According to the classification described by
Nabors et al for spinal meningeal cysts, extramedullary cysts of the spinal
canal can be divided into three main groups.
Group I : Meningeal cysts.
Classified into three types:
1.
Extradural meningeal cysts that contain no neural tissue
(arachnoid cysts-Ia and sacral meningoceles-Ib)
2.
Extradural meningeal cysts that contain neural tissue (tarlovs
cyst, cord herniation into cyst)
3.
Intradural meningeal cysts.
Group II : Nonmeningeal epidural cysts
(includes
nonneoplastic lesions such as juxtaarticular synovial cysts, pigmented
villonodular synovitis, and, rarely, herniated disks, as well as neoplastic
lesions such as dermoids, cystic nerve sheath lesions, and metastases. In
addition, trauma, hemorrhage, and inflammation can produce cystlike changes
that are visible on cross-sectional imaging)
Group III : Neurenteric cysts.
Spinal
Arachnoid cyst:
·
Probably arise from the herniation of the arachnoid through
congenital or acquired dural defects.
·
The cysts begin as diverticula and subsequently enlarge, possibly
because of a valvelike mechanism.
·
Postural changes and Valsalva's maneuver may produce symptoms.
·
These cysts usually arise in the mid-to-lower thoracic spine,
often at the junction of the meninges and the dorsal nerve root sleeves
proximal to the dorsal root ganglia.
·
Type 1A lesions most commonly project dorsally and may partially
protrude into the adjacent neural foramen.
·
“Arachnoid cyst” is a histologic diagnosis, and the cyst has
either no epithelial lining or an attenuated lining of arachnoidlike cells.
·
In the imaging literature, the terms “arachnoid cyst” and
“meningeal cyst” are used interchangeably.
Reference : CT
Myelography and MR Imaging of Extramedullary Cysts of the Spinal Canal in Adult
and Pediatric Patients, AJR January 2002 vol. 178 no. 1 201-207
No comments:
Post a Comment
Please leave your comments