Spontaneous intracerebral haemorrhage (ICH) is defined as a focal collection of blood within the brain parenchyma or ventricular system that is not caused by trauma.1 It is a heterogeneous condition resulting from several distinct underlying vasculopathies. Several interacting and overlapping risk factors may play a role in the vessel rupture.
The overall incidence of ICH ranges from 15 to 40 per 100,000 person-years.2–4 ICH accounts for 10–15 % of all strokes, but this proportion may be higher in Asian populations.5–7 The risk of ICH increases with age, being 9.6-fold higher in people over 85 years old compared with those less than 45 years of age.8 ICH incidence is higher in men, especially in Asian populations.3 Despite a significant improvement in ischaemic stroke management, ICH treatment has not significantly changed and this condition remains associated with a high case fatality rate in the first month, ranging from 13 to 61 % of patients, with a median of 40 % across studies.3
The clinical and epidemiological scenario of ICH has been changing in the last decades.2,9,10 Despite an overall stable incidence of ICH, the incidence among people older than 75 years has increased and the incidence among people younger than 60 years has decreased, with a larger proportion of lobar haemorrhages, suggesting that vasculopathies more strongly associated with the elderly, particularly cerebral amyloid angiopathy (CAA), represent an increasing proportion within the aetiological distribution of ICH.10 The poor prognosis of ICH may be partly due to our poor understanding of this heterogeneous disease. Herein, we review the different causes of ICH.
Anatomical Distribution (see Figure 1)
ICH location can be classified as deep, lobar and infratentorial (involving the cerebellum and/or the brainstem). The anatomical distribution of the haemorrhage and its extension to other compartments (subarachnoid, subdural, intraventricular) may bring clues to identify the underlying cause of the bleeding.
Our knowledge on the anatomical distribution remains imprecise because most estimates are based on hospital series, which suffer from bias (referral is less often considered for moribund patients or, at the other extreme, for patients with only mild deficits), and populationbased studies, which are unbiased might contain a small proportion of haemorrhages precluding any further anatomical subdivision.1,9,11 In population-based registries, deep ICH accounts for 60–65 % while lobar ICH accounts for 31–40 % of all ICH cases.9,11 Multiple ICH accounts from 0.7–4.7 %12,13 of all ICH cases.
The pooled 1-year survival estimate in nine population-based studies was 46 % (95 % confidence interval [CI] 43 to 49), while when location is considered the 1-year survival was 45–59 % after lobar ICH, 45 to 59 % after deep ICH and 40 to 54 % after infratentorial ICH.14
The most frequent cause of deep ICH is deep perforating vasculopathy that supervenes mostly in small perforating arterioles (50–700 µm in diameter) originating from the middle cerebral artery and from the basilar artery, thus explaining the classic location in the basal ganglia and brainstem. Deep ICH may be restricted to brain parenchyma or may extend to the ventricules. Intraventricular haemorrhage (IVH) is a frequent complication occurring in nearly 50 % of ICH patients, and it is a predictor of poor outcome.15 The risk of bleeding in patients with deep perforating vasculopathy might be enhanced in patients receiving oral anticoagulants16 and among patients with heavy alcohol consumption history.17
Hypertension was found to be twice as common a risk factor for patients with deep ICH than with lobar ICH, particularly in younger age groups (odds ratio [OR] 2.27, 95 % CI 1.94 to 2.66). These findings are, however, heavily influenced by studies with less robust methods. In the methodologically more rigorous studies, a smaller, but still statistically significant, excess of hypertension among patients with deep ICH was found (OR 1.50, 95 % CI 1.09 to 2.07). Further large, methodologically robust studies are needed to determine accurately the relative contribution of hypertension to deep and lobar ICH in different age groups.18 Although deep perforating vasculopathy is the most frequent cause, other disorders, such as intracranial vascular malformations (IVMs), may less frequently lead to deep ICH.19