Illustration of a brain with glowing ventricles connected to a shining bolt, representing reduced complications in EVD.

EVD Drains Compared: Which Type Reduces Your Risk of Complications?

Lena Voss in Health & Wellness June 2025 • 4 min read.

"A Prospective Study Reveals Bolt-Connected Drains Offer a Safer Alternative to Traditional Tunnelled Drains for Managing Intracranial Pressure"

When intracranial pressure (ICP) rises to dangerous levels, swift action is crucial. One of the most common and effective interventions is external ventricular drainage (EVD). This neurosurgical procedure involves placing a catheter into the brain's ventricles to drain cerebrospinal fluid (CSF), thereby reducing pressure. While EVD can be life-saving, it's also associated with a significant risk of complications, including infections, bleeding, and catheter malfunctions.

For years, the standard approach to EVD involved a technique called tunnelled EVD (T-EVD), where the catheter is threaded under the skin to a separate exit point. However, recent research has suggested that a newer method, bolt-connected EVD (BC-EVD), might offer a safer alternative. BC-EVD involves direct connection of the catheter to a bolt secured to the skull, potentially reducing the risk of infection and other complications.

Now, a prospective study published in Acta Neurochirurgica sheds new light on the comparison between these two EVD techniques. Researchers at Aalborg University Hospital in Denmark conducted a trial to determine if BC-EVD indeed leads to fewer complications than the traditional T-EVD method. Let's dive into the details of this study and what it could mean for patients requiring EVD.

T-EVD vs. BC-EVD: What the Study Revealed

Illustration of a brain with glowing ventricles connected to a shining bolt, representing reduced complications in EVD.

The Aalborg Bolt-Connected Drain (ABCD) study was designed to prospectively compare the outcomes of patients undergoing EVD using either the BC-EVD or T-EVD technique. From March 2017 to February 2018, patients requiring ventriculostomy were consecutively assigned to either the BC-EVD or T-EVD group based on the preference of the on-call neurosurgeon. This approach resulted in two distinct cohorts, as some surgeons favored the newer BC-EVD method while others remained more comfortable with the traditional T-EVD technique.

Data was meticulously collected from patient records, including CSF culture results and CT/MRI scans. Researchers tracked a range of complications, including:

CSF leakage
Accidental Discontinuation
Placement-related intracranial haemorrhage
Malfunction
Migration
Infection
Revision (reoperation)

The study included a total of 49 EVDs, with 32 performed using the T-EVD technique and 17 using the BC-EVD method. The results were striking: 19 of the 32 T-EVDs (59.4%) experienced complications, compared to only 3 of the 17 BC-EVDs (17.6%). This difference was statistically significant, indicating that T-EVD was associated with a significantly higher risk of complications (p = 0.007). The relative risk of complications with T-EVD was 3.4 times that of BC-EVD.

The Future of EVD: A Shift Towards Safer Techniques

The ABCD study provides compelling evidence that BC-EVD is associated with a lower risk of complications compared to T-EVD. While the authors acknowledge that T-EVD may still have a role in specific situations, such as in pediatric patients or when EVD is placed intraoperatively or in the occipital region, they conclude that BC-EVD should be considered the first-line choice for most EVD placements. As the field of neurosurgery continues to evolve, embracing safer and more effective techniques like BC-EVD is crucial for improving patient outcomes and minimizing the risks associated with this life-saving procedure.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1007/s00701-018-3737-z, Alternate LINK

Title: The Aalborg Bolt-Connected Drain (Abcd) Study: A Prospective Comparison Of Tunnelled And Bolt-Connected External Ventricular Drains

Subject: Neurology (clinical)

Journal: Acta Neurochirurgica

Publisher: Springer Science and Business Media LLC

Authors: Sofia Kamakh Asaad, Carsten Reidies Bjarkam

Published: 2018-11-23

Everything You Need To Know

What is external ventricular drainage (EVD) and why is it important in the context of managing intracranial pressure?

External ventricular drainage (EVD) is a neurosurgical procedure used to manage elevated intracranial pressure (ICP). This involves inserting a catheter into the brain's ventricles to drain cerebrospinal fluid (CSF), thereby reducing pressure. It is crucial because increased ICP can lead to severe neurological damage. The procedure has inherent risks, including infections, bleeding, and catheter malfunctions, which can have serious implications for patient health and recovery.

What are the key differences between tunnelled EVD (T-EVD) and bolt-connected EVD (BC-EVD)?

The two main types of EVDs discussed are tunnelled EVD (T-EVD) and bolt-connected EVD (BC-EVD). T-EVD involves threading the catheter under the skin to a separate exit point, while BC-EVD connects the catheter directly to a bolt secured to the skull. The study suggests that BC-EVD may offer a safer approach, potentially reducing the risk of infection and other complications associated with the procedure.

What was the primary goal of the Aalborg Bolt-Connected Drain (ABCD) study?

The Aalborg Bolt-Connected Drain (ABCD) study compared the outcomes of patients undergoing EVD using either the BC-EVD or T-EVD technique. Researchers tracked complications like CSF leakage, accidental discontinuation, placement-related intracranial hemorrhage, malfunction, migration, infection, and revision. The study aimed to determine if BC-EVD led to fewer complications compared to T-EVD.

What were the key findings of the ABCD study regarding the comparison of T-EVD and BC-EVD?

The ABCD study revealed that T-EVD was associated with a significantly higher risk of complications compared to BC-EVD. Specifically, 59.4% of T-EVDs experienced complications, compared to only 17.6% of BC-EVDs. The relative risk of complications with T-EVD was 3.4 times that of BC-EVD, highlighting the potential benefits of using BC-EVD to improve patient outcomes and decrease the incidence of complications. These findings have implications for how neurosurgeons approach EVD placement in the future.

What are the implications of the ABCD study's findings for the future of EVD procedures?

The study's findings suggest that BC-EVD should be considered the first-line choice for most EVD placements due to its lower risk of complications. However, T-EVD may still be suitable in specific situations. The implication is a potential shift in neurosurgical practice toward safer techniques, aiming to improve patient outcomes and minimize risks associated with EVD procedures. This shift represents an evolution in neurosurgical practices, prioritizing patient safety and more effective treatment approaches.