The brain stem contains within a small area the control centers for the heart rate and breathing, as well as all the nerves that transmit motor and sensory signals between the brain and the body. Blood vessels that supply the brain stem also supply the posterior portions of the cortex. According to "Adams and Victor's Principles of Neurology," a brain stem stroke can cause a wide array of symptoms, depending on the specific area involved. Occlusion of any one artery often leads to a combination of motor, sensory and other symptoms. Brain stem strokes can be catastrophic, leading to significant impairment and death.
Symptoms of Cranial Nerve Paralysis
Most of the cranial nerves originate from the brain stem. They control the face, eye movements, the motor part of speech and swallowing. Strokes that affect them can cause paralysis of eye movements, double vision, droopy eyelids and a small pupil. Difficulty articulating can lead to a nasal-sounding voice. Problems with swallowing can create a choking hazard. Use caution when feeding a patient who has suffered a brain stem stroke.
Paralysis
One or both sides of the body may be affected. Paralysis can affect the face, arm or an entire side of the body. If only one side of the body is paralyzed, symptoms in the face and eyes appear on the opposite side. These "crossed symptoms" are typical of brain stem disorders. Stroke that involves all of the motor nerves going to the body can cause complete paralysis and muteness while consciousness remains intact. This state is known as "locked in" syndrome, in which the patient is fully conscious but unable to communicate with anyone.
Vertigo and Balance Issues
According to "Adams and Victor's Principles of Neurology," brain stem strokes can affect the vestibular nucleus, which is responsible for the sense of equilibrium, and has connection to many areas including the eye muscles. When this nucleus is affected, symptoms include nausea, vomiting, vertigo and double vision. Ataxia, or impaired gait, is a common symptom of brain stem strokes.
Compromised Vision
Arteries that supply the brain stem also supply the areas in the cortex responsible for processing and interpreting visual signals. According to "Adam's and Victor's Principles of Neurology," brain stem strokes can cause the loss of one side of the visual field, sometimes accompanied by visual hallucinations. If both sides of the cortex are affected, blindness can be complete despite the optic nerves being intact.
Sensory Loss
Sensory loss can affect one side of the body. It can affect one type of sensation while sparing others. For example, the ability to sense pain and temperature may be lost while the ability to feel touch remains intact. The sense of position can be affected, leading to ataxia. As with motor symptoms, the classic presentation of brain stem lesions involves the loss of sensation on one side of the face, combined with the loss of sensation of the other side of the body.
Coma and Death
The reticular system is a part of the brain stem responsible for the level of alertness. According to "Adam's and Victor's Principles of Neurology," damage to this area, which can be caused by edema following the stroke, can lead to coma or death within minutes. Damage to the control centers of the heart and breathing can also lead to death.
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
