External Ventricular Drain Placement Stealth Study

External ventricular drain (EVD) placement is performed very often in neurosurgical
practices. EVD's are used most commonly to monitor intracranial pressure and divert
cerebrospinal fluid (CSF) in patients with increased intracranial pressures. Pathologies
where EVDs are most frequently needed include hydrocephalus, malignancy, and/or trauma. EVD's
are most commonly placed at the bedside using external anatomical landmarks to guide the
catheter into the frontal horn of the ipsilateral lateral ventricle. EVDs are often placed
due to acute neurological compromise and require timely insertion. This can increase the
associated risk and result in complications.

Accurate catheter placement is essential to achieving effective external CSF drainage without
complications or occlusion/failure of the catheter. Catheter placement is most commonly
performed via a freehand approach using external anatomical landmarks to help identify the
location of the lateral ventricle within the brain without the aid of imaging. Proper
identification of the ventricles on pre-procedure imaging, surgeon skill, and estimation of
pathologic perturbations to the normal location of the ventricles all factor into the success
of catheter placement. Multiple passes are often required. The accuracy rate from the
freehand technique has been reported to range from 40 to 98 percent. A very basic grading
scale has been developed to assess placement but does not include items such as the number of
passes until successful placement and presence of post placement hemorrhage or other
neurological complications. An increased number of passes increases the risk of post
placement hemorrhage and may damage the brain. Hemorrhage has been reported to occur after
catheter placement at rates ranging from 0.2 to 41 percent.

Current methods for EVD placement do not compensate for superficial brain vessels or
pathology that may alter the intracranial anatomy such as trauma, hemorrhage, or mass
lesions. Some studies have attempted to use CTA imaging to identify intracranial vessels in
an attempt to avoid them during placement.

Image guidance is a tool used very commonly for placement of EVD's and shunts in the
operating room. AxiEM Stealth is a noninvasive image localization modality that registers a
CT or MRI to the individual patients facial and scalp anatomy. A probe can then be used to
identify, in real-time, the underlying anatomy and trajectories. This imaging guidance may
improve the accuracy of EVD placement.

This study will compare the current standard of care of freehand placement of bedside
external ventricular catheters to the placement of EVD catheters with AxiEM Stealth image
guidance. Accuracy of the tip of the catheter, occurrence of post-placement hemorrhage, the
number of passes required for CSF flow, ventricle diameter, catheter clogging/failure, time
required for placement, patient demographics and other secondary outcome measures such as
Glasgow Outcome Scale (GOS) and Modified Rankin Score (MRS) will be collected. We hypothesize
that image guided EVD catheter placement will improve accuracy, decrease the number of brain
transgressions, and decrease complications of EVD placement.

What makes up an external ventricular drain and how does it work? An external ventricular
drain (EVD) is comprised of a catheter, drainage tubing, and a collection system. Once the
catheter is in the ventricular system, it works by measuring the intracranial pressure via a
transducer and drains excess CSF from the ventricular system to ensure pressures does not
exceed a set threshold. Normal intracranial pressures range from about 5-20 mmHg and are
usually around 10mmHg. The EVD system can be set at a certain level and when the intracranial
pressures rise above that level, CSF drains out the catheter into the collecting system. The
EVD system can be raised or lowered to create different intracranial pressure thresholds and
keep intracranial pressures controlled in patients that have a pathology, such as cerebral
swelling or ventricular obstruction, leading to increased pressures.

What is the current technique used to place an EVD? A sterile field is prepared about 10-12
centimeters posterior to the eye (either right or left as clinically indicated) and about 2-3
cm lateral to the midline of the skull. This point should be about 1 cm anterior to the
coronal suture. An incision is made at this point and a burr hole is created using a hand
drill. The EVD catheter is prepared using a stylet to help with movement through the brain
parenchyma. The catheter is advanced in a trajectory perpendicular to the skull, which
results in a direction that is towards the ipsilateral medial canthus and ipsilateral tragus
which are other landmarks that can be used. The catheter is advanced to 5-6 cm and the stylet
is removed to assess for CSF flow. If CSF flow is not appreciated, then the catheter is
passed softly for about 1 more centimeter. If CSF flow is still not appreciated, the catheter
is removed and the stylet replaced for another attempt. If unsuccessful after 3 attempts, the
catheter can be left in place and a head CT can be done to assess the adjustments that need
to be made. This can often take up to 10 passes or more if there is significant brain shift
due to mass effect or aberrant anatomy. Once CSF flow is obtained, the catheter is tunneled
posteriorly and anchored to the skin with a stitch. The incision is then closed and the
catheter is connected to the drainage tubing of the collection system. The presence of CSF
drainage is checked at multiple points during closure to ensure that the catheter remains in
good position.

How does Axiem Stealth work as an image guidance system and how is it used for EVD placement?
The first step for using the image guidance system is to upload the most recent (since
admission or within 6 hours from bleeding) head CT or MRI into the Stealth station that has
been obtained since admission. The Axiem Stealth imaging guidance system uses a probe (AxiEM
Registration Probe) and a side mount emitter (AxiEM Side Mount Emitter) to register the
patient's head in relation to the probe. A trajectory (entry point and target) is then
planned. This registration process takes an estimated 5-15 minutes to perform. A separate
stylet (StealthStation EM Stylet) is designed specifically for the catheter and slides down
the center of the catheter. A burr-hole is created at the predefined precise location and the
catheter is passed to the target under electromagnetic guidance.

Relevance of this research:

The novelty of this study is to investigate whether using image guidance technology can
improve EVD catheter placement. Image guidance is used very commonly for EVD and shunt
placement in the operating room with excellent accuracy and precision. We hypothesize that
using this same workflow at the bedside will improve accuracy; decrease the number of passes
needed for a successful placement, decrease the number of post-placement hemorrhagic events,
and help improve the effectiveness of the catheter as well as patient outcomes.

Inclusion Criteria:

- Patients undergoing bedside external ventricular drain placement determined by
attending physician

- Age ≥ 18 years and ≤ 88 years

- Male or Female

- Patients or consentable family member must sign a written informed consent prior to
EVD placement

- Stealth compatible head CT or MRI

Exclusion Criteria:

- Patients ≤ 18 and ≥ 88 years of age

- Prisoner status

- Subjects who decline participation into the study

- Subjects determined to be medically or neurologically to high of a risk for the study,
determined by attending physician

- Patients who undergo emergent EVD placement via emergency consent

- Subjects for whom self-consent or consent by a LAR cannot be obtained or cannot be
obtained

- Pregnant women

- Non-English speaking patients