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cerebral amyloid angiopathy ( caa ) , also known as congophilic angiopathy or cerebral amyloidosis , is a clinicopathologic condition resulting from the extracellular deposition of an amorphous eosinophilic substance ( a fibrillar protein , amyloid ) in the walls of small- and medium - sized arteries .
the amyloid material is only found in brain and therefore this disease is not related to any other form of systematic amyloidosis .
although caa can manifest in several ways , the most serious manifestation of caa in older people is the rupture of cerebral vessels , leading to intracerebral hemorrhage , accounting for about 10% of all types of pich .
the incidence of pich increases with age , and is rare in those younger than 55 years .
although caa most commonly occurs in sporadic form in the elderly , numerous familial forms also occur in the younger age group .
it is difficult to make a definitive diagnosis of caa in life , as it requires pathologic examination of the brain tissue .
however , recent developments in brain imaging techniques have greatly helped in allowing a diagnosis of  probable caa  to be made , as per boston criteria for diagnosis of caa - related hemorrhage [ table 1 ] .
caa may occur in the absence of clinical and/or pathologic evidence ( eg , amyloid plaques ) of alzheimer 's disease . in a setting of
diffusely increased vascular fragility , microhemorrhages could occur when they are not clinically apparent , but should be detected by magnetic resonance imaging ( mri ) .
the sensitivity of mri for hemosiderin provides unique opportunity to identify old microhemorrhages . although most studies define microhemorrhages as being smaller than 5 mm in diameter , an upper limit of 10 mm is sometimes used .
there is also a high prevalence of white matter lesions on ct and mri in patients with lobar pich and caa .
a 66-year - old normotensive , nondiabetic man , presented to our hospital with clinical features of stroke .
the patient had mild , progressive cognitive decline , and few episodes of transient ischemic attack beginning few weeks before the major stroke , for which he had not taken any medication .
ct and mr images of brain were obtained 2 weeks after the stroke . a plain axial ct image [ figure 1 ] showed right parietal lobe hematoma with diffuse cerebral white matter hypodensities . corresponding axial t1-weighted mr image [ figure 2 ] demonstrated subacute nature of right parietal hematoma .
t2-weighted [ figure 3 ] and flair [ figure 4 ] mri images showed extensive supratentorial white matter hyperintensities favoring caa - related inflammatory leukoencephalopathy .
the white matter changes were diffuse , concomitant , confluent ( grade 3 ) , more pronounced on the right side and involved both periventicular deep white matter and subcortical u - fibers .
multiple punctate ( grade 1 ) white matter hyperintensities were also visible in bilateral frontoparietal and left basal ganglia region . t2 * -weighted gradient - echo ( gre ) mr images [ figure 5 ] showed multiple focal hemosiderin deposits ( old microbleeds ) in the cortical and corticosubcortical location of right frontotemporal lobe , and solitary fresh microbleed in the left high posterofrontal region , as signal void areas , giving a characteristic  blooming effect . 
in addition , linear areas of signal void visible in the vicinity of the primary lobar hemorrhage , and right frontal lobe suggested subarachnoid hemosiderosis .
although diffusion weighted imaging ( dwi ) and the corresponding apparent diffusion coefficient ( adc ) mapping [ figure 6 ] revealed restricted diffusion within large lobar subacute bleed , but no other area in the brain demonstrated diffusion restriction , excluding acute infarct .
plain axial ct image reveals large , right parietal lobe hematoma causing mild compression of posterior part of the body of ipsilateral lateral ventricle ; and diffuse white matter hypodensities ( leukoaraiosis ) axial t1-weighted mr image demonstrates subacute right parietal hematoma and associated white matter hypointensities .
mild age - related generalized brain atrophy with prominence of cerebrospinal fluid spaces is also evident t2-weighted axial image reveals diffuse , asymmetrical , confluent ( grade 3 ) supratentorial white matter hyperintensities , being more pronounced on the right side , involving both periventicular deep white matter and subcortical u - fibers ( double arrow ) .
multiple punctate ( grade 1 ) hyperintense foci ( single arrow ) are also visible in bilateral frontoparietal and left basal ganglia region axial flair sequences demonstrate the lobar hematoma with irregular borders , and supratentorial white matter hyperintensities as seen in t2-weighted images t2fnx01-weighted gradient - echo mr images show multiple focal hemosiderin deposits ( old microbleeds ) in the cortical and corticosubcortical location of right frontotemporal lobe ( thick downarrow ) , and solitary fresh microbleed in the left high posterofrontal region ( thick up - arrow ) , seen as signal void areas ( blooming ) .
in addition , linear areas of signal void ( thin arrow ) in the vicinity of large primary lobar hemorrhage ( double arrow ) suggest subarachnoid hemosiderosis dwi and the corresponding adc mapping reveal restricted diffusion within the subacute bleed .
no other area in the brain parenchyma demonstrates diffusion restriction , thereby excluding acute cerebral infarct other potential causes of spontaneous hemorrhage , such as cavernous angioma or other vascular malformations , were excluded using mr angiography .
in addition , hemorrhages in locations more typical of hypertensive intracerebral hemorrhage ( ich ) , such as the basal ganglia and thalamus , were also excluded .
based on the above clinical and imaging findings and absence of other causes of cerebral hemorrhage , the patient fulfilled the boston criteria for diagnosis of probable caa . in our case , the patient was managed conservatively .
he was given diuretics to reduce the brain edema , and corticosteroid for coexisting cerebral amyloid inflammatory vasculopathy responsible for leukoencephalopathy and subacute progressive cognitive decline .
after a period of rehabilitation , the patient did show some improvement but was not able to live independently , and was discharged to be cared for by his family .
spontaneous ich is primarily caused by the rupture of small- and medium - sized arteries .
hypertension - induced fibrohyalinosis and deposition of -amyloid within the walls of small vessels are important causes of increased vascular fragility .
in addition to creating a higher risk for ich , both types of angiopathy favor the development of ischemic damage to the brain .
tissue changes , such as leukoaraiosis and a lacunar state , are therefore frequently observed in patients suffering from ich , and their presence has been suggested to indicate a higher risk for cerebral hemorrhage . in a study that compared the clinical features of pich due to caa and
those due to hypertension , the features of caa - related pich included lobar distribution affecting mainly lobar superficial areas , multiplicity of hemorrhage , bilaterality , repeated episodes , lobulated appearance , rupture into the subarachnoid space , and secondary intraventricular hemorrhage from the lobar hemorrhage . the location of cerebral microbleeds may help to determine the underlying cause of intracerebral hemorrhage .
an exclusively corticosubcortical distribution suggests amyloid angiopathy , whereas deeper microbleeds in the basal ganglia / thalami , brainstem , and cerebellum suggest hypertensive small vessel disease .
thus patients with caa tend to have corticosubcortical / lobar microbleeds and lobar hemorrhages , whereas patients with hypertensive disease tend to have deep microbleeds and deep hemorrhages .
the severity of a white matter hyperintensity ( leukoencephalopathy ) on t2w sequences was graded as punctuate ( grade 1 ) , early confluent ( grade 2 ) , or large confluent ( grade 3 ) .
the leukoencephalopathy in caa may be categorized as leukoencephalopathy with sparing of u - fibers or leukoencephalopathy with the involvement of u - fibers .
leukoencephalopathy with sparing of u - fibers is due to ischemia caused by diffuse narrowing of penetrating cortical vessels resulting from -amyloid deposition in the adventitia , whereas leukoencephalopathy that extends to involve u - fibers and is associated with edema , is related to perivascular inflammation secondary to -amyloid - induced vasculopathy . accumulating evidence suggests that white matter changes in caa increases over time and is linked to worsening of cognitive impairment.8 a set of clinical diagnostic criteria
have been proposed by the boston group in an attempt to unify the diagnosis of caa to be definite , probable with pathology , probable without pathology and possible .
recently , linn et al have proposed a modified boston criterion , in which they have suggested that inclusion of superficial siderosis ( ss ) as a criterion increases the sensitivity of the classic boston criteria for caa - related hemorrhage without the loss of specificity .
they have found that ss occurs with high prevalence in caa and is rare in the non - caa form of intracerebral hemorrhages .
although useful in diagnosing pich , ct provides limited information regarding the underlying cause , and in the detection of chronic asymptomatic microhemorrhages . in this context , attention is focused on mri because of its potential to reveal the residue of intracerebral hemorrhage throughout life , and even subtle white matter changes .
after an ich , hemosiderin remains stored in macrophages and , because of its magnetic properties , leads to focal dephasing of the mr signal , causing hemosiderin - containing areas to appear dark on t2-weighted spin - echo sequences .
this effect may be further enhanced by the use of imaging techniques with high sensitivity for differences in magnetic susceptibility , such as the gre sequence .
the susceptibility - weighted imaging ( swi ) has been used to evaluate the presence of microhemorrhages , and is found to be more sensitive than conventional gre techniques for the detection of blood products .
the differentiation of microhemorrhages from calcifications ( old calcified granulomas ) can sometimes be difficult in t2*w images without ct scans .
moreover , mr evidence of past microbleeds appears to be a better predictor of a patient 's risk for hemorrhage than are clinical findings , such as hypertension , or ct changes of leukoaraiosis . in this context , mri might help in selecting patients for different types of secondary prevention of stroke .
the major concern in the survivors of caa - related pich is the recurrent bleeding . a recurrence rate of 10% per year has been reported .
the recurrence of hemorrhage carries particularly poor prognosis with inhospital mortality of up to 70% .
some authors have suggested routine use of gre mri sequences to detect microbleeds in older people to avoid potentially dangerous anticoagulant or antiplatelet therapy .
however , the swi has been found to be more sensitive than conventional gre sequences in identifying caa - related microhemorrhages .
the usefulness of brain biopsy in diagnosis of caa has also been evaluated by many authors .
steven et al . took 28 cortical biopsy samples from postmortem brains with known caa .
microscopically , these samples demonstrated the presence of vascular amyloid as a sensitive marker for caa - related hemorrhage .
thus the examination of biopsies taken from cortical tissues also plays an important role in diagnosing this condition .
however , recent advances in immunopathology and pathogenesis of caa have helped to develop a specific antiamyloid drug , cerebril ( neurochem laval , canada ) , which has shown to reduce amyloid deposition and formation . at present , this drug is under phase 3 trial to prove its efficacy .
the management of caa - related intracranial hemorrhage is identical to the standard management of ich .
treatment of hypertension and other vascular risk factors , such as hypercholesterolemia , is usually advised . according to a recent progress trial , perindopril ,
an antihypertensive drug has shown reduction in caa - related ich by 77% over a follow - up period of 3.9 years . reduced consumption of alcohol is also an important part of secondary prevention .
cessation of cerebral hemorrhage recurrence associated with corticosteroid treatment in patients with caa has also been documented in the literature .
surgical evacuation of hematoma is indicated to lower the intracranial pressure , especially when hematoma causes significant mass effect and predisposes to herniation .
the anticoagulant and antiplatelet medications should be avoided in patients with caa , particularly in elderly individuals with atrial fibrillation , because of high bleeding rates associated with the use of these agents .
several studies have shown that low - dose aspirin ( eg , 75150 mg ) is highly effective in secondary prevention of intracranial bleed and risk of ischemic stroke .
we conclude that symptomatic pich is frequently preceded by microangiopathy - related ischemic damage and silent microhemorrhages as seen in our case .
such an mr finding certainly favors an angiopathic cause for the bleeding and thus may obviate more invasive diagnostic procedures .
the burden of asymptomatic cerebral microhemorrhages ( both old and fresh ) detectable by gre mri in patients with lobar pich related to caa is a good predictor of hemorrhage recurrence , and therefore highlights the importance of secondary prevention in caa - related pich .
cerebral amyloid angiopathy ( caa ) is an important cause of primary intracerebral hemorrhage ( pich ) in the elderly . 
 although there are no pathognomic clinical features of caa - related pich , the association of white matter changes with lobar , recurrent , or multiple simultaneous hemorrhages in older patients should raise the suspicion of its diagnosis . 
 a definitive diagnosis of caa requires pathologic examination of the affected tissue . 
 however , with modern imaging techniques , it is possible to diagnose the  probable caa  in patients presenting with pich . 
 gradient - echo magnetic resonance imaging is a very sensitive , noninvasive technique for identifying microhemorrhages in life . 
 the diagnosis of caa is important because of the likely implication it has on future management targeted to reduce risk of future bleeding .