Neurosurgery notes/Intradural arachnoid cyst

Intradural arachnoid cyst

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Spinal meningeal cysts
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Aug 8, 2026 10:10 PM GMT+0

Numbers

  • Spinal intradural arachnoid cysts are rare pathologic entities in adult populations.
  • Across the literature review cohort of 293 cases, the mean patient age was 51.4 years (ranging from 19 to 91 years).
  • Sex distribution is nearly equal, consisting of approximately 54% men and 46% women.
  • Cysts of primary (idiopathic) origin represent the vast majority of cases (87%), whereas secondary cysts account for 13%.

Pathophysiology

  • Pathology
    • CSF-filled sacs contained by the arachnoid mater.
    • The degree of communication with the surrounding CSF space is variable with some cysts freely communicating and others not at all
  • The exact etiopathogenesis of spinal intradural arachnoid cysts remains unclear.
  • Neurologic symptoms develop due to
    • Neuronal compression of spinal cord
    • Alterations in cerebrospinal fluid (CSF) flow dynamics.
  • Pulsatile wall movements in cysts can contribute to the deterioration of spinal cord symptoms.
  • In secondary cases, a preceding inflammatory arachnoidopathy leads to extensive arachnoidal scarring, altered CSF dynamics, and potential vascular myelopathy due to disturbed spinal cord blood flow.

Aetiology

  • Primary aetiology:
    • Considered idiopathic or congenital
  • Secondary aetiology:
    • Presumed to result from a preceding inflammatory arachnoidopathy.
    • The most common predisposing factors for secondary cysts include:
      • Spinal trauma (40%)
      • Iatrogenic causes, such as prior intradural spinal surgery or myelography (28%)
      • Central nervous system hemorrhage (16%)
      • Meningitis (16%)

Location

  • Thoracic: 80%
    • T5/T6 being the most common levels.
  • Cervical: 15%
  • Lumbar: 5%
notion image

Clinical Features

  • Lesions typically present insidiously with progressive neurologic symptoms.
  • The most common presenting symptoms include:
    • Pain (68% overall; specifically thoracic back pain and low back pain)
    • Sensory changes (58%)
    • Weakness (52%)
    • Gait difficulty (42%)
    • Incontinence / bowel or bladder dysfunction (24%)
  • The average duration of symptoms prior to initial presentation is approximately 26 to 28 months.

Radiology

  • MRI
    • focal buckling/compression of the spinal cord or a fluid structure with signal features similar to CSF.
    • Cysts span an average of 3.5 vertebral levels (range 1–17 levels).
  • CT myelography is also used in a subset of patients (24%).
  • Position Relative to Cord:
    • The majority of cysts are positioned dorsal to the spinal cord (90%), though some are ventral (9%) or lateral (1%).
  • Associated Findings:
    • A syrinx is observed in 35% of cases
    • Focal cord signal changes are observed in approximately 28% to 32% of patients.
A-D, Preoperative T2 MRI demonstrating spinal intradural arachnoid cysts of differing morphologies in our series. A and B, Case 13 with a T1-7 dorsal arachnoid cyst. C and D, Case 18 with a T3-8 ventral arachnoid cyst.
A-D, Preoperative T2 MRI demonstrating spinal intradural arachnoid cysts of differing morphologies in our series. A and B, Case 13 with a T1-7 dorsal arachnoid
cyst. C and D, Case 18 with a T3-8 ventral arachnoid cyst.

Risk Factors

  • Risk factors for developing secondary intradural arachnoid cysts include:
    • Prior history of spinal trauma
    • Previous spinal/intradural surgeries
    • Past central nervous system hemorrhages
    • Preceding central nervous system infections (such as meningitis)
  • Patients with secondary cysts face higher risk factors for poor surgical outcomes, including increased risk of radiographic progression and need for repeat surgery.

Management

Conservative

  • Indications
    • Asymptomatic patients
    • Symptoms do not correlate with the cyst's anatomical location

Surgery

  • Indications
    • Patients exhibiting neurological symptomatology correlated with spinal cord compression on imaging.
  • Surgical Approaches:
    • Open microsurgical approaches (e.g., wide thoracic laminectomies or laminotomies) using intraoperative ultrasound for localization.
    • Cyst fenestration or excision is the primary surgical strategy in 98% of cases.
    • Alternative interventions include cyst marsupialization or shunting procedures (e.g., cystoperitoneal or cystosubarachnoid shunts).
    • Endoscopic fenestration strategies are also described, offering reduced operative time and shorter hospital stays.

Outcome

  • Overall Results:
    • Primary surgical management yields clinical improvement or complete resolution of preoperative symptoms in 86% of patients.
      • Surgical fenestration resulted in a statistically significant reduction in thoracic back pain (P = .034).
  • Primary vs. Secondary Outcomes:
    • Primary Cysts: Have significantly better outcomes, with a 92% rate of symptomatic improvement or resolution.
    • Secondary Cysts: Demonstrate significantly worse outcomes, with only 44% reporting symptomatic improvement and 56% experiencing no change.
  • Complications & Recurrence:
    • Secondary cysts have a significantly higher rate of radiographic progression compared to primary cysts (21% vs. 8%; P = .032).
    • Secondary cysts require repeat surgical intervention more than twice as often as primary cysts (16% vs. 6%; P = .041).