Abstract
Most strokes are caused by the mechanisms already described, i.e., cardioembolism, atherosclerosis, and small-vessel disease, but at least 20% are due to other mechanisms. This is even more likely in younger patients (< 40 years old), and in older patients without atherosclerotic risk factors. The following is our approach to stroke diagnosis in younger patients and older patients in whom the cause remains obscure after the usual evaluation of the heart for sources of emboli and cerebral vessels for atherosclerosis, or who continue to have strokes despite standard treatment with antithrombotic agents and control of risk factors.
Most strokes are caused by the mechanisms already described, i.e., cardioembolism, atherosclerosis, and small-vessel disease, but at least 20% are due to other mechanisms. This is even more likely in younger patients (< 40 years old), and in older patients without atherosclerotic risk factors. The following is our approach to stroke diagnosis in younger patients and older patients in whom the cause remains obscure after the usual evaluation of the heart for sources of emboli and cerebral vessels for atherosclerosis, or who continue to have strokes despite standard treatment with antithrombotic agents and control of risk factors.
Causes
Extracranial Causes
1. Arterial dissection (carotid, vertebral, aortic) – see Chapter 8
Can be traumatic or spontaneous.
Inquire about personal or family history of arterial dissections (can be in other vessels in the body such as aortic or renal arteries), collagen vascular diseases (such as Ehlers–Danlos type 4 or Marfan syndrome).
Ask about any recent blunt trauma to head or neck, chiropractic manipulation of the neck, or sudden occupational/accidental movements of the head/neck.
2. Aortic arch atheroma or unstable non-stenotic carotid plaque
Vessel or cardiac imaging should always include the aortic arch.
Higher-grade aortic atheromas (grades 3–5) are associated with increased risk of strokes. Grading is based on plaque thickness and sessile versus mobile nature of the plaque.
Some carotid bifurcation plaques causing < 60% stenosis can still embolize. How to identify and manage them is still uncertain.
3. Paradoxical embolus of venous clot through a patent foramen ovale (PFO) or pulmonary arteriovenous malformation (AVM) – see Chapter 8
Echocardiogram or TCD ordered with bubble study help make the diagnosis.
Association of a PFO with an atrial septal aneurysm may increase the risk of initial or recurrent strokes, but this is still debated.
Larger PFO size and larger right-to-left shunts may also increase the stroke risk.
Pulmonary AVMs are best visualized on a CT of the chest with contrast.
Uncommon but can be fatal.
Usually occurs iatrogenically as a result of central venous catheter placement, surgical procedures, ventilator-induced barotrauma, decompression sickness, or aorto-esophageal fistula.
In the acute setting, multiple hypodensities can be seen in the parenchyma and intracranial vessels on non-contrast head CT.
There is an increased trend towards treating air embolism with hyperbaric chambers in capable centers.
5. Fibromuscular dysplasia (FMD) of extracranial carotid artery
More common in middle-aged women with hypertension.
Can lead to embolism if associated with aneurysm or web formation.
Treatment includes antiplatelets, anticoagulation, or less commonly endovascular stenting or vascular surgery.
Intracranial Causes
1. Cerebral venous sinus thrombosis – discussed in Chapter 11
2. Vasculitides (giant cell arteritis, primary CNS angiitis, polyarteritis nodosa, Takayasu aortitis, other collagen vascular diseases)
Commonly associated with insidious headaches.
Relapsing in nature, with imaging revealing strokes of different ages.
Vascular imaging may reveal beading of distal intracranial vessels.
CSF analysis usually has an inflammatory profile.
Treatment is with antiplatelets, steroids, and long-term immunosuppressive therapies.
3. Infection-related vasculopathies (e.g., HIV, VZV)
“Puff of smoke” in Japanese, for the classic appearance produced by the brittle collaterals found on conventional angiogram.
Refers to the progressive narrowing of the terminal ICAs and proximal branches of the arteries making up the circle of Willis.
Affects Asian populations predominantly, and women more than men.
Moyamoya syndrome (as opposed to moyamoya disease) is associated with predisposing conditions such as NF-1, SLE, Down syndrome, or sickle cell disease. It is important to test for these conditions in a patient with suspected moyamoya. Advanced atherosclerosis can also lead to a moyamoya syndrome.
Treatment usually includes antiplatelets and, in advanced cases, superficial temporal artery (STA)–MCA bypass or revascularization procedures based on angiogenesis such as encephalo-duro-arterio-synangiosis (EDAS) or encephalo-duro-arterio-myo-synangiosis (EDAMS).
5. Intravascular lymphoma
6. Reversible cerebral vasoconstriction syndrome (RCVS)
Classically associated with thunderclap headaches.
Risk factors include pregnancy or postpartum, use of sympathomimetics, immunosuppressants (e.g., FK508, cyclophosphamide), SSRIs, triptans or ergotamines.
May see beading of vessels during attack.
Usually a monophasic course.
CSF is often normal.
Treatment includes calcium channel blockers such as nimodipine or verapamil (given IV, PO, or IA), IV magnesium. There is no definitive role for steroids.
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