Abstract

A 45-year-old patient with known history of Aortic arch aneurysm presented in the emergency ward with features of rupture of the aneurysm into the left lung with compressive signs in the pulmonary parenchyma. Diagnosis was confirmed by magnetic resonance imaging. The patient underwent repair of thoracic aortic aneurysm with left upper lobectomy under general anesthesia and cardio-pulmonary bypass support. Transesophageal echocardiography (TEE) was used for an intraoperative monitoring. While imaging the thoracic aorta with TEE was underway, we accidentally visualized an image that was confirmed to be the spinal cord. So, in this article we discuss how the spinal cord monitoring can be made possible with TEE.

Keywords

Aortic aneurysm; Echocardiography, transesophageal;

1. Introduction

Spinal cord imaging by Transesophageal echocardiography (TEE) is very difficult, because both the intrathoracic esophagus and the aorta lie adjacently to the anterolateral vertebral bodies. Because of being shadowed by the vertebral column, the spinal cord is rarely identified on TEE, unless it is searched for, by echocardiographic imaging through an intervertebral disc as an acoustic window. Even with difficulty, if the image can be identified, TEE can be used as a monitoring tool in patients for whom the spinal cord monitoring is necessary.

2. Case report

A 45-year-old man, a known case of aneurysm of the arch of Aorta presented in the emergency ward with complaints of dyspnea of acute onset, vomiting, restlessness, and an episode of hemoptysis. There were no other symptoms like limb discoloration, limb pain, and etc. An urgent magnetic resonance imaging was done and it revealed aneurysmal dilatation of the arch of aorta extending beyond the origin of the left subclavian artery with a large thrombus in the aneurysm and calcification of the aneurysm wall. The aneurysm was causing morbid compression of the adjacent pulmonary parenchyma. A final diagnosis of Sacular Aortic aneurysm of upper thoracic aorta with rupture into the left lung was made and thus an urgent surgery was planned. Dacron patch repair of thoracic aortic aneurysm with left upper lobectomy under general anesthesia and cardio-pulmonary bypass (CPB) with total circulatory arrest was arranged. TEE (Agilent SONOS-5500, Philips) was applied for routine cardiac monitoring because the patient was not a good risk for surgery. After completing the cardiac imaging, we attempted to image the descending aorta by leftward rotation of the probe shaft from the midesophageal four chamber view. We observed a pulsatile echogenic mass with a surrounding ring (Fig. 1). At first we thought that it was the abnormal descending aorta. But as we moved the probe up and down, the image disappeared and reappeared intermittently and we contemplated that it might be the spinal cord. The image disappeared because of the interference from the bony vertebral bodies which shadowed the window. We also observed that the pulsatile movement disappeared as soon as the aorta was crossclamped and reappeared at the end of surgery on removing the aortic clamp.

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Fig. 1. TEE showing pulsatile echogenic mass with a ring. CSF = cerebro spinal fluid; TEE = transesophageal echocardiography.

3. Discussion

TEE imaging of the spinal cord has been described previously, however, the image quality is usually poor,1, 2 whereas in our case, it was clear with anatomic details of the spinal cord with visible bilateral ventral and dorsal nerve roots along with a pulsatile spinal nerve root motion. Both the intrathoracic aorta and the esophagus lie adjacently and anterolaterally to the vertebral bodies. The spinal cord is rarely visualized because of the shadowing by the vertebral column, unless it is being searched, and the echocardiographic imaging of the spinal cord is made possible based on the fact that the intervertebral disc serves as an acoustic window. Image can be obtained in the descending aortic view by slight leftward rotation of the probe shaft and slow advancement along the course until it comes across the intervertebral discs.

TEE visualization of spinal cord with pulsatile movement looks like a “bull’s eye” (Fig. 2) with the pulsantance of the iris.² TEE visualization of the spinal cord might help to assess the structural integrity of the spinal cord and associated structures or to identify a hematoma or herniated disc. Voci et al⁴ described a patient with thoracic aortic replacement for acute dissection in which the adequacy of the anterior spinal arterial supply could be shown intraoperatively and they were also able to identify the pulsatile arterial flow in the anterior spinal artery by pulsed wave Doppler. Imaging of the spinal cord was first described by Godet et al¹ and is presently feasible with conventional ultrasonography (USG) equipment in most awake and anesthetized patients. To detect the flow in spinal arteries, which run perpendicularly to the ultrasonography beam, the use of sensitive color Doppler equipment is needed. In our case, we tried to see the spinal artery flow by color Doppler, but this could not be visualized.

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Fig. 2. TEE spinal cord looks like bull’s eye. CSF = cerebro spinal fluid; TEE = transesophageal echocardiography.

Besides spinal artery blood flow, identification of nerve root motion can be regarded as an indirect evidence of spinal cord perfusion. This was shown by Orihashi et al⁵ in dog model in which the loss of nerve root motion was seen immediately after aortic cross clamp. We also observed, in our case, the loss of pulsatile movement of the spinal cord on application of aortic cross clamp and the reappearance of pulsatile spinal cord movement upon declamping of the aorta.

Most of discourses in the literature showed identification of spinal cord image in TEE on incidental monitoring of the descending thoracic aorta (Fig. 3), as in our case. Jens Lohser et al³ identified the spinal cord, when they routinely imaged the descending aorta to rule out iatrogenic aortic dissection after separation from CPB. Spinal cord ischemia in thoracic surgery is an important issue, which may be caused by inadvertent interruption of blood flow to the spinal cord during surgery of the thoracic aorta.⁶

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Fig. 3. Diagram showing the relation of esophagus, descending aorta, and vertebral column, which clarifies the incidental imaging of spinal cord while monitoring for descending thoracic aorta.

The use of TEE in aortic aneurysm surgery is a Class I indication⁷ and it is thought to be the most sensitive means for monitoring cardiac function.⁸ Along with other gadgets, we can use TEE as an additional tool for monitoring the spinal cord. However, it can’t be used during CPB and aortic cross clamping where the spinal cord pulsation is lost, but it can still detect any spinal cord ischemia as soon as aortic cross clamp is removed.

We consider that along with other measures, monitoring of the spinal cord can also be done by intraoperative use of TEE.