(172) Bubbles in the Brain: An Unusual Case of Gas-Containing Atrial Thrombus Leading to Pneumocephalus

Introduction: Pneumocephalus is defined as the presence of air within the intracranial cavity. It is a rare phenomenon but is often life-threatening. It is a complication often encountered in patients following traumatic accidents, surgical procedures or central nervous system infections. The development of pneumocephalus due to a gas-containing atrial thrombus, however, is an exceedingly rare occurrence. We report on a patient who presented as a stroke alert with a rapid decline in neurological status. This case highlights the importance of considering atypical etiologies for pneumocephalus, allowing for early recognition and prompt intervention.

Description: A 75-year-old male presented to the emergency room with complaints of left-sided weakness. Physical examination revealed an alert and oriented gentleman with decreased strength in his left upper and lower extremities and a left-sided facial droop. Cardiac examination showed a regular rate and rhythm with a grade 1/6 systolic ejection murmur. A CT brain demonstrated bilateral cortical infarcts. The patient did not receive TPA and was admitted for further management. On the second day of admission, the patient became obtunded. He was intubated for airway protection, and a subsequent CT brain scan showed development of pneumocephalus. The patient was transferred to the ICU and remained on mechanical ventilation with 100% FiO2. An echocardiogram with a bubble study revealed a large, echogenic, irregular, mobile thrombus in the superior cavity of the left atrium. A CT pulmonary embolism study showed a filling defect in the left atrium consistent with thrombus and associated gas within the thrombus. All four blood cultures drawn were positive for Streptococcus Salavarius and Mitis.

Discussion: A gas-containing left atrial thrombus poses a significant risk for complications. When the thrombus contains gas, the gas can be released into the surrounding brain tissue, leading to pneumocephalus. The presence of gas within the thrombus may arise from various factors. Common etiologies include an infected thrombus with a gas-producing organism and iatrogenic introduction of air into the venous system. Pneumocephalus is often a fatal condition and as such, strong emphasis should be placed on identifying risk factors for critically ill patients.