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CTA Dot Sign

Summary

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  • The CTA dot sign refers to a focal hyperdense dot within a cerebral artery on CT angiography
  • It indicates the presence of an intraluminal thrombus in acute ischaemic stroke
  • The sign is highly specific for vessel occlusion and aids in early diagnosis and treatment planning

Pathophysiology

  • Represents a cross-sectional view of an intraluminal thrombus within a cerebral artery
  • Typically seen in M1 segment of the middle cerebral artery (MCA) or basilar artery
  • Composed of red blood cells, platelets, and fibrin, causing local hyperdensity on CT

Demographics

  • Primarily observed in patients with acute ischaemic stroke
  • More common in older adults due to higher stroke incidence
  • No significant gender predilection reported

Diagnosis

  • Clinical presentation:
    • Sudden onset of neurological deficits
    • Symptoms vary based on the affected vascular territory
  • CT angiography (CTA) is the primary diagnostic modality
  • Differential diagnosis:
    • Calcified atherosclerotic plaque
    • Contrast material in small perforating arteries

Imaging

  • CT angiography findings:
    • Hyperdense dot within the lumen of an affected artery
    • Most commonly seen in M1 segment of MCA
    • Size typically 1-2 mm in diameter
  • Associated findings:
    • Vessel cutoff sign distal to the dot
    • Reduced contrast opacification in distal branches
  • Sensitivity and specificity:
    • High specificity (>95%) for vessel occlusion
    • Moderate sensitivity (50-70%) due to small size and partial volume effects

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  • A 60-year-old patient presented with left sided weakness and parasthesia.
  • Imaging showed a focus of enhancement within a right thalamic haematoma.
  • A follow-up CT showed enlargement of the haematoma.

Treatment

  • Rapid identification of CTA dot sign guides treatment decisions
  • Intravenous thrombolysis with recombinant tissue plasminogen activator (rtPA) within 4.5 hours of symptom onset
  • Mechanical thrombectomy for large vessel occlusions:
    • Considered up to 24 hours in selected patients
    • Particularly beneficial for M1 MCA occlusions
  • Antiplatelet therapy and management of risk factors for secondary prevention

Differential diagnosis

Differential Diagnosis Differentiating Feature
Cortical vein thrombosis CTA dot sign is located in subarachnoid space, not within cortical vein
Aneurysm CTA dot sign is smaller and lacks the typical saccular shape of aneurysms
Arteriovenous malformation CTA dot sign lacks the characteristic tangle of abnormal blood vessels
Calcification CTA dot sign enhances with contrast, unlike calcifications
Partial volume artefact CTA dot sign is consistently visible on multiple slices and projections
Moyamoya disease CTA dot sign is focal, not the diffuse network seen in Moyamoya
Vasculitis CTA dot sign is a single focal finding, not multifocal vessel irregularities
Dural arteriovenous fistula CTA dot sign lacks the abnormal arterial feeders and early venous drainage