Ruptured Posterior inferior cerebellar artery aneurysm [Neurosurgery Wiki]

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====== Ruptured Posterior inferior cerebellar artery aneurysm ======


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===== 📚 Definition =====

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.

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====== 🧠 Classification ======

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

===== 🧠 1. Anatomical Classification (by PICA Segment) =====

^ Segment ^ Name ^ Description ^
| P1 | Anterior medullary | From origin to inferior olive |
| P2 | Lateral medullary | Around lateral medulla |
| P3 | Tonsillomedullary | Near the cerebellar tonsil |
| P4 | Telovelotonsillar | Near the tela choroidea and 4th ventricle |
| P5 | Cortical | Distal cortical branches to vermis and hemisphere |

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

===== 💥 2. Clinical Classification (Based on Rupture) =====

  * 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)

===== 🧪 3. Etiological Classification =====

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

===== 🔬 4. Morphological Classification =====

  * **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

===== 🩻 5. Radiological Appearance =====

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

===== 🧮 6. Surgical Accessibility (Yasargil-style) =====

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

===== 📊 7. Treatment-Based Classification =====

  * **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



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

=== Endovascular Treatment ===

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

^ Endovascular Outcomes ^
| Proximal aneurysms | 85–90% technical success, ≤5% procedural complications |
| Distal aneurysms | Higher recurrence (up to 25%), risk of cerebellar infarction |

=== Surgical Treatment ===

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

^ Surgical Outcomes ^
| Distal aneurysms | 83% favorable outcomes (mRS 0–2) |
| Proximal aneurysms| Higher cranial nerve palsy risk (up to 20%) |

=== Key Decision Factors ===

^ Factor ^ Endovascular ^ Surgery ^
| Aneurysm location | Proximal PICA | Distal PICA |
| Morphology | Saccular, narrow neck | Complex, wide neck |
| PICA origin | Adjacent to aneurysm neck | Incorporated into dome |
| Clinical status | Poor-grade SAH | Mass effect symptoms |

=== Complications ===

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.