Pathology of Head Injury Flashcards
what are examples of primary insult?
focal and/or diffuse brain trauma
what are examples of secondary insults?
Hypotension – low arterial BP
Hypoxia – low blood oxygen
Infection
Haematoma – bleeding in/around brain
how is conscious level assessed?
Glasgow Coma Scale
how is the glasgow coma scale scored out of 15?
13-15 -mild injury
9-12 - moderate injury
3-8 -severe injury
what are potential significant consequences of head injury?
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)
describe anatomy of the scalp?
hair-bearing (usually!) Skin, Connective tissue, Aponeurotic fascia, Loose connective tissue, Pericranium
describe anatomy of the skull?
outer and inner “tables” of compact bone separated by spongy bone
describe anatomy of the 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)
describe anatomy of the brain?
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
why is the scalp 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
how much blood loss is associated with a scalp injury?
significatn blood loss
how are skull fractures caused?
application of force causing deformation of the skull; adult skulls less able to cope with distortion than those of infants
what are the two elements of the skull?
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
what are linear skull fractures commonly?
commonly temporo-parietal from blow or fall onto side or top of the head and may continue onto the skull base; “hinge” fracture
how are depressed skull fractures formed?
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
how is a comminuted (mosiac) fracture formed?
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.
how is a ring fracture formed?
“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
how is a contre-coup fracture formed?
Contre-coup” fracture: fracturing of the orbital plates (anterior fossa) caused by a fall onto the back of the head
what is an intracranial haemorrhage?
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
what is an extradural haemorrage?
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
what is lucid interval which may occur during an extra dural haemorrage?
“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
what is a subdural haemorrhage?
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)
what is a subarachnoid haemorrhage?
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
what are types of intrinsic brain injury?
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]
what is a diffuse traumatic axonal injury?
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
