Intradural prepontine chordoma in an 11-year-old boy. A case report

Chordomas are rare primary bone tumours. Despite their low-grade histological characteristics, chordomas often show a malignant disease course [2, 21, 23]. Symptoms usually develop gradually, related to the relatively slow-growing tumour compressing the surrounding structures. However, chordomas can present with acute and progressive clinical symptoms due to intratumoral haemorrhage as well [22]. The extent of initial surgical resection has been shown to be the most important predictor of local tumour recurrence and long-term survival [6, 10, 14, 23].

Intradural chordomas tend to show different biological behaviour compared to classic chordomas. In contrast to classic chordomas, purely intradural chordomas seem to have well-defined tumour margins, do not show bone invasion and are less adhesive to the surrounding structures all of which improves the resectability [20]. This is likely to be a reason for the lower recurrence rate compared to typical chordomas. In the literature, several cases of intradural chordomas are reported in children and adults (for review, see Dow et al. [9] and Masui et al. [15]). None of the reported cases showed tumour recurrence after surgery, even in cases of subtotal resection. In contrast, typical chordomas often show recurrence, metastatic features and progression to death despite adequate surgical resection, which is sometimes followed by adjuvant radiation therapy or chemotherapy [12]. However, AlOtaibi et al. [1] suggest in a recent systematic review that in the adult population, intradural chordomas show a comparable biological behaviour to typical cranial base chordomas.

Chordomas are thought to originate from remnants of the embryological notochord throughout the axial skeleton. Whereas typical chordomas are localised extradurally with possible transdural progression, this pathophysiologic mechanism does not explain a purely intradural localisation of chordomas.

Ecchordosis physaliphora (EP) are ectopic notochordal remnants that are usually asymptomatic. An incidence of 1.5–2 % in autopsy studies and approximately 1.7 % in MRI studies has been found [8, 17, 19]. EPs are typically found in the prepontine cistern, attached to the dorsal clivus with a small pedicle [13, 25]. Other distinctive features are that EPs generally occur in younger people compared to intradural chordomas and that EPs show no enhancement after gadolinium administration on MR imaging, whereas intradural chordomas show a variable enhancement [7, 17]. Although differentiating between symptomatic EPs and intradural chordomas based on histology is difficult and debated, Yamaguchi et al. [26] suggested some histological differentiating features. Symptomatic EPs and intradural chordomas tend to show a similar benign behaviour with a very low risk of tumour recurrence after surgical resection [7]. Chang et al. [5] suggest that EPs and intradural chordomas exist in a continuum from benign hamartomas to aggressive typical chordomas.

Treatment of a classic chordoma involves extensive surgery, sometimes combined with adjuvant radiation therapy [23]. There is not enough data available to postulate an evidence-based treatment for intradural chordomas in the paediatric population. One should consider that all of the reported cases (Table 1) were treated with a complete surgical resection without any adjuvant treatment, and none of these tumours did reoccur. Even cases in adults treated with a subtotal resection without adjuvant therapy did not show tumour recurrence after a 5-year follow-up [18]. Therefore, the role of adjuvant radiation therapy for intradural chordomas is debated. Considering the potential deleterious effect on the paediatric brain, radiation therapy should be avoided in the paediatric population. The authors postulate that a complete surgical resection without adjuvant radiation therapy should be the treatment of choice.