The brainstem describes the area at the base of the brain that connects the brain to the spinal cord. All signals traveling to and from the brain must pass through the brain stem. Cells of the brain require a constant supply of oxygenated blood in order to function. When blood flow becomes inhibited, a condition known as a stroke, brain cells die, causing permanent brain damage. A stroke affecting the brainstem increases the risk for serious complications.
Risk Factors
The risk factors for experiencing a brainstem stroke are the same as for any type of stroke. High blood pressure, a condition known as hypertension, remains the number one risk factor for a stroke, according to MedlinePlus and the National Institutes of Health. Other risk factors include diabetes, high cholesterol and the onset of heart disease. Atrial fibrillation, a type of arrhythmia, also increases the risk of a stroke because the heart fails to pump all the blood out, allowing blood to pool which increases the risk for blood clot formation.
Brainstem Structure
The brainstem consists of the midbrain, the pons and the medulla oblongata. The midbrain contains a bundle of nerve fibers that travel from the cerebral cortex, the main portion of the brain, to the body. The pons links to the cerebellum while the medulla oblongata lies between the pons and the spinal cord. Six major arteries supply blood to the brainstem and a blockage in any one of these increases the risk for a stroke.
Brainstem Functions
The brainstem controls many of the vital functions of the body, making a stroke in this section of the brain especially dangerous and life-threatening. The medulla oblongata controls the vital involuntary functions including heart rate, breathing and blood pressure. The midbrain functions in vision and hearing as well as eye and body movement. The pons controls movement, processes sensory input and functions in consciousness.
Effects of Stroke
Because nerve signals traveling from the cerebrum and cerebellum must travel through the brainstem, a stroke can interfere with these signals and result in paralysis, as described by the Ohio State University Medical Center. A brainstem stroke can change the breathing rate as well as affect the heart rate and blood pressure. A brainstem stroke can also affect sensations, such as the ability to feel pain or extreme temperature. This increases the risk for injury following a stroke. Brainstem strokes can affect eye movements which can result in dizziness and vertigo--the sensation of movement or spinning. These conditions increase the risk for falls, especially in patients who also experience muscle weakness from stroke.
Complications
A stroke affecting the brainstem increases the risk for serious complications. Brainstem strokes can lead to paralysis, on one or both sides of the body. Patients might also need the aid of a machine in order to breathe. Brainstem strokes can also lead to coma.
