Spine tumors 6 – Cysts and Summary

A few lesions within the spinal canal are predominantly cystic or nonenhancing. They are almost always intradural extramedullary. The three most common entities are arachnoid cysts, dermoid cysts, and neuroenteric cysts. A contrast enhanced myelogram can often give you a little bit more information about what the entity is by determining if it fills with contrast.

Case 1. Arachnoid cyst. Arachnoid cysts in the spine are somewhat uncommon but will have the same characteristics as CSF on all images. They may often be identified only by their deflection of the spinal cord and mass effect. Their main differential is arachnoid webs or adhesions which cause similar mass effect on the spinal cord. On myelography, they often fill with contrast but more slowly than the surrounding CSF.

Case 2. Dermoid. Dermal inclusion cysts, or dermoids, are complex lesions made out of tissue from more than one embryonal layer. Their characteristic feature is internal fat contents. Like intracranial dermoids, they can rupture and cause a chemical meningitis. Their appearance overlap with lipomas but they are more likely to have complex features

Case 3. Neuroenteric cysts. Neuroenteric cysts are relatively simple cystic lesions which often occur ventral to the brainstem or spinal cord. They often are similar to but not exactly like CSF, and can be T1 hyperintense. They are indolent lesions but can cause mass effect. They do not fill on myelography.

Cyst summary. These are three of the most common cystic lesions. They are best differentiated by whether they communicate with the thecal sac (arachoid cysts), have complex or fatty features (dermoids), or are ventral to the cord and slightly differ from CSF (neuroenteric cysts).

Summary of spine tumors by location. Overall, when thinking about spine tumor, you should take a location-based approach. If you haven’t seen the introduction video yet, then definitely check it out. When divided by intramedullary, intradural extramedullary, and extradural, this can help you decide what type of lesion you are dealing with. Overall, always remember that the spine is an extension of the central nervous system, and consider imaging the brain because that may help you hone your differential diagnosis.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in neuroradiology or may see patients with spine tumors.

Other videos on the spine tumor playlist are found here.

Spine tumors 5 – Extradural lesions

Lesions outside the thecal sac are categorized as extradural lesions. Remember that everything that isn’t in the thecal sac is extradural, including discs, bones, meninges, nerves, and blood vessels. Anything that can occur in the surrounding areas can have extradural components. Look for lesions that have mass effect on the dura and deflect both the dura and the thecal sac to the side. Many of these lesions will require a biopsy as they have a differential diagnosis on imaging. CT and diffusion weighted imaging are useful adjunct tools that can help you refine your diagnosis.

The rest of this lecture consists of a mix of case presentations of different extradural lesions with tips on how to refine your differential diagnosis.

Case 1 – Disc extrusion. These are one of the most common extradural pathologies, particularly in patients with a history of degenerative disc disease. They tend to be contiguous with the disc and follow the disc in signal. Don’t be alarmed if they have enhancement, particularly if the enhancement pattern is peripheral. These can be confused with schwannomas and meningiomas.

Case 2 – Lymphoma. Lymphoma can involve the bones at any spinal level and can result in pathologic fracture. Anytime you see involvement of the pedicles and posterior elements you should worry about pathologic fracture, particularly if there is soft tissue or epidural involvement and enhancement. When the bone is involved, think about performing a CT to see the pattern and extent of bone destruction. This lesion has a mixed lytic and sclerotic appearance with bone destruction and was ultimately proven to be lymphoma.

CT pattern of different bone lesions. When you have a bone lesion, the trabecular pattern and pattern of bone destruction can be helpful. Lesions such as benign vascular malformations (hemangiomas) have a classic trabecular or corduroy pattern, while Paget’s disease is characterized by cortical thickening.

Case 3 – Osteosarcoma. Bone sarcomas are aggressive lesions that have bone destruction and can have soft tissue components. Their characteristic finding is matrix deposition which is best seen on CT. Osteosarcomas tend to have fluffy cloudlike matrix (osteoid) while chondrosarcomas have arcs and rings with interrupted calcification (chondroid). This was a case of osteosarcoma.

 Benign versus pathologic fractures. It can be challenging to differentiate fractures from bone insufficiency or trauma from those with an underlying lesion (pathologic fracture). Pathologic fractures are more likely to have bowing of the posterior cortex, a surrounding soft tissue mass, and abnormality on DWI. Looking for lesions elsewhere in the body can be a clue that it is metastatic disease, lymphoma, or myeloma. Sometimes these diseases can also have diffuse involvement of all of the marrow which can manifest as low T1 intensity throughout all the vertebral bodies.

Epidural tumor. Ventral epidural tumor can form a curtain or drape appearance because the dorsal dura is tacked down to the vertebral body at the midline. When it becomes more circumferential, it can extent completely around the thecal sac and extent both cranially and caudally.

Case 4 – Chordoma. Chordoma’s are aggressive tumors arising from notochordal remnant cells that can occur anywhere along the spinal axis. They are most common in the sacrum > clivus > remaining spine. Their characteristic appearance is a lytic lesion with bone destruction and marked T2 hyperintensity.

Enhancement pattern of extradural lesions. The enhancement pattern can help differentiate extradural lesions which may look similar. Tumors tend to have solid enhancement, abscess has peripheral enhancement, and a hematoma may have little or no enhancement.

Case 5 – Spinal dural arteriovenous fistula (dural AVF). These lesions have a classic presentation in older gentlemen with progressive myelopathy and are often missed. On MRI, they usually have edema and possibly enhancement in the cord, but the key finding is squiggly vascular enhancement along the margins of the cord. The pathology is from an abnormal connection between a vein and artery in the nerve root sleeve and can be treated endovascularly or with surgery.

Case 6 – Angiolipoma. These are fat containing lesions most common in the thoracic spine along the dorsal epidural space. They will have fat density on CT and can slowly increase in size, causing myelopathy.

Summary. There are a lot of things that can cause extradural masses, but they most commonly arise from the surrounding structures like discs and bones. Hopefully this video will help you refine your differential in the future.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in neuroradiology or may see patients with spine tumors.

Other videos on the spine tumor playlist are found here.

Spine tumors 4 – Intradural Extramedullary Lesions

Lesions that occur within the thecal sac are categorized as intradural extramedullary lesions. The vast majority of these lesions are tumors. The most common are schwannomas (and other nerve sheath tumors) and meningiomas, but there are others that include ependymoma, metastatic disease, and lymphoma. Also remember that the intradural extramedullary space contains cerebrospinal fluid (CSF), so any process that diffusely affects CSF can affect this space.

Peripheral nerve sheath tumors are a group of benign and malignant nerve tumors including schwannomas and neurofibromas. These can expand the neural foramen and usually have well defined margins. Schwannomas tend to enhance a lot while neurofibromas enhance less.   Sarcoidosis is another common granulomatous disease that can affect the cord. The most common appearance is T2 abnormality within the cord with some enhancement. Enhancement is often along the surface of the cord.

Neurofibromatosis is a genetic syndrome with two types, type 1 and type 2. NF type 1 is characterized by multiple plexiform (involving more than one adjacent nerve root) neurofibromas. If neurofibromas increase in size rapidly, have necrosis, or cause pain, that can be a sign of malignant degeneration. NF type 2 is characterized by multiple masses including schwannomas, meningiomas, or ependymomas. NF type 2 is sometimes called MISME syndrome.

Schwannomas are probably the most common intradural extramedullary lesions. They are well defined lesions with avid enhancement. They often have central non-enhancement or cystic degeneration, but calcification or hemorrhage are less common.

Case 1 – Meningioma. Meningiomas are well demarcated intradural lesions which occur along the dura and deflect the spinal cord. They enhance avidly and usually don’t have necrosis. They frequently calcify, which you may appreciate more on CT. If they are more elongated and plaquelike they may be referred to as “en plaque” menigiomas. They can cross the dura and have components outside the dura as well.

Case 2 – Myxopapillary ependymoma. Myxopapillary ependymomas are relatively common tumors that occur around the conus and cauda equina. They usually enhance avidly. Necrosis or hemorrhage are more common than in schwannomas. They were previously grade 1 tumors but have been upgraded to grade 2 because they frequently recur.

Leptomeningeal metastases are a consideration anytime you see multiple intradural nodules. In adults, these are most commonly from the most common tumors such as melanoma, lung, and breat cancer. Lymphoma can also occur along the cauda equina. In pediatric patients you should also think about intracranial tumors that spread in the CSF, like medulloblastoma, pineal

Case 3 – Paraganglioma. Spinal paragangliomas are rare spine tumors that have a lot of abnormal surrounding vessels and are prone to hemorrhage. Think about them anytime you see an enhancing tumor in the spine with a lot of flow voids. The other thing you might think about is a hemangioblastoma, but they are more likely to be cystic.

Case 4 – Lipoma. Fat containing lesions along the conus are common and can be lipomas or dermoids. Clues are fat-suppression of FS images, chemical shift artifact, and fat density on CT. If it is thin and linear along the filum terminale, it is likely a benign fatty filum terminale.

Summary. Intradural extramedullary lesions are among the most common spinal lesions and it is important to have a clear differential when you see them.

The level of this lecture is appropriate for radiology residents, radiology fellows, and trainees in other specialties who have an interest in neuroradiology or may see patients with spine tumors.

Other videos on the spine tumor playlist are found here