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A ruptured posterior inferior cerebellar artery (PICA) aneurysm is a pathological dilatation of the PICA wall that has burst, resulting in bleeding into the subarachnoid space—typically within the posterior fossa.

It most often presents as posterior fossa subarachnoid hemorrhage (SAH) and can be life-threatening due to the confined space near the brainstem, risk of hydrocephalus, and critical neurovascular structures.

These aneurysms are rare, accounting for less than 1%–2% of all intracranial aneurysms, but pose significant surgical and endovascular challenges due to their deep location and proximity to vital structures.

A ruptured PICA aneurysm can be classified according to anatomical, clinical, morphological, and therapeutic criteria. Below is a structured breakdown.

• Most common aneurysm sites: P1 and P2, especially at the vertebral-PICA junction.

• Presents with posterior fossa SAH (subarachnoid hemorrhage), especially in the cisterna magna or fourth ventricle.
• Grading systems:
  • Fisher Grade (blood load on CT)
  • Hunt and Hess Grade (clinical severity)
  • WFNS Grade (GCS + focal deficit)

• Saccular (true) aneurysm
• Dissecting aneurysm ← common in vertebrobasilar system
• Fusiform aneurysm
• Mycotic aneurysm (infective)
• Pseudoaneurysm (trauma/iatrogenic)

• Shape: saccular, fusiform, dissecting
• Size:
  • Small: < 7 mm
  • Medium: 7–12 mm
  • Large: 13–24 mm
  • Giant: ≥ 25 mm
• Neck width:
  • Narrow-neck: < 4 mm
  • Wide-neck: ≥ 4 mm or dome-to-neck ratio < 2

• Identified by CTA, MRA or DSA
• Blood in posterior fossa, fourth ventricle, cerebellomedullary cistern
• Possible complications:
  • Obstructive hydrocephalus
  • Brainstem compression

• Surgically accessible: vertebral-PICA junction
• Surgically challenging: distal PICA (P3–P5), near brainstem or 4th ventricle

• Microsurgical clipping
• Endovascular approaches:
  • Coiling
  • Stent-assisted coiling
  • Flow diverters (select cases)
• Parent artery occlusion
• Bypass with trapping (dissecting/fusiform)

• Decision-making depends on:
  • Aneurysm morphology
  • Segmental location
  • Clinical status
  • Institutional expertise

Ruptured PICA aneurysms require individualized management based on aneurysm location, morphology, and patient factors.

Preferred for proximal PICA aneurysms (VA-PICA junction, anterior/lateral medullary segments)

Coiling techniques:

Selective coiling: For saccular aneurysms with narrow necks and preserved PICA origin

Balloon-assisted coiling: For wide-necked aneurysms

Stent-assisted coiling: For complex cases requiring parent artery preservation

Parent vessel occlusion (PVO):

Used for dissecting/fusiform aneurysms

Safe if collateral flow is confirmed

Preferred for distal PICA aneurysms (tonsillomedullary to cortical segments)

Approaches:

Far-lateral/suboccipital craniotomy: For proximal aneurysms

Telovelar/retromastoid: For distal/cortical branches

Techniques:

Clipping: For saccular aneurysms with clear necks

Trapping with bypass: For fusiform/dissecting aneurysms

Brainstem ischemia: Risk from occlusion of medullary perforators (proximal PICA)

Cerebellar infarction: More common in distal PVO without collateral supply

Rebleeding: Higher risk in partially coiled aneurysms (8–12%)

Summary: Proximal ruptured PICA aneurysms are usually managed with endovascular coiling or PVO, while distal lesions are better suited for surgical clipping. Multidisciplinary evaluation is essential for optimal outcomes.