Pseudomeningocele with Nerve root Avulsion on MRI

A middle aged male with history of trauma due to a motor vehicle accident. 

Now complaints of Right arm weakness and parasthesias. A “frostbite” sensation which progressed to a sharp right shoulder and neck pain with a burning sensation.

There is typical history of impact caused his head to flex on left, to the contralateral side. 

MRI Sag T2 right ward section

Coronal FIESTA

MRI Sag T2 right far lateral section for end on view of neural foramen show abnormal T2 hyper intensity in the region of neural foramen at C6-7 and C7-D1 level with non visualization of normal punctate iso intense dots of nerve roots. Cystic outpouching noted iso intense to Csf along the course of corresponding right sided exiting nerve roots on Coronal FIESTA can be attributed to pseuomeningoceles. Redundant nerve roots noted just at the top of these pseudo meningoceles implies to an associated Nerve root avulsion. 

Diagnosis: Traumatic Pseudomeningocele with Nerve root avulsion. 

Discussion:
Pseudomeningoceles represent a tear in the meningeal sheath that surrounds the nerve roots and extravasation of CSF into the neighboring tissues. Because they are filled with fluid, they are easily identifiable on T2-weighted MR images and MR Myelography, does not require any intra thecal contrast.
MR can adequately demonstrate the traumatic pseudomeningoceles however myelography and CT myelography remain the gold standard. In another recent study, neurosurgeons when asked which method they prefer and use to evaluate the avulsed brachial plexus before surgery. Eighty percent prefer post myelography CT, 20% prefer MRI, and 41% use both methods, whereas the remaining participants expressed no preference. As per Volle et al. the sensitivities of cervical myelography, CT myelography and MR are 100%, 45% and 6% respectively, for demonstration of nerve root avulsions. Xray and CT myelography not only show the level of avulsion but also documented overall size and morphology of the associated pseudomeningocele. The difficulty with MR imaging is it can demonstrate pseudomeningocele as an indirect evidence of nerve root avulsion. But the fact is that Pseudo meningocele can occur without root avulsion and root avulsions may occur without pseudomeningoceles.
Recent advances in high resolution MR imaging with steady state sequences may allow evaluation of exiting nerve root avulsion. In infants, the use of MRI is recommended because post myelography CT is a minimally invasive procedure, needs contrast and radiation exposure. Adequate information can be provided by noninvasive MRI. MR myelography is helpful in depicting pseudomeningoceles in a fashion similar to conventional myelography, but it is a supplemental method because most of the lesions are identifiable on MRI.

Intraspinal mass, a nerve sheath tumor on MRI; Importance of MR Myelography

MRI Lumbar spine

Sagittal T2

Sagittal T1, Sag and Cor MR Myelogram

Axial T2 sections at the level of abnormality

Findings: 

A solitary well-demarcated ovoid solid mass caudal to conus medullaris.
Lesion is intra dural and extra medullary on MR Myelography. 

No question of compression over cord as lesion is caudal to conus. Nerve roots of caudal equina are splayed in thecal sac and compressed by the side of mass.

Size of the lesion ~28x11mm, hyperintense T2w images.

Lesion not broad based to dura, not extending out of neural foramen on axial T2w images.

No obvious bony canal remodeling.

Imaging wise DDs : An extramedullary Intradural lesion, Nerve sheath tumor possible. 
Meningioma unlikely as lesion is not broad based to dura and signals are hyperintense on T2 w images as not necessary but Menigoma are iso to hypo intense.

Histopathology: Nerve sheath tumor - Schwannoma.


Intra spinal masses

Mass lesions in spinal canal are classified as epidural, intradural and intramedullary.
Techniques for demonstration includes Xray Myelography, CT Myelography and MR Myelography. At present times MR Myelography is ideal and investigation of choice.
The different patterns on MR Myelography by which a lesion may be partly elucidated, whether it is intramedullary, intradural or epidural is as follow.

In above case, lesion is at the center of spinal canal, completely occupying the spinal canal with obliteration of Csf spaces, making an acute angle on either side on MR Myelo. The pattern resembles to B but it can not be intramedullary lesion as cord has already ended above the level of lesion. So its intradural and extramedullary. Above patterns are applicable only at the level of cord.

MR Myelography

Magnetic Resonance Myelography is studying the spinal canal and subarachnoid space by high-resolution MRI, a sequence in which strong T2 weighting is used to provide high contrast between the 'dark' spinal cord and the surrounding 'bright' Csf space.
MR myelography is an additional sequence, has become part of an entire MR examination and virtually replaced the traditional X-ray myelography which used contrast with radiation exposure. It was a procedure, to be done under aseptic precaution. Lumbar puncture was done first for intrathecal injection of iodinated contrast followed by x ray shoots in AP and Lateral view. Overall its was a time consuming procedure.
MR Myelo on the contrary requires no intrathecal contrast, its a T2 weighted fast spin echo pulse sequence. Due to its strong T2 weighting it uses its inherent contrast. No radiation exposure. No risk and complications of lumbar puncture. Its a Fast sequence it hardly takes couple of seconds.