Acute aortic dissection presenting as hemifacial weakness

Sandy M. Green, MD, Massachusetts General Hospital, Boston, MA; and Mahender Macha, MD, University of Michigan Medical Center, Ann Arbor, MI

Published Online: April 7, 2008 - 1:46:28 PM (CDT)

Thoracic aortic dissection is an uncommon condition with catastrophic consequences; it involves a tear in the aortic intima with dissection of blood into the media or adventitia. Although the exact etiology of thoracic aortic dissection is unknown, several factors are thought to predispose people to this condition, including age, chronic hypertension, cystic medial necrosis, and trauma. Despite having an uncertain etiology, 96% of acute thoracic aortic dissections traditionally have been thought to be characterized by a combination of three key clinical features¹:

1. Acute onset of chest pain that is tearing or ripping in character;
2. Mediastinal and/or aortic widening on a chest radiograph; and
3. Variation in pulse or blood pressure (BP) between the extremities or carotids.

Patients with thoracic aortic dissection who present without any of these three cardinal features have been reported, as well as some patients who present with only focal neurologic signs.^2-9 Lack of awareness of these atypical presentations may lead to a delay in diagnosing this rapidly fatal condition. We report the case of an acute type A dissection involving the ascending aorta in a patient who presented with symptoms normally associated with stroke.

CASE PRESENTATION

A 46-year-old African American woman with a history of chronic hypertension presented to the emergency department with a 2-day history of left facial weakness and numbness, tearing from the left eye, and an inability to completely close her left eye. She reported that the onset of symptoms was sudden, and her condition had been gradually improving. The patient denied any chest pain, shortness of breath, peripheral weakness or numbness, changes in visual acuity, or any other focal neurologic symptoms. She also denied any preceding illnesses but noted that 1 month earlier she lost her balance on one occasion and fell. She was taking hydrochlorothiazide for hypertension and conjugated estrogen (Premarin) for menopausal symptoms. Her family history was significant for cerebrovascular accidents in her mother and her sister when they were in their 60s.

Figure—MRI/MRA of the thorax showing the involvement of the ascending aorta, aortic arch, carotids, and descending portion of the thoracic aorta. The arrows point to the dissection itself.

The physical examination was notable for a heart rate of 65 beats/min and a BP of 110/61 mm Hg that was equal in both arms. Cardiac examination showed no rubs, murmurs, or gallops, and first and second heart sounds were normal. The lungs were clear to auscultation. Neurologic examination revealed normal muscle strength and sensation in the upper and lower extremities with 2+ deep tendon reflexes. Decreased sensation was noted on the left side of the patient?s face, with possible central deficit in the distribution of the left facial nerve. A stroke was suspected, and carotid/vertebral ultrasonography was performed. The ultrasound showed right vertebral flow reversal, occlusion of the right external carotid artery, low flow in the common carotid artery, and possible occlusion of the right subclavian artery. A chest radiograph was obtained and showed no abnormalities.

The patient underwent a magnetic resonance imaging study of the brain with angiography of the head and neck (MRI/MRA). This demonstrated an early infarct of the right insular cortex. No significant aneurysm or stenosis of the carotids or vertebrals was noted but a linear intraluminal signal was seen within the aortic arch, with possible extension into the innominate and the right proximal common carotid artery suggesting aortic dissection.

MRI/MRA of the chest revealed an intimal flap starting at the level of the sinotubular junction and extending into the ascending aorta aortic arch and descending portions of the thoracic aorta without apparent involvement of the aortic valve (Figure). The flap extended into the brachiocephalic artery up to the level of the takeoff of the vertebral and common carotid arteries on the right. It did not extend beyond the level of the hiatus into the abdomen. Transesophageal echocardiography was performed to confirm the diagnosis of aortic dissection and to assess the involvement of the aortic valve. No significant aortic regurgitation or root dilation was found.

The patient was urgently taken to the operating room. The ascending aorta and proximal arch were replaced with a Dacron graft, and the aortic valve was resuspended at the level of the sinotubular ridge after it was confirmed that the tear did not extend to the valve annulus proximally. The patient did well postoperatively and had no residual neurologic or cardiac symptoms.

DISCUSSION

The incidence of thoracic aortic dissection is only 3 per 100,000 individuals.¹⁰ If not recognized and treated quickly, aortic dissection can be fatal. Aortic dissection, when not surgically treated, has a mortality rate that is estimated to be about 1% per hour, so neglect of atypical or painless presentations of this condition can lead to high rates of morbidity and mortality.^11,12

Symptoms and signs
Aortic dissection is classically described as presenting with the acute onset of severe chest, back, or abdominal pain that is tearing or ripping in character. In early studies, this pattern of pain was found in 90% of cases of aortic dissection; fewer than 10% of patients presented with atypical symptoms.^13,14 When this pain was combined with other typical features of aortic dissection, such as mediastinal widening on chest radiography or peripheral pulse defect, it was historically thought that nearly 96% of dissections could be clinically diagnosed.¹

Atypical presentations
Atypical symptoms have been thought to be rare, but several studies suggest that such presentations may be more prevalent than first thought. One retrospective study of 464 patients with aortic dissection from the International Registry of Acute Aortic Dissection showed that only 72.7% of all dissections presented with a sudden onset of chest pain (78.9% in type A dissections and 62.9% in type B dissections); 61.6% with mediastinal widening (62.6% of type A dissections and 56% of type B dissections); and 15.1% with peripheral pulse defect (18.7% of type A dissections vs 9.2% of type B dissections).¹¹ As a result of the prevalence of nonclassic presentations, such as syncope, cerebrovascular accident, or atypical pain, the authors concluded that classic signs and symptoms are often absent. In addition, in a small retrospective study of 235 patients with aortic dissection at a large academic referral center, the diagnosis was missed during the initial clinical evaluation in 38% of confirmed cases and not made until postmortem examination in 28% of cases.¹²

A variety of atypical and painless presentations of aortic dissection has been reported in the literature. Atypical symptoms usually have a neurologic or cardiac origin. Extremity weakness, paralysis, gastrointestinal bleeding, sensory-motor deficits, syncope, and dyspnea have all been reported, often without pain or any other classic finding. In these cases of "painless" dissection, often the only factor predisposing the physician to suspect dissection is the presence of long-standing hypertension, which is found in over 78% of cases. In the absence of classic signs and symptoms, the diagnosis of aortic dissection is challenging to make.

Noninvasive imaging
The difficulties in diagnosing aortic dissection are compounded by the previous dependence on a patient?s presenting symptoms and a physician?s high index of suspicion. With the advent of new imaging technology, such as MRA, echocardiography, and computed tomography (CT) scanning with angiography, and the added expertise in their use, aortic dissections now can be detected despite unusual presentations.^14,15

In our patient, the high probability of a dissection based on the MRI/MRA images of her head and neck in conjunction with the treating physician?s high clinical suspicion led to a chest MRI/MRA being acquired despite the patient?s unusual presentation. Chest MRI/MRA has a high degree of sensitivity and specificity for identifying type A dissections, with some studies reporting sensitivities and specificities as high as 100%.^15,16 Without the presence of a high degree of clinical suspicion and the judicious use of imaging, this patient?s dissection might have gone undetected.

Additional imaging modalities, such as echocardiography (both transthoracic and transesophageal) and CT scanning have been shown to be highly effective in making and confirming the diagnosis of thoracic aortic dissections, with sensitivities and specificities slightly lower than MRI/MRA. Chest radiography has been found to be the worst imaging modality across all clinical presentations, with less than 40% of patients in some series demonstrating any radiographic abnormality. The limited specificity and infrequent appearance of abnormalities on chest radiography make it nondiagnostic.¹⁷

CONCLUSION

Acute thoracic aortic dissection is a catastrophic condition that leads to high rates of morbidity and mortality if not caught early. Although abrupt sharp or tearing pain, mediastinal widening on chest radiography, and pulse deficits are observed in the majority of cases, our case report demonstrates that patients with aortic dissections may present with neurological symptoms alone. This stresses the need for physicians to maintain a high index of suspicion for aortic dissection and make judicious use of imaging in any patient presenting with an acute onset of neurologic symptoms, regardless of the presence of chest pain or other classic signs of aortic dissection.

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