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Parenchymal Hemorrhage

What Is It, Causes, Treatment, and More

Author: Lily Guo

Editors: Ahaana Singh, Ian Mannarino, MD, MBA

Illustrator: Jillian Dunbar

What is a parenchymal hemorrhage?

A parenchymal hemorrhage, or an intraparenchymal hemorrhage (IPH), is a bleed that occurs within the brain parenchyma, the functional tissue in the brain consisting of neurons and glial cells. A hemorrhage, or the profuse release of blood from a ruptured blood vessel in the brain, disrupts normal blood flow and subsequently deprives the brain of oxygen. As a result, the brain cells can die, which damages the affected nerves and the related functions they control as well. Spontaneous IPH accounts for less than 20% of stroke cases, but it is associated with the highest mortality rates of all forms of stroke. IPH can be classified as primary or secondary, depending on the cause. Primary IPH accounts for about 80% of cases, occurring when there is a spontaneous rupture of damaged arteries. Meanwhile, secondary IPH is due to an underlying condition that increases the likelihood of hemorrhage. 

What causes a parenchymal hemorrhage?

Hypertension, or high blood pressure, is the main risk factor for primary IPH, as it increases the likelihood that small vessels in the brain parenchyma will rupture. Another cause of primary IPH is cerebral amyloid angiopathy (CAA). In CAA, abnormal proteins called amyloids accumulate on the walls of the brain arteries, which can lead to rupture and subsequent hemorrhage. 

Meanwhile, secondary IPH can occur as a result of various underlying conditions. Most commonly, it is the result of coagulopathy, or the inability to form blood clots due to either a coagulation factor deficiency or a severe platelet deficiency, the latter of which is known as thrombocytopenia. Secondary IPH may also be caused by sickle cell disease, an inherited red blood cell disorder that causes red blood cells to form into a sickle shape. The sickle-shaped red blood cells are unable to move easily through blood vessels, and they carry less oxygen. In other cases, secondary IPH may be due to brain tumors. 

Yet another condition often associated with parenchymal hemorrhage is cerebral venous sinus thrombosis (CVST). CVST occurs when there is a clot in the vein responsible for draining blood from the brain. The clot causes the blood flow to back up, leading to leakage of blood into surrounding tissues. 

Two other conditions that can lead to secondary IPH are arteriovenous malformation and Moyamoya disease. Arteriovenous malformation is characterized by abnormally formed connections between arteries and veins, which can disrupt normal blood supply to the brain and increase risk of rupture. Moyamoya disease, a rare condition seen most often in Japan, involves defective arteries in the brain, leading to arterial narrowing and increased risk of hemorrhage.

Additional significant risk factors include smoking, alcohol intake, and use of sympathomimetic drugs, such as amphetamines. Lastly, trauma or infection, particularly from the hepatitis C virus, can raise the possibility of parenchymal hemorrhages. 

What are the signs and symptoms of a parenchymal hemorrhage?

Signs and symptoms of a parenchymal hemorrhage often include headaches, seizures, and focal neurological deficits, such as speech, vision, and hearing problems. The severity and type of symptoms may depend on the location of the bleed within the brain. Other common signs include nausea and vomiting, lethargy, limb weakness, and sensory defects, such as numbness of the face and limbs. If the bleed is large, individuals may experience impaired consciousness. 

In severe cases, brain damage may lead to physical or mental disability. 

How is a parenchymal hemorrhage diagnosed?

To diagnose parenchymal hemorrhage, blood coagulation studies are often required. This includes analyzing a blood sample to look at partial thromboplastin time (PTT) which assesses the time it takes for blood to clot. Additionally, imaging studies using computerized tomography (CT) scans of the head can show bleeds in various parts of the brain. Computed tomographic angiography/venography, involving injection of radiographic dye into the blood vessels leading to the brain, can be used to identify CVST. Magnetic resonance imaging (MRI) can also be performed to look for other underlying causes, such as a brain tumor or ischemic stroke, as well as to identify patterns consistent with CAA or high blood pressure. Additional studies, such as cardiopulmonary monitoring, intracranial pressure monitoring, and electroencephalogram may be performed, respectively, to assess heart and lung function, monitor rise in pressure around the brain, and rule out other diagnoses such as seizure.

How is a parenchymal hemorrhage treated?

Parenchymal hemorrhages can be life-threatening and should be treated promptly. Maintaining adequate blood pressure along with a normal intracranial pressure is critical in individuals with IPH. If intracranial pressure is increased, medications such as mannitol or hypertonic saline may be administered. Additionally, identifying and treating the underlying cause of the IPH is important. Those with secondary IPH due to coagulation factor deficiency or thrombocytopenia should receive factor replacement therapy or platelet therapy. If the individual is taking anticoagulation or blood-thinning medications, the symptoms and outcomes may worsen. Accordingly, Vitamin K or protamine sulfate is often administered to reverse the effects of these medications. 

In the case that the individual becomes unresponsive as a result of the hemorrhage, airway management is often necessary in order to mitigate the risk of secondary injury from aspiration, severely decreased oxygen levels in the blood (i.e., hypoxemia), and excessive carbon dioxide in the blood (i.e., hypercapnia). If the parenchymal hemorrhage occurs in the cerebellum, a portion of the brain that is in a tight compartment near the brainstem, cerebellar decompression surgery may be indicated. Minimally invasive approaches for surgery may include small incisions, burr holes, and insertion of a catheter into the clot for drainage. Open craniotomy, involving the surgical removal of part of the skull, can also be performed to treat certain parenchymal hemorrhages. 

What are the most important facts to know about parenchymal hemorrhage?

A parenchymal hemorrhage is a bleed that occurs within the brain parenchyma and can lead to the disruption of oxygen in brain cells and subsequent functional tissue death. There are two types of parenchymal hemorrhages: primary and secondary. The former involves spontaneous rupture of damaged arteries, while the latter involves predisposition to the disease due to the presence of other conditions, like coagulopathies, tumors, central venous sinus thrombosis (CVST), and arteriovenous malformation, among others. Hypertension, which weakens brain vessels, is the primary risk factor for IPH. The second most common cause is cerebral amyloid angiopathy (CAA), with the accumulation of amyloid plaque leading to deterioration of vessels. Sudden acute-onset headache, nausea and vomiting, and focal neurological deficits differentiate intraparenchymal hemorrhage from other diagnoses.  Blood coagulation studies, as well as imaging in the form of CT scans, angiography, and MRI should be used to look for the presence and location of hemorrhage. Timely assessment is critical, and treatment can include blood pressure management, airway protection, or medication. If necessary, surgery can be performed to reduce cerebral pressure.

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