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Questions and Answers
What can an impacting force to the head produce?
What can an impacting force to the head produce?
What type of acceleration occurs when the force passes through the centre of the head?
What type of acceleration occurs when the force passes through the centre of the head?
What can cause subdural hemorrhage without an actual blow or fall on the head?
What can cause subdural hemorrhage without an actual blow or fall on the head?
What occurs when the head is in rotation and deceleration or acceleration is transmitted to the brain?
What occurs when the head is in rotation and deceleration or acceleration is transmitted to the brain?
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What is the result of the brain's momentum causing continuous motion after the skull has stopped moving?
What is the result of the brain's momentum causing continuous motion after the skull has stopped moving?
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What is damaged due to the brain being restrained by the falx and tentorium?
What is damaged due to the brain being restrained by the falx and tentorium?
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What is the result of an impact against the wide wall of the skull?
What is the result of an impact against the wide wall of the skull?
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Why is the cerebellum less liable to damage from rotatory movement of the head?
Why is the cerebellum less liable to damage from rotatory movement of the head?
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What is the location of the contrecoup lesion in relation to the impact site?
What is the location of the contrecoup lesion in relation to the impact site?
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What is the result of a blow on the occipital region of the head?
What is the result of a blow on the occipital region of the head?
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What is the mechanism of concussion of the brain?
What is the mechanism of concussion of the brain?
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What is the result of a fall on the side of the head?
What is the result of a fall on the side of the head?
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What is the characteristic of a severe concussion?
What is the characteristic of a severe concussion?
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What is the result of a blow on the parietal area of the head?
What is the result of a blow on the parietal area of the head?
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What is the characteristic of muscles during established concussion?
What is the characteristic of muscles during established concussion?
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What is the duration of post-traumatic amnesia?
What is the duration of post-traumatic amnesia?
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What is the most acceptable cause of concussion?
What is the most acceptable cause of concussion?
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What is the characteristic of respiration during established concussion?
What is the characteristic of respiration during established concussion?
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What is the feature of diffuse axonal injury?
What is the feature of diffuse axonal injury?
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What is the characteristic of pupils during established concussion?
What is the characteristic of pupils during established concussion?
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What is the finding on autopsy in diffuse axonal injury?
What is the finding on autopsy in diffuse axonal injury?
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What is the characteristic of pulse during established concussion?
What is the characteristic of pulse during established concussion?
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Study Notes
Head Injuries
- An impacting force to the head can produce linear acceleration, rotational acceleration, or a combination of both.
Linear Acceleration
- Occurs when the force passes through the center of the head, accelerating it in a straight line.
- Examples: impact to the front and back of the head.
Rotational or Angular Acceleration
- Occurs when the head rotates about its center, causing injury to the side of the head.
- Combination of linear and angular acceleration is more injurious.
Mechanism of Cerebral Injuries
- Damage can occur without actual blow or fall on the head, e.g., by shaking an infant (child abuse).
- A blow can cause linear or rotational change in velocity, leading to brain damage.
- Forces involved: linear acceleration/deceleration, centrifugal, and rotational velocity.
- Linear acceleration forces can cause compressional or rarefactional forces.
Brain Damage
- Acceleration or deceleration with a rotational element can cause brain damage.
- Deceleration or acceleration of the head in rotation can cause the brain to glide within the dura, leading to gliding or shear strain.
- The area of the skull depressed can cause compression and a typical cone-shaped contusion.
Contrecoup Lesion
- Located in an area opposite the side of impact.
- Caused by local distortion of the skull and sudden rotation of the head, resulting in shear strain.
- Formation of a cavity or vacuum on the opposite side.
Effects of Blows to Different Areas of the Head
- Blow on the occipital region: injures frontal lobe and tip of temporal lobe.
- Blow on the front of the head: damages inner and lower part of the back of the brain or brain stem.
- Fall on the side: contusion of the opposite side.
- Fall on the top of the head: contusion of the ventral surface of the cerebral hemisphere.
- Blow on the parietal area: lesion on the opposite hemisphere or medial side of the same hemisphere.
Concussion of Brain
- Occurs due to acceleration/deceleration of the head, causing shearing or stretching of nerve fibers and axonal damage.
- Severe injuries occur in coronal head motion only, while sagittal head motion produces mild or moderate injury.
Mechanism of Concussion
- At a low level of acceleration/deceleration, there is physiological dysfunction.
- With increased physical force, there is immediate structural damage of axons and immediate stoppage of all activities.
Effects of Concussion
- Mild concussion: consciousness is not lost, no confusion or disorientation (± amnesia).
- Severe concussion: amnesia and loss of consciousness.
Cerebral Concussion
- Can be produced by direct violence to the head or indirect violence (e.g., fall upon the feet or buttocks).
- During established concussion: muscles are flaccid, pupils are dilated and unreacting, pulse is weak and slow, and respiration is shallow.
Post-Traumatic Amnesia
- Ranges from minutes to days, and duration is usually proportional to the severity of the injury.
Commotio Cerebri
- Severe movement of the head causes shearing stress in the brain, leading to small or punctate hemorrhages throughout the brain.
Diffuse Axonal Injury (DAI)
- Occurs when head acceleration occurs over a long period, as in a traffic accident or fall from a considerable height.
- Features of DAI: focal lesions in the corpus callosum, parasagittal white matter, septum, wall of the III ventricle, and dorsolateral brainstem, as well as microscopic evidence of numerous axonal swelling and axonal bulbs.
On Autopsy
- Petechial hemorrhages in the cortex, roof of the IV ventricle, and piamater of the upper segments of the cervical cord.
- Oedema, foci of myelin degeneration, and in mild DAI, some axons may be damaged.
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Description
Learn about the effects of impacting forces on the head, including linear and rotational acceleration, and their relation to cerebral injuries.
