Moymoya Disease

Abstract

A rare cerebrovascular disease, Moyamoya disease is considered to be progressive bilateral constriction or obstruction of the terminal portion of the carotid arteries, which are found internally. The expanded and fragile collateral flow, observed at the base of the brain reveal “puff of smoke” form, which are known as moyamoya vessels.  The pathophysiology of MMD is not completely clear and its possible causes include genetic association to chromosome 17, angiogenesis, autoimmune, therapeutic cranial radiation as well as infection of the head and neck.  Gender difference has been observed with a female to male ratio of approximately 2:1.  Most patients are symptomatic and they may present with ischemic or hemorrhagic strokes, seizure, headache or cognitive or psychiatric changes. The diagnosis of MMD depends on the clinical presentation and radiographic imaging utilizing the Suzuki Grading System.  Surgical treatment with direct and indirect cerebral revascularization is necessary to halt the progression of the disease. This article will present a case of MMD and review the prevalence, etiology, clinical presentation, diagnosis and therapeutic management of the disease.

 Introduction

A rare cerebrovascular disease, Moyamoya disease is considered to be progressive bilateral constriction or obstruction of the terminal portion of the carotid arteries, which are found internally (ICAs) or its main braches including anterior (ACA) and middle cerebral arteries (MCA) (Burke et al., 2009; Kuroda & Houkin, 2008; Scott & Smith, 2009; Suzuki &Takaku, 1969). The dilated and fragile collateral circulations, which are found at the origin of the brain show  a “puff of smoke” form and are called moyamoya vessels, for which this disease entity is named (Burke et al., 2009; Kuroda & Houkin, 2008; Smith & Scott, 2005; Suzuki &Takaku, 1969).

Case Study

ES was a 26-year old female who had a history of seizure disorder, von Willebrand disease and diabetes mellitus.  The patient presented to the emergency department with headache, dizziness, lightheadedness, nausea and vertigo-type symptoms.  She was discharged home and returned with a progressing headache, stiff neck and neck pain.  The neurological examination was unremarkable; the patient was alert and oriented to person, place and time, and had no focal neurological deficits.

The lumbar puncture revealed bloody cerebral spinal fluid.  The cerebral computed tomography (CT) demonstrated evidence of intraventricular hemorrhage, old right frontal and parietal lobe infarct, and right periventricular white matter hypodensity. CT angiogram showed diminished flow within the intracranial distribution of the carotid arteries, which are found internally. The angiography of the brain showed bilateral obstruction of terminal carotid arteries, found internally and absent flow into both ACA and MCA (Figures 1).  There were networks of small vessels at the terminus of internal carotid and anterior cerebral arteries with a “puff of smoke” form, which is exhibited by the  moyamoya vessels (Figure 2).  The temporal arteries were relatively large but there was no evidence of extracranial collateral circulation.  The patient was diagnosed of having stage 3-4 MMD on the Suzuki Grading System and was later referred for a revascularization procedure.

Epidemiology

MMD was first described in Japan and is now recognized throughout the world (Caldarelli et al., 2001; Kraemer et al., 2008; Suzuki &Takaku, 1969; Yilmaz et al., 2001).  Japan has the highest prevalence of MMD and familial forms contribute to 15% of the disease (Kuroda & Houkin, 2008). A detection rate of the disease of “0.94 per 100,000 patient-years and a prevalence of 10.5 per 100,000 patients” has been documented and analyzed in the Japanese population (Baba et al., 2008).  There are two peaks of age distribution for MMD. The ratio between female to male is nearly a female 2:1 (Baba et al., 2008; Kuroda and Houkin, 2008).  The highest peak is observed between individuals, who are between the ages forty five and forty nine. The second highest peak is found in children, who are between the ages five and nine (Baba et al., 2008; Kuroda and Houkin, 2008).  MMD has been under recognized as a “cause of ischemic

as a cause of ischemic or hemorrhagic stroke in western countries” (Yilmaz et al., 2001).  The incidence of MMD in Caucasians is 1/10th of that observed in Japanese (Uchino et al., 2005).

Etiology

The pathophysiology of MMD is not completely clear and patients with this diagnosis do not carry conventional risk factors for strokes such as age >55 years, history of atrial fibrillation or heart disease, hypertension, dyslipidemia, smoking, diabetes mellitus, contraceptive pills or hormone therapy (Reeves et al., 2009; Smith & Scott, 2005). A probable link between MMD and chromosome 17 has been demonstrated in a substantial number of Japanese and some Caucasian patients but irregularly occurring MMD continues to be the most common and prevalent form (Burke et al., 2009; Kuroda & Houkin, 2008; Yamauchi et al., 2000). The pathological findings of thickening intima, smooth muscle cell hyperplasia and luminal thrombosis without atherosclerotic or inflammatory changes in the affected vessels indicate a significant role of angiogenesis in the development of MMD (Scott & Smith, 2009; Ullrich et al., 2007).  Microthrombi from the luminal thrombosis may lead to endothelial injury, coagulating innermost membrane and smooth the proliferation of muscle cell. In some cases, the deficiency of  Protein S, lupus anticoagulant, and anticardiolipin antibodies have been witnesses, which indicated a probable “autoimmune mechanism in MMD” (Kuroda et al., 2008).  If infection is found in the head and neck, MMD may be developed in patients (Yamada et al., 1997). Moyamoya syndrome is a secondary form of MMD that is associated with other clinical conditions such as neurofibromatosis, sickle cell disease, cranial therapeutic radiation or Down’s syndrome (Scott & Smith, 2009; Uchino et al., 2005 Ullrich & Robertson et al., 2007).

Presentation

Approximately 18% of patients with MMD are asymptomatic and those with symptoms may present with (Baba et al., 2007) ischemic, hemorrhagic, epileptic or “other” symptoms such as headache, chorieform movements, cognitive or psychiatric changes (Burke et al., 2009). Most childhood moyamoya cases present with ischemic events, whereas adult patients present more commonly with ischemic symptoms, intracranial bleeding, or both (Kuroda & Houkin, 2008; Han et al., 2000; Han et al, 2000). The incidence of ischemia and hemorrhage associated with MMDis 0.53 and 0.2 patients per 100,000 people, respectively (ref). Intracranial bleeding may be attributed to the rupture of moyamoya vessels, fluid filled sacs found in the circle of Willis or on open perforators, or dilated collateral arteries, which are found on the surface of the brain (ref). Intracerebral hematoma is the main reason of death of patients, who have MMD (Burke et al, 2009). The presentations in Caucasian patients are different in their “lack of bimodal age of onset, prevalence of the ischemic symptoms at all ages and more benign symptoms at presentation, and better response to surgical treatment” (Yilmaz et al., 2001; Hallemeier et al., 2006; Kraemer et al., 2008).

The dilatation of meningeal and leptomeningealcollateral vessels predisposes patients to migraine-like headache frequently refractory to medicaltherapies (Seol et al., 2005). Dilated moyamoya vessels in the basal ganglion may also contribute to chorieform movements in some patients (Pamar et al., 2000; Scott et al., 2004).  The “morning glory disk” is an enlargedoptic disk which is occasionally seen with vascular anomalies in the retina of patients withMMD (Lee &Traboulsi, 2008, Scott & Smith, 2009).

 Diagnosis

On basis of clinical presentation and radiographic imaging, the diagnosis of MMD is made. This includes the primary and secondary findings. Precise and accurate procedures have been established for diagnosis and the main findings comprise of bilateral constriction or obstruction of the terminal parts of the ICA or at its major branches and abundant collateral formation, including moyamoya vessels (Burke et al.; Kuriyama et al., 2008; Fukui, 1997).  Some patients may initially present with unilateral vascular abnormalities and a large percentage of them will eventually develop contralateral disease (Kelly et al., 2006; Kuroda et al., 2005). Cerebral infarction, white matter wounds, atrophy, and internal bleeding are considered to be the secondary findings. (ref).

The work-up of a suspected case of MMD usually begins with cerebral CT scan which can readily identify secondary findings (Burke et al., 2009; Smith & Scott, 2005).  CT angiography may be used to visualize the intracranial stenoses but cerebral angiography is considered to be the best imaging technique available, which would be used to reveal the primary findings of MMD (Burke et al.; Kuriyama et al., 2008; Scott & Smith, 2009).  The Suzuki Grading System describes six angiographic stages which indicate the severity of MMD: (1) a narrowing of the carotid forks bilaterally, (2) development of moyamoya vessels, (3) increasing ICA stenosis involving ACA and MCA, and prominence of moyamoya vessels, (4) occlusion of ICAs and the entire circle of Willis with appearance of extracranial collaterals and diminished moyamoya vessels, (5) further progression of Stage 4 and (6) complete absence of moyamoya vessels and major cerebral arteries with collateral circulation, which is produced only by the carotid arteries, found externally. (Burke et al., 2009; Scott & Smith, 2009; Suzuki & Kodama, 1983). Most cases of MMD are diagnosed at stage 3 of the grading system (ref).

Magnetic resonance imaging (MRI) and angiography (MRA) are considered to be the most consistent and reliable methods for the construction the internal images of the primary and secondary findings as well as postoperative results of MMD (Burke et al., 2009). Because of outstanding and brilliant analytical result and controlled or restricted nature of the procedure, MRA is now recommended as the primary diagnostic imaging for MMD (Smith & Scott, 2005).  Conventional cerebral angiography may be necessary in a few patients when smaller vessel occlusions and moyamoya collateral vessels are not well visualized with MRI and MRA (Kuriyama et al., 2008; Smith & Scott. 2005).  A definitive diagnosis of MMD requires the presence of bilateral distal ICA stenosis or occlusion and intra or extracranial collateral circulation demonstrated by cerebral angiography or MRI and MRA (Kuriyama et al., 2008).

Treatment

Patients with milder symptoms are usually treated conservatively with medical therapy but there is little evidence of its short-range or long-standing effectiveness and efficiency (Burke et al., 2009).  In order to prevent emboli, antiplatelet agents have been used (Smith et al., 2004; Smith & Scott, 2005) but chronic anticoagulation with warfarinis rarely used (Bowen et al., 2005, Smith & Scott2005).  Calcium-channel blockersmay relieve intractable headaches or reduced the incidence and severity of TIA (Scott & Smith, 2009). Patients with more severe symptoms are treated with one of the three revascularization procedures: direct, indirect, and combined techniques (Burke et al., 2009; Yilmaz et al., 2001; Hallemeier et al., 2006; Kuroda & Houkin, 2008; Smith & Scott, 2009).  “Extracranial-intracranial arterial bypass” is performed in the direct revascularization with “anastomosis of the superficial temporal artery (STA) to MCA” (Burke et al., 2009; Kuroda & Houkin, 2008; Smith & Scott, 2009).  The indirect revascularization involves placing vascularized tissues such as dura, temparalis muscle or STA itself, directly contacting the brain to promote neorevascularization to the underlying cerebral cortex (Burke et al., 2009; Kuroda & Houkin, 2008; Smith & Scott, 2009).

Prognosis

MMD has a variable natural history and the progression of the disease can either be slow or sudden and severe, accompanied with neurological deterioration (Scott et al., 2004; Smith & Scott, 2005). MMD in children progresses more rapidly than that in adult (Burke et al., 2009). The disease eventually progresses in most patients; medical therapy alone cannot be used to stop the progression of the disease at this stage (Kuroda et al., 2005). Symptomatic progression is found in two third of patients for over a period of fiver years and surgery reduces the rateof progression to 2.6% (ref). When the diagnosis is made, the neurological condition is used instead of the patient’s age to determine the long-term prognosis and the early the diagnosis and treatment substantially improve the patient’s long-term outcome (Scott et al., 2004; Smith & Scott, 2005).

Conclusion

A rare cerebrovascular disease, Moyamoya disease is considered to be progressive bilateral constriction or obstruction of the terminal portion of the carotid d and it  requires a strong clinical suspicion to make a correct diagnosis, particularly if a young female patient without typical risks for CVA presents with cerebrovacular accident or seizure disorder. The diagnosis may be confirmed with radiographic imaging.  Surgical treatment with direct and indirect cerebral revascularization halts the progression of the disease in the majority of patients and a potentially good outcome may be expected. An understanding of this clinical entity will help nurse practitioners make the correct diagnosis, provide properly care in the acute setting, make appropriate referral for definitive surgical correction as well as explain the nature of the disease to patients and their families.

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