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INTRODUCTION — Reversible cerebral vasoconstriction syndromes (RCVS) are a group of conditions that show reversible multifocal narrowing of the cerebral arteries with clinical manifestations that typically include thunderclap headache and less commonly focal neurologic deficits related to brain edema, stroke, or seizure. The clinical outcome is usually benign, although major strokes can result in severe disability and death in a minority.
This topic will review RCVS. Other conditions associated with thunderclap headache are discussed separately. (See "Approach to the patient with thunderclap headache".)
TERMINOLOGY — Over the past 60 years, patients with RCVS have been misinterpreted as having primary angiitis of the central nervous system or aneurysmal subarachnoid hemorrhage due to overlapping features such as headache, strokes, and cerebral angiographic narrowing. Moreover, RCVS has remained under-recognized because this enigmatic reversible angiographic phenomenon has been reported using variable terminology, including the following:
●Migrainous vasospasm or migraine angiitis [1,2]
●Call-Fleming syndrome (or Call syndrome) [3,4]
●Thunderclap headache associated vasospasm [5-7]
●Drug-induced cerebral arteritis 
●Postpartum cerebral angiopathy [9,10]
●Benign angiopathy of the central nervous system 
●Central nervous system pseudovasculitis 
It is now apparent that patients with reversible cerebral arterial narrowing have nearly identical clinical, laboratory, imaging, and prognostic features regardless of the associated condition [13-15]. The descriptive term "reversible cerebral vasoconstriction syndromes" (RCVS) has been proposed to facilitate the recognition and management of this group of disorders . The adoption of the broad term RCVS, along with its main clinical and imaging features, has encouraged relatively large retrospective and prospective studies that have helped characterize the syndrome [16-23].
PATHOPHYSIOLOGY — The pathophysiology of the abrupt-onset headache and of the prolonged but reversible vasoconstriction is not known. Reversible angiographic narrowing suggests an abnormality in the control of cerebrovascular tone . It remains unclear whether the angiographic abnormalities trigger the headaches or result from severe headache, but there certainly is a close relationship [25,26]. The anatomic basis to explain both the vasoconstriction and headaches is the innervation of cerebral blood vessels with sensory afferents from the trigeminal nerve (V1) and dorsal root of C2. Cerebral vasoconstriction, when severe or progressive, likely results in the ensuing ischemic strokes, and brain hemorrhages probably reflect postischemic reperfusion injury due to the dynamic and reversible nature of the arterial narrowing.
The presence of reversible lesions suggesting transient brain edema in patients with RCVS and the high frequency of reversible cerebral angiographic abnormalities in patients with the posterior reversible leukoencephalopathy syndrome (PRES), also known as the reversible posterior leukoencephalopathy syndrome, suggest an overlapping pathophysiology between RCVS and PRES [27-30]. (See "Reversible posterior leukoencephalopathy syndrome".)
EPIDEMIOLOGY — The true incidence of RCVS is unknown; clinical experience suggests RCVS is fairly common . RCVS is being reported with increasing frequency, presumably due to greater awareness of the syndrome, higher detection rates due to the widespread use of relatively noninvasive imaging tests such as CT and MR angiography, and perhaps the escalating use of illicit drugs and vasoconstrictive medications .
In adults, RCVS predominantly affects women, with female to male ratios ranging from 2:1 to 10:1, depending on the case series. In contrast, a 2017 review of pediatric RCVS found that most cases affected boys (11 of 13) .
RCVS occurs in individuals of all ages and races. The mean age of affected individuals across published studies is 42 to 44 years, with an age range of 4 months to 65 years [17,23,31,33-35]. Cases have been documented from numerous countries including France, the United States, Mexico, Canada, Spain, Italy, South Africa, China, India, Japan, and Australia.
Risk factors — RCVS has been associated with a variety of conditions including pregnancy [8,36], migraine [1,2,37], use of vasoconstrictive drugs [8,9,31,38] and other medications [29,39], neurosurgical procedures , hypercalcemia , unruptured saccular aneurysms [5,42], cervical artery dissection [42,43], cerebral venous thrombosis [44,45], and others [34,46,47].
The individual risk factors and associated conditions related to RCVS (table 1) appear unrelated (ie, without a common pathophysiological theme) and may simply reflect the biases of investigators in attributing risk. Indeed, the variable nosology previously used by diverse physician groups (eg, stroke neurologists, headache specialists, obstetricians, internists, and rheumatologists) to report this clinical-angiographic syndrome reflects uncertainties concerning the pathogenesis and clinical approach. Authors have implicated the listed conditions, including commonly used medications such as serotonergic antidepressants, based on their known vasoconstrictive effects or the temporal relationship with the onset headaches . However, epidemiologic evidence to support a causal relationship is lacking. Some authors have speculated that the vasoconstriction is related to transient vasculitis, but there is no evidence to support a role for inflammation. Cerebrospinal fluid examination and extensive serological tests are normal, and pathological studies of the brain and temporal arteries have shown no abnormality .
CLINICAL FEATURES — The clinical presentation of RCVS is usually dramatic, with sudden, excruciating headaches that reach peak intensity within seconds, meeting the definition for "thunderclap headache" [5,49]. The thunderclap headaches tend to recur over a span of days to weeks. Approximately one-third of patients develop ischemic or hemorrhagic strokes, or reversible brain edema [16,17,23].
Less than 10 percent of patients with RCVS present with subacute or less severe headaches; the absence of headache at onset is exceptional [17,23,50]. Many patients report trigger factors, such as orgasm, physical exertion, acute stressful or emotional situations, straining, coughing, sneezing, bathing, and swimming. Generalized tonic-clonic seizures are reported in 0 to 21 percent of patients at the time of presentation; however, recurrent seizures are rare.
The onset headaches are usually diffuse or located in the occipital region or vertex. They are often accompanied with nausea and photosensitivity. The character of these headaches is usually different from the patient's prior migraine headaches, if any. Most patients experience moderate pain relief within a few minutes to hours, only to be followed by sudden, severe exacerbations that can recur for days. In one study, patients reported an average of four recurrences .
Headache remains the only symptom in one-half to three-fourths of patients; the rest go on to develop focal deficits from underlying strokes or cerebral edema. In published series, the frequency of focal neurologic deficits ranged from 9 to 63 percent, being higher in inpatient case series. Hemiplegia, tremor, hyperreflexia, ataxia, and aphasia can develop. Visual deficits, including scotomas, blurring, hemianopia, and cortical blindness, are common. Many patients show features of Balint syndrome, which is made up of the triad of simultanagnosia (the inability to integrate a visual scene despite adequate acuity to resolve individual elements), optic ataxia (the inability to reach accurately under visual guidance), and ocular apraxia (the inability to direct gaze accurately to a new target, frequently leading to difficulty reading) [23,51].
The systemic examination is usually unrevealing, although the initial blood pressure can be elevated due to either severe headache pain, the disease itself, or the associated condition (eg, eclampsia, cocaine exposure).
The resolution of the different components of RCVS, including headaches, focal deficits, and angiographic narrowing, does not always follow the same time course. As stated, the thunderclap headaches resolve over days to weeks. Most patients show resolution of visual and other focal neurologic signs or symptoms within days to weeks; however, some are left with minor or moderate permanent deficits. Angiographic resolution can last longer (up to three months). Less than five percent experience progressive cerebral arterial vasoconstriction culminating in massive strokes, brain edema, severe morbidity, or death [48,52-54].
EVALUATION AND DIAGNOSIS — The diagnosis of RCVS is based upon the characteristic clinical, brain imaging, and angiographic features. A study published in 2016 provides criteria to diagnose RCVS and distinguish it from primary angiitis of the central nervous system (PACNS) (table 2) . The following criteria have 98 to 100 percent specificity and a similarly high positive predictive value (ie, the likelihood that a patient with a positive finding has the disease) and can be used for bedside diagnosis at the time of admission, even without cerebral angiography or documentation of vasoconstriction reversal on follow-up imaging:
●Recurrent thunderclap headache, OR
●Single thunderclap headache combined with either normal neuroimaging, border zone infarcts, or vasogenic edema, OR
●No thunderclap headache but abnormal angiography and no brain lesions on neuroimaging (the absence of brain lesions virtually rules out PACNS)
Urgent brain and vascular imaging (see 'Brain imaging' below and 'Neurovascular imaging' below) is necessary to exclude secondary causes of thunderclap headache (table 3). Because RCVS is associated with a risk of stroke, brain edema, severe morbidity, and even death, it is reasonable to admit patients for observation for the first few days after symptom onset.
Laboratory findings — Routine tests (eg, complete blood count, electrolytes, liver and renal function tests) and tests for inflammation (eg, erythrocyte sedimentation rate, rheumatoid factor, and antinuclear cytoplasmic antibodies) are typically normal in patients with RCVS.
Urine vanillylmandelic acid and 5-hydroxyindoleacetic acid are useful to rule out systemic diseases and evaluate for vasoactive tumors (eg, pheochromocytoma, carcinoid) that are associated with RCVS. Serum and urine toxicology screens should be performed to investigate for exposure to illicit vasoconstrictive drugs such as marijuana and cocaine. Cerebrospinal fluid examination findings are normal (ie, protein level <60 mg/dL, ≤5 white blood cells per mm3) in more than 85 percent of patients ; minor abnormalities can result from ischemic or hemorrhagic strokes.
There is no role for brain biopsy or temporal artery biopsy unless the diagnosis remains unclear despite a thorough evaluation and there is at least moderate suspicion for cerebral vasculitis.
Brain imaging — Between 30 and 70 percent of patients with RCVS have no abnormality on initial brain scans, despite having widespread cerebral vasoconstriction [17,23,26,31,55,56]. However, approximately 75 percent of admitted patients eventually develop parenchymal lesions (image 1 and image 2). The most frequent lesions are ischemic stroke and cortical surface (nonaneurysmal or convexal) subarachnoid hemorrhage, followed by reversible vasogenic brain edema and parenchymal hemorrhage [17,23,31]. Any combination of lesions can be present. Brain scans remain normal in approximately 25 percent of cases reported from in-hospital settings; this number is much higher in emergency department case series.
Infarcts are often bilateral and symmetrical, located in arterial "watershed" regions of the cerebral hemispheres or in the cortical-subcortical junction. Larger infarcts are often wedge-shaped. Perfusion-weighted MRI may show areas of hypoperfusion in watershed regions. Cortical surface hemorrhages are typically minor, restricted to a few sulcal spaces [27,57,58]. Several studies have shown that RCVS is the most frequent cause of cortical surface (convexal) subarachnoid hemorrhage (image 3 and image 1) in individuals below age 60 years [59-61]. Single as well as multiple lobar hemorrhages can occur, and brain hemorrhages can develop a few days after onset, which again suggests a mechanistic role for reperfusion injury. Subdural hemorrhage has been reported . Fluid-attenuated inversion recovery (FLAIR) MRI often shows indirect signs of RCVS in the form of dot (ie, the dot sign) or linear hyperintensities within sulcal spaces, which are believed to represent slow flow within dilated surface vessels [63,64].
Neurovascular imaging — Abnormal cerebral angiography is the primary diagnostic feature of RCVS. Cerebral angiographic abnormalities are dynamic and progress proximally, resulting in a "sausage on a string" appearance of the circle of Willis arteries and their branches. Smooth, tapered narrowing followed by abnormal dilated segments of second- and third-order branches of the cerebral arteries (image 1) is the most characteristic abnormality.
Transfemoral, CT, or MR angiography (MRA) can be used to document the segmental cerebral arterial narrowing and vasodilatation (image 4). Transcranial Doppler ultrasound has been used for diagnosis; however, normal results do not exclude this diagnosis . This noninvasive bedside tool has utility in monitoring the progression of vasoconstriction .
Initial cerebral angiography can be normal because the condition starts distally; one study found that 21 percent had normal findings on initial MRA and 9 percent had normal findings on both MRA and transcranial Doppler ultrasonography . In patients with a high degree of clinical suspicion for RCVS, a follow-up study may be justified after three to five days.
Angiography may reveal concomitant cervicocephalic arterial dissection or unruptured aneurysms [5,43,65,66]. In some patients, the extracranial internal carotid or vertebral artery can be affected by RCVS. Systemic arteries are rarely involved [67,68]. The time course of vasoconstriction is variable but most patients show resolution within three months.
DIFFERENTIAL DIAGNOSIS — To the experienced clinician, RCVS is an instantly recognizable entity based on certain features (see 'Clinical features' above). Most patients report severe thunderclap headaches and have benign cerebrospinal fluid findings, characteristic brain imaging features, and vascular abnormalities that resolve over a few weeks (table 4). The syndrome is known to occur in certain clinical settings (table 1). Individually, however, the clinical and imaging features carry a wide range of differential diagnoses.
The presence of recurrent thunderclap headaches is pathognomonic for RCVS . Nevertheless, isolated thunderclap headaches can signify a variety of ominous conditions, including aneurysmal subarachnoid hemorrhage, parenchymal hemorrhage, cerebral artery dissection, and cerebral venous sinus thrombosis (table 3). These conditions are differentiated with appropriate brain imaging. (See "Approach to the patient with thunderclap headache", section on 'Etiologies' and "Approach to the patient with thunderclap headache", section on 'Diagnostic evaluation' and "Spontaneous cerebral and cervical artery dissection: Clinical features and diagnosis" and "Etiology, clinical features, and diagnosis of cerebral venous thrombosis".)
●Aneurysmal subarachnoid hemorrhage is a major consideration because of the presence of thunderclap headaches, subarachnoid blood, and cerebral artery narrowing [20,57,58]. However, the recurrent nature of thunderclap headaches related to RCVS, the superficial location and small quantity of subarachnoid blood, and the widespread, symmetric vasoconstriction distinguish RCVS from aneurysmal bleeds . (See "Clinical manifestations and diagnosis of aneurysmal subarachnoid hemorrhage".)
●Primary thunderclap headache may be considered if imaging findings are negative and the patient does not prove to have vasoconstriction (see "Approach to the patient with thunderclap headache", section on 'Primary thunderclap headache'). In one study, 39 percent of patients presenting with thunderclap headache and normal brain MRI findings proved to have vasoconstriction on MR angiography, and those with and without vasoconstriction had similar clinical features, suggesting that RCVS and primary thunderclap headache belong to the same spectrum of disorders .
Migraine is another consideration in the differential diagnosis of RCVS, and the misdiagnosis of migraine can lead to inappropriate treatment with antimigraine agents such as triptans, which can exacerbate vasoconstriction and stroke [4,69]. Although there may be some overlap, RCVS appears distinct from migraine because, unlike migraine, RCVS rarely recurs, the sudden-onset headaches of RCVS are quite different from migraine, the brain and vascular imaging abnormalities are inconsistent with migraine, and the angiographic abnormalities persist for several weeks. (See "Pathophysiology, clinical manifestations, and diagnosis of migraine in adults" and "Pathophysiology, clinical features, and diagnosis of migraine in children".)
Angiographic differential — The angiographic abnormalities of RCVS can raise concern for intracranial atherosclerosis, infectious arteritis, vasculitis, Moyamoya disease (see "Moyamoya disease: Etiology, clinical features, and diagnosis"), fibromuscular dysplasia, and other cerebral arteriopathies. A detailed medical history and laboratory testing usually helps to rule out these conditions.
Historically, it was considered difficult to exclude primary angiitis of the central nervous system (PACNS) from RCVS because features such as headache, focal deficits, stroke, seizures, and angiographic irregularities are common to both conditions (see "Primary angiitis of the central nervous system in adults"). While there is overlap, the nature of the headaches and imaging abnormalities are quite different [16,17,23,31,50,70,71]. Patients with PACNS usually have an insidious progressive clinical course with chronic headaches, and rarely have thunderclap headache that is typical of RCVS. The characteristic vasoconstriction of RCVS usually manifests as smooth, tapered narrowing followed by abnormal dilated segments of second- and third-order branches of the cerebral arteries. This angiographic appearance distinguishes RCVS from PACNS, where the arterial narrowing is much more irregular. Brain imaging in RCVS can be normal or show watershed infarcts or lobar hemorrhages, whereas PACNS is usually associated with accumulating T2-hyperintense brain lesions, leptomeningeal enhancement, and scattered deep infarcts.
In a report that compared 159 patients with RCVS and 47 patients with PACNS, several features had 98 to 100 percent specificity for the diagnosis of RCVS (table 2) . These were: 1) recurrent thunderclap headache; or 2) single thunderclap headache combined with either normal neuroimaging, border zone infarcts, or vasogenic edema; or 3) no thunderclap headache but abnormal angiography and no brain lesions on neuroimaging. Note that the absence of brain lesions virtually rules out PACNS.
In rare cases, severe and prolonged vasoconstriction can induce secondary inflammation and render the angiographic changes irreversible, making the distinction between vasculitis and vasoconstriction extremely difficult . In challenging cases, high-resolution contrast MRI may help since anecdotal reports suggest a lack of contrast enhancement of the cerebral arteries in RCVS, but not inflammatory cerebral vasculitis .
MANAGEMENT — There is no proven or established therapy for RCVS. While most patients fully recover with time, up to one-third can develop transient symptoms in the initial few days, and rare cases can develop a progressive clinical course . Therefore, it is reasonable to admit patients for observation, pain control, and supportive care for the first few days after symptom onset.
Supportive care — Patients with severe angiographic abnormalities are often admitted to the intensive care unit for neurologic monitoring and blood pressure management. The goals of blood pressure control need careful consideration. Theoretically, pharmacologically-induced hypertension can induce further cerebral vasoconstriction or result in brain hemorrhage, and in the setting of cerebral vasoconstriction, even mild hypotension can trigger ischemic stroke .
The pain of RCVS-associated headache is extreme and frequently warrants round-the-clock use of opioid analgesics. Triptans and the ergot derivatives are contraindicated because of their vasoconstrictive actions [4,69].
Acute seizures may warrant treatment, though seizures are usually present only upon presentation and do not recur. Therefore, long-term seizure prophylaxis is probably unnecessary.
Vasoconstriction — In the absence of controlled trials, management of vasoconstriction is guided by observational data and expert opinion. Empiric therapy is not justified for patients who present with thunderclap headache but have not yet undergone vascular imaging. However, even when cerebral vasoconstriction has been documented, specific treatment remains undefined. Because clinical and angiographic resolution occur spontaneously without any medical intervention in approximately 90 percent of patients with RCVS, we generally do not use any agent to treat vasoconstriction.
While the literature is replete with various treatment approaches showing good outcome, these reports probably reflect publication bias. Calcium channel blockers such as nimodipine and verapamil  and brief courses of glucocorticoids , magnesium sulfate , serotonin antagonists, and dantrolene  have been administered in an effort to relieve the vasoconstriction. Data from two prospective case series suggest that nimodipine does not affect the time course of cerebral vasoconstriction [17,18]. However, nimodipine might relieve the number and intensity of headaches and has documented effects on the smaller vasculature not easily imaged by angiography. Calcium channel blockers can be discontinued after resolution of symptoms or angiographic abnormalities, if they are used.
Glucocorticoids are often administered to minimize the risk of delaying treatment in patients who may actually have primary angiitis of the central nervous system (PACNS), a condition that shares certain features with RCVS (see 'Differential diagnosis' above) and is believed to be progressive and potentially fatal without prompt immunosuppressive therapy. Unfortunately, many patients remain on glucocorticoids for prolonged durations and incur the risk of serious steroid-related adverse effects. We suggest not using empiric glucocorticoid therapy for several reasons:
●There is little evidence that a therapeutic delay of a few days would increase the risk for worse outcome in PACNS; even with diagnostically challenging cases, the diagnosis usually becomes apparent after a brief period of observation.
●Glucocorticoids may be associated with worse outcome in RCVS [23,78].
Bedside efforts should focus on distinguishing RCVS from PACNS on the basis of the initial clinical and imaging features and reserve empiric glucocorticoid therapy for the rare patient with a rapidly worsening clinical course while the diagnosis remains uncertain.
Balloon angioplasty and direct intra-arterial administration of nicardipine, papaverine, milrinone, and nimodipine have been used with variable success [79-81]. In patients with RCVS, intra-arterial infusion of vasodilators into a single constricted artery can promptly reverse vasoconstriction in multiple brain arteries, including the contralateral arteries. A similar response has rarely been observed in RCVS mimics such as PACNS and intracranial atherosclerosis. On this basis, the demonstration of arterial dilatation using intra-arterial vasodilator infusions has been proposed as a "diagnostic test" for RCVS . However, intra-arterial interventions carry a risk for reperfusion injury. Therefore, we reserve intra-arterial measures for patients exhibiting clear signs of clinical progression, particularly since over 90 to 95 percent of RCVS patients have a benign, self-limited syndrome despite the presence of severe angiographic vasoconstriction and ischemic or hemorrhagic brain lesions. Unfortunately, no known clinical or imaging features reliably predict disease progression.
Prevention and counseling — It is logical to avoid further exposure to any potential precipitating factors, such as marijuana, cocaine, exercise stimulants, amphetamines, and other vasoconstrictive medications which can worsen the clinical course, as well as to counsel patients about the possible risk of recurrence with re-exposure. Patients should avoid physical exertion, the Valsalva maneuver, and other known triggers of recurrent headaches for a few weeks.
Usual stroke preventive medications, such as antiplatelets, anticoagulants, and cholesterol-lowering agents, are probably not indicated.
There are no known genetic implications of RCVS.
PROGNOSIS — Most patients with RCVS have complete resolution of headaches and angiographic abnormalities within days to weeks. Less than 15 to 20 percent are left with residual deficits from stroke, and in most cases the deficits are relatively minor (ie, 90 to 95 percent have a modified Rankin scale score (table 5) of 0 to 2 at discharge). Progressive vasoconstriction resulting in progressive symptoms  or death [48,52-54] can occur in rare cases. Retrospective data suggest that baseline infarction and glucocorticoid exposure are predictors of poor outcome .
It should be noted that "reversibility" in the term RCVS refers to the dynamic and reversible nature of vasoconstriction; clinical deficits from brain damage might persist and the vasoconstriction (particularly if severe and prolonged) may not fully reverse in some patients. Recurrence of an "episode" of RCVS is rare and usually manifests as an isolated thunderclap headache without complications such as stroke [83,84]. Some patients go on to have intractable chronic migraine-like headaches or depression .
SUMMARY AND RECOMMENDATIONS
●Reversible cerebral vasoconstriction syndromes (RCVS) are a group of conditions characterized by reversible narrowing and dilatation of the cerebral arteries. (See 'Terminology' above.)
●The etiology of RCVS is unknown, though the reversible nature of the vasoconstriction suggests an abnormality in the control of cerebrovascular tone. (See 'Pathophysiology' above.)
●RCVS occurs in individuals of all ages and races. The mean age of onset of RCVS is 42 years. In adults, RCVS affects women two to ten times more often than men. In children, RCVS may be more common in boys. A variety of diverse conditions have been associated with RCVS including exposure to vasoconstrictive drugs and medications, sexual intercourse, and recent pregnancy. (See 'Pathophysiology' above and 'Epidemiology' above.)
●The clinical presentation of RCVS is usually dramatic with sudden, severe "thunderclap" headaches that simulate aneurysmal subarachnoid hemorrhage; however, in patients with RCVS, thunderclap headaches often recur over a span of one to four weeks. (See 'Clinical features' above.)
●The following criteria can be used for bedside diagnosis of RCVS at the time of admission (see 'Evaluation and diagnosis' above):
•Recurrent thunderclap headache; or
•Single thunderclap headache combined with either normal neuroimaging, border zone infarcts, or vasogenic edema; or
•No thunderclap headache but abnormal angiography and no brain lesions on neuroimaging; the absence of brain lesions virtually rules out primary angiitis of the central nervous system
●Despite the presence of widespread cerebral vasoconstriction, the admission brain scan is normal in over 50 percent of patients with RCVS. In the ensuing days, many patients go on to develop complications such as ischemic strokes, convexal (nonaneurysmal) subarachnoid hemorrhages, lobar hemorrhages, and reversible brain edema, alone or in combination. (See 'Brain imaging' above.)
●Cerebral angiographic abnormalities are dynamic and progress proximally, resulting in a "sausage on a string" appearance of the circle of Willis arteries and their branches. These abnormalities resolve spontaneously (without specific therapy) over a few weeks. (See 'Neurovascular imaging' above.)
●There is no proven therapy for RCVS. Supportive care is directed towards managing blood pressure, severe headaches, and other complications such as seizures. Oral calcium channel blockers are often administered to treat vasoconstriction but the supporting evidence for this strategy is weak. Intra-arterial vasodilator therapy has been attempted in fulminant cases with variable success. (See 'Management' above.)
●The clinical outcome is benign in 95 percent of patients. Rare patients develop severe irreversible deficits or death from progressive strokes or cerebral edema. Recurrence of an episode of RCVS is rare. (See 'Prognosis' above.)
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