A concussion is a type of mild traumatic brain injury resulting from a jolt or blow to the head or body that causes the brain to move rapidly within the skull. This sudden movement can lead to temporary changes in brain function. Concussions are a common injury, and individuals often experience a range of symptoms, with nausea being a frequently reported one. This article explores the underlying reasons why concussions can cause nausea.
The Brain’s Nausea Network
The sensation of nausea involves a complex network within the brain and body. A key region is the chemoreceptor trigger zone (CTZ), also known as the area postrema, located in the medulla oblongata of the brainstem. This area lies outside the brain’s protective blood-brain barrier, allowing it to detect substances in the blood and cerebrospinal fluid that might induce vomiting. Once stimulated, the CTZ sends signals to other parts of the brain that coordinate the nausea and vomiting response.
The vestibular system, found in the inner ear, is responsible for balance and spatial orientation. Signals from the vestibular system travel along the eighth cranial nerve to the brainstem, contributing to feelings of motion sickness and nausea. The vagus nerve also plays a significant role, transmitting sensory information from the gastrointestinal tract to the brain, which can initiate nausea as a protective response. These systems collectively process various inputs to trigger nausea.
Mechanisms of Concussion-Induced Nausea
A concussion can disrupt the delicate balance of the brain’s nausea network through several pathways. The jolt to the head can directly impact the vestibular system, leading to its dysfunction. This disruption can cause dizziness, vertigo, and a sensation similar to motion sickness, which strongly triggers nausea.
Concussions can also affect the autonomic nervous system, which controls involuntary bodily functions like heart rate, blood pressure, and digestion. Dysregulation of this system can lead to imbalances that stimulate the vagus nerve, contributing to gastrointestinal discomfort and nausea.
The brain injury can cause neuroinflammation and alter neurotransmitter levels. Changes in chemicals like serotonin and dopamine in brain areas responsible for nausea control can directly stimulate these centers. This chemical disruption interferes with how the brain processes and sends signals related to digestion, which can result in nausea.
Even subtle changes in pressure within the skull following a concussion can irritate or compress brain regions involved in nausea. The physical forces of a concussion can cause microscopic damage to brain cells and disrupt normal brain function. This can lead to a temporary alteration in how the brain operates, impacting various systems, including those that regulate nausea.
The Interplay of Concussion Symptoms and Nausea
Nausea after a concussion rarely occurs in isolation; it often interacts with other common symptoms, intensifying the overall experience. Headaches are a common symptom following a concussion, and severe headaches often accompany nausea. Pain signals from a headache can influence the brain’s nausea centers, intensifying it.
Dizziness and vertigo, which stem from vestibular system disruption, are powerful triggers for motion sickness-like nausea. When the brain receives conflicting signals about movement and balance, it can lead to significant discomfort and an urge to vomit.
Sensitivity to light (photophobia) and sound (phonophobia) are common concussion symptoms. Overstimulation from bright lights or loud noises can worsen overall discomfort and heighten the sensation of nausea in an already sensitive brain.
General fatigue is a symptom that can lower an individual’s tolerance for other physical complaints, intensifying nausea. The brain redirects energy towards healing after an injury, which can lead to feelings of drowsiness and exhaustion.
When Nausea Signals a Need for Medical Care
While nausea is a common symptom after a concussion, certain signs indicate a need for immediate medical attention. Worsening nausea or persistent vomiting are red flags for medical evaluation. Repeated vomiting, especially, can indicate a more serious brain injury.
Nausea accompanied by other severe symptoms should prompt a visit to the emergency room. These include loss of consciousness, a headache that gets worse over time, increasing confusion, or slurred speech. Weakness or numbness in the arms or legs, seizures, or difficulty waking up are serious indicators.
Any nausea that does not improve, or significantly interferes with daily activities, should be discussed with a medical professional. A healthcare provider should evaluate any suspected concussion.