An external ventricular drain, also referred to as an EVD in clinical practice, is used for the external drainage of Cerebrospinal fluid. It consists of a thin, radiopaque plastic catheter (usually made of polyurethane) that is inserted through a burr hole into the internal Ventricular spaces and drained externally.
Indication
Obstruction of CSF flow, for example due to hemorrhage or reduced CSF resorption, can lead to Hydrocephalus with a consequent life-threatening increase in intracranial pressure. The most common indications for EVD placement are the following conditions[^6]:
Subarachnoid hemorrhage (approx. 43 %)
Intracerebral hemorrhages (approx. 27 %)
Traumatic brain injury (approx. 16 %)
Intraventricular hemorrhages (approx. 13 %)
Tumors (approx. 12 %)
Placement
External ventricular drains can be placed either in the operating room or directly at the patient's bedside. There are two different methods for securing a placed EVD. An EVD can either be exteriorized and secured via tunneling or secured with a bolt that is screwed directly into the burr hole. The usual target for placement is the ipsilateral frontal horn of the lateral ventricle.
Placement aids
Various aids have been described in the literature to facilitate EVD placement:
Aid | Description |
Mixed reality[^7] | Bedside EVD placement using mixed reality. |
CT-guided EVD placement[^8] | CT-guided placement based on direct reconstruction of the planned trajectory for EVDs with a bolt system. |
Navigation-guided[^9] | EVD placement using Neuronavigation. |
Ultrasound-guided[^10] | EVD placement using ultrasound |
Thomale device[^11] | EVD placement using a mobile device to optimize angulation. |
Complications
Malposition
A retrospective study by Toma et al.[^1] showed in 2009 that only 40 % of EVDs placed freehand were positioned in the ipsilateral ventricle. A larger meta-analysis from 2023 showed a malposition rate of approximately 28 %[^6].
Hemorrhage
The risk of EVD-associated hemorrhage is approximately 5 % [^6].
Risk of infection
The incidence of EVD-associated infection is approximately 5- 9.5 %[^2] [^6]. Duration of implantation, CSF leakage, blood in the CSF, and flushing of the EVD are known risk factors that increase the risk of infection [^2] [^3] [^4]. The use of prophylactic antibiotics in patients with an external ventricular drain is controversial. Study data suggest that prophylactic antibiotic therapy does not reduce the risk of infection in patients with an external ventricular drain[^5]