The placement of a quad lumen monitor can allow for the collection of different types of data including intracranial pressure, brain tissue oxygenation, cerebral blood flow, and electrical activity. Our protocol allows different types of information to be collected in severe traumatic brain injury patients at the bedside using a simple procedure involving a single burr hole. Immobilize the head securely to ensure that it does not move during burr hole placement.
Rolled towels and tape can be used to help secure the patient's head. Begin by identifying the correct location for the bolt placement. 11 centimeters from the nasion or one centimeter anterior to the coronal suture, and two to three centimeters laterally at about the mid-pupillary line.
Sterilize the area with Betadine solution and use 1%lidocaine with epinephrine for local analgesia. While the Betadine is drying, thread each probe through a locking nut, and subsequently insert each probe through one of the lumens of the bolt. Place the intracranial pressure brain tissue oxygen probe preferentially in the tallest lumen.
The other probes can be fit through any of the remaining lumens. Confirm that the distance from the end of the bolt to the tip of each probe is two and a half to three centimeters, and advance the depth electrode until the most proximal electrode is just outside the end of the bolt. Once the probe has been placed the appropriate distance from the end of the bolt, tighten the locking nut on the lumen of the bolt, and then on the probe itself to lock the probe in place.
Then loosen the nut from the lumen and remove each probe with its locking nut in place, placing each probe on the sterile table next to the bolt. When all of the probes are ready, use a scalpel to make a one to two centimeter incision in the marked region, and use a blunt tipped instrument to separate the subgaleal tissues to expose the periosteum. Use a hex bit to tighten a 5.3 millimeter drill bit to the cranial drill, and place the drill perpendicular to the skull.
Using continuous pressure while rotating the instrument, drill until there is a tactile change in pressure, and continue drilling with counter upward support to avoid plunging the drill into the cortex. Remove the drill and clear the burr hole of any bone chips or debris. Use a scalpel to incise the dura in a cruciate fashion and confirm that the dura is completely open.
To insert the cranial bolt, hold the bolt by the plastic wings and thread the bolt through the burr hole with a firm clockwise twisting motion. Insert the thinnest pre-measured probe until the locking nut meets the lumen, followed by the rest of the probes. Insert the depth electrode with the stylet in place, and tighten the electrode on the lumen.
Then gently loosen the locking nut from the probe, just enough to remove the stylet, before re-tightening the nut. When all of the probes have been inserted, have available personnel connect the intracranial pressure brain tissue oxygen probe to the bedside monitor, to assess the intracranial pressure and brain tissue oxygen. Then use durable tape to gently loop each probe to secure it to its lumen to create strain resistance.
If desired, wrap the probes and bolt with sterile gauze at the completion of the procedure. All probes project through the bolt into the brain parenchyma within millimeters of each other. Here, scout computed tomography, or CT coronal and sagittal images, demonstrating the trajectory of probes at approximately 1.5 and two to three centimeters respectively below the inner table of the skull are shown.
In this axial CT image, a probe placed after non-surgical severe traumatic brain injury with excellent placement can be observed. Note that with standard windowing, relatively dense probes may obscure subtle peri-probe hematomas. This axial CT image of a probe placed after surgical severe traumatic brain injury illustrates the location of a bolt and probes contralateral to the hemicraniectomy site.
These incorrectly placed probes after non-surgical severe traumatic brain injury are approaching the frontal horn of the lateral ventricle, indicating that they are greater than three centimeters below the inner table of the skull, which may affect measurements obtained by the probes. Place the probes at the proper depth from the bottom of the bolt and tighten the locking nuts tightly enough that the probes do not get dislodged without becoming damaged. If intracranial pressures are high and refractory to treatment, an external ventricular drain can also be placed to drain cerebrospinal fluid and relieve intracranial pressure.
A continuous scalp electroencephalography electrode can be placed to correlate potential seizure activity with the depth electrode findings.
