How does a concussion cause nausea and vomiting?

From the Guidelines

A concussion causes nausea and vomiting through the disruption of brain function following head trauma, affecting the vestibular system and triggering the nausea response, as well as activating the chemoreceptor trigger zone and the brain's vomiting center 1.

Key Mechanisms

• Disruption of the vestibular system in the inner ear and brainstem, which controls balance and spatial orientation, sends conflicting signals to the brain about body position, triggering the nausea response.
• The trauma activates the chemoreceptor trigger zone in the medulla oblongata, which detects toxins and can initiate vomiting.
• Inflammation and chemical changes following injury also contribute to these symptoms.
• The brain's vomiting center may be directly affected by the trauma or by increased intracranial pressure.

Clinical Implications

• These symptoms typically resolve within days to weeks as the brain heals, but persistent nausea and vomiting, especially worsening symptoms, warrant immediate medical attention as they could indicate a more serious brain injury requiring intervention.
• According to the 2024 American Heart Association and American Red Cross guidelines for first aid, signs and symptoms of concussions include headache, nausea, impaired balance, difficulties concentrating, confusion, emotional lability, and fatigue 1.
• The presence of nausea, vomiting, severe headache, or depressed skull fracture has been identified as having a positive predictive value for patients requiring neurosurgical intervention 1.

From the Research

Concussion and Nausea/Vomiting

• A concussion can cause nausea and vomiting due to the stimulation of vomiting centers in the brain 2.
• The exact mechanism of how a concussion leads to nausea and vomiting is not fully understood, but it is thought to be related to the acceleration forces that occur during a head injury, which can cause damage to the brain and lead to the stimulation of vomiting centers 2.
• Nausea and vomiting are common complications after minor head trauma and can increase the risk of intracranial pressure rising 3.

Treatment of Nausea and Vomiting

• Ondansetron and metoclopramide are two antiemetic medications that have been shown to be effective in reducing the severity of nausea and vomiting in patients with minor head trauma 3.
• A study comparing the antiemetic effects of ondansetron and metoclopramide found that both medications were effective in reducing nausea and vomiting, but ondansetron had a lower incidence of side effects such as drowsiness and anxiety 3.
• Another study found that ondansetron was not more effective than droperidol and dimenhydrinate in preventing nausea and vomiting in children undergoing strabismus surgery, and that the combination of droperidol and dimenhydrinate was significantly less costly than ondansetron 4.

Association between Ondansetron and Symptom Persistence

• A study found that ondansetron use was associated with a higher risk of persistent post-concussion symptoms at 1 month in children with concussions 5.
• However, the study noted that this association may be related to the limitations of the design and that further research is needed to fully understand the relationship between ondansetron use and symptom persistence in children with concussions 5.

Use of Ondansetron in Acute Gastroenteritis

• Ondansetron has been used to control vomiting related to acute gastroenteritis in infants and children, and has been shown to be effective in reducing the severity of vomiting and the need for intravenous fluids 6.
• However, the use of ondansetron in acute gastroenteritis is not directly related to the treatment of nausea and vomiting caused by concussions, and further research is needed to fully understand the effectiveness of ondansetron in this context 6.