Traumatic Brain Injury (TBI)

Traumatic Brain Injury (TBI)

David Ray Velez, MD

Table of Contents

Types
Secondary Brain Injury
Classification
Treatment

See Also:
*See Intracranial Pressure (ICP)

Types

Epidural Hematoma (EDH)

  • Definition: Bleeding Between the Dura Mater and Skull
  • Most Common Source: Middle Meningeal Artery
    • Often Associated with Temporal Bone Fractures
  • CT Appearance:
    • Lentiform/Biconvex
    • Does Not Cross Midline
  • Often Associated with a “Lucid Interval” – A Relatively Normal Period of Time from the Initial Concussion to the Subsequent Coma

Epidural Hematoma (EDH) 1

Subdural Hematoma (SDH)

  • Definition: Bleeding Between the Dura Mater and Arachnoid Mater
  • The Most Common Intracranial Hemorrhage
  • Source: Venous Plexus/Bridging Veins
    • Acceleration/Deceleration Injury
  • CT Appearance:
    • Crescent-Shaped
    • Crosses Midline
  • Can Be Chronic in Elderly After Falls

Subdural Hematoma (SDH) 2

Subarachnoid Hemorrhage (SAH)

  • Definition: Bleeding Between the Brain and Arachnoid Mater
  • Causes:
    • Trauma (#1)
    • Ruptured Aneurysm (#2)
    • Arteriovenous Malformation (AVM)
  • Aneurysmal Bleeds are Often Described as a “Thunderclap” Headache that is the “Worst of Life”
  • Xanthochromia (Yellow Coloring) of the Cerebrospinal Fluid (CSF) is Pathognomonic

Subarachnoid Hemorrhage (SAH) 3

Diffuse Axonal Injury (DAI)

  • Definition: A Diffuse Shearing Injury of the Brain Axons
  • Most Common Cause: Rotational Force of Acceleration/Deceleration Impact
  • May Not Be Apparent on CT Imaging (Low Diagnostic Yield)
  • MRI Appearance:
    • Punctate Hemorrhages
    • Blurring of Grey-White Interface
  • Often Identified Once Patient Has an Original CT Scan on Presentation but Fails to Clinically Improve After 6-24 Hours Prompting an MRI
  • Adams Classification:
    • Grade 1: Mild DAI with Microscopic White Matter Changes in the Cerebral Cortex, Corpus Callosum, and Brainstem
    • Grade 2: Moderate DAI with Gross Focal Lesions in the Corpus Callosum
    • Grade 3: Severe DAI with Findings of Grade 2 and Additional Focal Lesions in the Brainstem
  • Generally Indicates a Poor Prognosis

Diffuse Axonal Injury (DAI) on MRI 4

Cerebral Contusion (Parenchymal/Hemorrhagic Contusion)

  • Definition: Bruising of the Brain from Multiple Punctate Hemorrhages
    • May See Surrounding Edema and Necrosis
  • Most Remain Small and Surgically Insignificant
  • Often Evolve Over Time and May Worsen or Not Even Be Evident on the Initial CT
  • Often See “Coup and Countercoup” Injuries
    • “Coup” – Injury at the Site of Head Impact
    • “Countercoup” – Injury Remote from the Site of Head Impact (Classically Directly Opposite)
  • Most Common Sites: Frontal Base and Anterior Temporal Lobes

Secondary Brain Injury

Definition: Injury That Develops After the Initial/Primary Brain Injury from Metabolic and Physiologic Derangements

Primary Risk Factors

  • Hypotension
    • Reduced CPP Causes Ischemia
    • Autoregulation with Arteriole Vasodilation Causes Increased ICP
    • A Single Episode of Hypotension Doubles the Associated Mortality
  • Hypoxia

Classification

TBI Classification

  • Mild: GCS 13-15
  • Moderate: GCS 9-12
  • Severe: GCS ≤ 8
Glasgow Coma Scale (GCS)
# Motor (6) Verbal (5) Eyes (4)
1 None None (1T: Intubated) None
2 Decerebrate Incomprehensible Open to Pain
3 Decorticate Inappropriate Open to Speech
4 Withdraws to Pain Confused Spontaneous
5 Localizes Oriented
6 Obeys Commands
Brain Injury Guidelines (BIG)
Variables BIG 1 BIG 2 BIG 3
LOC Yes/No Yes/No Yes/No
Neuro Exam Normal Normal Abnormal
Intoxication No No/Yes No/Yes
CAP (Coumadin, Aspirin, Plavix) No No Yes
Skull Fracture No Non-displaced Displaced
SDH < 4 mm 5-7 mm > 8 mm
EDH < 4 mm 5-7 mm > 8 mm
IPH (Locations) < 4 mm (x1) 5-7 mm (x2) > 8 mm (Multiple)
SAH Trace Localized Scattered
IVH No No Yes

Treatment

Basic Management

  • Avoid Hypoxia and Hypotension – High Risk for Secondary Brain Injury
  • Reverse Any Coagulopathy
  • Start Prophylactic Anticoagulation Within 24-48 Hours of a Stable Head CT
  • Seizure Prophylaxis: Levetiracetam (Keppra) for 1 Week
    • Indicated for Severe TBI (Not Mild-Moderate)
    • Reduces Risk of Early Seizures
    • No Reduced Risk for Late Seizures or Post-Traumatic Epilepsy
  • Fluid Management:
    • NS is Generally Preferred Over LR (LR is Relatively Hypotonic and May Worsen Cerebral Edema)
    • Avoid Dextrose-Containing Solutions (Worsen Neurologic Injury)

Management Based on BIG Criteria

  • BIG 1: Observe for 6 Hours
  • BIG 2: Admit and Observe for 24 Hours
  • BIG 3: Admit to ICU, Repeat Head CT, and Consult Neurosurgery

Intracranial Pressure (ICP) Monitoring and Management

Surgical Decompression Indications

  • Epidural Hematoma (EDH):
    • > 30 cc Volume
    • GCS ≤ 8 with Pupil Abnormality
  • Subdural Hematoma (SDH):
    • > 10 mm Thick
    • > 5 mm Midline Shift
    • GCS ≤ 8 and Decreased by ≥ 2 Since Injury
    • GCS ≤ 8 with Pupil Abnormality
    • ICP > 20 mmHg
  • Subarachnoid Hemorrhage (SAH):
    • Posterior Fossa Causing Mass Effects
    • > 50 cc Volume
    • > 20 cc Volume, > 5 mm Midline Shift, and GCS ≤ 8

Evolving Therapies

  • Beta-Blockers (Propranolol)
    • Goal: Reduce Blood Pressure and Inhibit Catecholamine Surge-Mediated Inflammation in the Brain
    • Exact Role is Still Evolving
  • Amantadine (NMDA Antagonist)
    • May Improve Cognitive Function After Severe TBI – Clinical Effect Debated
    • May Accelerate the Pace of Functional Recovery without Significant Change in the Ultimate Level of Improvement

Two Factors are 100% Specific for Poor Outcome in the Absence of Cofounding Factors:

  • Absent or Extensor Motor Response on Day #3
  • Absent Pupillary or Corneal Reflexes on Day #3

References

  1. Yogarajah M, Agu CC, Sivasambu B, Mittler MA. HbSC Disease and Spontaneous Epidural Hematoma with Kernohan’s Notch Phenomena. Case Rep Hematol. 2015;2015:470873. (License: CC BY-3.0)
  2. Krishnamoorthy V, Sharma D, Prathep S, Vavilala MS. Myocardial dysfunction in acute traumatic brain injury relieved by surgical decompression. Case Rep Anesthesiol. 2013;2013:482596. (License: CC BY-3.0)
  3. Lasry O, Marcoux J. The use of intravenous Milrinone to treat cerebral vasospasm following traumatic subarachnoid hemorrhage. Springerplus. 2014 Oct 27;3:633. (License: CC BY-4.0)
  4. Gandy S, Ikonomovic MD, Mitsis E, Elder G, Ahlers ST, Barth J, Stone JR, DeKosky ST. Chronic traumatic encephalopathy: clinical-biomarker correlations and current concepts in pathogenesis. Mol Neurodegener. 2014 Sep 17;9:37. (License: CC BY-2.0)