Posterior fossa decompression [Neurosurgery Wiki]

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====== Posterior fossa decompression ======

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**Definition:**  
*Posterior fossa decompression* is a neurosurgical procedure designed to relieve compression at the craniovertebral junction, most commonly for **Chiari malformation type I**, but also used in cases of **posterior fossa tumors**, **hydrocephalus**, or **intracranial hypertension**.
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===== Indications =====

[[Posterior Fossa Decompression Indications]].

===== Posterior fossa decompression Technique =====

===== Surgical Technique =====

==== 1. Patient Positioning ====
  * **Prone** or **Park bench** position
  * Head fixed in Mayfield clamp
  * Slight neck flexion to expose the occipitocervical junction without kinking the medulla

==== 2. Incision and Exposure ====
  * Midline **occipital incision** from inion to C2 spinous process
  * Subperiosteal dissection to expose:
    - Occipital bone
    - Posterior arch of C1
    - Superior lamina of C2 (in extended decompressions)

==== 3. Bony Decompression ====
  * **Suboccipital craniectomy**
    - Typically 2–3 cm wide, exposing the foramen magnum
  * **C1 laminectomy** (partial or complete)
    - Relieves compression at cervicomedullary junction

==== 4. Dural Opening (optional, case-dependent) ====
  * Y- or U-shaped durotomy
  * Allows direct decompression of cerebellar tonsils and posterior fossa contents

==== 5. Duraplasty ====
  * Performed using **autologous graft**, **synthetic patch**, or **pericranium**
  * Prevents postoperative CSF leak and improves subarachnoid flow

==== 6. Tonsillar Reduction (select cases) ====
  * **Coagulation** or **subpial resection** of cerebellar tonsils
  * Only in symptomatic, obstructive cases or when syrinx persists

==== 7. Closure ====
  * Watertight dural closure critical
  * Muscle and skin layers closed in standard fashion
  * Subfascial drain optional

===== Postoperative Considerations =====
  * Monitor for CSF leak, pseudomeningocele, or infection
  * Serial MRI to assess decompression and syrinx resolution (if present)
  * Pain control and gradual mobilization

===== Complications =====
  * CSF leak
  * Pseudomeningocele
  * Meningitis
  * Cerebellar ptosis (over-decompression)
  * Neurological worsening (rare)