Introduction[edit | edit source]There are various classification determinants utilized to classify traumatic brain injury (TBI). The clinical presentation and prognosis depend on the individual nature of the injury with often coexisting types of traumatic brain injury. The classification is important for acute management, treatment, and prognosis as well as neurorehabilitation requirements. [1] Show
Traumatic Brain Injury Subtypes. There are several different variants of traumatic brain injury, which often coexist and have significant overlap. They can be broadly divided into focal and diffuse injuries, although it is worth noting that true focal injuries are rare and blast injuries lack a pure neuropathological correlate. The clinical presentation and prognosis of a traumatic brain injury varies depending on the individual nature of the injury. The inherent variability makes it challenging to establish the optimal treatment and there is recognition of the value of an individualised approach. [2] 5 Classification determinants are detailed below. 1.Primary v Secondary Injuries[edit | edit source]Dependant on the timing and impact nature, ie. mechanical or non-mechanical, and accompanying pathophysiological processes. Primary Injury[edit | edit source]Occurs at the time of injury and is induced by mechanical forces. Two main mechanisms that cause primary injury are:
Primary injury due to acceleration-deceleration results from unrestricted movement of the head and leads to shear, tensile, and compressive strains. These forces can cause intran acranial hematoma, diffuse vascular injury, and injury to cranial nerves and the pituitary stalk. [5] Secondary Injury[edit | edit source]A secondary injury is not mechanically induced. It may be delayed from the moment of impact, and it may superimpose injury on a brain already affected by a mechanical injury. [5] The secondary damage is caused by casa cade of processes impacting “cerebral blood flow (hyper or hypoperfusion), impaired cerebrovascular autoregulation, cerebral metabolic dysfunction an,d impaired cerebral oxygenation.” [6] The ischemia and oedema are secondary injury types. See Pathophysiology The outcome of a head injury is determined by the above types, with primary injury extent being only sensitive to preventative measures, and secondary injury extend being susceptible to neuroprotective therapeutic interventions. Cellular and Molecular Activities Resulting in Secondary Brain Injury. Following a traumatic insult to the brain, an extensive series of various cellular processes is initiated that leads to further neuronal dysfunction and death. This contributes to the complexity of traumatic brain injury but also provides a variety of therapeutic targets. [7] 2.Focal v Diffuse Injuries[edit | edit source]Focal Injury[edit | edit source]Usually due to contact and causing scalp injury, it might present as skull fracture, contusions and/or intracranial haemorrhage. Those injuries are detectable by CT, MRI or PET scans. Contusions are the bleeding on the brain and include fracture contusion, coup contusion (at the site of the impact) and contrecoup contusion (directly opposite to the impact site). This mechanism is related to the moving of intracranial content in the skull and impinging on in the internal surface of the skull. Commonly observed injury is coup-contrecoup injury presenting with a contusion on opposite sides of the brain. Diffuse Injury[edit | edit source]Usually due to acceleration/deceleration injury and concussion resulting in diffuse axonal injury (DAI) and brain swelling. A diffuse axonal injury is difficult to diagnose with commonly available CT or MRI scans, and is demonstrated by histological white matter injury of the cerebral hemispheres, the corpus callosum, the brain stem and, less commonly, the cerebellum. A diffuse axonal injury might be accompanied by some focal lesions, but again only diagnosable microscopically. The tearing of the nerve tissue disrupts the brain’s regular communication metabolic processes. This disturbance in the brain can produce temporary or permanent widespread brain damage, coma, or death. The shaken baby syndrome is a type of diffuse axonal injury. These injuries are commonly found together. A 19-year-old male patient with diffuse axonal injury and Glasgow Coma Scale score of 8 after a motorcycle accident. While T2 conventional sequences (A) are rather insensitive for hemorrhagic lesions, T2*-GRE (B) shows numerous foci of signal loss (circles) in the subcortical white matter corresponding to areas of extravascular blood. Susceptibility weighted imaging (C) is even more sensitive than the previous two sequences, exhibiting more conspicuous (circles) and numerous lesions (squares) on both cerebral hemispheres. The images were performed sequentially during the same examination at a 3 Tesla scanner. [9] 3. Opened v Closed Injuries[edit | edit source]Open / Penetrating Injury[edit | edit source]Open/ Penetrating Injury occurs from the impact of a bullet, knife, or other sharp object that forces hair, skin, bone, and fragments from the object into the brain and dura mater is breached. The area of damage is determined by the trajectory of the object and possible ricocheting when travelling through different density tissues (i.e., skull compared to the brain). A "through-and-through" injury occurs when an object enters the skull, goes through the brain, and exits the skull and has a complex impact on the brain tissue with penetration injuries, additional shearing, stretching, and rupture of brain tissue. Closed / Non-Penetrating Injury[edit | edit source]A closed injury is an injury to the brain caused by an outside force without any penetration of the skull. The most serious complication is the brain oedema within constrained space of the skull and resultant increase in the intracranial pressure and compression of brain structures and cranial nerves. 4. Degree of Severity[edit | edit source]TBI degree of severity assessment can be context dependent, subjective, and are influenced by the point-of-view and experience of the clinical assessor. This situation is not unique to the TBI diagnosis. However, the assessed degree of severity can effect a person with TBI's available rehabilitation and assistance resources[10]. Examples of differing viewpoints of TBI severity:[10]
A study published in 2021 investigated the classification of concussion and mild TBI and found that these diagnoses present on a spectrum and cannot be applied in a binary way. Further study and research into new classification methods involving dynamic risk profiles may provide more precise treatment targets[11]. A 2020 study states that the term ‘concussion’ is commonly used to describe a patient's clinical presentation, but does not identify the underlying pathological process. Based on this line of reasoning, concussion cannot be considered a true diagnosis. However, there is growing evidence of diffuse axonal injury as a likely pathological substrate for concussion, thereby providing a framework to develop true diagnostic criteria. Further research is indicated[12]. Measures of Severity[edit | edit source]The main measures of severity used to classify the injury include:
Duration of Loss of Consciousness[edit | edit source]Describing alteration in consciousness duration:
Post-traumatic Amnesia (PTA)[edit | edit source]Post-traumatic Amnesia is described by the time elapsed from injury to the moment when patient presents with continuous memory of what is happening around them. Overview of Classification Criteria for traumatic brain injury severity based on Glasgow Coma Scale, Loss of Consciousness, Post-traumatic Amnesia and structural imaging:
5. Symptoms[edit | edit source]Traumatic brain injury can have wide-ranging physical, cognitive, psychological and physiological effects occurring immediately or elapsed. The symptoms might differ depending on the severity of TBI, but some are not specific to the type of injury. Mild Traumatic Brain Injury[edit | edit source]
Moderate to Severe Traumatic Brain Injury[edit | edit source]
Resources[edit | edit source]References[edit | edit source]
Can you recover from diffuse brain injury?4: Can I Recover Fully? For some, recovering from a diffuse axonal brain injury is possible—but there are no guarantees with such injuries. The severity of the brain lesions, which areas of the brain they are in, your treatment, and many other factors can affect whether or not you make a full recovery.
What is a diffuse brain injury?Diffuse axonal injury is the shearing (tearing) of the brain's long connecting nerve fibers (axons) that happens when the brain is injured as it shifts and rotates inside the bony skull. DAI usually causes coma and injury to many different parts of the brain.
What happens if you lose consciousness after a head injury?If the loss of consciousness is lengthy, it is called a coma. In many cases, the trauma also causes negative changes in motor functions and respiration. Some individuals with severe injuries regain consciousness while individuals with the most severe injuries may never regain consciousness.
What causes loss of consciousness in brain injury?Diffuse injuries (such as a concussion or diffuse axonal injury) will typically cause an overall decreased level of consciousness. Whereas, focal injuries (such as an ICH or a contusion) will have symptoms based on the brain area affected (Fig.
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