Spinal Cord Herniation

Arachnoiditis/Adhesion

Post-Traumatic Pseudomeningocele

Linear or rounded low signal with ill-defined margins surrounding cord due to normal CSF motion

Typically most prevalent in dorsal thoracic spine

Include axial GE images to minimize artifact and exclude vascular flow voids

Geometric distortion and signal loss secondary to dephasing

T1 images show focal central signal loss with peripheral “halo” of ↑ signal related to spatial mismapping

Image quality: Fast spin echo > conventional spin echo < gradient echo

Smaller voxel size, lower field strength decrease artifact amount

Appropriate geometric orientation of frequency encode direction parallel to pedicle screws shows thecal sac best

Nonenhancing extramedullary loculated CSF intensity collection displacing cord or nerve roots

May be suggested by mass effect on cord and nerve roots without direct wall visualization

Partial filling of cyst may occur with CT myelography, with wind-sock type

Nonenhancing intradural mass similar to CSF intensity within cauda equina

Should not track CSF on all pulse sequences, as would arachnoid cyst

Should not enhance, unless complicated by infection

If lumbar in child, look for associated dermal sinus track

Enhancing intradural/extramedullary mass and dural tail

Calcified lesions may show little enhancement, very low T1/T2 signal

May show target pattern with central calcification, peripheral homogeneous tumor enhancement

Well-circumscribed, dumbbell-shaped, enhancing spinal mass

May be solid, yet show T1 homogeneous hypointensity

T1 hypointensity may also reflect cyst formation

Serpentine flow voids with well-defined margins

Variable pattern depending upon type (fistula vs. AVM) and location (cord vs. pial vs. transpatial)

Most common is type 1, with vessels on dorsal cord surface with cord T2 hyperintensity due to venous hypertension

Smooth/nodular enhancement along cord, roots is best clue

Without contrast, leptomeningeal mets may show ill-defined cord & cauda with “dirty” CSF appearance

Herniation of spinal cord through defect in dura of ventral canal

Focal anterior displacement of cord with expansion of dorsal subarachnoid space in upper thoracic spine

Distinguish from posterior arachnoid cyst by more abrupt cord deformity with idiopathic herniation

Focal tethering of cord to dura from prior surgery, infection, or SAH

Shown by distortion of location and morphology of cord within thecal sac

May be associated with arachnoid cysts, superficial siderosis, cord edema

CSF collection typically associated with upper cervical fracture (odontoid) with ventral CSF collection and displacement of cord posteriorly

Multisegmental posterior displacement of cervical cord in face of significant cervical trauma

Distinguish from acute epidural hemorrhage that shows isointense T1 signal, heterogeneous T2 signal

Uncommon presentation of arachnoiditis due to prior trauma, lumbar surgery, subarachnoid hemorrhage, myelography, spinal anesthesia

End-stage arachnoiditis with diffuse or nodular low signal on all pulse sequences involving dura and cord surface, cauda equina

CNS parasitic infection caused by pork tapeworm, Taenia solium

Intradural cyst with evidence of similar lesions in brain most helpful clue

Parenchymal, leptomeningeal, intraventricular, spinal form with cyst size up to 2 cm

Solid exophytic component may mimic ID/EM lesion

Look for contiguous extension into cord on sagittal/axial planes

Contrast enhancement may show contiguous nature of intramedullary mass