Spinal Meningeal Cyst

05 November 2004 

CLASSIFICATION

I:          extradural meningeal cyst without spinal nerve root fibres

            A: “extradural meningeal cyst” (“extradural arachnoid cyst”)

            B: “sacral meningocele” (“occult sacral meningocele”)

II:         extradural meningeal cyst with spinal nerve rot fibres

            (“Tarlov’s perineural cyst”         vs         spinal nerve root diverticula”)

            communication              vs         noncommunication

III:        spinal intradural meningeal cyst (“intradural arachnoid cyst”)

AETIOLOGY

Congenital: diverticula of dura, herniation of arachnoid through a dural defect

Acquired: trauma, post meningitic,  SAH, post LP, post spinal anesthetic, post myelography

Valve like mechanism to explain cyst expansion

Intradural cysts as faults along septum posticum

CLINICAL

Thoracic type I more frequent in adolescents

Sacral Type I more often in adults

Thoracic & cervical Type I usually spasticity & sensory level

Lumbar Type I usually low back pain & radiculopathy

Type II cysts often asymptomatic; if sx usually sciatica or bowel/bladder prob

Intradural arachnoid cysts usually posterior to thoracic spinal cord

PATHOLOGY

Extradural cyst = arachnoid cyst

Inner arachnoid lining with single cell layer often absent

Fibrous connective tissue

Communication between cyst & subarachnoid space

RADIOLOGY

Myelography

Delayed CT myelography

MRI

TREATMENT:

aspiration: always recurs

excision ltd by adhesion to cord or nerve roots, anterior to cord location

close communication / ostium

fenestration, marsupialisation

shunt