Cerebral amyloid angiopathy [CAA], also known as congophilic angiopathy,1-4 is a well known clinicopathological entity since the beginning of the century and has attained the limelight over the past decade for two reasons, firstly as a probable cause for non traumatic primary cerebral haemorrhage resulting in stroke in normotensive elderly patient5-11 and secondly due to its occurrence in senile dementia of Alzheimer type (SDAT)[92% of affected brains] and Alzheimer’s disease (AD)).12-15 CAA is also associated with transient ischaemic attacks,16 subarachnoid haemorrhage,17 Down syndrome, post irradiation necrosis,18 multiple sclerosis,19 leucoencephalopathy,20 spongiform encephalopathy,21 and dementia pugilistica.21 CAA specially affects the cerebral vessels mainly in the leptomeninges and superficial cerebral cortex of the elderly.22, 23

Recognition of this entity has specific clinical significance. As the heavy amyloid laden micro vessels are brittle, therefore haemorrhage may be precipitated by minor trauma or neurosurgical procedures such as shunt replacement.1,24 Thus, conservative (nonsurgical) management is advocated for this group of patients whenever possible.25

The prevalence of CAA has not been studied in the Indian population. Thus we undertook this present study, to ascertain the incidence of CAA in the ageing Indian population, and to determine whether it contributes to the high incidence of cerebral haemorrhage.

A retrospective study was performed in the laboratory of neuropathology, department of pathology, Seth G S Medical College and KEM Hospital, Mumbai, on 50 postmortem brains from over 70 years of age, irrespective of the clinical diagnosis, taken from complete necropsies over a period of 11 years. 10 to 12 sections were taken from cerebral cortex (Frontal, parietal, occipital and temporal lobes), cerebellum and basal ganglia, hippocampus, hypothalamus, amygdaloidal nucleus, dentate nucleus and blood vessels at the base of brain. Paraffin sections (7 micron thickness) were prepared and stained with haematoxylin and eosin stain. All these sections were also stained with Congo red stain at an alkaline pH. The sections were examined with transmitted light and polarized light using A. O. microscope. Vessels within the brain parenchyma and in the leptomeninges that demonstrated any congophilic material with apple green birefringence in their walls were labelled as amyloid containing blood vessels (Figs. 1 and 2). Severity of CAA in a given section was assessed by applying the method used by Vinters.2 The intraparenchymal and leptomeningeal vessels were graded separately. A three point grading system was used depending on the number of vessels affected and the intensity of the birefringence

Fig. 1 : Parenchymal vessel showing obliterative onion skin like intimal change. Amyloid deposition is seen in the intima and the inner media with congo red stain X 400	Fig. 2 : Green birefringence seen in the intima and inner media using polarized light X 400

A score of grade I to III was given to each section according to increasing presence of CAA positive blood vessels (grade I - if 1-2 vessels were positive, II - if 3-5 vessels and III - if more than 5 vessels were positive). Scores of grade III were taken as severe case of CAA. Each section was also examined for the presence of extra vascular amyloid cores, which would suggest senile plaques.

Amyloid can be detected by histochemical, immunological and electron microscopic methods.1-4,25 The characteristic of congophilia and the demonstration of apple green birefringence under polarized light remain one of the simplest and most reliable methods of amyloid detection.1-4

CAA is a common finding in the brains of Caucasians over 70 years of age.22,23 It is only rarely reported in Indians and the incidence of CAA in the general population is not known. The present study confirms a lower incidences of CAA in Indians compared with Caucasians. Our results not only show a lower incidence of CAA in Indians, the involvement also tends to be less severe which is similar to the observations made in a Chinese study by Ng et al1 (Table 4). Using the similar method of assessment as Vinters,2 only 1 of our 7 cases are severely involved compared to his series where 14 out of 30 cases (47%) have severe CAA. The relatively mild degree of involvement of vessels by CAA in Indians may also help explain the low incidence of CAA associated cerebral haemorrhage. Of the 25 brains which showed evidence of cerebrovascular disease (Table 2) only 2 patients died of spontaneous cerebral haemorrhage and the rest died of unrelated illnesses.

Vascular abnormalities observed were glomerular formations of vessels, aneurysmal vessels, obliterated changes (onion peel), double barreling, perivascular infiltrate, arteriolar degeneration and fibrinoid necrosis.26,27 CAA caused by amyloid beta-protein (Abeta) is particularly associated with clinical and pathological features of Alzheimer’s disease.4 However the review of the clinical history of our 7 CAA patients did not reveal symptomatology of dementia, nor did they have associated senile plaques.

Thus to conclude, from our study it appears that CAA affects Indians less frequently and less severely and it may not be responsible for the high incidence of cerebral haemorrhage among Indians. Its significance in Indians is much less than that in Caucasians. However further studies are required to corroborate our findings.