Hemorrhagic stroke make up approximately 20% of all stroke cases. Two thirds of the hemorrhagic strokes are in the form of intracerebral hemorrhage (ICH). The remainder is subarachnoid hemorrhage which is discussed elsewhere. The overwhelming majority of ICH is secondary to hypertension. Other causes include vascular malformations such as AVM and cavernous angioma, coagulopathy, AA, underlying tumor, illicit drug use, venous occlusion, vasculitis, and encephalitis. Noncontrast CT is the modality of choice for initial evaluation. MRI is reserved for searching for an underlying cause. Cerebellar ICH is a neurosurgical emergency due to the danger of hydrocephalus, brainstem compression, and death. Hypertensive ICH at other locations is rarely treated surgically.
Hypertensive Intracerebral Hemorrhage
The most common locations of hypertensive ICH, in decreasing order of frequency, are the putamen, caudate nucleus, thalamus, lobe of a hemisphere (lobar), cerebellum, and pons. Clinical and imaging findings unusual for hypertensive ICH should invoke a workup for other potential causes which usually involves MRI/MRA and sometimes digital subtraction angiography (DSA). Intraventricular extension and large-sized hematoma are two imaging findings that predict a worse prognosis.
AVMs are congenital malformations of the cerebral vessels that develop as a result of failure of regression of the primitive connections between the arteries and veins. AVMs have a 2-4% annual risk of hemorrhage. AVMs are the leading cause of ICH in young adults. Hemorrhage can occur anywhere in the brain. Subarachnoid and intraventricular extension is common. Owing to compressive effect of the acute hematoma, AVMs may be difficult to diagnose on MRA and even on DSA in the acute phase. Follow-up may be needed to establish the diagnosis.
AA is a major cause of ICH in the normotensive elderly. The clinical hallmark of AA is repeated lobar ICH. MRI is critical in demonstrating old hemorrhages. Susceptibility weighted imaging shows innumerable small foci of hemosiderin deposition throughout the subcortical regions.
Primary brain tumors and metastases may present with hemorrhage. It may be difficult to realize the presence of an underlying mass lesion. Generally, the configuration of surrounding edema differs in that tumors have a fingerlike vasogenic edema whereas pure hematomas have a halolike edema. In tumor-related ICH, there may be a portion of the tumor that does not contain hemorrhage. On postcontrast images, an area of nodular enhancement implies underlying tumor.
Noncontrast CT is the test of choice for rapidly detecting the presence of intracranial hemorrhage.
Possible Findings - Hematomas have high attenuation. - Hematoma in a very anemic or coagulopathic patient may have less hyperattenuation. - Hypoattenuation, representing edema and extracted serum, surrounding the hematoma that becomes larger and better defined over time. - Mass effect, midline shift, intraventricular extension, and hydrocephalus. - Serpentine tubular structures in the vicinity of hematoma in case of AVM rupture. - Fluid-fluid levels in hematoma imply coagulopathy.
Magnetic Resonance Imaging
MRI provides a more comprehensive evaluation in the expense of time. MRI is primarily used for evaluation of underlying etiology of hemorrhage. It is highly sensitive to acute ICH, although the appearances are complex and depend on multiple factors. These include the paramagnetic form of hemoglobin present, clot matrix formation, changes in erythrocyte hydration, and changes in the degree of red blood cell packing.
- There is a characteristic sequence of signal changes as the ICH forms and evolves. This sequence is listed in the subsequent text, and is most characteristic of intraparenchymal hemorrhage.
- Gradient echo T2*-weighted sequences highlight changes in magnetic susceptibility, and are very sensitive to acute and chronic hemorrhage.
Issues After Imaging Medical therapy is centered on management of blood pressure, intracranial pressure, and seizure control. Surgical evacuation may be needed to relieve significant mass effect.