1. Introduction to Traumatic Brain Injury
Brian L. Edlow

2. Goals
Understand that traumatic brain injury is a process, not an event
Understand the 4 main pathophysiologic mechanisms involved in traumatic brain injury
Understand basic strategies for treatment

3. Severe Traumatic Brain Injury (TBI)
Definition: Head trauma associated with a Glasgow Coma Score of ≤ 8
Best Eye Response
Best Verbal Response
Best Motor Response
No eye opening
Eye opening to pain
Eye opening to verbal command
Eye opening spontaneously
No verbal response
Incomprehensible sounds
Inappropriate words
Confused words
Appropriate verbal responses
No motor response
Extension to pain
Flexion to pain
Withdrawal from pain
Localizing to pain
Obeys commands
Talk about the basic principle of having objective markers. Facilitates diagnosis, prognosis, and clinical trials.
Coma Score of 13 or higher correlates with a mild brain injury, 9 to 12 is a moderate injury and 8 or less a severe brain injury.

4. Severe TBI - Demographics
(Population 300 million)
1.5 million cases per year in U.S.
Causes: Motor vehicle accident (~45%), falls (~30%), occupational accidents (~10%), recreational accidents (~10%), assaults (~5%)
Highest risk: children, adolescent/young adult men, elderly
Discuss motorcycles and case of KL

5. Severe TBI - Pathophysiology
TBI is a process, not an event!
Secondary injury can be more damaging than primary injury
4 Main Mechanisms of Brain Injury
Brain Contusion
Increased intracranial pressure ( ICP)
Diffuse Axonal Injury
Stroke (ischemic and/or hemorrhagic)
Mention PV’s case and how the final blow was from secondary injury (Duret hemorrhage in pons) that led to his death

6. Mechanism 1: Brain Contusion
A brain contusion is defined by cell death accompanied by hemorrhage (leakage of blood)
The soft brain tissue is vulnerable to contusion in head trauma
The contusion often occurs at a site distant from the point of impact
Ask class to point out areas of contusion - what lobes are involved. Ask them to guess where the point of impact was. Have each group look at the neuroanatomy on their models. (Answer: patient fell backwards and impact side was occipital region, but contra-coup injury caused contusions on orbital surfaces of frontal lobes and tips of temporal lobes.
Gross brain image from

7. Mechanism 2: ICP - Understanding the Determinants of Intracranial Pressure -
The volume of the intracranial vault =
Intracranial Contents:
80% brain tissue
10% blood
10% cerebrospinal fluid
An increase in the volume of any of these intracranial contents causes increased intracranial pressure
Once the initial injury is established, what other concurrent processes contribute to brain injury?
The brain can swell (edema)
Excess blood can accumulate due to hemorrhage
Cerebrospinal fluid can accumulate due to blockage of outflow

8. Skull image from www.mnsu.edu
Mechanism 2: ICP
Key Concept #1: The intracranial vault is a fixed volume --> Bone does not expand!
Skull image from

9. Mechanism 2: ICP - Understanding the Physics of Intracranial Pressure -
(mmHg)
ICP > 20 mmHg
Once the initial injury is established, what other concurrent processes contribute to brain injury?
Volume (mL)
Intracranial Pressure Rises as Brain+Bood+CSF volume Increases

10. Mechanism 2: ICP - Understanding the Physics of Intracranial Pressure -
CPP
Once the initial injury is established, what other concurrent processes contribute to brain injury?
This patient has dangerously high intracranial pressures, which increase the likelihood of morbidity and mortality

11. Mechanism 2: ICP
Key Concept #2: There is only one way out of the intracranial vault --> the opening at the base of the skull known as the foramen magnum
3D CT Angiogram from /66000/66173.asp
Skull base image from

12. Mechanism 2: ICP Key Concept #3:
When the brain is squeezed through the foramen magnum (herniation), the brainstem is compressed, the patient stops breathing, and the patient dies
Discuss herniation --> medical emergency, death is impending Emphasize that there are many types of herniation, but brainstem herniation is the most acutely lifethreatening.
Herniation schematic from Robbins and Cotran. Pathologic Basis of Disease. 7th ed. Philadelphia: Elselvier; 2005.

13. Causes of ICP: Epidural Hematomas
Epidural hematomas are accumulations of blood between inner part of skull and outer part of dura (outer layer of meninges). Ask class about soft tissue swelling in Image A.
Figure 7-15 Examples (A, B-arrows) of epidural hematomas in CT scans on the patient's right side. The smaller lesion in A is obviously of traumatic origin; this patient has soft tissue damage, a fractured skull, blood in the substance of the brain, and blood in the anterior horn of the lateral ventricle and in the third ventricle. The cause of the larger lesion (B) is not obvious.
Slides from Haines:Fundamental Neuroscience for Basic and Clinical Applications 3e -

14. Causes of ICP: Sudural Hematomas
Sudural hematomas are blood accumulations between inner part of dura and the arachnoid. Mention the layers of the dura, but emphasize the spatial relationships.
Figure 7-16 An example of a subdural hematoma (arrows) in CT scan on the patient's left side. This lesion is long and thin and extends for considerable distance over the surface of the hemisphere: note the shift in the midline.
Slide from Haines:Fundamental Neuroscience for Basic and Clinical Applications 3e -

15. Causes of ICP: Swelling
Highlight the point that edema and hemorrhage often go hand in hand in severe TBI. Also discuss fractures.
Observe swelling (darker tissue) on brain CT scan of a 7-month-old victim of child abuse. What other injuries are present?
Head CT from rad.usuhs.mil/rad/ home/peds/ihsdarrow.jpg

16. Causes of ICP: Swelling
Swelling in this case is from a hemorrhagic brain tumor. The tumor is not in this section.
Observe diffuse swelling (yellow tissue) and expansion of brain tissue into ventricles
Gross brain specimen from neuropathology.neoucom.edu

17. Causes of ICP: Swelling
Observe widening and flattening of gyri on brain surface
Brain surface image from www-medlib.med.utah.edu

18. Mechanism 3: Diffuse Axonal Injury
Occurs in up to 1/2 of traumatic brain injuries1
Is a diffuse form of injury, meaning that damage occurs over a more widespread area than in focal brain injury
Involves the shearing of axons in the white matter tracts
Start by asking: What is an axon?
When the brain is accelerated, parts of differing densities and distances from the axis of rotation slide over one another, stretching axons that traverse junctions between areas of different density, especially gray-white matter junctions (Wasserman, 2004). Two thirds of DAI lesions occur in areas where grey and white matter meet (Wasserman, 2004).
Address the features of a vegetative state and bring up recent fMRI article about brain activation. 1:

19. Mechanism 3: Diffuse Axonal Injury
Is one of the major causes of unconsciousness and persistent vegetative state after head trauma.
Over 90% of patients with severe DAI never regaining consciousness (those that do wake up often remain significantly impaired)
Start by asking: What is an axon?

20. Mechanism 3: Diffuse Axonal Injury
Start by asking: What is an axon?
A microscopic view of axonal degeneration

21. Mechanism 4: Stroke Ischemic Stroke Hemorrhagic Stroke
Caused by decreased oxygen delivery to brain tissue
Can occur in trauma secondary to swelling, which compresses nearby arteries
Hemorrhagic Stroke
Decreased oxygen delivery because blood is leaking into brain tissue and not entering the capillary network
Can occur as a primary or secondary injury

22. Severe TBI - Basic Principles of Clinical Management
Monitor intracranial pressure (invasively) and intervene to lower ICP when necessary
Elevate head of bed
Medications to decrease swelling
Decrease brain activity to reduce blood delivery and swelling --> “medically induced coma”
Hypothermia
Surgical Decompression when risk for herniation is high
Seizure prophylaxis
Seizures occur in up to 20% of severe TBI patients, with ~50% occurring within first 24 hours1
Other priorities
Adequate nutrition, correction of electrolyte abnormalities, strict control of blood sugar, strict temperature regulation
Mention that Casey will be giving talk on surgical interventions in traumatic brain injury. Ask class why medically induced coma or hypothermia would lead to decreased swelling and better outcomes?
1: “Post-traumatic Seizures and Epilepsy.” May 29, 2006.

23. Severe TBI - Prognosis
The Impact of ICP: Patients with mean ICP greater than 20 mmHg during hospitalization have 47% mortality vs. patients with mean ICP below 20 mmHg, who have 17% mortality (p < 0.001)1
17% will have seizures during the 2-year post-trauma period2
The length of time a patient spends in a coma correlates to both post-traumatic amnesia and recovery times
What is the definition of prognosis?
Coma lasting seconds to minutes results in PTA that lasts hours to days; recovery plateau occurs over days to weeks.
Coma that lasts hours to days results in PTA lasting days to weeks; recovery plateau occurs over months.
Coma lasting weeks results in PTA that lasts months; recovery plateau occurs over months to years.
1: Balestreri M, Czosnyka M et al. Impact of intracranial pressure and cerebral perfusion pressure on severe disability and mortality after head injury. Neurocrit Care. 2006,;4(1):8-13.
2: Englander J; Bushnik T et al. Analyzing risk factors for late posttraumatic seizures: a prospective, multicenter investigation. Arch Phys Med Rehabil 2003 Mar;84(3):

24. Severe TBI - Prognosis - The Stories of DM and PV -
Case 1 - DM
18-year-old boy hit by car while riding bike
Severe TBI with frequent spikes in ICP, ventilator dependant
2 weeks in coma
Walked out of hospital after 2.5 weeks, able to communicate with family
Case 2 - PV
38-year-old man falls down stairs in bar
Severe TBI --> goes in and out of coma for 2 weeks
2 weeks into hospital course, swelling increases so much that temporal lobe herniates into brain stem, causing permanent loss of consciousness
Dies after 1.5 months in hospital of brain infection, respiratory failure
What is the definition of prognosis?

25. Looking to the future…
Mention that Casey will be giving talk on surgical interventions in traumatic brain injury
Will new imaging technologies lead to advances in patient care?