Monday, January 22, 2024

Ecchordosis physaliphora

Inspired by a patient

Ecchordosis physaliphora
Last revised by Yoshi Yu on 9 Nov 2023

Ecchordosis physaliphora is a congenital benign hamartomatous lesion derived from notochord remnants, usually located in the retroclival prepontine region, but can be found anywhere from the skull base to the sacrum.

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

Unlike chordomas which are often symptomatic due to brainstem or cranial nerve compression, patients with ecchordosis physaliphora are usually asymptomatic. They are found in ~2% of autopsies.

Ecchordosis physaliphora arise from remaining notochord cells along the axis of the spine after embryogenesis. Unfortunately, ecchordosis physaliphora and chordoma are histologically indistinguishable, other than by examining the margins, the latter demonstrating infiltrative growth.
Radiographic features


CT is generally not sensitive for such lesions, mainly because of posterior fossa artifacts and the near CSF density of the mass. The bony clival defect is, however, visible as a well-demarcated smoothly corticated region, without aggressive features.

Occasionally an osseous stalk is seen at the base of the lesion which is said to be pathognomonic in this context.

A stalk-like connection to the clivus is usually seen if high-resolution images are obtained.

Apart from the characteristic location (retroclival, prepontine, and intradural), MRI findings are non-specific, with signal similar to CSF:

T1: hypointense

T2: hyperintense

T1 C+ (Gd): ​variable; however, most cases have not shown substantial enhancement 1
History and etymology

Rudolf Virchow (1821-1902), a German physician and pathologist first described a similar lesion in 1857 and mistook it as a degenerative process affecting the spheno-occipital synchondrosis with cartilaginous components and termed it "ecchondrosis physaliphora" which comes from the Greek "chondros" meaning cartilage and "physalis" meaning bubble. Friedrich von Muller suggested a notochordal origin in 1858. In 1898 Ribbert confirmed its notochordal origin and coined the modern term of "ecchordosis physaliphora".

Differential diagnosis

The differential diagnosis of retroclival intradural lesions consists mainly of :

chordoma: generally symptomatic and enhances after contrast administration

benign notochordal cell tumor (BNCT)

skull base metastasis

dermoid cyst

epidermoid cyst

arachnoid cyst: communicates with subarachnoid space, follows CSF intensity pattern and no enhancement

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