What Does the Brainstem Do?
The brainstem is a gateway from your brain to the rest of your body’s nerve pathways, the peripheral nervous system. In fact, 10 of the 12 cranial nerves (nerves 3–12) start at the brainstem. These pairs of nerves relay information between your brain and your head, neck, chest, and abdomen, explains the National Cancer Institute (NCI). The cranial nerves connect to and control the muscles of the voice box, heart, lungs, stomach, and intestines.
Together with the cranial nerves, the brainstem is necessary for many other processes, including:
- coordinating movement and balance
- beating of the heart
- chewing and swallowing
- digesting food
- tasting, smelling, hearing, seeing, and feeling (sense of touch)
- regulating your sleep-wake cycle
Conditions that involve or affect the brainstem can disrupt any of these vital functions.
From the base of the brain to the spinal cord, the main structures of the brainstem include:
- Diencephalon: This structure consists of the thalamus, hypothalamus, and epithalamus. These structures serve as a relay station for sensory input from the body.
- Midbrain: This part of the brainstem processes what you hear, regulates eye movement and reflexes, and mediates pain responses, among other functions.
- Pons: Cranial nerves originating here direct facial and tongue movement, provide hearing input, assist with balance and the body’s orientation in space, and help regulate breathing.
- Medulla oblongata: This part connects the pons to the spinal cord. It is responsible for relaying signals to and from the muscles.
- Reticular formation: This structure extends from the medulla oblongata to the diencephalon. It contains nerves responsible for movement coordination, regulating heartbeat, breathing, and maintaining blood pressure. It also plays a role in sleep cycle regulation.
Like other parts of the brain, many types of conditions can affect the brainstem. These include, but are not limited to:
- Chiari malformation: This is a condition in which the brainstem is pushed or protrudes outside the base of the skull and into the spinal column. There are several types of Chiari malformation with differing severity.
- Brainstem stroke: A stroke is when any part of the brain is deprived of oxygen.
- Psychiatric and neurologic conditions: A genetic study implicates the volume of the brainstem to autism spectrum disorder, bipolar disorder, and schizophrenia, among other conditions.
- Locked-in syndrome: This is a rare condition in which a person is fully conscious but unable to move, speak, or change facial expression. The person may be able to communicate with blinking or eye gaze devices.
- Amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease): A condition in which nerves between the brain and the muscles deteriorate and die. According to the National Institute of Neurological Disorders and Stroke (NINDS), research and development is leading to a better understanding of ALS and treatment options.
- Neurofibromatosis type II: This condition causes the growth of benign tumors on nerves throughout the body. This type of neurofibromatosis commonly causes tumor growth on the cochlear nerves, leading to progressive hearing loss. Auditory brainstem implants that bypass the cochlear nerves may help maintain or restore hearing in people with this condition.
- Tumor: A tumor affecting the brainstem can be benign or malignant (cancerous). Either way, a brain tumor can affect a cranial nerve or other neural tissue of the brainstem and disrupt function.
- Traumatic brain injury (TBI): The brainstem is commonly affected in a type of TBI called a diffuse axonal injury.
- Long COVID-19: This post-COVID-19 condition may result in problems with the brainstem. One hypothesis suggests that symptoms such as shortness of breath, persistent cough, or digestive issues may be from brainstem damage related to COVID-19.
Symptoms of a brainstem problem depend on which brainstem structures are affected. Unexplained signs and symptoms may include:
- respiratory symptoms, such as shortness of breath or coughing
- digestive symptoms, such as nausea, vomiting, or diarrhea
- heart problems, such as a fast heart rate or chest pain
- balance and coordination issues
- movement-related symptoms, such as tremor or inability to move
- changes in the senses, such as loss of sensation, smell, or hearing
- double vision
- psychological symptoms, such as anxiety, insomnia, or difficulty concentrating
Some of these symptoms can be related to common, self-limiting illnesses, such as infections. See your doctor for new or unusual symptoms that last longer than a few days. Your physician can help determine the cause.
In infants, detecting hearing loss early is critical to their language development. Brainstem evoked response audiometry is a method of identifying babies with hearing problems. This test measures the brainstem response to signals generated by the equipment.
Here are some questions that people ask about the brainstem.
What are the main functions of the brainstem?
Your brainstem controls most of your body’s automatic functions, including breathing, heartbeat, and digestion.
How long does it take to recover from a brainstem injury?
The time of recovery depends on which brainstem structures are affected and why. Surgery can correct some brainstem injuries, such as certain types of Chiari malformation. Some patients with brainstem injury, such as stroke, require complex care for life.
Can you live if your brainstem is damaged?
Depending on the location and extent, you may be able to live with brainstem damage. Some conditions are progressive, and the outlook is poor for these. However, new research is offering hope to people living with brainstem problems.
Can the brainstem repair itself?
The brain may help heal itself in two ways. It can create new neurons and neural pathways to replace the injured ones. It can also transfer functions to different places within the brain. The medical community may refer to this process as neurorehabilitation.
The brainstem is responsible for most of the automatic functions of your body, including breathing. Most of the cranial nerves exit the brainstem, which connects the brain to the spinal cord. Structures within the brainstem include the midbrain, pons, and medulla oblongata. Injury or disease can affect the brainstem, causing a range of potential symptoms. Always see a doctor for new or unusual symptoms that cannot be explained by other causes.