Brain Injury: Levels of Severity & States of Consciousness

Brain injuries fall under one of two categories: trauma or disease—also referred to as traumatic or non-traumatic brain injuries. Because the brain does not simply heal like a cut or other injuries of the body, recovery depends heavily on the cause of the injury, the severity of the patient’s symptoms, and the physician’s ability to provide timely treatment according to the standard of care

After a brain injury, damage can be difficult to detect. What happens in the following seconds and minutes after an injury has occurred is crucial, as the long term impact is dependent on how quickly action is taken. The outcome of this damage can range from requiring physical therapy to being in a state of long-term unconsciousness. 

Determining the source of the injury and whether it’s traumatic or non-traumatic are the first steps toward delivering the appropriate care a suffering patient needs.

What are the Leading Causes of Traumatic Brain Damage?

A traumatic brain injury (TBI) can be caused many different ways. Whether from a bed, a ladder, down the stairs, or in the bath, falls are the most common cause of traumatic brain injury, particularly in older adults and young children.

However, falls alone do not account for the totality of TBIs.

The following are other instances where TBIs are likely to occur:

Vehicle-Related Collisions. Collisions involving cars, motorcycles or bicycles—or pedestrians.

Violence. Gunshot wounds, domestic violence, child abuse, or other assaults, such as  shaken baby syndrome—a traumatic brain injury in infants caused by violent shaking.

Sports Injuries. Injuries resulting from a number of sports, including soccer, boxing, football, baseball, lacrosse, skateboarding, hockey, or other high-impact or extreme sports. 

Explosive Blasts and Other Combat Injuries. Explosive blasts are a common cause of TBIs in active-duty military personnel. Although how the damage occurs isn’t yet well understood, many researchers believe that the pressure wave passing through the brain significantly disrupts brain function.

TBI also results from penetrating wounds, severe blows to the head with shrapnel or debris, or bodily collisions with objects following a blast.

What are the Leading Causes of Non-Traumatic Brain Damage?

A non-traumatic brain injury may also be called an acquired brain injury (ABI). This type of brain injury is the result of an illness or condition of the body and is not the result of trauma to the head. Anoxic brain injuries also fall into this category.

The most common causes of a non-traumatic brain injury are:

  • Stroke 
  • Lack of oxygen or hypoxia
  • Tumors
  • Other illnesses such as cancer
  • Brain infections or inflammation
  • Other infections

Levels of Severity

Like any injury, brain injuries can range from the mild to the extremely severe. Correctly diagnosing the level of severity of a brain injury is paramount to correctly treating it.

Mild Brain Injury and Concussion

A concussionalso known as mild brain injury or mild head injury—is commonly caused by falls, road crashes, assaults, or sports accidents. 

The effects of a concussion can leave people with symptoms including dizziness, nausea, confusion or an inability to process or retain information, sensitivity to light, and vision distortion.

Moderate Brain Injury

A moderate brain injury is defined as loss of consciousness between 15 minutes and six hours or a period of post-traumatic amnesia of up to 24 hours. Patients with moderate head injury are likely to suffer from a number of residual symptoms.

The most commonly reported symptoms are physical effects, including tiredness, headaches, and dizziness; cognitive effects, such as difficulties with thinking, attention, memory planning, organizing, concentration, and word-finding problems; and behavioral problems like chronic irritability.

A large proportion of people find that upon returning to work, they feel that they are not functioning at their highest level. For the majority of people, these residual symptoms gradually improve, although this can take upwards of six to nine months.

Severe Brain Injury

Severe brain injury is usually defined as a patient being in an unconscious state for six hours or more or post-traumatic amnesia lasting 24 hours or more. These patients are likely to be hospitalized and receive rehabilitation once the acute phase has passed. Depending on the length of time in a coma, these patients tend to have more serious physical deficits, making recovery that much more difficult.

A further category of very severe injury is defined by a period of unconsciousness lasting 48 hours or more or a period of post-traumatic amnesia lasting seven days or more. The longer the length of coma and period of post-traumatic amnesia, the poorer the outcome is likely to be. 

States of Consciousness

A brain injury, regardless of cause, can generate problems with arousal, consciousness, awareness, alertness, and responsiveness. Generally, there are five abnormal states of consciousness that can result from a brain injury: stupor, coma, persistent vegetative state, locked-in syndrome, and brain death.


Stupor is a state in which the patient is unresponsive but can be aroused briefly by a strong stimulus, such as sharp pain. 


Coma is a state in which the patient is totally unconscious, unresponsive, unaware, and unarousable. Patients in a coma do not respond to external stimuli such as pain or light and do not have sleep-wake cycles. 

A coma results from widespread and diffuse trauma to the brain, including the cerebral hemispheres of the upper brain and the lower brain or brainstem. Coma’s generally last a shorter duration, from a few days to a few weeks. After this time, some patients gradually come out of the coma, some progress to a more vegetative state, and others die.

Vegetative State

Patients in a vegetative state are unconscious and unaware of their surroundings, but they continue to have a sleep-wake cycle and can have periods of alertness. Unlike a coma, where the patient’s eyes are closed, patients in a vegetative state often open their eyes and may move, groan, or show reflex responses. 

A vegetative state can result from diffuse injury to the cerebral hemispheres of the brain without damage to the lower brain and brainstem. Anoxia, or lack of oxygen to the brain, which is a common complication of cardiac arrest, can also bring about a vegetative state.

Persistent Vegetative State

Many patients emerge from a vegetative state within a few weeks, but those who do not recover within 30 days are said to be in a persistent vegetative state (PVS). The chances of recovery depend on the extent of injury to the brain and the patient’s age. 

Younger patients have a better chance of recovery than older patients. 

Generally, adults have a 50 percent chance, and children have a 60 percent chance of recovering consciousness from a PVS within the first six months. After a year, the chances that a PVS patient will regain consciousness are very low, and most patients who do recover consciousness experience significant disability. 

Locked-In Syndrome

Locked-in syndrome is a condition in which a patient is aware and awake but cannot move anything but their eyes or communicate due to complete and utter paralysis of the body.

Brain Death

Brain Death is caused by severe injury or lack of oxygen to the brain and involves these critical factors: no ability to generate a breath and coma—permanent cessation of activity in the brain and brainstem, the cause of which is known and for which there are no other explanations.

The hearts of brain-dead patients may continue to beat but removing supportive equipment will lead to cardiac arrest. Brain death is considered irreversible.

Treatments for Brain Injuries

Depending on the severity of a brain injury, there are a few ways brain injuries can be treated: medication, surgery, and rehabilitation.


Medications to limit secondary damage to the brain immediately after an injury may include anti-seizure medications for moderate to severe traumatic brain injury sufferers. 

Coma-inducing drugs are sometimes used to put patients into a temporary coma as a comatose brain needs less oxygen to function, also limiting further brain damage. This can be helpful if the blood vessels that supply oxygen to the brain are damaged and not functioning properly. 

Lastly, diuretics reduce the amount of fluid in tissues and increase urine output. Diuretics are given intravenously to people with traumatic brain injury to help reduce pressure inside the skull and on the brain.


Emergency surgery can be used to mitigate additional damage to brain tissues. It may be used to address the following problems: removing hematomas or clotted blood; repairing skull fractures, addressing bleeding in the brain; or opening a window in the skull, allowing pressure to be relieved around the brain.


Most people who have suffered a significant brain injury will require some degree of rehabilitation. They may even need to relearn basic skills, such as walking or talking. The goal is to improve their abilities to perform daily activities over time.

Treatment usually begins in the hospital and continues at an inpatient rehabilitation unit, a residential treatment facility, or through outpatient services. The type and duration of rehabilitation are different for everyone, depending on the severity of the brain injury and what part of the brain was injured.

Negligent Treatment of a Brain Injury

Brain injury, whether caused by injury or illness, is difficult for physicians to detect, often leading to delayed or missed diagnosis, minimizing the chances of a successful recovery. 

Patients who are treated with the utmost care and in accordance with the standard of care are more likely to see positive outcomes immediately and throughout recovery. A physician who fails to diagnose a brain injury, or fails to treat a brain injury appropriately, may further harm a patient.

A patient with a brain injury, whether mild or severe, is more than likely looking at a long recovery period, including intensive therapies and expensive medications. 

If you or a loved one has been injured or died due to the actions of a negligent physician, there may be recourse with a medical malpractice claim. 

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