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Background
CTA of the head and neck is one of the most performed neuroimaging examinations performed in the acute care setting. Prior studies have demonstrated a growth in the use of CTA head of 1100% (compound annual growth rate [CAGR] 25%) and CTA neck of 1300% (CAGR 27%) between 2007 and 2017. Much of this growth may be attributed to studies demonstrating the efficacy of early thrombectomy in cases of large vessel occlusion (LVO). Additional studies have demonstrated efficacy of CTA head and neck in evaluation for subarachnoid hemorrhage in headache to avoid lumbar puncture. CTA head and neck covers a large range of anatomic structures, from the head through the upper thoracic cage, including arterial and venous structures. Given the wide area of coverage, a variety of detection errors are possible if focus is directed only on expect pathology or the large arteries of the head and neck. This educational exhibit seeks to identify important “blind spots” and easily missed pathology on CTA of the head and neck.

Educational Goals / Teaching Points
The goal of this educational exhibit is to outline a range of possible blind spots on CTA imaging of the head and neck. “Good calls” and “potential learning opportunities” were queried from our institution’s peer learning platform; emergency and neuroradiologists were also asked to contribute instructive cases from personal teaching files. Findings were categorized into patterns based on anatomy and pathologic process. We focused our review on clinically actionable abnormality that may impact patient care if missed.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Blind spots within CTA of the head and neck were organized into broad anatomic sites: arterial, venous, thoracic vasculature, soft tissues of the neck, and osseus findings. Blind spots in arterial structures included peripheral intracranial occlusions (most often distal to the first segments of the anterior and posterior cerebral arteries) and aneurysms of the carotid bifurcation and basilar tip. At the intracranial venous structures, a potential blind spot was venous sinus thrombosis, particularly of the sigmoid sinus and jugular bulb. In the neck soft tissues, potential blind spots included pharyngeal mass lesions and cervical lymphadenopathy. Within visualized thoracic structures, blind spots included aortic aneurysm, arch vessel stenosis, pulmonary emboli, lung nodules, and mediastinal lymphadenopathy. Osseus structures may reveal fractures, aggressive osseus lesions and spinal canal stenosis.

Conclusion
This educational exhibit demonstrates a range of possible blind spots in the evaluation of CTA head and neck studies, categorized by anatomic site and illustrated by case review. Radiologists may improve their detection of clinically impactful findings by ensuring full evaluation of each of the highlighted anatomic ranges within their search pattern. This exhibit may prompt radiologists to include specific sites and within report templates to aid detection and minimize detection error.