A 16-year-old African-American male with no past medical history presented with gait instability and somnolence. He had intermittent neurological complaints during the prior 4 months, including dizziness, left arm paresthesias, decreased hearing, and inability to control his hands. During these 4 months, his primary physician ordered a brain magnetic resonance imaging (MRI) in the second month and a head computed tomography (CT) scan in the third month; both were unremarkable. There was no history of recent trauma or of sickle cell disease. The night prior to presentation, his family noted gait instability and decreased level of arousal. He had decreased oral intake and vomiting with no fevers. He was taken to an emergency department (ED), where he was diagnosed with vertigo and sent home with prescriptions for meclizine and ondansetron. His symptoms progressed, leading to reevaluation in a second ED. Head CT scan revealed a large area of hypodensity in the cerebellum. The boy was transferred for intensive care unit (ICU)-level care.
On admission to the pediatric ICU, the patient was sleepy but able to be roused, responding slowly to questions with the need for frequent redirection. Horizontal nystagmus, decreased hearing on the left side, left facial droop, left-sided weakness, and dysarthria were present. Repeat head CT on arrival to the ICU showed a large, left cerebellar hemispheric stroke (Figure 1). An acute stroke protocol was initiated and the neurocritical care service was consulted. His symptoms progressed with poor gag reflex, inability to swallow oral secretions, and agitation requiring intubation for airway protection. He was taken for “stat” CT angiography of the head and neck, which showed bilateral vertebral artery occlusions. To further define his pathology and for potential intervention, a conventional angiogram was performed.
Computed tomography of head without contrast demonstrating a cerebellar stroke.
Images courtesy of Margaret Z. Tsien, MD.
The angiogram showed evidence of bilateral vertebral artery dissections with complete thrombotic occlusion of the right vertebral artery, large thrombus with sluggish flow and a pseudoaneurysm in the left vertebral artery, as well as complete occlusion of the basilar artery, both posterior cerebral arteries, and cerebellar arteries (Figure 2). A stent retriever device was used. Embolectomy with complete recanalization of the basilar artery was achieved, and clot retrieval from the left vertebral artery and posterior cerebral arteries was also performed. These interventions were successful in restoring adequate flow to the posterior cerebral circulation; however, a large infarction in the cerebellum was already irreversible.
Left vertebral artery with pseudoaneurysm (1) and large thrombus (2) partially obstructing flow with possible intimal flap indicating likely dissection. Left posterior cerebral artery with recurrent flow obstruction (3) but with multiple collaterals. Right vertebral artery with retrograde flow from dye injected into the left vertebral artery (4).
The findings on the cerebral angiogram, including stenosis and dilations in the internal carotid arteries forming the characteristic “string-of-beads” appearance (Figure 3), suggested fibromuscular dysplasia (FMD) as the etiology of his spontaneous dissections, leading to his stroke. Because of the extracranial bilateral vertebral artery dissections and the presence of artery-to-artery embolism, he was placed on systemic anticoagulation. His course was complicated by significant cerebellar swelling due to strokes and possible reperfusion injury, requiring decompressive suboccipital craniectomy and duroplasty. During his ICU course, the boy had hemorrhagic conversion of his strokes, fever, hypertension, and tachycardia thought to be secondary to dysautonomic syndrome. He required tracheostomy and gastrostomy placement. In the most recent clinic visit, approximately 5 months after his hospitalization, the patient continued to have significant neurologic sequelae, including dysarthria, ataxic eye movements, decreased fine motor performance, and a severely ataxic gait. He requires assistance with all activities of daily living but is no longer dependent on tracheostomy and gastrostomy tubes.
Classic “string-of-beads” appearance of right internal carotid artery.
FMD is a non-inflammatory, non-atherosclerotic vasculopathy that causes deformation of arteries, resulting in stenosis, occlusion, aneurysm formation, or dissection. The pathogenesis of the disease remains unknown despite suggestions of a genetic, hormonal, or mechanical origin. The epidemiology of FMD is still being evaluated; however, a national registry for FMD established in 2003 has shown the following characteristics of those diagnosed: 91% female, mean age of 55.7 years, and 95.4% white.1 Our patient does not meet this classic phenotype. FMD in the pediatric population has focused mainly on renal artery stenosis presenting with hypertension. There are a few existing case reports of strokes in pediatric patients caused by FMD.2–6 FMD presents with stroke, aneurysm, or dissection in 17% to 20% of cases.1 Most often, FMD presents with non-specific complaints, such as headaches or hypertension, making it very difficult to diagnosis.
Classically, the diagnosis is made by conventional angiography, but it can also be made by pathology. The increase in the general use of noninvasive imaging like CT angiogram and MR angiogram has likely contributed to the increasing rate of incidental diagnosis. Of note, CT angiograms do not always detect dissections, as demonstrated in our patient. The definitive diagnosis of dissections and FMD in our patient was made via conventional angiography. Eighty to 90% of FMD cases have the classic “string-of-beads” radiographic finding. FMD can also present in imaging as tubular stenosis, dissection, or aneurysm.9 The “string-of-beads” angiographic finding represents multifocal stenosis and mural dilation. This usually correlates with pathologic findings of medial fibroplasia: disorganization and replacement of smooth muscle by a chaotic composition of fibroblasts and collagen.10,11 Other pathologic findings, such as intimal fibroplasia and medial hyperplasia, are rarely found and can sometimes be seen in other pathologies such as arterial injury from trauma or post-arteritis. Given the relative lack of pathologic samples taken from patients, the nearest thing to a gold standard for diagnosing FMD is angiography.
FMD can involve almost any artery in the body, and the treatment depends on the presentation. Data from the national registry show 66% renal artery involvement, 56% carotid artery involvement, and 18% with vertebral artery involvement.1 Our patient had angiographic FMD findings involving both carotid arteries, both vertebral arteries, and multiple areas in the posterior cerebral circulation. More than 90% of infarcts from dissection are thromboembolic rather than from low-flow states; therefore, anticoagulation was initiated for prevention of both clot propagation and new ischemic strokes. The use of anticoagulation for extra-cranial carotid or vertebral dissections has been in practice since the 1970s, although the treatment remains somewhat controversial.12 Our patient had a hemorrhagic conversion of his strokes, and his anticoagulation was discontinued.
FMD is a rare disorder with poorly described pathophysiology. Our patient had unique demographics and pattern of involvement. His intermittent symptoms and negative imaging suggest he was likely experiencing transient ischemic attacks (TIAs) during the 4 months preceding his diagnosis. When our patient presented to the ED, he was initially sent home with a diagnosis of vertigo. Had this patient been an adult, TIA/stroke would have been higher on the differential diagnosis, as his presentation was classic for both. His age, atypical demographics for FMD, and overall decreased awareness of FMD likely contributed to the delayed diagnosis. The aggressive treatment provided to our patient probably prevented the development of devastating brainstem, thalamic, and occipital strokes as commonly seen in cases of complete acute basilar artery occlusions. Unfortunately, despite multiple interventions, by the time of his diagnosis he had already infarcted his cerebellum, for which treatment is largely supportive. This case reminds us that strokes are not just an adult disease and that classic presentations can occur even in unconventional patients. In pediatric patients, stroke leads to mortality approximately 10% to 25% of the time and commonly leads to persistent neurologic deficits.13 Early recognition of stroke syndromes in the pediatric population becomes of paramount importance given the evolving availability of acute reperfusion strategies for acute ischemic stroke.
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- Chiu NC, DeLong GR, Heinz ER. Intracranial fibromuscular dysplasia in a 5-year-old child. Pediatric Neurology. 1996;14:262–264. doi:10.1016/0887-8994(96)00023-9 [CrossRef]
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