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The term "concussion" is often used for mild TBI. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) state that mild TBI is due to a non-invasive or mechanical force that results in transient disorientation, confusion, or unconsciousness lasting not more than 30 minutes; possibly associated with temporary neurobehavioral deficits, and a GCS no worse than 13. 

How do doctors diagnose a concussion?

Concussions can often lead to a confused mental condition. A doctor may inquire or do tests to diagnose a person's concentration, memory, or problem-solving ability. 

A doctor will inquire about how the injury happened and a person's medical history. They will also look carefully at the face, head, and neck.

They can also employ the Glasgow coma scale to diagnose a concussion. Doctors will examine and rate the following:

• Ability to open their eyes and to talk.
• A motor response, such as bending a leg at the knees

If the head injury is moderate or severe, it may be essential to do a brain scan.

Concussion and post-concussive symptoms

Typically the only consistent finding in patients with mild TBI is a concussion, whereas patients with moderate or severe TBI typically have concussive symptoms plus a combination of injuries.

The five significant subtypes of concussion include headache, cognitive, vestibular, mood and ocular-motor. One meta-analysis demonstrated that headaches and cognitive are the most common subtypes in adults and children.

The World Health Organization's definition of the post-concussive syndrome includes the presence of three or more of these symptoms after a head injury: 

• headache,
• dizziness,
• fatigue,
• irritability,
• impairment of memory,
• insomnia and
• difficulty with concentrating and performing mental tasks, 
• reduced tolerance to emotional excitement, stress, or alcohol.

In 2017, at least one sports-related concussion in the US was reported by 15% of high school students. Approximately 30% of children and adults more than 30 days after injury experience persistent post-concussive symptoms.

Hemorrhages

Traumatic subarachnoid hemorrhage (SAH) is the most usual CT outcome of TBI, occurring in 30% to 40% of patients with moderate to severe TBI and 5% of patients with mild TBI. 

SAH is related to a poorer outcome in moderate or severe TBI patients. However, it is unclear whether the SAH is simply a marker of the severity of the injury or if the poorer outcome is due to constriction of the blood vessel. SAH is usually linked with other injuries too. 

Subdural hematomas (SDH) are seen in about 20% of patients with moderate to severe TBI and about 30% of fatal TBI and are the most usual type of mass lesion in TBI.  

SDH occurs in only 3% of patients with mild TBI. SDH that leads to hospitalizations or deaths are most commonly secondary to motor vehicle-related injury in younger adults and falls in older adults. 

Epidural hematoma (EDH) occurs in about 10% of patients with moderate to severe TBI and about 1% of patients with mild TBI. 

The occurrence of EDH is most significant among people in adolescence and young adults between 20-30 years old. Most cases of EDH are caused by assaults, traffic accidents, and falls. 

Intracerebral hematomas occur in 10% -30% of patients with moderate to severe TBI and <1% of patients with mild TBI.

Cerebral contusions

Occur in 20% -30% of patients with moderate to severe TBI and 6% of patients with mild TBI.

Axonal injury

Probably present in most patients with TBI to some degree, although the low-grade axonal injury is mostly microscopic and not detectable on CT scan.

Diffuse axonal injury (DAI) is presented to some degree in all TBI-related deaths and those leading to a persistent vegetative state. The presence of DAI raises the likelihood of a poor outcome. 

The initial CT is standard in 50%- 80% of patients diagnosed with DAI ultimately, but MRI shows the presence of axonal injury in 70% of patients with moderate to severe TBI.

Skull fractures

This occurs in 5% of patients with mTBI and about 50% of those with severe TBI. Most skull fractures are due to motor vehicle-related injuries,  falls, or assaults. 

The most common are simple linear fractures, comprising greater than 50% of all skull fractures. A depressed skull fracture is present in less than 1% of patients with mild TBI. 

Penetrating or blast injury

Penetrating injuries are categorized as high- or low-velocity and maybe non-intentional, self-inflicted, or assault-related. A gunshot wound to the head is associated with 50% mortality.

Blast injuries are a leading cause of TBI in active duty military personnel in war zones, accounting for about 60% of severe TBI.