Arteriovenous Malformations and Fistulas (AVM/AVF) of the Spinal Cord Workup

Updated: Apr 21, 2022
  • Author: Glenn A Gonzalez, MD; Chief Editor: Brian H Kopell, MD  more...
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Workup

Imaging Studies

Imaging protocols are less standardized for the spine and spinal cord than for the brain. The most important difficulties for optimization of sequences are due to the many interfaces that exist in this region, such as bone–cerebrospinal fluid (CSF) and spinal cord–CSF, the proximity of the lungs, and the mobile character and size of the spinal cord and its adjacent structures. [13]

Plain radiography is not usually helpful for diagnosis. Computed tomography (CT) scanning may reveal dilated vessels in the thecal sac, but findings are usually normal. If a patient presents with symptoms of subarachnoid hemorrhage, CT scanning demonstrates blood in the spinal fluid.

Myelography findings, with or without CT, show dilated vessels in the intradural space. This imaging modality is very sensitive and shows these abnormalities in detail. This is an invasive procedure that requires injection of a contrast agent into the thecal sac. Postprocedural headache is not uncommon.

On magnetic resonance imaging (MRI), soft tissue and neural elements are visualized in detail. Dilated intradural vessels can be seen as flow voids or can be seen filling with contrast. Edema or hemorrhage in the spinal cord parenchyma can be assessed. The exact fistula site cannot be localized. Sequences indispensable to a basic MRI clinical protocol for any spine or spinal cord examination are fast spin echo (FSE) T2 and spin echo (SE) T1. All spinal investigations should have sequences in both sagittal and axial planes to identify exact location and to attain better visualization of lesions. Advanced sequences may be employed as well. [13]

Magnetic resonance angiography (MRA) and CT angiography (CTA) are noninvasive modalities that can be used to identify abnormal vessels. However, resolution of these modalities is not yet optimal. The pathology must be confirmed by spinal angiography. [10]

Spinal digital subtraction angiography (DSA) is the gold standard for the diagnosis of spinal AVM and is an indispensable tool for treatment planning. [8]

Arteriography is the criterion standard for visualizing AVMs. This dynamic study allows visualization of the pathology in real time, enabling assessment of high-flow versus low-flow AVMs. In addition, the location of the fistula can be visualized. Arteriography is an invasive procedure that may cause morbidity such as spinal cord ischemia, cerebrovascular accident, or vascular dissection. Comparison of a prospective series of consecutive right transradial diagnostic cerebral arteriograms versus a procedural staging system revealed that neurointerventionalists can achieve high success rates and low crossover rates after performing this procedure. [14]

Vascular malformations of the spine frequently have distinguishing characteristics on imaging that are imperative for the radiologist to recognize to provide proper guidance for diagnosis and treatment. [2]  Advances in neurovascular imaging, along with increased utilization of these advances, have resulted in more frequent identification of these lesions. [1]  Often, radiologists are the first to guide the clinician toward an adequate diagnosis. [10]  Clinical challenges that neuroradiologists may face include "when" and "where" concerning the use of each technique and for which pathology or clinical scenario each technique is most useful. [13]

Typically, spinal MRI is ordered as a first-line screening method to detect spinal vascular malformations. If a spinal vascular malformation is still suspected, digital subtraction angiography (DSA) must be performed to display the very small vessels of the spinal cord. Because of complications involved with DSA, MRA or CTA can be used to determine the spinal cord level of the feeding artery, thus limiting the amount of time needed before the DSA procedure is performed. [15]

No laboratory studies are useful for the diagnosis of spinal cord vascular malformations. However, if the patient presents with symptoms of subarachnoid hemorrhage, lumbar puncture or computed tomography (CT) scan reveals blood in the spinal fluid.