Background

It can be challenging to differentiate between dorsal arachnoid webs, ventral cord herniation and spinal arachnoid cysts of the thoracic cord. All of which can cause anterior displacement of the thoracic cord. This displacement often triggers a range of neurological symptoms such as weakness, pain, paralysis, paraesthesia and numbness which are difficult to clinically differentiate. These conditions require different management strategies which can be time critical, so early diagnosis is essential.

Objective

To provide clear imaging features to aid differentiation of anterior thoracic cord displacement to improve diagnostic confidence.

Methods

A series of MRIs of rare pathologies (n=6) were reviewed and collated illustrating the key imaging differentiators of anterior thoracic cord displacement.

Results

The ‘scalpel’ sign is an important differentiating feature in dorsal arachnoid web. The C-shaped indentation of the thoracic cord along with the absence of the visualised CSF signal between the ventral theca and the vertebral body are key indications for ventral cord herniation. An arachnoid cyst can be difficult to visualise, however, a smooth indentation on the cord with possible CSF flow signal will aid making the diagnosis.

Conclusions

Identification of some of the distinctive appearances of the anteriorly displaced thoracic cord can aid diagnosis and guide management including neurosurgical intervention where required.