Painless Aortic Dissection Presenting as Paraplegia

Abstract

Acute dissection of the aorta can be life-threatening. As a presenting manifestation of aortic dissection, neurologic complications such as paraplegia are rare.

Herein, we report the case of a 51-year-old man who presented with sudden-onset paraplegia and ischemia of the legs, with no chest or back pain. His medical history included coronary artery bypass grafting. Physical examination revealed pulseless lower extremities, and computed tomography showed aortic dissection from the ascending aorta to the common iliac arteries bilaterally. A lumbar catheter was inserted for cerebrospinal fluid drainage, and axillary arterial cannulation was established. With the use of cardiopulmonary bypass, the aortic dissection was corrected, and the previous coronary artery grafts were reattached. The surgery restored spinal and lower-extremity perfusion, and the patient walked unaided from the hospital upon his discharge 5 days later.

Although acute aortic dissection presenting as paraplegia is rare, it should be considered in patients who have pulseless femoral arteries bilaterally and sudden-onset paraplegia, despite no pain in the chest or back. Prompt diagnosis and intervention can prevent morbidity and death.

Acute aortic dissection is the leading cause of death among aortic pathologic conditions. In aortic dissection, the layers of the media are separated by a column of circulating blood with variable proximal and distal extension throughout the length of the aorta.¹

Once acute aortic dissection has occurred, symptoms and signs can be produced by rupture or the occlusion of a major vessel. Pain is the most common and dramatic symptom. Although most patients experience sudden severe pain at the moment of dissection, the dissection very rarely can be painless. In 2% to 5% of patients, paraplegia rapidly develops as the intercostal arteries are separated from the aortic lumen by the dissection.²

We present the unusual case of a patient who presented with neurologic symptoms of aortic dissection but without pain: paresis and paresthesia of the lower extremities were the only symptoms.

Case Report

In May 2009, a 51-year-old man was admitted to our emergency department because of a sudden inability to walk. He had been well until 1 hour before admission, when he noticed the sudden onset of weakness and numbness of the legs. He had no chest, back, or leg pain.

His medical history included coronary artery bypass grafting (2 years before) and hypertension. He was routinely taking antihypertensive drugs. His vital signs were as follows: blood pressure, 160/95 mmHg; pulse, 86 beats/min and regular; respiration rate, 18 breaths/min; body temperature, 36.8 °C; and oxygen saturation on pulse oximetry, 94%. Results of a general physical examination were essentially normal, as were evaluations of the cardiac and respiratory systems. An electrocardiogram did not suggest acute ischemia. Both of the patient's legs were pale, cold, and pulseless. Examination of the nervous system, including higher mental functions, vision, and the cranial nerves, yielded normal findings. Deep tendon reflexes were absent in the patient's legs, and he had motor deficits in the lower extremities. Computed tomography revealed aortic dissection from the ascending aorta to the common iliac arteries bilaterally (Figs. 1 and 2). There was no rupture.

Fig. 1 Computed tomogram shows aortic dissection along the intima of the posterior aorta. F = false lumen; T = true lumen

Fig. 2 Enhanced computed tomogram shows acute DeBakey type I aortic dissection with malperfusion of the left kidney.

The patient underwent emergent surgery. A lumbar catheter was inserted for cerebrospinal fluid (CSF) drainage, with a CSF opening pressure of 16 mmHg and intradural pressure maintained at 10 mmHg. A right axillary arterial cannula and a right femoral venous cannula were inserted before sternotomy, as a precaution; however, cardiopulmonary bypass (CPB) was not begun. The remarkably enlarged and hardened ascending aorta was approximately 6 cm in diameter. The ascending aortic dissection occupied the right side of the mediastinal space; it was extremely adhesive to the adjacent tissues and structures, including the pulmonary artery, the atria, and the right pleural membrane. We gently dissected the pericardial adhesions. The coronary artery bypass grafts (2 radial arteries and the left internal mammary artery) were carefully dissected from the surrounding tissues and adhesions. The right atrium was freed. A 2-stage single venous cannula was extended from the femoral vein to the right atrium. Cardiopulmonary bypass was instituted, and the patient's body temperature was cooled to 24 °C. The ascending aorta was cross-clamped, and cardiac arrest was established with use of cold crystalloid cardioplegic solution, administered antegrade and retrograde, with topical cold saline irrigation. Flow was decreased to a rate of 500 to 600 mL/min (8–10 mL/kg/min) at 24 °C rectal temperature. The brachiocephalic and left common carotid arteries were individually clamped with soft vascular clamps, and the aortic cross-clamp was released. Intermittent retrograde cold-blood cardioplegic solution with terminal warm-blood solution was used for myocardial protection. During CPB, the ascending aorta was longitudinally opened and meticulously inspected. A large dissection was observed above the right and noncoronary commissure. An intimal-entry tear in the proximal ascending aorta extended from the aortic root to the distal part of the aortic arch; in addition, the proximal anastomosis of the radial artery grafts included the anterior and right lateral wall of the false lumen at the ascending aorta. The aortic valve was mildly regurgitant and free from dissection.

Glue was applied to fill the entire space between the dissected fragile layers of the distal aorta. A 28-mm HEMASHIELD PLATINUM woven double-velour vascular graft (MAQUET GmbH & Co. KG; Rastatt, Germany) was anastomosed to the aortic arch proximally by means of the open anastomosis technique while low-flow perfusion through the axillary artery continued. After completion of the distal anastomosis, the flow through the axillary artery cannula was gradually increased as the soft clamps on the brachiocephalic and left common carotid arteries were released. Air was removed from the vessels and grafts, which were then filled with blood, and the distal graft was cross-clamped. A normal flow rate was achieved through the axillary artery cannula, and commissural resuspension was performed because of the mild regurgitation of the aortic valve. Subsequently, rewarming was begun in accordance with the time necessary for proximal repair, and the proximal Dacron graft was anastomosed to the aorta in a supracoronary position (Fig. 3). In addition, Teflon felt was attached to the aortic wall with continuous sutures on its outer boundary. Finally, the radial artery grafts were reimplanted on the Dacron grafts. Air was removed from the grafts, and the cross-clamp was released from the proximal graft.

Fig. 3 Drawing shows replacement of the supracoronary ascending aorta with a Dacron graft. CxOM = circumflex obtuse marginal artery; RCA = right coronary artery

The CPB and aortic cross-clamping times were 138 and 83 minutes, respectively. The patient was weaned from CPB and admitted to the intensive care unit with low-dose inotropic support. He was extubated 10 hours after the operation, and his intensive care unit stay lasted 23 hours. The CSF drain was withdrawn 2 days after the operation. The patient's lower-extremity malperfusion improved, indicating that flow had been reestablished within the true lumen. During the uncomplicated postoperative course, his paraplegia progressively improved, and he walked unaided from the hospital upon discharge on the 5th postoperative day. On postoperative computed tomography, the lower-extremity malperfusion was corrected; however, malperfusion of the left kidney continued (Fig. 4). As of February 2012, the patient was well and asymptomatic.

Fig. 4 Postoperative enhanced computed tomogram shows restored perfusion to the lower extremities but not to the left kidney.

Discussion

Acute aortic dissection is a sudden event in which blood leaves the normal aortic channel through a usually discrete point in the intimal tear and rapidly dissects the inner layer of media from the outer layer, producing a false channel. The extent and nature of the involvement of the branches, including the coronary and iliac arteries, are important determinants of the clinical syndrome with which the patient presents. These include confusion or coma (indicating cerebral malperfusion or stroke); electrocardiographic changes, or elevated creatine kinase–MB fraction or cardiac troponin levels (indicating cardiac malperfusion or myocardial dysfunction); loss of pulses, sensory function, or motor function (iliofemoral or brachiocephalic malperfusion; creatinine elevation or low urine output (renal malperfusion); paraplegia (spinal malperfusion); or abdominal tenderness, bowel ischemia, or elevated liver enzymes (mesenteric malperfusion).³

In 2% to 5% of patients, paraplegia develops as the intercostal arteries are separated from the aortic lumen by dissection.² The sudden onset of weakness and paresthesia (paraplegia), as in our patient, can result from temporary obstruction of the spinal arteries and interruption of blood flow to the spinal cord, especially to crucial zones such as the lower thoracic and lumbar segments.⁴ Accordingly, ischemia of the spinal cord contributes to the neurologic syndrome of aortic dissection. Aortic dissection that presents primarily as paraplegia is rare.⁵ Painless acute aortic dissection in which paraplegia is the only presenting symptom is even rarer.^6,7

Aortic dissection presenting as a neurologic syndrome has been previously reported. In 1944, Weisman and Adams⁸ described 38 cases of ischemic necrosis of the spinal cord from fatal aortic dissection. They proposed that paralysis and anesthesia occurred upon occlusion of the intercostal and lumbar arteries by the dissection of the aortic wall, with consequent infarction of the spinal cord. In 1986, Gerber and colleagues⁴ described the cases of 3 patients who presented with painless acute neurologic syndromes from an aortic dissection. In 1988, Rosen⁹ reported on a patient whose only symptom was transient ischemic myelopathy.

Whereas dissection of the aorta can be painless and at times unknown to the patient, pain is typically the most common and dramatic symptom. Many individual cases of painless aortic dissection have been reported. The prevalence of painlessness in aortic dissection has varied in different series. In an early and chiefly postmortem series, predominantly of chronic dissection of the aorta, Baer and Goldburgh¹⁰ reported that 24 of 44 patients with aortic dissection had no recorded history of pain. In a large review, Hirst and associates¹¹ reported that 57 of 409 patients whose symptoms were recorded did not report pain. Our patient presented with acute paraplegia, with no history or evidence of trauma. Because of the pulseless bilateral femoral and distal arteries, we primarily suspected a vascular pathologic condition or aortic dissection.

Organ malperfusion caused by aortic dissection is associated with substantial postoperative morbidity and death. In 2007, Geirsson and colleagues³ evaluated the significance of malperfusion syndromes in 221 consecutive patients who had acute type A aortic dissection. Spinal malperfusion was present in 5 patients (2.3%). One patient died in the hospital; the other 4 survived and were all discharged with paraplegia. The overall surgical mortality rate in that study was 12.7%. The subgroup of patients with any malperfusion syndrome had an in-hospital mortality rate of 30.5%, versus 6.2% in patients with no malperfusion.

If aortic dissection produces spinal cord ischemia, the condition obviously requires rapid treatment. Dissection of the aorta carries a very poor prognosis unless it is treated immediately, so it is very important to differentiate this condition from other spinal vascular pathologic phenomena that produce paraplegia and are painless. Complete recovery from paraplegia caused by aortic dissection has been reported after rapid recognition of the condition and timely intervention.

Clinically, ischemia of the lower extremities is most commonly recognized when bilateral or unilateral femoral pulses are lost. Bossone and coworkers¹² reported that one third of patients with type A dissection had pulse deficits and that 29% of those patients had limb ischemia. In a patient with aortic dissection and lower-extremity ischemia, one option is to repair the aorta to reestablish flow within the true lumen and restore flow to the lower extremities. Fann and co-authors¹³ found that approximately 90% of peripheral pulse deficits caused by dissection could be restored by repairing the thoracic aorta. However, in a series reported by Elefteriades and coworkers,¹⁴ 25% of patients who underwent aortic graft replacement still required subsequent fenestration for persistent lower-extremity ischemia. An alternative to aortic repair is percutaneous balloon fenestration. Stent-grafting of the aorta to compress the false lumen can also restore blood flow to the distal aorta and lower extremities. However, if these techniques are unavailable or unsuccessful, open procedures should be performed. Open techniques to alleviate extremity malperfusion include cross-femoral bypass for unilateral ischemia, axillary–bifemoral bypass for bilateral involvement, and femorofemoral bypass if the dissection extends into the femoral bifurcation.¹⁵

In our patient, the true lumen of the abdominal aorta was interrupted by the false lumen. We think that the appearance of the interruption on computed tomography was because of a flap-closure effect of the dissected segment. The rapid restoration of flow into the true lumen may have improved perfusion of the spinal cord and diminished the lower-limb ischemia—perhaps indicating satisfactory flow from the remaining intact branches of the intercostal arteries, iliolumbar artery, and lateral sacral arteries inside the true lumen.

In any patient with aortic dissections or aneurysms, we prefer to cannulate the axillary artery. In this patient, axillary artery cannulation rapidly improved flow in the true lumen and might have stopped the false lumen from compressing the spinal arteries. After CPB, the patient's lower-extremity perfusion improved, and the distal pulses returned. Had the malperfusion persisted after the operation, we would have considered fenestration. In addition, the immediate preoperative drainage of the patient's CSF could have contributed to his complete neurologic recovery. In our opinion, the value of CSF drainage in the resolution of paraplegia is directly related to its implementation before irreversible ischemic damage occurs.

In conclusion, we report a case of painless aortic dissection that presented as sudden-onset paraplegia. The patient fully recovered after emergent surgery and had no neurologic deficits. Although painless paraplegia in association with acute aortic dissection is rare, aortic dissection should be considered in the differential diagnosis of patients who present emergently with acute-onset paraplegia (whether painful or painless) and pulseless femoral arteries bilaterally.