Overview

An External Ventricular Drainage (EVD) is the temporary drainage of cerebrospinal fluid (CSF) from the fluid filled cavities of the brain (lateral ventricles) to a closed collection system outside the body.

Indications

• To relieve hydrocephalus ie. the accumulation of brain fluid within the intracranial cavity
  • Subarachnoid haemorrhage
  • Infection-meningitis
  • Obstruction due to tumour
• To reduce intracranial pressure due to brain swelling
  • In a setting of head injury, stroke
• Intracranial pressure monitoring
  • Head injury
• To achieve brain relaxation during surgery

Complications

The cause of this condition is irritation of the fifth cranial nerve (the Trigeminal nerve) which is responsible for providing facial sensation. This irritation is occasionally due to benign tumours or multiple sclerosis, either of which can usually be detected by a high quality MRI of the brain.

In the majority of cases, however, imaging of the brain does not reveal a cause of the nerve irritation. In such cases a small vessel (usually an artery but occasionally a vein) is often found at operation to be compressing the root entry zone of the Trigeminal nerve at the brainstem.

Procedure Description

• General anaesthesia
• Patient is cleaned and local anaesthetic is infiltrated
• A linear incision is made either frontal or parietal based on the entry point selected by the surgeon.
• A burr hole is drilled till the inner table of the skull is breached
• The underlying dura is then incised and its edges and pia are coagulated
• The catheter is inserted into the ventricle and egress of brain fluid signals successful entry
• Incision is closed and patient is sent back to ICU for close monitoring