A sudden blow to the head can trigger a cascade of physical reactions, and the feeling of coldness, shivers, or chills is a common response. This sensation often appears immediately after impact, even in a warm environment. While not always a sign of severe injury, the cold feeling indicates the body’s internal systems are reacting to the sudden physical trauma. Several mechanisms explain why temperature perception and regulation can be temporarily thrown off balance after a head injury.
The Body’s Immediate Stress Response
The feeling of coldness is an immediate consequence of the body initiating the “fight-or-flight” response. Physical trauma instantly alerts the body to a potential threat, prompting the release of stress hormones like adrenaline (epinephrine). This hormonal surge prepares the body for action by prioritizing blood flow to core areas.
Adrenaline causes peripheral vasoconstriction, narrowing blood vessels in the extremities and skin. This process shunts blood away from the surface of the body and directs it toward the core organs, heart, lungs, and large muscles. The intent is to conserve heat and minimize potential blood loss from surface wounds.
Since the warmth-carrying blood is diverted internally, the skin and extremities, such as the hands and feet, feel cold to the touch. This change in surface temperature can trigger shivering or chills, even if the core body temperature remains normal.
When Temperature Regulation Goes Awry
A more complex cause of feeling cold relates directly to the mechanical force impacting the brain’s internal control center. The hypothalamus, a small structure located deep within the brain, functions as the body’s thermostat, maintaining a steady internal temperature (thermoregulation). It constantly monitors blood temperature and sends signals to initiate cooling measures like sweating or warming measures.
A head injury, even a mild traumatic brain injury (TBI) like a concussion, can temporarily disrupt the signaling pathways of the hypothalamus. The physical jolt can interfere with its ability to correctly interpret the body’s thermal state or alter its ideal temperature “set point.” This malfunction leads to thermal dysregulation, where the body inappropriately triggers a warming response, such as shivering or the sensation of cold.
When the hypothalamus is compromised, it may misfire and initiate vasoconstriction, making the person feel cold despite a normal environment. This neurological disruption is different from the immediate adrenaline response because it represents a temporary failure of the brain’s homeostatic control. Such thermal instability can cause body temperature to fluctuate or a person to feel cold days after the initial trauma.
Recognizing Signs of Severe Injury
While a temporary cold feeling can be a benign stress response, it can also accompany severe complications like intracranial bleeding or profound shock. It is important to recognize emergency warning signs. If the cold feeling becomes severe, persistent, or is accompanied by extreme paleness, check for other neurological symptoms. Any sign of worsening brain function requires immediate medical attention.
Immediate medical evaluation is necessary if the injured person exhibits any of the following serious indicators of brain injury:
- A severe or worsening headache that does not stop.
- Repeated vomiting or persistent nausea indicating increased pressure within the skull.
- Loss of consciousness, even if brief, or growing confusion.
- Slurred speech or unusual behavior.
- Weakness, tingling, or numbness on one side of the body.
- Seizures.
- Pupils that are unequal in size.