Blood clots in the brain can lead to a stroke. If the clot dissolves before permanent damage occurs, symptoms are transient, and the event is known as a TIA, or transient ischemic attack. Symptoms of a stroke depend on the location of the clot, the size of the artery affected and the area of brain it supplies. Symptoms can include any type of brain function. Strokes can be mild, almost unnoticed, or can lead to severe disability and death.
Blood Clots Affecting the Frontal, Parietal and Temporal Lobes
Two major arteries supply the blood to frontal, parietal and temporal lobes. As described in "Adams and Victor's Principles of Neurology," these areas control higher thinking, planning, motor function, sensation and memory. A stroke affecting the middle cerebral artery, which supplies the outer, or lateral, part of the brain, can cause symptoms that include paralysis and loss of sensation on the opposite side of the body, loss of half of the visual field, seizures and inability to speak or to understand speech. Paralysis can affect the entire opposite, half of the body, or just part of it. Disinhibition and personality changes can occur.
The anterior cerebral artery supplies the inner side of the brain. Strokes in this artery can lead to paralysis and loss of sensation of the opposite foot and leg, or to paralysis of both feet and both legs, while sparing the upper body and face. Urinary incontinence may occur. Unsteady gait and memory loss are other common symptoms.
Blood Clots Affecting the Brainstem
Brainstem strokes can cause many different constellations of symptoms, depending on the exact area affected. According to "Harrison's Principles of Internal Medicine," brainstem strokes cause paralysis and loss of sensation on the same side of the body as the clot, combined with paralysis of the face and eye movements on the other side. Damage to the centers of respiration and heart rate can lead to death. If an area known as the reticular formation is affected, the patient can lapse into a coma. Damage to the cerebellum can cause loss of balance, unsteady gait and tremor. A clot in the basilar artery can lead to "locked-in syndrome," in which the patient is alert and aware of his surroundings, but is paralyzed and unable to communicate with anyone.
Also affected in brain stem strokes are the occipital lobes, the posterior lobes of the cortex, which receive their blood supply from arteries that go through the brainstem. Symptoms include loss of part of the visual field, difficulty reading, inability to recognize faces and blindness.
Lacunar Blood Clots
The large cerebral arteries send small branches that penetrate deep into the brain. Strokes in these arteries can affect the motor fibers that lead from the motor area of the cortex to the body. As explained in "Adams and Victor's Principles of Neurology," since the fibers are concentrated in a small area, lacunar strokes can cause a dense stroke, meaning the entire opposite half of the body is paralyzed, with no area spared. A lacunar stroke may cause loss of sensation only, without any motor involvement. Speech may be affected.
References
- "Adams and Victor's Principles of Neurology"; Maurice Victor and Allan Ropper; 2001
- "Harrison's Principles of Internal Medicine"; Anthony Fauci et al.; 2008
