OR / Prep · Neurosurgery · percutaneous
You’re scrubbing into
External ventricular drain insertion
Why are we operating?
A catheter into the lateral ventricle through a frontal burr hole at Kocher's point: the emergency treatment of hydrocephalus and raised intracranial pressure, and the ICU's window on the pressure itself.
Indication: Acute hydrocephalus (haemorrhage, tumour, infection), refractory intracranial hypertension needing CSF drainage, and pressure monitoring with a therapeutic option attached.
The operation in 4 steps
01Kocher's point
The entry is marked about 11 cm back from the nasion and 3 cm from the midline, at the mid-pupillary line, in front of the coronal suture on the non-dominant side where possible.
Why: Kocher's point is chosen to miss everything that matters: in front of the motor strip, lateral to the sagittal sinus, and above the frontal horn's widest target. The measurements are the operation.
02Burr hole and dural opening
A small scalp incision, a burr hole through both tables of the skull, and a cruciate opening of the dura just wide enough for the catheter.
Why: The skull's two tables are traversed with a stop-limited drill for exactly the reason you imagine: what lies one millimetre beyond the inner table does not forgive a plunge.
03Ventricular cannulation
The catheter is passed perpendicular to the skull, aimed at the ipsilateral medial canthus and the tragus, with CSF expected at 5 to 6 cm; it is never advanced past 7 cm.
Why: The trajectory triangulates the frontal horn without any imaging in the room. The depth limit is absolute: passes beyond it are how catheters find the basal ganglia, and a third failed pass earns a CT, not a fourth pass.
04Tunnelling and levelling
The catheter is tunnelled under the scalp to a separate exit site, secured, connected to the drainage system, and the chamber levelled against the tragus at the prescribed height.
Why: The tunnel separates the skin flora from the drill hole, the main defence against ventriculitis, and the levelling turns hydrostatics into therapy: the set height IS the prescription for how much CSF drains.
Anatomy you need
The brain and its ventricles: Kocher's point triangulates the frontal horn of the lateral ventricle you are looking at.
What can go wrong
Watch it done
External ventricular drain (EVD)
Why the drain goes in, where Kocher's point is, and how the height of the bag sets the pressure.
Source: Cleveland Clinic · Watch on YouTube
Conceptual teaching for learners preparing to observe and assist under supervision, not operative instructions. Five minutes from now you should know why this operation exists, what its shape is, and which structures it is designed not to injure.