Aortic Dissection Presenting Primarily as Acute Spinal Cord Damage: A Case Report and Literature Review

Abstract

Acute aortic dissection is a rare, life-threatening condition. Clinical manifestations generally include the acute onset of severe chest or back pain. Aortic dissection presenting with signs and symptoms of acute spinal cord damage is the most severe complication and is particularly rare. This paper reports a case of aortic dissection in a 50-year-old man with a 10-year history of hypertension manifesting as acute spinal cord damage (bilateral lower extremity weakness and loss of all types of sensation), acute skeletal muscle ischaemic necrosis with increased levels of creatine kinase, and acute kidney failure with increased levels of serum creatinine and decreased glomerular filtration rate. The patient refused surgical treatment. His clinical condition progressively worsened and he died 3 days later. This case indicates the importance of considering aortic dissection in patients presenting with acute spinal cord damage, acute skeletal muscle necrosis or acute kidney failure, which may allow early diagnosis and reduce the mortality rate.

Introduction

Aortic dissection (AD) is a rare, life-threatening condition with a worldwide mortality rate of 3.2 per 100 000 people, per year. ¹ It commonly presents initially with the acute onset of severe chest, abdominal or back pain. Clinical manifestations presenting primarily as acute onset of paraplegia, acute skeletal muscle necrosis or acute kidney failure with painless AD are particularly rare, ¹ with few reports in the literature. AD characterized by the acute onset of paraplegia, oliguria or muscle pain is often misdiagnosed as various other conditions, such as acute myelitis or spinal haemorrhage, acute kidney failure, polymyositis or even multiple organ failure of unknown cause, leading to a delay in diagnosis and an increase in mortality. A rare case of AD presenting primarily as acute spinal cord damage, acute kidney failure and acute skeletal muscle necrosis is presented here.

Case Report

A 50-year-old man with a 10-year history of hypertension was admitted to the First Affiliated Hospital of Liaoning Medical College, Jinzhou, China, in October 2010, with acute paraplegia of the lower extremities. In addition, the patient demonstrated loss of all types of sensation in the lower extremities, bladder and bowel dysfunction, and sudden onset of pain in the muscles of the lower limbs, suggesting transverse spinal cord damage resulting from anterior and posterior spinal artery occlusion. The bilateral lower extremity weakness worsened rapidly, muscle strength reaching its lowest value within 1 h. He developed oliguria and whole-body oedema within 24 h of admission. The patient had a history of overtiredness before admission, which may have contributed to the onset of AD.

On physical examination, the patient's systolic/diastolic blood pressures were 180/110 mmHg and muscle power in both lower extremities was grade 0 on a scale of 0 – 5 (0, no contraction; 5, normal power). The dorsalis pedis artery pulse was not palpable and skin temperature in both lower limbs was slightly lower than normal. The patient's family had ascribed his low skin temperature to the cold weather.

Laboratory investigations showed the following mean values (reference range): white blood count of 5240 /mm³ (4000 – 10 000 /mm³), haemoglobin 12.2 g/dl (12 – 16 g/dl), haematocrit 32.4% (40 – 50%), platelet count 80 × 10³ /mm³ (100 – 300 × 10³ /mm³), blood urea nitrogen 17.6 mg/dl (7 – 20 mg/dl), serum creatinine 560 μmol/l (44 – 133 μmol/l), creatine kinase (CK) 1007 U/l (30 – 170 U/l), glomerular filtration rate 13 ml/min (110 – 140 ml/min), CK-MB isoenzyme 12 U/l (0 – 25 U/l) and troponin < 0.03 ng/ml (0 – 0.03 ng/ml).

Ultrasonography and magnetic resonance imaging (MRI) were conducted to confirm the diagnosis of AD and to detect the site, size and number of aortic tears, and the presence of true or false lumens and intimal flap. On ultrasonography the aortic root and ascending aorta were seen to be widened. An AD was manifested by the presence of a true lumen and a false lumen in the thoracic aorta, the two lumens being divided by an intimal flap (Fig. 1A). An enlarged left ventricle was also seen (Fig. 1B). MRI revealed a true and a false lumen in both the thoracic and the abdominal aorta, with deformation of the true lumen and thrombus in the false lumen (Fig. 2). MRI of the spinal cord revealed a long T₂ signal at the thoracic level (Fig. 3). Using the classification of DeBakey et al., ² the AD was designated as type I because of the site of the tear and the extent of the AD.

FIGURE 1:

Representative ultrasonographic images from the present case of a 50-year-old man with thoracic aortic dissection: (A) showing a widened aortic root and ascending aorta, with a dissection manifested by the presence of a true lumen (TL) and a false lumen (FL) separated by an intimal flap (AO, aorta); and (B) showing an enlarged left ventricle (LV)

FIGURE 2:

Representative magnetic resonance images from the present case of a 50-year-old man showing: (A) thoracic aortic dissection; and (B) the abdominal aorta. Thrombus is seen in the false lumen (FL) and there is a corresponding deformation in the true lumen (TL)

FIGURE 3:

Representative magnetic resonance image from the present case of a 50-year-old man with aortic dissection, showing a long T₂ signal at the thoracic level

The patient and his family refused surgical treatment. The clinical signs worsened, with progressively increasing chest pain, increased perspiration, growing confusion and decreasing blood pressure despite active medical treatment. The patient died on the third day after admission.

Discussion

A systematic literature search of the PubMed database using the key words ‘aortic dissection', AND ‘paraparesis' OR ‘paraplegia' OR ‘spinal cord' was carried out for relevant articles published in English between January 2000 and December 2011. This yielded 339 articles, in which 16 cases of AD presenting as acute spinal cord damage were reported. The abstract was read to make an initial decision about suitability for inclusion in the literature review. The decision regarding selection from the 339 articles mainly related to whether the article reported a case that was of a rare or uncommon presentation and had life-threatening symptoms, as well as the number of cases that the article included and the method of diagnosis. Duplicate literature citations of the same cases were also removed. This process resulted in five articles being retained in the current literature review.^3–7

The typical clinical manifestations of AD are severe chest, abdominal or back pain. AD presenting as acute spinal cord damage is a rare but serious complication. ³ The mortality rate is increased if the diagnosis is delayed. In the case presented here, the patient did not complain of pain but presented with paraplegia; this is consistent with previous reports of severe neurological complications (such as paraplegia, loss of some or all types of sensation and difficulty in micturition) occurring in patients with AD due to spinal cord ischaemia.^4–8

In 1944, Weisman and Adams ⁹ first reported patients with spinal cord ischaemia resulting from occlusion of the intercostal and lumbar arteries in AD, and proposed that paraplegia in AD is attributable to vascular obstruction. Ischaemia usually results from obstruction of the segmental medullary arteries that supply the anterior spinal artery which, in turn, supplies the spinal cord (along with the posterior spinal artery derived from the vertebral arteries and the spinal branches derived from the intercostal and lumbar arteries). ¹⁰ The anterior spinal artery is also supplied by the radicular arteries, especially in the T10 – T12 region, where blood flow is normally lower than in other regions, making the spinal cord in the T10 – T12 region more reliant on the supply from the anterior spinal artery and more sensitive to insufficient blood flow. ¹¹ When AD occurs, obstruction of the aortic branches occludes the blood supply to the spinal cord and other organs, leading to insufficient tissue perfusion and subsequent ischaemia. Because of the anatomical arrangement of the arterial supplies, the clinical symptoms of spinal cord ischaemia would be expected to occur after mesenteric ischaemia. ¹² However, the spinal cord is not as tolerant of ischaemia as the mesentery, ¹² so the symptoms of spinal ischaemia are much more severe than those of mesenteric ischaemia. The clinical manifestations of AD are, therefore, characterized by abdominal pain as an initial complaint but with acute paraplegia as the main manifestation. ¹² In the present case, however, the patient did not complain of abdominal pain as an initial symptom, which might be explained by the greater number of vascular branches in the mesentery than in the spinal cord. Instead, the patient presented with typical symptoms of transverse spinal cord damage complicated by acute renal failure and acute ischaemic necrosis of skeletal muscle, suggestive of anterior and posterior spinal artery damage. ¹³

Spinal cord injury from AD may be difficult to distinguish from other spinal cord diseases, such as acute transverse myelitis, vascular diseases of the spinal cord and spinal vascular malformations. It has been reported that the onset of paraplegia in AD is typically abrupt, progressing over only minutes or possibly a few hours. ¹⁴ Compared with AD, transverse myelitis progresses relatively slowly and there are no signs of any other organs being affected. Haemorrhage resulting from vascular disease of the spinal cord presents with sudden onset, bilateral lower limb paraplegia and severe chest or abdominal pain, and can be particularly difficult to distinguish from the spinal ischaemia induced by AD. The former, however, usually does not affect multiple organs, whereas AD is usually complicated by acute renal failure, decreased pulse in the dorsalis pedis artery, shock syndrome, platelet reduction and an elevated level of CK. Moreover, a higher T₁ signal revealed by spinal MRI indicates a diagnosis of haemorrhagic vascular disease of the spinal cord, while a lower T₁ signal means ischaemic vascular disease of the spinal cord, including AD. In patients with spinal vascular malformations, the typical presentation is acute onset and the limbs are affected, intermittent claudication being the main manifestation. ¹⁵ MRI reveals the vascular steal phenomenon, in which oxygenated arterial blood shunted through the vascular malformation causes the surrounding normal parenchyma to become hypoperfused. Spinal angiography can help in reaching the correct diagnosis.

In the present case report, the thoracic and abdominal regions of the aorta were seen on ultrasonography and MRI to be divided into a true and a false lumen by an intimal flap, confirming the cause of spinal ischaemia. The pathogenesis of AD is mainly associated with degenerative changes in the media, often due to atherosclerosis, Marfan's syndrome or hypertension, or inflammatory injuries of the media. ¹⁶ Hypertension is the most common predisposing factor for AD.^17,18 The main characteristic of hypertension in AD is that blood pressure remains elevated even when shock develops. In the present case, the patient had a history of hypertension. Chronic high blood pressure can induce hypertrophy and degeneration of the smooth muscle cells in the artery wall, resulting in necrosis in the media. A history of hypertension is commonly present, but systolic blood pressure in AD of Stanford classification type A has been found to be < 150 mmHg in 64% of patients, whereas 71% of patients with AD of type B present with a systolic blood pressure of  150 mmHg; ¹⁹ blood pressure is often elevated when the onset of AD is acute. ²⁰

Management of AD includes pain management, controlling the intimal tear and reducing blood pressure. ²¹ Systolic blood pressure should be < 100 mmHg, with a mean blood pressure of 60 – 70 mmHg. Once the clinical condition of the patient is stable, ultrasonography, computed tomographic angiography and MRI can be performed to confirm the diagnosis of AD and to decide whether surgery is indicated. Surgical repair is usually considered in patients with DeBakey type I or II AD, especially when complicated by incomplete closure of the aorta.^22,23 In patients with DeBakey type III AD, vascular grafting of the descending aorta is required. ²⁴ For patients in whom multiple organs are affected, re-establishment of the blood circulation in the intercostal, renal or superior mesenteric arteries should be considered. ²⁵ In the present case, the patient was in a serious clinical condition with progressively worsening signs and symptoms; his family members chose to cease treatment and the patient died shortly after discharge from hospital. The cause of death in AD is usually rupture of the aortic aneurysm, leading to shock syndrome and cardiac tamponade.

In conclusion, the clinical features of AD presenting as acute spinal injury are usually complete transverse spinal cord damage without a history of infection and the onset of paraplegia within 1 – 2 h, accompanied by hypertension, varying degrees of chest or abdominal pain, shock syndrome with high blood pressure, unexplained blood in the urine, acute renal failure, high levels of serum enzymes, anaemia, a progressive reduction in platelet count and a reduction in the dorsalis pedis artery pulse. Emergency physicians should not rule out the possibility of AD in the differential diagnosis of acute myelitis, vascular myelopathy or spinal cord compression.