External Direction of the EVD Catheter: Technical Considerations

External ventricular drains (EVDs) are temporary cerebrospinal fluid (CSF) diversion devices commonly used in neurosurgery and neurocritical care. These catheters are placed within the ventricles of the brain, which is the most frequent location, and do not feature a valve system.[1] [2] Typically, an EVD follows a tunneled subcutaneous pathway and is connected to the exterior. An EVD is indicated for both diagnostic and therapeutic purposes, with three primary indications: (1) monitoring intracranial pressure (ICP), (2) draining CSF to manage conditions such as intracranial hypertension (ICH) or hydrocephalus, and (3) delivering intrathecal medications like antibiotics or fibrinolytics.[3] EVDs are increasingly employed in patients with traumatic brain injury (TBI) and intraventricular hemorrhage to evacuate CSF.[4] [5] The external direction of the catheter of an EVD, when exiting and being fixed to the scalp, depends on various factors, including the location of the ventricular access and the surgeon's preference. However, the trajectory is generally chosen to minimize complications, ensure stable fixation, and optimize patient management. Below are key considerations. The options for external direction when fixed to the scalp are the following:

• Direction toward the ear (lateral): This is one of the most common directions. It allows the catheter to follow a short and natural path from the exit point to the drainage system, reducing the risk of torsion or accidental traction. It is ideal for keeping the catheter fixed and protected at the skin level, as it remains relatively discreet and away from areas that could interfere with wound management or dressings.

• Direction toward the frontal region, which is useful when the ventricular access point is more posterior (e.g., drainage through occipital or parietal access). In supine patients, this direction may cause discomfort due to catheter pressure against the pillow. It is less commonly used, but it can be an option if the external drainage system is positioned toward the head of the patient.

• Direction toward the occipital region (posterior): This approach is less frequently used but feasible when the ventricular access point is anterior (e.g., Kocher's point). This trajectory might complicate drainage system management since the catheter crosses areas that may interfere with dressings or patient positioning. In supine patients, this direction could lead to discomfort or displacement risks due to pressure on the scalp.

• Direction perpendicular to the scalp (vertical): In some cases, the catheter is fixed directly upward without specific orientation toward the ear, front, or occiput, especially if the exit point is small and well secured. However, this could leave the catheter more exposed to accidental traction. We need to have some aspects in mind, like the ventricular access point. If the access is frontal (e.g., Kocher's point), directing the catheter toward the ear is usually the most logical choice. For parietal or occipital access, the direction may vary depending on the drainage system's location.

The catheter's path should be as straight and short as possible from the exit point to the drainage system to avoid kinking or obstruction (see [Fig. 1]). These pros and cons come into play when selecting the appropriate orientation of the EVD catheter in accordance with the medical, comfort, and operative requirements of the patient ([Table 1]). Certain characteristics that are proposed are related to each of the pathological conditions with reference to the most efficient linear direction for EVD catheter insertion.

Fig. 1 An illustration of the possible direction for the external direction of an EVD catheter exiting through the scalp.

Table 1 Pros and cons of each approach

Approach	Pros	Cons
Frontal region	• Easier access for surgical placement • Often preferred for shorter catheter lengths	• Can be cosmetically noticeable • Potential risk of skin irritation or infection at the incision site • May be less ideal for certain anatomical conditions
Perpendicular to the scalp (vertical)	• Direct and straightforward path for fluid drainage • Provides stable positioning, reducing the risk of catheter displacement	• May cause discomfort or pressure on the scalp • Difficult to manage for prolonged periods due to the position • It may restrict patient movement
Ear (lateral)	• Positioned near the ear for ease of access • Good for patients who may need to lie on their side • May be more comfortable for certain patients	• It may cause issues with the ear or jaw area if not properly positioned • Slightly more prone to accidental displacement or kinking of the catheter
Occipital region (posterior)	• It can be more discreet for cosmetic reasons • Suitable for patients with particular anatomical features • Reduces interference with frontal structures	• Challenging access during surgical placement • Potentially harder to monitor and manage for the care team • Can be uncomfortable if the patient lies on their back for extended periods

A few examples may be Subaracnoid hemorrhage (SAH) or brain trauma injury with no surgery; in this context, the most appropriate position would be the frontal region or perpendicular to the scalp, and the reason for that is in case of TBI without any surgical intervention, the easy access frontal region is most often the preferred site as it facilitates the efficient supervision and drainage of CSF, which is aimed at providing pressure relief. This placement can also help alleviate some of the patient's cosmetic and comfort issues. The vertical direction is also beneficial as the patient has direct drainage, enabling precise pressure readings and direct removal of excess CSF that is deemed undesirable. In decompressive craniectomy, the best direction is the occipital region (posterior) because in the cases where the patient has a decompressive craniectomy, the occipital site is most of the time able to avoid the place where the craniectomy was done. This positioning, on the other hand, is less likely to result in direct trauma to the craniotomy site while also ensuring that the craniopuncture is effective.

In cases of medical condition-linked brain edema, the optimal approach depends on the specific condition and location of the edema, rather than a predetermined preference for frontal or lateral approaches. While the frontal approach may be suitable for some cases of medical edema resulting from encephalitis or metabolic diseases, it is not universally opted for. The choice of approach is based on factors such as the underlying cause, extent of edema, and potential surgical interventions required. It offers adequate drainage and is less likely to be uncomfortable. Lateral positioning near the ear may be appropriate if the person requires long-term management, considering it favors better positioning and movement of the person, which is ideal for edema associated with medical disease management.

We believe that the proposed observations will contribute to a better understanding of the importance of the external segment of the proximal catheter for improving outcomes in our patients in neurotrauma and neurocritical care.

Publikationsverlauf

Artikel online veröffentlicht:
09. April 2025

• References

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• 4 Fried HI, Nathan BR, Rowe AS. et al. The insertion and management of external ventricular drains: an evidence-based consensus statement—a statement for healthcare professionals from the Neurocritical Care Society. Neurocrit Care 2016; 24 (01) 61-81
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