A concussion, classified as a mild traumatic brain injury (TBI), results from a sudden blow or jolt to the head that causes the brain to move rapidly inside the skull, temporarily disrupting its normal function. Many people who sustain this injury experience a variety of physical symptoms. Nausea and vomiting are very common physical symptoms that can manifest immediately after the injury.
The Mechanism: Why Concussions Cause Nausea and Vomiting
Gastrointestinal symptoms following a head injury stem from multiple disruptions within the central nervous system. One primary cause is the trauma’s effect on the brain’s vomiting center and the chemoreceptor trigger zone (CTZ). Both are located in the brainstem’s medulla oblongata. The sudden impact and subsequent chemical changes stimulate these areas, initiating the vomiting reflex.
Another significant contributor is the disruption of the vestibular system, which controls balance and spatial orientation. This system involves structures in the inner ear and brainstem. When jarred by the injury, it sends conflicting signals to the brain, similar to severe motion sickness. This imbalance leads to a strong sensation of dizziness and subsequent nausea.
Concussions also involve an acute inflammatory response and microstructural damage within the brain tissue. The release of inflammatory mediators sensitizes the CTZ, making the person more susceptible to feeling sick. The injury can also lead to rapid, though often temporary, changes in intracranial pressure (ICP).
Elevated ICP, even if mild, can directly stimulate the vomiting center. This is the body’s protective mechanism reacting to the pressure changes inside the skull. These interwoven neurological and inflammatory effects combine to create the physical sensation of nausea and, in many cases, lead to vomiting.
Warning Signs: When Vomiting Signals a Medical Emergency
While some initial vomiting is expected after a concussion, certain characteristics can indicate a more serious underlying injury, such as bleeding or swelling within the brain. Repeated vomiting, especially if it occurs multiple times, is a serious red flag. This persistent or increasing vomiting suggests a worsening of intracranial pressure that requires prompt intervention and immediate medical evaluation.
Another concerning sign is vomiting that begins hours after the initial injury, known as delayed vomiting. Symptoms that appear late can result from slowly developing swelling or a blood clot that is gradually expanding and putting pressure on the brain. Delayed onset of nausea and vomiting should always prompt a visit to a medical provider to rule out a more severe complication.
Vomiting accompanied by other severe neurological changes is also a sign of a medical emergency. This includes a severe headache that gets progressively worse, slurred speech, or a loss of consciousness lasting longer than 30 seconds. If the injured person is difficult to wake up, confused, or exhibits unequal pupil sizes, emergency medical help must be called immediately.
The intensity and timing of the vomiting provide important clues about the severity of the head trauma. Any significant change in the person’s condition, such as increasing frequency or the inability to stay awake, suggests that the brain’s condition is deteriorating and should not be managed at home. The priority is to seek urgent care to allow for neuroimaging and prevent further damage.
Related Symptoms of Concussion
Nausea and vomiting rarely occur in isolation after a concussion, but rather as part of a wider constellation of post-injury symptoms. Physical symptoms commonly accompanying gastrointestinal distress include a headache, which is frequently reported. Dizziness and balance problems are also prevalent, stemming from the same vestibular disruption that contributes to nausea.
Cognitive symptoms typically involve a feeling of being dazed or “in a fog,” where the person feels slowed down. Difficulty with concentration, memory problems, and trouble thinking clearly or following conversations can also be observed. These effects reflect the temporary disruption to the brain’s information processing capabilities.
Emotional and psychological symptoms may also manifest, sometimes developing days after the initial impact. These can include heightened irritability, anxiety, mood swings, or sadness uncharacteristic for the individual. The combination of physical discomfort and cognitive struggle often contributes to emotional distress.
Other common physical manifestations include sensitivity to light and noise, blurred or double vision, and fatigue. While physical symptoms like nausea and headache may be more prominent immediately after the injury, emotional and cognitive changes can sometimes emerge or intensify later on.