Pathology of Head Injury

Question 1

How common are head ijuries and their admissions?

Answer 1

o 250 hospital admissions annually per 100,000 of the population

o 100 people per 100,000 left with serious permanent neurological deficit

o 10 people per 100,000 die

o In UK commonest causes are road traffic accidents and alcohol-related incidents including assaults

Question 2

What is a primary insult and a secondary insult?

Answer 2

Primary insult: Focal and/or diffuse brain trauma

Secondary insult(s):

Hypotension – low arterial BP

Hypoxia – low blood oxygen

Infection

Haematoma – bleeding in/around brain

Question 3

What is the itial assessment of a patient with a head injury?

Answer 3

Conscious level assessed using Glasgow Coma Scale

Scored out of 15 (GCS 15 fully conscious)

Correlates with severity of head injury:

13-15 - mild injury

9-12 - moderate injury

3-8 - severe injury

Question 4

What are some consequnces of head injuries?

Answer 4

Permanent physical disability

Post traumatic epilepsy

Intracranial infection

Psychiatric illness

Chronic subdural haemorrhage

‘Punch-drunk’ dementia - repeated low level head injuries

Fatal outcome (uncommon)

Question 5

What can head injuries be caused by and their forensic significance?

Answer 5

Head injuries can result from accidental, homicidal and sometimes suicidal incidents

Accidental very common, e.g. falls, especially from a height, road traffic collisions

Homicidal also frequent and may be a consequence of being struck by a weapon, e.g. hammer, axe, brick, or from a fall sustained as part of an assault

Natural disease can also cause collapse with resulting head injury which can prove misleading on initial investigation

Question 6

What are the layers of the scalp?

Answer 6

Skin, Connective tissue, Aponeurotic fascia, Loose connective tissue, Pericranium

Question 7

Skull: outer and inner “tables” of compact bone separated by ____________

Answer 7

Skull: outer and inner “tables” of compact bone separated by spongy bone

Question 8

What are the meninges of the brain

Answer 8

Meninges: dura mater (dense, tough, fibrous, adherent to inner surface of the skull), arachnoid mater (delicate, transparent, envelopes the brain), pia mater (delicate, applied to the brain surface)

Question 9

Brainstem and cerebellum are together called the hindbrain and are positioned within the posterior cranial fossa

The brainstem is the part of the brain which contains the __________ providing neurological control of respiration (breathing) and heart function

Answer 9

vital centres

Question 10

What are scalp injuries ismilar to?

Answer 10

Similar to those which can affect the skin, e.g. abrasions, bruises, lacerations, incisions (and burns/scalds)

Question 11

Are scalp lacerations and incisions similar?

Answer 11

Scalp is a common site for laceration because it is closely applied to the skull and tearing associated with the application of force more likely to occur in these circumstances (“anvil” effect); the lacerations may be surprisingly cleanly cut, potentially mimicking an incised wound

Question 12

_____________ to the head may not be visible on the surface of the scalp

Answer 12

Blunt force injury to the head may not be visible on the surface of the scalp

Question 13

What can hair do to injuries to the scalp?

Answer 13

Hair can obscure sizeable injuries to the scalp - shaving advisable at autopsy!

Question 14

Skull fractures caused by application of force causing deformation of the skull; _____ skulls less able to cope with distortion than those of ______

Answer 14

Skull fractures caused by application of force causing deformation of the skull; adult skulls less able to cope with distortion than those of infants

Question 15

What are the different fractures of the skull?

Answer 15

Linear

Depressed Comminuted (mosaic)

“Ring” fracture

“Contre-coup” fracture

Question 16

What is a linear fracture of the skull?

Answer 16

commonly temporo-parietal from blow or fall onto side or top of the head and may continue onto the skull base; “hinge” fracture

Question 17

What is a depressed fracture of the skull?

Answer 17

focal impact which may push fragments inwards to damage the meninges, blood vessels and the brain; risk of meningitis and post-traumatic epilepsy. Not typical of a fall from standing onto a flat surface, e.g. pavement - fractures tend to be linear in this scenario

Question 18

What is a comminuted (mosaic) fracture of the skull?

Answer 18

fragmented skull

Question 19

What is a ring fracture of the skull?

Answer 19

fracture line encircling the foramen magnum caused by a fall from height, usually landing on the feet, but sometimes the head, leading to the skull base and cervical spine being forced together

Question 20

What is a contre-coup fracture of the skull?

Answer 20

fracturing of the orbital plates (anterior fossa) caused by a fall onto the back of the head

Question 21

How are intracranial haemorrhages named?

Answer 21

Named by their position within the skull in relation to the meninges, i.e. extradural, subdural and subarachnoid haemorrhage

Question 22

What is an intracranial haemorrhage and what is are its consequences?

Answer 22

Accumulation of blood within the rigid skull causes an increase in intracranial pressure (ICP) and results in compression of the brain à this compression causes symptoms, including reduction in conscious level

As ICP increases, without intervention, ultimately death will occur by compression of the brainstem due to herniation of the cerebellar tonsils into the Foramen Magnum

Question 23

What is an Extradural Haemorrhage?

Answer 23

Bleeding occurring between the dura and the skull; accumulating blood strips the dura off the inner surface of the skull

Question 24

What is the common cause of a extradural haemorrhage?

Answer 24

Vast majority arise from damage to an artery in association with a skull fracture (80-90%) and, therefore, under higher pressure than with venous bleeding, but very occasionally large venous channels can cause EDH

Classically caused by bleeding from the middle meningeal artery where it crosses the inner aspect of the squamous temporal bone due to fracture of the squamous temporal bone with secondary damage to the artery in the vicinity of the fracture

Question 25

How and when do symptoms develop in a extradural haemorrhage?

Answer 25

The accumulation of blood (haematoma) can cause raised intracranial pressure with developing neurological symptoms; the time period for the development of symptoms is variable, can be rapid, but can take many hours

Question 26

“Lucid interval” can occur in extradural haemorrhage, what is it?

Answer 26

“Lucid interval” can occur - victim of injury initially seems to be okay, without neurological symptoms, but can deteriorate catastrophically later, which can be a source of difficulty for clinical staff who may be accused of being negligent if they fail to recognise the possibility of intracranial bleeding

Question 27

What is a subdural haemorrhage?

Answer 27

Bleeding occurring beneath the dura (and above the arachnoid)

Question 28

What is the cause of a subdural haemorrhage?

Answer 28

Usually caused by bleeding from bridging veins which pass from the surface of the brain to drain into the large venous channels within the dura

Any motion which causes rotational or “shearing” forces can cause the veins to be stretch and torn due to the relative movement between the brain and the dura

Frequently occurs without a skull fracture

Question 29

Who is at more risk of a subdural haemorrhage?

Answer 29

Individuals with atrophic (small) brains are at increased risk because the smaller brain has greater capacity for movement and the veins may be already stretched to some degree

Question 30

Can a lucid interval be seen in subdrual haemorrhage aswell?

Answer 30

“Lucid interval” may be seen with SDH

Question 31

What is a chronic subdural haemorrhage?

Answer 31

Can get chronic subdural haemorrhage, particularly in elderly, and may be a cause of chronic confusion (and may be mistaken for dementia)

Question 32

What is a subarachnoid haemorrhage?

Answer 32

bleeding beneath the arachnoid membrane (and above the brain)

Question 33

What is the cause of a subarachnoid haemorrhage?

Answer 33

most common cause of SAH is actually natural disease - rupture of a cerebral artery (“berry”) aneurysm

frequently seen in association with cerebral contusions (bruising to the brain)

Question 34

What is a traumatic basal SAH?

Answer 34

“Traumatic Basal SAH” is a specific entity in forensic medicine

TBSAH is typically a result of a forceful impact to the upper part of the side of the neck causing abrupt rotational movement of the head leading to rupture of the vertebro-basilar circulation and a concentration of SAH on the base of the brain; precise mechanism leading to rupture is still not certain

Question 35

Is a subarachnoid haemorrhage fast acting?

Answer 35

Collapse is usually rapid and death can occur very quickly due to the irritant effects of blood in the subarachnoid space

Question 36

What is cerebral oedema? and its effects

Answer 36

when fluid builds up around the brain, causing an increase in pressure

common and rapid result of brain injury, especially in children (“malignant cerebral oedema”)

Can develop in minutes and lead to massive brain swelling with raised intracranial pressure and “coning”

Question 37

What is cerebral contusion and laceration?

Answer 37

direct mechanical damage to the brain substance

May occur anywhere on the brain

cerebral contusion - bruises on brain surface

cerebral lacerations - tears on brain surface - more significant damage which usually involves underlying white matter also

Question 38

What is a “Coup” contusion?

Answer 38

occurs when a head is struck a heavy blow - the contusion is found directly under the site of impact

Question 39

What are “Contre-coup” contusions?

Answer 39

caused by a moving head striking a fixed object or unyielding surface - contusions are found diametrically opposite the site of head impact, e.g. a fall onto the back of the head would result in contusions on the frontal and temporal poles and on the undersurface of the frontal lobes

Question 40

What is an axon

Answer 40

axon: elongated processes of nerve cells which permit transmission of signals between different parts of the brain and between the brain and body

Question 41

What is Diffuse Traumatic Axonal Injury?

Answer 41

a brain injury in which scattered lesions in white matter tracts as well as gray matter occur over a widespread area

DAI not just caused by trauma, therefore, use the term “traumatic DAI” (tDAI)

Teating of nerve fibres (axons) in the white matter of the brain

Question 42

How do you diagnose Diffuse Traumatic Axonal Injury?

Answer 42

tDAI is a diagnosis which can only be made by microscopy of the brain tissue (special staining techniques - APP - are frequently required to detect the damage), but may get concomitant damage to small blood vessels within the brain which raise suspicions of tDAI.

Question 43

What causes Diffuse Traumatic Axonal Injury?

Answer 43

Usual scenarios associated with tDAI are vehicular collisions and falls from a height; serious rotational forces applied to the brain tissue causing shearing of axons

“Diffuse Vascular Injury”

Question 44

What areas are more suscetible to tDAI?

Answer 44

Certain areas of the brain are particularly susceptible to displaying tDAI: corpus callosum, para-sagittal white matter, posterior internal capsule and dorsolateral aspects of the rostral brainstem, as well as the cerebellar peduncles

Question 45

What are victems like when a tDAI is fully developed?

Answer 45

Clinically, victims are comatose when tDAI is fully developed

Often unconscious immediatley, particularly if brianstem affected

Question 46

WHat may concussion be?

Answer 46

Concussion: may well be the clinical manifestation of lesser degrees of axonal injury - may have retrograde amnesia

Question 47

image shwoing differences between subdural and extradural haemorrhage

Answer 47