Traumatic Brain Injury (TBI)


Epidemiology


Physiology

Primary Brain Injury

  • General Comments: primary brain injury occurs at the time of trauma
  • Mechanisms of Primary Brain Injury
    • Diffuse Axonal Injury Due to Shearing: usually involves the hemispheric gray-white matter junction, corpus callosum, and/or midbrain
      • Usually present with coma without an increase in intracranial pressure
    • Focal Cerebral Contusion: common in basal frontal and temporal regions (due to susceptibility to direct impact on the basal skull surface during acceleration/deceleration injuries)
      • These are the most frequently observed lesions
      • Intraparenchymal hematoma may occur from coalescence of cerebral contusions or disruption of intraparenchymal blood vessels
    • Extra-Axial Hematoma
      • Epidural Hematoma (see Epidural Hematoma): due to tear in dural vessels (middle meningeal artery, etc)
        • Almost always associated with skull fracture
        • Tend to not be associated with underlying parenchymal brain injury
      • Intraventricular Hemorrhage: due to tearing of subependymal veins, extension from adjacent intraparenchymal hemorrhage, or extension from subarachnoid hemorrhage
      • Subarachnoid Hemorrhage (SAH) (see Subarachnoid Hemorrhage): due to disruption of small pial vessels, extension from intraventricular hemorrhage, or extension from superficial parenchymal hemorrhage
        • Tend to occur in the sylvian fissures and interpeduncular cisterns
      • Subdural Hematoma (SDH) (see Subdural Hematoma): due to damage to bridging veins (which drain cerebral cortical surfaces to dural venous sinuses) or from extension from superficial cortical contusions
        • Tend to be associated with underlying parenchymal brain injury

Secondary Brain Injury

  • General Comments: secondary brain injury occurs subsequent to the initial trauma and continues for hours-days
  • Mechanisms of Secondary Brain Injury
    • Apoptosis
    • Electrolyte Imbalance
    • Inflammatory Response
    • Mitochondrial Dysfunction
    • Neurotransmitter-Mediated Excitotoxicity Resulting in Glutamate, Free-Radical Injury to Cell Membranes
    • Secondary Brain Ischemia Resulting from Vasospasm, Focal Microvascular Occlusion, and Vascular Injury

Other Aspects

  • Impaired Cerebral Autoregulation
    • Normally, Via Autoregulation, the Brain Maintains an Adequate Cerebral Blood Flow Across a Wide Range of Mean Arterial Blood Pressures (MAP) From 50-100 Meg Hg
    • In TBI, Cerebral Autoregulation is Impaired in Approximately 33% of TBI Cases: resulting in the brain demonstrating “pressure-passive” hemodynamics
      • Increased MAP (hypertension) may then result in increased cerebral blood flow and hypermedia, resulting in elevated intracranial pressure (ICP)
      • Decreased MAP (hypotension) may result in brain hypoperfusion and ischemia

Diagnosis

Head CT (see Head Computed Tomography)

Brain MRI (see Brain Magnetic Resonance Imaging)

External Ventricular Drain (EVD) (see External Ventricular Drain)


Glasgow Coma Scale (GCS) (see Glasgow Coma Scale)


Clinical Manifestations

Hematologic Manifestations

Neurologic Manifestations

Pulmonary Manifestations

Other Manifestations


Treatment

General Measures

Deep Venous Thrombosis (DVT) Prophylaxis (see Deep Venous Thrombosis)

Hemodynamic Management

Hemostatic Therapy

Infection Prophylaxis

Management of Increased Intracranial Pressure (see Increased Intracranial Pressure)

Analgesia

Brain Tissue Oxygen Monitor (PbtO2) (see Brain Tissue Oxygen Monitor)

Corticosteroids (see Corticosteroids)

Decompressive Craniectomy (see Decompressive Craniectomy)

Elevation of Head of to Bed to 30 Degrees

Hypertonic Saline (see Hypertonic Saline)

Hyperventilation

Intracranial Pressure (ICP) Monitoring (see Increased Intracranial Pressure)

Mannitol (see Mannitol)

Optimization of Cerebral Venous Drainage

Sedation (see Sedation)

Therapeutic Hypothermia (see Therapeutic Hypothermia)

Treatment of Fever (see Fever)

Treatment of Hyponatremia (see Hyponatremia)

Management of Seizures (see Seizures)

Management of Serum Glucose

Management of Body Temperature

Rationale

Treatment of Fever (see Fever)

Therapeutic Hypothermia (see Therapeutic Hypothermia)

Nutrition

Renal Management

Respiratory Management

Indications for Intubation/Mechanical Ventilation

Strategies for Mechanical Ventilation (see Mechanical Ventilation-General)

Clinical Efficacy

Recommendations (Guidelines for the Management of Severe Traumatic Brain Injury, 2007) [MEDLINE]

Surgical Management

Epidural Hematoma (see Epidural Hematoma)

Subdural Hematoma (see Subdural Hematoma)

Intracerebral Hemorrhage (see Intracerebral Hemorrhage)

Penetrating Brain Injury

Depressed Skull Fracture

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Prognosis


References

General

Clinical

Treatment

General

Sedation

Hemodynamic Management

Hemostatic Therapy

Corticosteroids

Management of Increased Intracranial Pressure

Management of Seizures

Management of Serum Glucose

Management of Body Temperature

Therapeutic Hypothermia

Surgery