Author: Charbel Saade
Institute: Royal Prnce Alfred Hospital Sydney Australia

Patient Presentation

54 year old male presents to Radiology with ongoing headaches, right sided weakness progressivly getting worse and blurred vision on the right eye. On examination the patient showed uneven pupil dilation, mild confusion, hypertension and a Heart Rate of 93 bpm.

Anatomy

The normal cerebral vasculature is complex in location, vascular distribution and morphology. An AVM is known as an Arterio-Venous Malaformation. An AVM occurs when the arteries connect directly to the veins without any capillary network, and therefore this creates a problem in that the high-pressure fistula pushes oxygenated blood into he viens whereby they are unable to handle the pressure of the blood comming from the artery, thus, resulting in venous dilatation since they are accepting larger volumes of blood at higher pressures. As a result of this, the weakened blood vessels are prone to forming aneurysms and vascular wall weakness. The surrounding normal tissue may be damaged since the large blood circulation through the AVM and the loss of a cpaillary bed reduces the oxygenated perfusion of the affected organ.

Image Courtesy of www.neurosurgery.ufl.edu

There are 4 typesof AVMS they are Arteriovenous Malformations, Cavernoma, Venous Malformation and Capillary Telangiectasia. Each Type of AVM is classified according to pressure. All Arteriovenous Malformations are High Pressure and the other types are low pressure.

Scanning Technique

Comments:

This scanning Protocol requies a manual triggering at the level of C4. When viewing the dynamic scan as soon as you see the contrast fill then start your scan with a 10 sec delay from triggering.

This protocol is based on the Siemens Dual Source CT scanner with Dual Energy Subtraction.

Images

The images above on the top row represents a 3D volumetric study showing the feeding vessels of the AVM. The second image to its right represents a subtracted 3D volume with dual energy CT. The image on the second row demonstrates a Dual Energy Subtraction of the Cerebral Vascularture and the Vascular network of the AVM. The third demonstrates the 3D Dual Energy Subtraction of the vessels and also the 3D volume MIP. The MIP is used to differenctiate between the arteries and viens respectively.

Diagnosis

This patient upon presentation shows evidence of an intraparenchymal bleed and marked calcification in the pre contrast study. The Dual Energy Subtraction demonstrates the intensive internal and external vasculature of the AVM. The AVM consists of marked vessel dilation in the arteries and viens and also superiorly there is evidence of aneurysms in the interlobular viens. This patient presentation was due to an hypertensive bleed from a Aneurysm which was formed on the AVM branches in the venous system.

This study is diagnostic with good demonstration of vascular (both arterial and venous) morphology of the AVM.

The Prognosis of this patient is to evacuate the intraparenchymal bleed with a shunt and then reduce the AVM collateral supply.

The information contained in this monthly case presentation is for educational purposes only and is not intended to be relied upon for desirable practice of medical Imaging in any department. Any health care practitioner and technician reading this information is reminded that they must use their own learning, training and expertise in dealing with their individual patients as per their specific departmental protocol. This material does not replace that duty and is not intended by Charbel Saade to be used for any purpose in that regard.

The drugs and doses described are consistent with the scanning protocol, however, before administration, dose selection and contrast type, careful patient analysis should be adhered to according to departmental policy and procedure. Charbel Saade releases himself from any medico-legal issues relating to poor scanning and interpretation of information from this case study. As a guide to all please use your specific departmental protocols and consult with referring physicians regarding each individual patient..