You are here

Posterior Fossa Decompression


The posterior fossa is one of the three 'cranial fossa', or hollows at the base of the skull (cranium). It is a small hollow which contains the brainstem and the cerebellum. Certain conditions, such as traumatic brain injury, haemorrhage, brain tumour or congenital developmental condition called 'Chiari malformation', can compress the cerebellum and brainstem, forcing portions of these structures into the spinal canal.


Posterior fossa decompression aims to reduce pressure on the cerebellum and spinal cord. Pressure in the posterior fossa can cause headaches, drowsiness, balance, visual disturbance, as well as rarely speech, weakness and numbness. In Chiari malformation, there is impediment to the flow of cerebrospinal fluid (CSF) and – although sometimes there are no symptoms at all – in other cases it can cause a number of debilitating symptoms, including headaches, numbness and weakness, and development of spinal cord cysts (syringomyelia).

Preoperative Instructions

Before all neurosurgical procedures, including posterior fossa decompression, you should…

  • Avoid any oral intake (“nothing by mouth”) after midnight the night before the procedure. Medications can be taken with very small sips of water.
  • Inform your doctor of blood thinning medications because you will need to stop them a few days before the procedure.
  • Avoid any non-steroidal anti-inflammatory medication (NSAIDs) at least 1 week ahead of the procedure.
  • Avoid dental treatment (within three weeks) or any other form of surgery (within three months) of the planned procedure.
  • Inform the office as soon as possible if you develop any symptoms of infection, e.g. a cold or flu, before surgery.


A posterior fossa decompression procedure is carried out under general anaesthesia and generally takes 2-3 hours. The procedure itself involves a 5-6cm incision at the midline of the back of the head and the top of the neck, where a small section of bone (around 2.5cm in diameter) at the base of the skull is removed. This procedure is known as a suboccipital craniectomy. Often, a section of the C1 vertebra below may also be removed (this is a 'cervical laminectomy'). The dura (the outer membrane around the brain) is opened and an extra tissue graft is attached (expansile duraplasty) to permit more space in the posterior fossa. Once the surgery is complete, the incision is closed with sutures or staples.

Postoperative Instructions

Patients generally spend 3-5 days in hospital after the procedure. For up to 12 weeks after the procedure, it is normal for patients to have headaches and moderate amounts of neck pain, as well as numbness and a degree of fatigue. It is also not uncommon to have problems concentrating and to have some emotional changes, such as increased irritability, anxiety or even depression. Detailed instructions about postoperative care will be provided. However, if any of the following symptoms occur after returning home, you should contact us immediately…

  • Headache not improved with prescribed pain medications.
  • Temperature over 38 °C.
  • Signs of wound infection e.g. swelling, redness, tenderness, pain (or if wound opens or there is any seepage after removal of staples).
  • Neck stiffness or rigidity, light sensitivity.
  • Seizure.
  • Weakness / numbness.
  • Drowsiness.
  • Balance issues.
  • Nausea / vomiting.


General surgical risks apply (e.g. risks associated with anaesthesia, wound infection, internal bleeding, blood clots such as DVT’s or Pulmonary Emboli). Specifically, there is a risk of stroke resulting in damage to the cerebellum, and leakage of cerebrospinal fluid (CSF) through the wound is another major concern for posterior fossa decompression. Additional procedures may need to be performed, including insertion of lumbar drain or revision surgery.

Related Information

Chiari Malformation and Syringomyelia