Pathology of Head Injury Flashcards
How common are head ijuries and their admissions?
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
What is a primary insult and a secondary insult?
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
What is the itial assessment of a patient with a head injury?
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
What are some consequnces of head injuries?
Permanent physical disability
Post traumatic epilepsy
Intracranial infection
Psychiatric illness
Chronic subdural haemorrhage
‘Punch-drunk’ dementia - repeated low level head injuries
Fatal outcome (uncommon)
What can head injuries be caused by and their forensic significance?
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
What are the layers of the scalp?
Skin, Connective tissue, Aponeurotic fascia, Loose connective tissue, Pericranium
Skull: outer and inner “tables” of compact bone separated by ____________
Skull: outer and inner “tables” of compact bone separated by spongy bone
What are the meninges of the brain
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)
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
vital centres
What are scalp injuries ismilar to?
Similar to those which can affect the skin, e.g. abrasions, bruises, lacerations, incisions (and burns/scalds)
Are scalp lacerations and incisions similar?
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
_____________ to the head may not be visible on the surface of the scalp
Blunt force injury to the head may not be visible on the surface of the scalp
What can hair do to injuries to the scalp?
Hair can obscure sizeable injuries to the scalp - shaving advisable at autopsy!
Skull fractures caused by application of force causing deformation of the skull; _____ skulls less able to cope with distortion than those of ______
Skull fractures caused by application of force causing deformation of the skull; adult skulls less able to cope with distortion than those of infants
What are the different fractures of the skull?
Linear
Depressed Comminuted (mosaic)
“Ring” fracture
“Contre-coup” fracture
What is a linear fracture of the skull?
commonly temporo-parietal from blow or fall onto side or top of the head and may continue onto the skull base; “hinge” fracture
What is a depressed fracture of the skull?
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
What is a comminuted (mosaic) fracture of the skull?
fragmented skull
What is a ring fracture of the skull?
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
What is a contre-coup fracture of the skull?
fracturing of the orbital plates (anterior fossa) caused by a fall onto the back of the head
How are intracranial haemorrhages named?
Named by their position within the skull in relation to the meninges, i.e. extradural, subdural and subarachnoid haemorrhage
What is an intracranial haemorrhage and what is are its consequences?
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
What is an Extradural Haemorrhage?
Bleeding occurring between the dura and the skull; accumulating blood strips the dura off the inner surface of the skull
What is the common cause of a extradural haemorrhage?
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
How and when do symptoms develop in a extradural haemorrhage?
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
“Lucid interval” can occur in extradural haemorrhage, what is it?
“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)
What is the cause of a subdural haemorrhage?
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
Who is at more risk of a subdural haemorrhage?
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
Can a lucid interval be seen in subdrual haemorrhage aswell?
“Lucid interval” may be seen with SDH
What is a chronic subdural haemorrhage?
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)
What is the cause of a subarachnoid haemorrhage?
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)
What is a traumatic basal SAH?
“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
Is a subarachnoid haemorrhage fast acting?
Collapse is usually rapid and death can occur very quickly due to the irritant effects of blood in the subarachnoid space
What is cerebral oedema? and its effects
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”
What is cerebral contusion and laceration?
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
What is a “Coup” contusion?
occurs when a head is struck a heavy blow - the contusion is found directly under the site of impact
What are “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
What is an axon
axon: elongated processes of nerve cells which permit transmission of signals between different parts of the brain and between the brain and body
What is Diffuse Traumatic Axonal Injury?
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
How do you diagnose Diffuse Traumatic Axonal Injury?
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.
What causes Diffuse Traumatic Axonal 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
“Diffuse Vascular Injury”
What areas are more suscetible to tDAI?
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
What are victems like when a tDAI is fully developed?
Clinically, victims are comatose when tDAI is fully developed
Often unconscious immediatley, particularly if brianstem affected
WHat may concussion be?
Concussion: may well be the clinical manifestation of lesser degrees of axonal injury - may have retrograde amnesia
image shwoing differences between subdural and extradural haemorrhage
