Overview 

Traumatic brain injury (TBI) is a leading cause of death and disability in people under the age of 40 in the UK. Each year, over 1 million people in England and Wales arrive at hospital with a head injury and approximately 40,000 present with traumatic brain injury. Traumatic brain injury is a disruption in normal brain function caused by an external force. This may result from a blow or jolt to the head, or from an object damaging the brain.¹ TBIs can range from mild concussions to severe brain damage, and the impact on individuals can vary widely depending on the severity of the injury.¹

Common causes of traumatic brain injury 

Traumatic brain injury is usually caused by various external forces damaging the head. The most common causes of traumatic brain injury include the following:

• Falls: slipping in the bathroom, falling down the stairs, tripping on uneven surfaces, or falling from heights are some of the most common causes of traumatic brain injury. Especially among children and older adults² 
• Motor vehicle accidents: including car crashes, motorcycle accidents, and collisions involving pedestrians and cyclists³
• Sport-related injuries: traumatic brain injuries can be caused by playing sports including, football, rugby, hockey, boxing, cycling and skiing⁴
• Physical assault: traumatic brain injuries can result from domestic violence, street fights, or other physical altercations⁵ 
• Penetrating injuries: a penetrating (open-wound) injury is an open wound to the head from a foreign object (e.g., bullet or knife)⁶ 

Symptoms 

The symptoms of a traumatic brain injury can vary depending on various factors such as the type of injury and the severity and location of the injury. Some symptoms of traumatic brain injury can appear straight after the injury while some symptoms can appear days or weeks later.^7,8

Mild traumatic brain injury (concussion)

Physical symptoms

• Headache
• Nausea or vomiting
• Fatigue or drowsiness
• Problems with speech
• Dizziness or loss of balance
• Sensitivity to light or sound

Sensory symptoms 

• Blurred vision
• Ringing in the ears
• Changes in the ability to smell
• Altered taste

Cognitive symptoms

• Difficulty concentrating or remembering
• Mood changes or mood swings
• Feeling depressed or anxious

Sleep disturbances

• Sleeping more than usual
• Difficulty falling asleep
• Sleeping less than usual

Moderate to severe traumatic brain injury

Physical symptoms

• Persistent headache or headache that worsens
• Repeated vomiting or nausea
• Convulsions or seizures
• Dilation of one or both pupils of the eyes
• Clear fluids draining from the nose or ears
• Inability to awaken from sleep
• Weakness or numbness in fingers and toes
• Loss of coordination

Cognitive and behavioural symptoms

• Profound confusion
• Agitation, combativeness, or other unusual behaviour
• Slurred speech
• Coma and other disorders of consciousness

Sensory symptoms

• Loss of consciousness from several minutes to hours
• Persistent dizziness or loss of balance

Different types of traumatic brain injuries 

Traumatic brain injuries can be classified into two main categories: closed and penetrating (open) injuries. Closed brain injuries occur when an external force impacts the head without breaking the skull. The brain moves within the skull, causing injury. A penetrating brain injury occurs when an object breaks through the skull and enters the brain tissue.⁸

Several different types of traumatic brain injuries can occur within these two categories.

Concussion 

A concussion is one of the most common but least serious types of brain injury. A concussion results from a blow or jolt to the head, causing the brain to move rapidly back and forth. It can lead to temporary loss of normal brain function.⁹

Concussions are typically categorised as a mild form of traumatic brain injury because they generally are not life-threatening and the symptoms are usually temporary, resolving with proper rest and care. However, symptoms of a concussion can persist after the initial injury, a condition known as post-concussion syndrome.⁹ 

Contusion 

A contusion is a bruise on the brain tissue, often caused by a direct impact on the head. This bruising results from small blood vessels leaking blood into the brain tissue. Contusions can lead to bleeding and swelling within the brain. Contusions in which two injuries occur at two different parts of the brain are referred to as coup-contrecoup injury.¹⁰

Diffuse axonal injury (DAI)

Diffuse axonal injury is a severe type of traumatic brain injury and results from when the brain rapidly shifts inside the skull, causing the long connecting fibres in the brain (axons) to tear. This type of injury is typically caused by shaking or strong rotational forces, such as car accidents or falls.¹¹

Penetrating injury

A penetrating injury occurs when an object, such as a bullet or a sharp instrument, pierces the skull and enters the brain tissue. This type of injury can cause severe damage to specific brain areas.⁶

Hematoma

A hematoma is a collection of blood outside of blood vessels. Types of hematomas related to traumatic brain injury can include:

• Epidural hematoma: Blood collects between the skull and the dura mater (the brain's outer covering)¹²
• Subdural hematoma: Blood collects between the dura mater and the brain itself¹³
• Intracerebral hematoma: Blood collects within the brain tissue¹⁴

Chronic traumatic encephalopathy (CTE)

Chronic traumatic encephalopathy is a progressive, degenerative brain disease found in individuals with a history of repetitive brain trauma, such as athletes and military personnel. It can only be definitively diagnosed postmortem.¹⁵

Summary

In summary, traumatic brain injuries result from external forces such as blows, bumps, or penetrating objects disrupting normal brain function. These injuries can range from mild concussions to severe brain damage, and their effects vary widely depending on the severity. 

Common causes of TBI include falls, motor vehicle accidents, sports-related injuries, physical assaults, and penetrating injuries. Falls are particularly prevalent among children and older adults, while motor vehicle accidents, sports injuries, and assaults also contribute significantly. Penetrating injuries involve objects like bullets or knives entering the brain, causing severe localised damage.

Symptoms of TBI vary by severity and injury type. Mild TBIs, or concussions, can cause headaches, dizziness, and cognitive disturbances, usually resolving with rest. However, more severe TBIs can result in persistent headaches, seizures, loss of coordination, profound confusion, and coma. 

Traumatic brain injuries can be categorised as closed or penetrating. Closed injuries occur when an external force impacts the head without breaking the skull, causing the brain to move within it. Penetrating injuries involve objects piercing the skull and entering brain tissue. Specific types of TBIs include concussions, contusions, diffuse axonal injuries, penetrating injuries, hematomas, and chronic traumatic encephalopathy.