Traumatic brain injury (TBI) is an alteration of brain function caused by an external force. It is currently understood as a dynamic and progressive process, rather than an isolated injury, with short-, medium-, and long-term effects.
It is a global health problem, with millions of cases annually and a substantial disability burden, particularly affecting older adults (falls) and young adults (traffic accidents).
Pathophysiology: a process in phases
TBI progresses through different interrelated stages:
- Primary injury: immediate and irreversible damage (contusions, hematomas, diffuse axonal injury).
- Secondary injury: a neurochemical cascade (edema, inflammation, excitotoxicity, hypoxia) that worsens the initial damage.
- Tertiary injury: delayed processes such as neurodegeneration and programmed cell death.
A key concept is delayed deterioration: apparently stable patients may worsen hours later because of hematoma expansion or increased edema.
Intracranial pressure and cerebral perfusion
The Monro-Kellie doctrine states that the skull is a closed space containing the brain, blood, and cerebrospinal fluid. When one increases, the others must compensate.
The critical variable is cerebral perfusion pressure (CPP):
CPP = Mean arterial pressure – Intracranial pressure
An increase in intracranial pressure can cause cerebral ischemia and herniation, potentially fatal conditions.
Clinical assessment: beyond the Glasgow scale
The Glasgow Coma Scale (GCS) remains essential for classifying TBI:
- Mild: 13-15
- Moderate: 9-12
- Severe: ≤8
However, it is now recognized that it is not sufficient on its own. The modern approach incorporates:
- Serum biomarkers
- Advanced neuroimaging
- Clinical and contextual factors
Diagnosis: imaging and biomarkers
Computed tomography (CT) is the key initial test for detecting severe injuries.
Magnetic resonance imaging (MRI) can identify subtler injuries, especially diffuse axonal injury.
In recent years, biomarkers such as the following have emerged:
- GFAP: indicates astroglial damage
- UCH-L1: indicates neuronal damage
These make it possible to improve screening and detect injuries even when CT findings are normal.
Artificial intelligence and advanced diagnosis
Artificial intelligence (AI) is transforming TBI assessment through:
- Automated image analysis
- Prediction of clinical course
- Early detection of complications
Even so, it does not replace clinical judgment and requires validation in different contexts.
Neurocritical care
The primary goal is to prevent secondary injury and maintain cerebral perfusion.
Key strategies include:
- Intracranial pressure control
- Multimodal neuromonitoring
- Osmotherapy: mannitol or hypertonic saline
- External ventricular drainage
- Decompressive craniectomy in refractory cases
Prophylactic hyperventilation is no longer routinely recommended because of the risk of ischemia.
Cognitive and behavioral sequelae
Getting through the acute phase does not imply complete recovery. TBI can cause:
- Memory and attention deficits
- Executive dysfunction
- Personality changes
- Anxiety, depression, and irritability
These changes are organic, not voluntary, and require understanding from those around the person.
Chronic traumatic encephalopathy (CTE)
CTE is a neurodegenerative disease associated with repeated head trauma.
It has been described in:
- Contact athletes
- Military personnel
- Victims of repeated violence
It may progress to cognitive decline, behavioral changes, and dementia.
Neurorehabilitation
Recovery depends to a great extent on:
- Early initiation
- Multidisciplinary approach
- Previous functional capacity
It includes:
- Physical therapy
- Neuropsychology
- Occupational therapy
- Speech-language therapy
It is based on neuroplasticity, that is, the brain’s capacity to reorganize.
Innovation and the future
The most promising areas include:
- Advanced biomarkers
- Artificial intelligence
- Neuroprotective therapies
- Personalized medicine
Although many are still under investigation, they point to the future of TBI management.
Conclusion
TBI should be understood as a complex and evolving disease, not merely as an acute injury.
The current approach combines multidimensional assessment, advanced neurocritical care, and intensive rehabilitation, with the goal of improving long-term survival and quality of life.
