diagnosis for lesions of the clivus. 2. To identify imaging characteristics that support one diagnosis or another. 3. To review the histopathologic diagnoses of clival lesions. 4. To determine criteria on imaging that predict the diagnosis of a clival mass.

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