Cardiovascular Board Review

A young man with acute weakness of his right arm

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A 42-year-old man was working at his computer when he suddenly became disoriented and lightheaded, had difficulty concentrating, and could not move his right arm. He could walk without difficulty, but he had a tingling sensation in his right leg. He did not lose consciousness or have any associated palpitations, chest pain, shortness of breath, nausea, vomiting, headaches, or visual changes.

He called 911, and an ambulance arrived 15 minutes later. By that time his symptoms had started to resolve. Now, in the emergency department, his only residual symptom is mild numbness of his right arm and shoulder.

Until now he has been healthy except for a history of dyslipidemia. He takes no prescription or over-the-counter medications and has no drug allergies. He has smoked one pack of cigarettes daily for the past 28 years and also smokes marijuana several times each month. He drinks alcohol occasionally. His family has no history of stroke, premature coronary artery disease, or sudden cardiac death.

INITIAL EVALUATION

His heart rate is 88 beats per minute, blood pressure 142/82 mm Hg, and blood oxygen saturation 98% while breathing room air. He is alert and in no acute distress and answers questions appropriately.

His breathing sounds are normal, without crackles or wheezes. His heart has normal first and second sounds, a normal rate and rhythm, and no extra sounds or murmurs. His abdomen is normal. His extremities are warm and well perfused with normal peripheral pulses and no edema.

On neurologic examination, his cranial nerves and visual fields are normal, and his strength is normal in all muscle groups except for the right upper arm, which is slightly weaker than the left when tested against resistance. Reflexes and response to light touch and pinprick are normal.

His serum chemistry levels, renal function, and blood counts are normal. His total cholesterol level is 155 mg/dL, high-density lipoprotein cholesterol 38 mg/dL, low-density lipoprotein cholesterol 108 mg/dL, and triglycerides 1,286 mg/dL. Electrocardiography is normal with sinus rhythm at a rate of 74.

Magnetic resonance imaging (MRI) of the head and neck with magnetic resonance angiography (MRA) of the intracranial and extracranial vessels is performed. Diffusion-weighted images show a hyperintense lesion in the left insular cortex, consistent with an infarct in the distribution of a branch of the left middle cerebral artery. There is no intracranial hemorrhage. All intracranial and extracranial major vessels are patent, and no stenoses are seen.

DIFFERENTIAL DIAGNOSIS

1. Which is the most likely cause of this patient’s stroke?

  • Vertebral or carotid atherosclerosis
  • Cervical arterial dissection
  • A hematologic disorder
  • Cocaine abuse
  • Cardiac embolism

Atherosclerosis

Although 85% of all strokes are ischemic, and most ischemic strokes are caused by occlusive atherosclerosis of large vessels, most ischemic strokes occur in patients older than 65 years. In patients younger than 55 years, only about 10% of strokes are caused by large-vessel atherosclerotic disease, thus lowering the initial probability that this is the cause of our patient’s stroke.1 Furthermore, our patient’s MRA study showed no carotid artery stenoses, which effectively eliminates this as the cause of his stroke, as the diagnostic sensitivity of MRA for detecting carotid stenosis is approximately 97%.

Cervical arterial dissection

Cervical arterial dissection causes up to 20% of strokes in patients younger than 45 years.2 Dissections usually involve the extracranial portion of the vessel, and involve the internal carotid arteries at least three times as often as the vertebral arteries. In many cases the dissection is preceded by mild neck trauma, which may be as minor as a vigorous cough or turning of the head.

Typical features of dissection include neck pain, headache, and Horner syndrome, followed minutes to hours later by symptoms of ocular or cerebral ischemia, usually a transient ischemic attack rather than a stroke. Neurologic symptoms are most commonly due to thrombosis at the dissection site with distal embolization. Inherited disorders that are associated with increased risk of cervical arterial dissection include Ehlers-Danlos syndrome type IV, Marfan syndrome, autosomal-dominant polycystic kidney disease, osteogenesis imperfecta type I, and fibromuscular dysplasia.3 MRA and computed tomographic angiography are the diagnostic tests of choice.

Our patient’s symptoms began suddenly, without a history of trauma or neck pain, making arterial dissection less likely as the cause of his stroke. No dissection was seen on MRA, which also minimizes its likelihood.4

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