43 Intra-arterial Contrast Injection during Computed Tomography Angiography
43.1 Case Description
43.1.1 Clinical Presentation
A 79-year-old female patient presented with right-sided facial weakness. Medical history included metastatic breast carcinoma, hypertension, and previous surgical management of a giant anterior communicating artery (AComm) aneurysm over 30 years previously. She was a nonsmoker, with no other relevant comorbidities and cardiovascular risk factors. Family history was noncontributory.
43.1.2 Imaging Workup and Investigations
Noncontrast computed (NCCT) of the brain showed evidence of previous surgery, and a complex, multilobulated, hyperdense, partly calcified mass in the region of the inferior anterior interhemispheric fissure, in keeping with the known history of previously treated giant AComm aneurysm. There was no evidence of acute infarction (Fig. 43.1a, b).
CT angiography (CTA) was also performed (Fig. 43.2a–g). Iodinated contrast material was administered through peripheral vascular access in the right antecubital fossa. A total of 60 mL of contrast material was administered at an injection rate of 4 mL per second. On the CTA, only the right carotid and vertebral arteries were seen filling in the neck (Fig. 43.2a). Intracranially, there was contrast opacification of the right middle cerebral artery (MCA), and bilateral anterior cerebral artery (ACA) territories, but no filling of the left internal carotid artery (ICA), left MCA or left posterior cerebral artery (PCA) territory (Fig. 43.2b–g). In the posterior circulation, the right vertebral artery, basilar artery, and right cerebellar and right PCA branches were filling. There was opacification of the left anterior inferior cerebellar artery and left superior cerebellar artery territories, but no filling of the left vertebral artery or left posterior inferior cerebellar artery territory (Fig. 43.2b, c, g). The visualized intracranial arteries were densely opacified with contrast, avid enhancement of leptomeningeal vessels, and greater than expected brain parenchymal enhancement, giving an appearance which could be referred to as a “superscan.”
The previously treated aneurysm did not fill on CTA. An incidental note was also made of dense sclerosis and thickening of the bones of the cranial vault, and a destructive process involving the left occipital condyle (arrow), in keeping with boney metastatic disease.
Stroke mimic: inadvertent intra-arterial administration of iodinated contrast material for CTA.
The referring physicians were immediately notified that an inadvertent intra-arterial contrast administration had occurred, the vascular access in the right antecubital fossa, which was believed to be venous had instead been inadvertently placed in the right brachial artery. The cannula was immediately removed, and hemostasis achieved with local pressure. The patient was observed, and had no adverse effects after the injection or on the next day, and required no further management. There was no recurrence of the right transient facial weakness, examination showed no focal neurological deficit, and further management was not instigated.
Inadvertent intra-arterial injection of contrast for CT studies is rare, but is of potential significance when it does occur. There are two main concerns: first, regarding the potential adverse clinical effects of an intra-arterial injection; second, regarding the potential for either a nondiagnostic study or misinterpretation of the appearances on subsequent CT.
43.2.2 Workup and Diagnosis
Correlation with the provided patient history can prove to be not only invaluable for the interpreting radiologist but also help avoid misinterpretation. For example, in this case, it would be extremely unlikely that a patient with nonfilling of almost the entire left hemisphere on CTA would have symptoms only of a transient right facial weakness. While it is possible that a patient with large artery occlusion could present in such a way, if there was excellent collateralization to the occluded territory, for example, through the circle of Willis or leptomeningeal collaterals, no such “collateralization” was evident on CTA in this case. This discrepancy between imaging appearance and history can alert the radiologist to the fact that something is amiss.
From an inadvertent intra-arterial access point of view, indicators in the patient history suggestive of an intra-arterial rather than venous injection would include a report of intense pain on administration of the administered drug, pulsatile return of blood from the access cannula, vascular access in a site such as the antecubital fossa where there is proximity of an artery to vein, and possibly later symptoms of complicating distal limb ischemia. 1
Examination and Investigations
When obtaining peripheral vascular access, distinguishing a superficial vessel as an artery rather than vein is not always straightforward. Absence of sensation of pulsation is not always reliable, and partial occlusion of arterial flow by an applied tourniquet may be one reason for this. 1 Awareness of the common patterns of arterial variation in the upper limb can facilitate early detection of inadvertent intra-arterial cannulation, and the possibility of this occurring should be kept in mind whenever cannulation is performed in the antecubital fossa or ventromedial aspect of the forearm.
In situations where cannulation has been performed, and there is uncertainty as to whether artery or vein has been accessed, blood gas analysis can be performed to help distinguish arterial from venous access. 2