THE FORENSIC NEUROPATHOLOGY OF BLUNT FORCE TRAUMA

OF THE BRAIN Part 1: An Introduction

Bennet I. Omalu, M.D., M.P.H.Forensic Pathologist/ Neuropathologist

SYNONYMS• Brain Trauma• Neuro-trauma• Traumatic Brain Injury [TBI]• Cranio-Cerebral Injury• Blunt Force Trauma of the Head• TBI causes 44% of traumatic deaths in the US

Blunt force trauma of the brain can be induced by

transference of Kinetic Energy [KE] to the brain by

an un-yielding object or surface with a relatively

broad surface area like a base ball bat or a floor

OTHER COMMON MODALITIES OF BRAIN TRAUMA

• Penetrating Force Trauma of the Head– E.g.: Stab or incised wounds

• Gunshot/ Firearm Wounds of the Head– E.g.: Hand-guns, rifles, shot-guns etc

• Asphyxiation [Diffuse Hypoxic-Ischemic Cerebral Injury] – E.g.: Hanging, smothering, Carbon Monoxide intoxication etc

• Toxic Injuries e.g. mercury, arsenic, methotrexate

• Blunt Force Trauma of the Head is the most prevalent cause of brain injuries

BIO-MECHANICAL LOADING [BML]• Mechanism of transference of K.E. to the

brain; three major types:– Impact Bio-Mechanical Loading

• Transference of energy by direct impact of the head– E.g.: a fall from a height and impact of the head on a floor– E.g.: a base ball bat hitting the head in an assault

– Inertial Bio-Mechanical Loading• Transference of energy to the head by acceleration-

deceleration shearing forces without impact– E.g.: when a baby is shaken excessively– E.g.: sudden jerk of the head in the elderly without impact

– Combined Impact-Inertial Bio-Mechanical Loading

BIO-MECHANICAL LOADING [BML]• Angular or rotational acceleration-deceleration is

more deleterious to the brain than linear acceleration-deceleration

• There is a selective topographic vulnerability of the brain to modalities of bio-mechanical loading– E.g.: the splenium of the corpus callosum is most vulnerable

to diffuse shearing of the brain

• Impact BML is more likely to generate focal traumatic brain injury

• Inertial BML is more likely to generate diffuse traumatic brain injury

DEFINITIONS• Primary Brain InjuryDirect and immediate consequence of trauma to the brain

e.g. cerebral contusion

• Secondary Brain InjuryIndirect and delayed consequence of trauma to the brain

e.g. cerebral edema, cerebral herniation

• Closed Head InjuryBrain injury with intact dura mater

• Open Head InjuryBrain injury with lacerated or disrupted dura materMajor complications: Streptococcal meningitis anddural fistula

DEFINITIONS• Focal Traumatic Brain InjuryLocalized injury of the brain e.g. lobar cerebral contusion, subdural hemorrhage• Diffuse Traumatic Brain InjuryGeneralized injury to all regions of the brain e.g. diffuse shearing of the brain: Diffuse Traumatic Axonal Injury, Diffuse Hypoxic Injury• Brain Injury Grading: Glasgow Coma ScaleWithin 48 hours:Severe TBI: GCS 1–8Moderate TBI: GCS 9–12Mild TBI: GCS 13-15

GLASGOW COMA SCALEBest Eye Response. (4) 1. No eye opening. 2. Eye opening to pain. 3. Eye opening to verbal command. 4. Eyes open spontaneously

Best Verbal Response. (5) 1. No verbal response 2. Incomprehensible sounds. 3. Inappropriate words. 4. Confused 5. Orientated

Best Motor Response. (6) 1. No motor response. 2. Extension to pain. 3. Flexion to pain. 4. Withdrawal from pain. 5. Localising pain. 6. Obeys Commands.

 

A minimum score of 3

A maximum score of 15

Teasdale G., Jennett B., LANCET (ii) 81-83, 1974.

MILD TRAUMATIC BRAIN INJURYPhysiological disruption of brain function due to trauma, as manifested by at least one of the following: 1. Any period of loss of consciousness 2. Any loss of memory for events immediately before or after

the trauma 3. Any alteration in mental state at the time of the accident

(e.g., feeling dazed, disoriented, or confused) 4. Focal neurological deficit(s) that may or may not be

transient  But where the severity of the injury does not exceed the following: a. Post-traumatic amnesia (PTA) not greater than 24 hours b. After 30 minutes, an initial Glasgow Coma Scale (GCS) of

13-15 c. Loss of consciousness of approximately 30 minutes or less

MANIFESTATIONS OF BFT OF THE HEAD•Abrasions/ Contusions/ Lacerations of Scalp

•Galeal Hemorrhages

•Fractures of the skull

•Intra-cranial hemorrhages

•Cerebral contusions/ lacerations

•Congestive brain swelling and cerebral edema

•Hypoxic-ischemic brain injury

•Traumatic axonal injury

•Diffuse vascular injury

•Cerebral fat embolism

EPIDEMIOLOGYEPIDEMIOLOGY

• 500,000 - 750,000 cases of CNS trauma per year in the U.S.

10% are fatal

30 - 50% are moderate/ severe

5 - 10% result in residual deficits

• 150/100,000 population have sequelae of CNS trauma

• Leading cause of death in people under 45 years of age

• Accounts for 1% of all deaths

• Accounts for 30% of deaths from trauma

• Accounts for 50% of deaths due to road traffic accidents