Transcranial Doppler detection of cerebral fat emboli and relation to paradoxical embolism: a pilot study

The fat embolism syndrome is clinically characterized by dyspnea, skin petechiae, and neurological dysfunction. It is associated mainly with long bone fracture and bone marrow fat passage to the systemic circulation. An intracardiac right-to-left shunt (RLS) could allow larger fat particles to reach the systemic circulation. Transcranial Doppler can be a useful tool to detect both RLS and the fat particles reaching the brain.

We prospectively studied patients with femur shaft fracture with RLS evaluation, daily transcranial Doppler with embolus detection studies, and neurological examinations to evaluate the relation of RLS and microembolic signals to the development of fat embolism syndrome. Forty-two patients were included; 14 had an RLS detected. Seven patients developed neurological symptoms; all of them had a positive RLS (P=<0.001). The patients with an RLS showed higher counts and higher intensities of microembolic signals (P=<0.05 and P=<0.01, respectively) compared with those who did not have an RLS identified. The presence of high microembolic signal counts and intensities in patients with RLS was strongly predictive of the occurrence of neurological symptoms (odds ratio, 204; 95% confidence interval, 11 to 3724; P<0.001) with a positive predictive value of 86% and negative predictive value of 97%.

In patients with long bone fractures, the presence of an RLS is associated with larger and more frequent microembolic signals to the brain detected by transcranial Doppler study and can predict the development of neurological symptoms.