Ecchordosis physaliphora

Ecchordosis physaliphora is a congenital benign hamartomatous lesions derived from notochord remnants. It is usually located in the retroclival prepontine region. It is due to remaining notochord cells along the axis of the spine after embryogenesis.

Definition

There has been some controversy as to whether intradural chordoma and large ecchordosis physaliphora are different entities. Some authors (Wolfe et al.) proposed the name intradural chordoma for all intradural notochord remnant lesions ⁸. Others (Rodriguez et al.) proposed than all intradural notochord remnant lesions should be called ecchodrosis physaliphora, until chordoma are pathologically proven to arise from the intradural compartment ⁹. However, they are currently considered distinct pathologies with common origin. 

Clinical presentation

Contrarily to chordoma, patients with ecchordosis physaliphora are usually asymptomatic. It is found in approximately 2% of autopsies.  Patients with chordoma present with brain stem or cranial nerves symptoms.

Pathology

Ecchordosis physaliphora and chordoma are histologically indistinguishable, apart from an infiltrative growth in chordoma. They both have a common origin from the notochord.

Radiographic features

CT

CT-scan is generally not sensitive for such lesions, mainly because of posterior fossae artifcats.

MRI

Apart from the characteristic location (retroclival, prepontine & intradural), MRI findings are not specific:

• T1 : hypointense
• T2 : hyperintense
• T1 C+ : +/- enhancement (50 % in some series ¹)

Differential diagnosis

The differential diagnosis of retroclival intradural lesions consists mainly of ⁴:

• chordoma
• benign notochordal cell tumor (BNCT)
• skull base metastasis
• dermoid cyst
• epidermoid cyst
• arachnoid cyst

Etymology

Hubert von Luschka (1820 - 1875), a german pathologist, first described the finding of pathologic ectopic notochordal tissue at the posterior clivus in 1856.