Meningeal Cyst Classification¶

Nabors Classification¶

The Nabors classification organizes spinal meningeal cysts into three types based on their relationship to the nerve roots and meninges:

Type I — Extradural Meningeal Cyst (No Nerve Root Fibers)¶

Extradural arachnoid cyst or diverticulum
CSF-filled, no nerve root fibers within the cyst
Arises from a dural defect, most common in thoracic spine
Can cause cord compression
Also known as: extradural arachnoid cyst, dural diverticulum

Type II — Extradural Meningeal Cyst (With Nerve Root Fibers)¶

Tarlov cyst (perineural cyst)
Extradural, with nerve root fibers within or traversing the cyst wall
Most common in the sacral spine (S2–S3)
Usually incidental and asymptomatic

Type III — Intradural Meningeal Cyst¶

Intradural arachnoid cyst
CSF-filled cyst within the thecal sac
Most common in the thoracic spine, dorsal to the cord
Can cause cord compression and myelopathy

Clinical Pearl

The Nabors classification is clinically useful because it guides management: Type I (extradural, no nerve roots) and Type III (intradural) can be surgically excised or fenestrated when symptomatic. Type II (Tarlov cysts with nerve fibers) are more complex to treat because the nerve root is incorporated into the cyst wall, and surgery risks nerve injury.

Key Points¶

Nabors Type I: extradural, no nerve root fibers (extradural arachnoid cyst)
Nabors Type II: extradural, with nerve root fibers (Tarlov cyst)
Nabors Type III: intradural (intradural arachnoid cyst)
Classification guides surgical approach and management
All types follow CSF signal on MRI

References¶

Nabors MW, Pait TG, Byrd EB, Karim NO, Davis DO, Kobrine AI, Rizzoli HV. Updated assessment and current classification of spinal meningeal cysts. J Neurosurg. 1988;68(3):366-77. Available from: https://pubmed.ncbi.nlm.nih.gov/3343608/
Classification of spinal meningeal cysts. Radiopaedia.org. Available from: https://radiopaedia.org/articles/classification-of-spinal-meningeal-cysts-1
Kim IS, Hong JT, Son BC, Lee SW. Noncommunicating spinal extradural meningeal cyst in thoracolumbar spine. J Korean Neurosurg Soc. 2010;48(6):534-7. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC3053550/
Lim Y, Selbi W. Tarlov cyst. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK582154/