2 Free-floating Thrombus of the Left Internal Carotid Artery

Free-floating Thrombus of the Left Internal Carotid Artery

A 54-year-old woman was admitted to the emergency department with right-sided weakness and aphasia that had started 50 minutes prior to her presentation. She had a history of non-Hodgkin’s lymphoma, diagnosed 4 years ago. She had stopped taking methotrexate 2 days p rior to admission because of the following hematologic abnormalities: thrombocytosis (750/nL; normal range 150–400/nL), leukopenia (3.86/nL; normal range 4.5–11.0/nL), and anemia (93 g/L; normal range 120–157 g/L). She was also taking oral steroids on a long-term basis for coexisting Sjögren’s syndrome. The neurologic examination on admission revealed incomplete motor aphasia, a mild right-sided hemiparesis, and a right facial paresis (National Institute of Health Stroke Scale [NIHSS] score of 7).

Initial Neuroradiologic Findings

Admission cranial CT showed no signs of acute cerebral ischemia. Cerebral MRI the following day revealed multiple small cortical and subcortical ischemic lesions in the left anterior cerebral artery (ACA) and middle cerebral artery (MCA) territories. A contrast-enhanced MR angiogram (MRA) of the extracranial brain-supplying vessels was initially reported to show right distal vertebral artery narrowing as an anatomic variant but otherwise normal findings especially with regard to the left internal carotid artery (ICA) (Fig. B2.1, Fig. B2.2, Fig. B2.3).

Diagnosis

Multiple small, embolic cerebral infarctions in the left ACA and MCA territory of unknown origin.

Question to Answer by Ultrasound Techniques

To find or exclude an embolic source in the left common carotid artery (CCA) or ICA.

Initial Neurosonologic Findings (Day 1)

Extracranial Duplex Sonography

B-mode imaging of the left ICA distal to the carotid bifurcation displayed a lumen reduction of 50% caused by a mildly hyperechoic floating structure (12.5 × 5 mm) that was partially adherent to the lateral vessel wall (Fig. B2.4). Doppler spectra and blood flow velocities were regular even at the maximum of stenosis. There were no pathologic findings in the right CCA and ICA (see Videos B2.1 and B2.2).

Transcranial Duplex Sonography

All detectable intracranial vessels revealed normal and symmetric flow signals. However, several microembolic signals were recorded during insonation of the left MCA (Fig. B2.5; see also Video A4.1).

Conclusion

Partially floating, unstable, continuously microemboli emitting thrombus in the left proximal ICA causing a lumen reduction of ~50%.

Clinical Course

Because of the patient’s complex hematologic history, rt-PA treatment was contraindicated according to current guidelines. Instead, she was given intravenous partial thromboplastin time (PTT)-guided heparin. The pattern of multiple small infarctions in the left ACA and MCA territory indicated an artery-to-artery embolic etiology, caused by the floating thrombus within the left ICA. On re-evaluation of the MR angiograms, a circumscribed signal of reduced intensity was observed in the left ICA directly above the carotid bifurcation, in accordance with the initial duplex results (Fig. B2.6). Carotid endarterectomy (CEA) was considered to be the best treatment. The patient had surgery on the same day (Fig. B2.7). Postoperative follow-up was uneventful.

The etiology of the intravascular thrombus was unclear, but the underlying hematologic disease with severe thrombocytosis was suggestive for a paraneoplastic coagulopathy (anticardiolipin antibody levels were not raised). Blood culture and transesophageal echocardiography excluded an infectious cause. The intravenous heparin was replaced by low-dose subcutaneous heparinization after 10 days, which was continued until a therapeutic decision regarding the lymphoma was made. The neurologic deficits improved markedly and the patient was discharged with a mild right-sided hemiparesis and amnesic aphasia.

Fig. B2.1 MR diffusion-weighted image (b = 1,000), axial plane. Ischemic lesions in the basal ganglia and in the left-sided MCA territory.

Fig. B2.2 MR diffusion-weighted image (b = 1,000), axial plane. Multiple ischemic cortical lesions within the left-sided ACA and MCA territory.

Fig. B2.3 Extracranial contrast-enhanced MRA, coronal MIP. Normal aspect in the conventional MIP projection.

Fig. B2.4 Extracranial duplex, longitudinal plane. B-mode sonography reveals a floating thrombus (12.5 × 5 mm) that is partially adherent to the lateral vessel wall in the right proximal ICA, directly above the carotid bifurcation, reducing the lumen by approximately 50%.