carotid artery, carotid artery dissection, diagnosis, fibromuscular dysplasia, internal carotid artery, management
M Lambert. Spontaneous Internal Carotid Artery Dissection Secondary to Fibromuscular Dysplasia: A Case Report. The Internet Journal of Advanced Nursing Practice. 2008 Volume 10 Number 1.
Fibromuscular dysplasia is not well understood by practitioners, and as a result is often under-diagnosed. Although the etiology of fibromuscular dysplasia is unknown, this disease is frequently associated with stroke and vascular dissections. Approximately 12-15% of spontaneous carotid artery dissections can be attributed to the presence of fibromuscular dysplasia. This article will discuss symptoms and presentations that mask an early diagnosis of fibromuscular dysplasia, and will highlight the vulnerable populations often affected. Advanced practice providers must be aware of the complexity of symptoms and presentations of patients with an underlying diagnosis of fibromuscular dysplasia. Early diagnosis and intervention are required to minimize catastrophic events and long-term deficits.
Fibromuscular dysplasia (FMD) is classified as a nonatherosclerotic, noninflammatory vascular disease. Anomalies are frequently seen in the renal, carotid, and vertebral arteries. To a lesser extent, the visceral arteries and arteries of the extremities may be affected . FMD lesions weaken arterial walls and predispose the craniocervical arteries to dissection. This disease is a predisposing factor in 10-20% of carotid artery dissections .
FMD primarily affects women of child-bearing age, and occurs up to four times as often in women than in men . Clinically, researchers are considering whether hormonal factors are involved . However, current research is limited and samples are small, leading to no conclusive causative links to the disease. Diagnosis to date has typically been made by the classic angiographic finding of the “string of beads”
(Figure 1) . Although rarely attained, the pathologic specimen is diagnostic .
Clinical Manifestations of Cerebrovascular Fibromuscular Dysplasia
Clinical manifestations of symptoms are determined by the arteries affected and the cerebral territory the vessels supply. Hypertension can be attributed to the renal artery (RA), while facial palsies, Horner’s Syndrome, and transient ischemic attacks (TIAs) can be attributed to either the carotid artery (CA) or vertebral artery (VA) . For a detailed classification of symptoms based on the vascular territories affected after an ischemic or hemorrhagic stroke refer to Table 1 .
To further complicate the clinical presentation, 26% of these patients will have the disease diagnosed in more than one vascular bed . Clinicians must be aware that symptoms alone may not provide adequate guidance in the diagnosis of FMD. Past medical history and unusual symptoms for an age group, accompanied with laboratory and angiographic images, will assist in the diagnosis.
Within the central nervous system (CNS), headaches, vascular dissections, and stroke are the most common clinical presentations . However, symptoms such as vertigo, tinnitus, or syncope may be the primary presenting problem . In some cases, headache and neck pain may be the only presenting complaints prior to a spontaneous internal carotid artery (ICA) dissection . Physical examination may reveal a carotid bruit, leading to an incidental finding of FMD .
For some time, neurologists have known FMD to be an important cause of stroke in young adults . The presentation of a carotid or vertebral dissection with an accompanying anterior circulation ischemic stroke affects 10-25% of all ischemic strokes in young adults . Ninety-five percent of diagnoses of FMD involve the ICA, followed by the VA 60-85% of the time . FMD is associated with single or multiple aneurysms found most frequently along the ICA and middle cerebral artery (MCA) . To gain a better understanding of the angiographic diagnosis of FMD, a description of a classification system will be discussed.
Classification is based on the angiographic appearance of the vessel, which correlates with the dominant arterial wall affected . Therefore, vessels will either be labeled as medial dysplasia, intimal dysplasia, or adventitial fibroplasia . Subcategories further assist the practitioner in identifying commonalities in symptoms and the types of patients that FMD affects. The “string of beads” is the most common angiographic finding for FMD in both the RA and ICA, followed by concentric stenosis (Figures1&2) .
Although this classification was originally developed for use in the RAs, the system has been applied successfully to all vascular beds affected by FMD . Dissection was once a subcategory, but has now been referenced as a cause. Refer to Table 2 for the
Angiographic Classification of FMD .
The patient was a fifteen-year-old Caucasian, right-handed, female who presented to the emergency department (ED) with a sudden onset right-sided facial pain and uncontrolled twitching of the right eye and cheek. The patient was reportedly walking off the volleyball court when she collapsed to her knees and was observed having twitching on the right side of her face. Upon arrival to the ED, the patient exhibited right-sided weakness and slurred speech.
A recent history revealed the patient had experienced a migraine headache in the frontal-temporal region the previous night that resolved with acetaminophen (Tylenol). The patient awakened the next morning in her normal state of health. Additional history reported by her parents included a recent outbreak of shingles to her left eye and nasal region. The patient was treated with a seven-day course of valacyclovir (Valtrex) with resolution. Further history included recurrent opthalmic lesions since the age of seven that required anti-viral treatment at least two times per year. The virus was always presumed to be herpes. No additional medical or surgical problems noted in her history.
The patient had no known allergies and no use of chronic medications. The patient's paternal grandfather died of a stroke at age 48. The maternal grandmother died of a stroke at age 53. The family was unaware of any diagnoses of FMD or carotid/vertebral artery dissections within their immediate family. The patient’s mother has type II diabetes mellitus. The family did not recall any history of vasculitis or coagulopathic disorders. No history of tobacco, alcohol, or illicit drug use existed. Additionally, the patient did not use contraceptives.
On initial physical examination, the blood pressure was documented as 140/84, heart rate 102, respirations 16, and temperature 98.2 F. No audible carotid bruit was heard. However, a grade 2/6 systolic murmur was prominent at the left costal margin.
Cranial nerves II through XII were intact bilaterally. The motor exam noted 5/5 strengths on her left side; however, on her right side, she was noted to have the following strengths: 4/5 in deltoids, biceps, wrist extension, triceps, hip flexor, hip abduction, hip adduction, and quadriceps. Her extensor hallucis longus and her gastrocnemius strength was 4/5 on the right. The deep tendon reflexes were 3/5 in the Achilles, quadriceps biceps, brachial radialis, and triceps tendons bilaterally. The patient was noted to have intact sensation to light touch and sharp/dull discrimination in all extremities. No ataxia was present, and gait was not assessed.
An initial brain computed tomography (CT) with no contrast revealed a hypodensity at the level of the operculum, and no evidence of an acute bleed. An electroencephalogram (EEG) revealed an asymmetric slowing during sleep, indicating a deep lesion of the left hemisphere, in keeping with the patient's known history. A brain and neck magnetic resonance imaging (MRI) with and without contrast revealed a left basal ganglia stroke, a narrowing of the left ICA at the bifurcation, and decreased flow in the posterior left MCA region. A bilateral carotid, vertebral, and cerebral arteriogram demonstrated evidence of dissection involving the supra-ophthalmic and supraclinoid segments, and bifurcation of the left ICA with evident involvement of the left A-1 and M-1 segments, the latter extending into the left MCA bifurcation. The left internal carotid bifurcation was narrowed approximately 50% and showed evidence of beading that was likely representative of FMD.
Forty-eight hours after admission, a repeat brain CT without contrast revealed a new infarct in the left anterior cerebral artery (ACA) distribution. The left MCA infarct was unchanged, and there was no evidence of hemorrhagic conversion. The development of a second infarct in a different distribution strongly suggested a dissection upstream of the common carotid at the aortic arch, at the ICA origin from the carotid bifurcation. A transesophageal echocardiogram (TEE) revealed no patent foramen ovale (PFO), no atrial septal wall defect (ASD), no valvular abnormalities, no vegetations, and an ejection fraction of sixty to sixty-five percent. A lumbar puncture revealed no unusual chemistries or culture.
Treatment included the patient being started on weight based heparin. Transition to warfarin (Coumadin) occurred when a therapeutic INR value of 2-3 was attained. The partial seizures were addressed with the addition of phenytoin (Dilantin) 300 mg orally daily. Both medications would be re-evaluated in three months at a follow-up visit with the neurologist.
Determining Differential Diagnoses
A thorough history of the patient and first-degree relatives provides invaluable information when attempting to rule out conditions that may be associated with or look similar to FMD. The clinician acts as an investigator, taking note of even the smallest of details. For example, if the patient complained of a “thunder-clap” headache one may suspect a subarachnoid hemorrhage (SAH)” . Despite age or risk factors, unilateral weakness and aphasia require an immediate head CT without contrast to rule out either an ischemic or a hemorrhagic stroke . A diagnosis of an ischemic event in a 15 year-old Caucasian female with no history of recent trauma must cue the provider to think of FMD as a differential diagnosis . A review of current data will assist in determining appropriate differentials:
A 15 year-old Caucasian female with no prior neurologic complications.
Recent complaint of a migraine headache and history of herpetic lesions.
No history of hypertension, elevated cholesterol, smoking, or diabetes.
Maternal and paternal grandparents died at an early age from stroke.
Left MCA/ACA infarct, left ICA narrowing, dissection at the bifurcation of the left ICA, and evidence of beading similar to FMD
FMD can be determined only by angiographic findings or a pathological specimen. Emergent brain and vascular imaging and, specifically, catheter-based angiography remain the gold standard for the determination of cerebrovascular FMD . A head CT without contrast is the first scan required to differentiate between an ischemic and a hemorrhagic stroke . In the absence of a hemorrhagic event, the clinician must consider that an ischemic event has occurred. Magnetic resonance imaging (MRI) of the brain and contrast-enhanced magnetic resonance angiography (CE MRA) of the neck and brain sufficiently detail the “string of beads” pattern seen in most diagnoses of FMD . A CT angiogram (CTA) of the neck and brain provides an alternative for those individuals who cannot tolerate a MRI. CTA is particularly useful in the identification of stenosis, dissections, and aneurysms that may be associated with FMD . Duplex ultrasonography (DU) is unable to detect FMD in the vertebral and intracranial carotid arteries . However, in patients with carotid dissections, abnormal flow patterns have been identified in more than 90% of patients . DU, used in combination with angiography or magnetic resonance, is almost always confirmatory of dissections and may prove advantageous in the diagnosis of FMD .
Current Medical Treatment
At this time, no curative treatment exists for the diagnosis of FMD. Treatment is determined by the presenting problem. A carotid artery dissection with no cerebral hemorrhagic event will require intravenous weight-based heparin to be initiated. Once achieving a target international normalized ratio (INR) of 2-3, the patient will be changed to oral warfarin (Coumadin) for a time frame of three to six months . The affected vessel has the highest potential to recanalize during the first three months while on anticoagulation therapy. Therefore, an MRA in three months will re-evaluate the state of the vessel and the need for further treatment. If luminal irregularities persist, the patient will continue antiplatelet therapy. An additional follow-up and MRA study in three months that reveals continued luminal irregularities will likely require the initiation of an anti-platelet agent such as clopidogrel (Plavix) . However, the duration the patient should remain on anti-platelet therapy remains unclear. Current research indicates that, if the patient remains asymptomatic after six months, he or she will likely not experience a repeat event, therefore negating any further medical treatment.
Current Surgical Treatment
Surgical management for cerebrovascular FMD should be reserved for those patients who remain symptomatic despite medical therapy, and have severely stenotic lesions with evidence of cerebral hypoperfusion . Patients who present with a SAH and have angiographic evidence of aneurysms may require emergent surgical intervention. These aneurysms may require coiling or clipping to prevent further bleeding .
Currently, percutaneous transluminal angioplasty (PTA) is the first therapeutic option in the symptomatic FMD patient . PTA is considered to be a safer option than traditional surgical procedures such as an endarectomy . Stenting may be considered when patients have recurring symptoms and have failed traditional anticoagulation therapy or balloon angioplasty . Clinicians should be aware that very little comparative interventional data exist to support one procedure over another in the patient with cerebrovascular FMD. Although carotid stenting is an alternative, little is known of the long-term results and the possible complications . Stenting should not be considered as a primary therapy .
This case study demonstrates the catastrophic events that occur in a symptomatic patient with FMD. Following current guidelines and research can aid in the prevention and minimization of the complications of FMD. Although cerebrovascular FMD remains a relatively obscure diagnosis, clinicians must become aware of not only the short-term implications but also the long-term outcomes. Increasing funding for researchers is a necessary step for those dedicated to finding answers to this complex disease.
The author would like to thank the Fibromuscular Dysplasia Society of America for allowing the use of the angiographic images displayed in this article.
Monique Lambert 10116 Forest Spring Lane Pearland, Texas, 77584 Email: Monique.firstname.lastname@example.org