Pathology of Head Injury

Question 1

what are examples of primary insult?

Answer 1

focal and/or diffuse brain trauma

Question 2

what are examples of secondary insults?

Answer 2

Hypotension – low arterial BP

Hypoxia – low blood oxygen
Infection

Haematoma – bleeding in/around brain

Question 3

how is conscious level assessed?

Answer 3

Glasgow Coma Scale

Question 4

how is the glasgow coma scale scored out of 15?

Answer 4

13-15 -mild injury
9-12 - moderate injury
3-8 -severe injury

Question 5

what are potential significant consequences of head injury?

Answer 5

Permanent physical disability

Post traumatic epilepsy

Intracranial infection (meninigitis, encephalitis, brain abcess)

Psychiatric illness (depression, post traumatic stress)

Chronic subdural haemorrhage

‘Punch-drunk’ dementia (boxers, lot of physical contact with head

Fatal outcome (uncommon)

Question 6

describe anatomy of the scalp?

Answer 6

hair-bearing (usually!) Skin, Connective tissue, Aponeurotic fascia, Loose connective tissue, Pericranium

Question 7

describe anatomy of the skull?

Answer 7

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

Question 8

describe anatomy of the meninges?

Answer 8

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

describe anatomy of the brain?

Answer 9

cerebrum vs cerebellum; brainstem and spinal cord

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 vital centres providing neurological control of respiration (breathing) and heart function

Question 10

why is the scalp a common site for laceration?

Answer 10

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 11

how much blood loss is associated with a scalp injury?

Answer 11

significatn blood loss

Question 12

how are skull fractures caused?

Answer 12

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

Question 13

what are the two elements of the skull?

Answer 13

Two elements to the skull: (i) skull vault (upper part) which includes frontal bone, squamous temporal bones and occipital bone, separated by sutures (ii) skull base (upon which the brain rests) which can be divided into the anterior, middle and posterior cranial fossae

Question 14

what are linear skull fractures commonly?

Answer 14

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

Question 15

how are depressed skull fractures formed?

Answer 15

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 16

how is a comminuted (mosiac) fracture formed?

Answer 16

Cob-Web Fractures
They are caused by heavy blunt weapons with large striking surface such as rice pounder, coconut, sledge hammer, fallen on projections etc.

Question 17

how is a ring fracture formed?

Answer 17

“Ring” fracture: 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 18

how is a contre-coup fracture formed?

Answer 18

Contre-coup” fracture: fracturing of the orbital plates (anterior fossa) caused by a fall onto the back of the head

Question 19

what is an intracranial haemorrhage?

Answer 19

Accumulation of blood within the rigid skull causes an increase in intracranial pressure (ICP) and results in compression of the brain 🡪 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 → coning

Question 20

what is an extradural haemorrage?

Answer 20

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

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

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 21

what is lucid interval which may occur during an extra dural haemorrage?

Answer 21

“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 22

what is a subdural haemorrhage?

Answer 22

Bleeding occurring beneath the dura (and above the arachnoid)
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
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
“Lucid interval” may be seen with SDH
Can get chronic subdural haemorrhage, particularly in elderly, and may be a cause of chronic confusion (and may be mistaken for dementia)

Question 23

what is a subarachnoid haemorrhage?

Answer 23

bleeding beneath the arachnoid membrane (and above the brain)
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)
“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
Collapse is usually rapid and death can occur very quickly due to the irritant effects of blood in the subarachnoid space

Question 24

what are types of intrinsic brain injury?

Answer 24

Cerebral oedema: 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”
Cerebral contusion and laceration: direct mechanical damage to the brain substance
May occur anywhere on the brain
“Coup” contusion: occurs when a head is struck a heavy blow - the contusion is found directly under the site of impact
“Contre-coup” contusions: 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 [NB: contre-coup fractures]

Question 25

what is a diffuse traumatic axonal injury?

Answer 25

axon: elongated processes of nerve cells which permit transmission of signals between different parts of the brain and between the brain and body
DAI not just caused by trauma, therefore, use the term “traumatic DAI” (tDAI)
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.
“Diffuse Vascular Injury”
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
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
Clinically, victims are comatose when tDAI is fully developed
Concussion: may well be the clinical manifestation of lesser degrees of axonal injury - may have retrograde amnesia