Pathogenesis and Types

The risk factors for ICH include hypertension, advancing age, vascular malformations, cerebral amyloid angiopathy, anticoagulant and fibrinolytic agents, brain tumors, sympathomimetic agents, and vasculitis. Hypertension is the primary risk factor across all ages, with the highest representation in those aged 40 to 69 years, whereas cerebral amyloid angiopathy is a more common risk factor in patients older than 70 years. In younger persons, sympathomimetic agents, especially cocaine, and vascular malformations are dominant factors. Brain tumors associated with ICH are typically the malignant varieties, either primary (particularly glioblastoma multiforme) or metastatic, including melanoma, choriocarcinoma, bronchogenic, renal cell, and thyroid carcinoma.

Warfarin-related ICH is an important group, particularly in senior or middle-aged individuals who are more likely to be taking this medication because of underlying atrial fibrillation; here a leading risk factor is excessive prolongation of the international normalized ratio (INR). This variety of ICH is associated with a particularly high mortality because of the generally large hematoma volumes that develop due to frequent enlargement of the hematoma within the initial hours after onset of symptoms. The ICHs that occur after treatment of acute ischemic stroke with thrombolytics are also generally large sized, tending to occur within hours of completion of the thrombolytic treatment, and typically are located in the area of the manifesting cerebral infarction.

The locations of ICH and their approximate frequency are putaminal (35%), lobar (25%), thalamic (20%), cerebellar (10%), pontine (5%), and caudate (5%) (see Plate 9-37). The predominant location of ICH in deep subcortical and brainstem locations reflects the anatomic distribution of chronic changes within the wall of deep small penetrating arteries subjected to chronic hypertension. In contrast, the more superficiallylocated lobar ICHs reflect the classic pathoanatomy related to cerebral amyloid angiopathy.

The clinical presentation of an ICH has a number of general features that are frequent with all topographic varieties and particularly reflect the clinical symptomatology that results from a rapidly expanding intracranial mass lesion. These include headache, vomiting, and depressed levels of consciousness. Although these are not constant features, their presence is virtually diagnostic of an ICH, in particular if a gradual decline in the level of consciousness occurs in parallel with a gradual increase in the severity of the presenting focal neurologic deficits. The specific findings on neurologic examination are related to the particular localization of the ICH within the brain.

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