Forensic Pathology Chapter 5 - Head and spinal injuries

What type of injuries are the most common and important in forensic practice?

those of the head and neck

sound reasons for this dominance of head injures:

• the head is the target of choice in the great majority of assaults involving blunt trauma

• when the victim is pushed or knocked to the ground, they often strike their head

• the brain and its coverings are vulnerable to degrees of blunt trauma that would rarely be lethal if applied to other areas

Bones of the skull

superior view - frontal bone, ethmoid bone, sphenoid bone, temporal bone, parietal bone, occipital bone

inferior view - maxilla, zygomatic bone, mastoid process

What is the foramen magnum?

where the spinal cord connects to the brain (ring fractures occur here, when falls on legs from heights occur)

Injury to the scalp - hair covered areas

in hair-covered areas, care must always be taken at autopsy to palpate the scalp in any case in which there is a possibility of injury, otherwise abrasions, swelling, bruising, and even lacerations may be missed

when a lesion is found or suspected, the hair must be carefully shaved away to expose the scalp for further examination and photography

Bruising of the scalp

bruising may be difficult to detect until the hair has been removed - marked swelling is a common feature of extensive bruising, as the liberated blood cannot extend downward because of the rigidity of the underlying skull; however, this subsides, or at least diffuses after death

bleeding under the scalp may be mobile, especially under gravity - thus a bruise or hematoma under the anterior scalp may slide downwards within hours to appear in the orbit, simulating a black eye from direct trauma

a temporal bruise may later appear behind the ear, suggesting primary neck impact - as with bruises elsewhere, those under the scalp may be obvious immediately after infliction or their appearance may be delayed, either during life or as a postmortem phenomenon

he shape of an inflicting weapon or object is poorly reproduced on the scalp, again due to the padding effect of the hair - where the scalp is free of hair all traumatic lesions are similar to elsewhere on the body, with the exception that blunt impact may cause very sharply defined lacerations

Laceration of the scalp - avulsions

lacerations of the scalp bleed profusely, and dangerous and even fatal blood loss can occur from an extensive scalp injury if it's not checked by treatment - the most gross injury is avulsion of a large area of scalp, which can be torn from the head, thereby exposing the skull

this may happen if the hair becomes entangled in machinery

a more common cause nowadays is a traffic accident, where a rotating vehicle tire comes into contact with the head, causing a "flaying" injury similar to that seen on limbs

Laceration of the scalp - differentiation between incised wound and laceration

scalp injuries may bleed profusely even after death, especially if the head is in a dependent position

a major problem in scalp injuries is the differentiation between incised wounds and lacerations from blunt injury - the scalp is the best example of a surface tissue lying over an unyielding bony support

violent compression will crush the scalp against the underlying skull, so a blow from a blunt rod-like weapon may split the skin and underlying tissues in a sharply demarcated fashion

Laceration of the scalp

close examination, using a lens if necessary, will show that a blunt laceration has:

• bruised margins, even though this zone may be narrow

• head hairs crossing the wound, which have not been cut

• fascial strands, hair bulbs, and perhaps small nerves and vessels in the depths of the wound

Scalp injuries from falls

injuries on the back point of the head are commonly caused by falling

falls backwards against a ridge may cause a transverse laceration, which may be undercut and partly detached from the underlying bone so that a flap of scalp is loosened from the skull

falls usually injure the occipital protuberance, the forehead or the parieto-temporal areas

injuries on the vertex should always raise the suspicion of assault, as it is unusual to fall upon the top of the head, even from a considerable height

Facial injuries

damage to the face is common, but unless gross, with skeletal damage, is rarely fatal in itself unless it leads to bleeding into the air passages

Kicking

kicking of the face is regrettably common and again the prominences suffer most - bruising, laceration and fractures may result from kicking under the side of the jaw; similar lesions occur on the maxillary areas and the eyebrows

patterned abrasions from boot soles may be seen or crescentic marks from toecaps

brush abrasions from glancing kicks may be present on the cheeks or forehead as the sole of the shoe scrapes across the skin

it is uncommon to suffer a pure black eye from a kick without other facial injuries

Black eyes

the usual periorbital hematoma or black eye is usually caused by a direct punch or kick into the eye-socket, but the pathologist must always consider the several alternative explanations

a black eye may be the result of:

• direct violence, which may or may not be associated with abrasion or laceration on the upper cheek, eyebrow, nose, or other part of the face

• gravitational seepage of blood beneath the scalp from a bruise or laceration on or above the eyebrow - survival and at least a partially upright posture of the head must have been maintained for at least some minutes between the time of injury and death

• percolation of blood into the orbit from a fracture of the anterior fossa of the skull - this is often from a countercoup injury caused by a fall on to the back of the head, leading to secondary fracture of the paper-thin bone of the orbital roof; it is invariably associated with countercoup contusion of the frontal lobes of the brain

Damage to the ear

the external ear often suffers from blows to the head and is an obvious target in child abuse

the ear may be bitten and even partly detached, a fate which occasionally is suffered by the nose, in such cases the advice of a forensic odontologist may be invaluable, as teeth marks may form vital evidence

Falls

the skulls of small infants could be fractured against a variety of floor surfaces from passive falls of only 34 inches

falls in old people very frequently cause fractures of the post-cranial skeleton

osteoporosis is the major reason for the large number of such injuries from falls

Falls from a height

falls from a considerable height are common in suicide and in some accidents, especially to children - occasionally deaths from a high fall may be homicidal

the primary impact is usually the site of the most severe injury, but this is not always the case, as it may strike 2 areas simultaneously or it may bounce or ricochet so that 2 or more major impact occur in quick succession

if the body falls on the head, there is likely to be a massive fracture, often a scalp laceration and possibly extrusion of brain

both vault and base can fracture and sometimes the base is driven down over the cervical spine, the latter projecting into the posterior fossa (causes a ring fracture)

Posterior cranial fossa

the most inferior of the fossae, it houses the cerebellum, medulla oblongata, and pons

Falls from a height - falling onto the feet

where the fall is onto the feet, the deceleration stress can break the axial skeleton at a number of points - the legs can be broken at any point often bilaterally

the femoral neck can be snapped off, the hip joints can dislocate and over-ride, or the pelvis may fracture - the latter is often through the sacroiliac joints, the upward force driving the sacrum down as a wedge into the pelvis

if the lower limbs and pelvic girdle remain intact, the transmitted force may then fracture the spine, often at mid or upper thoracic level

Forensic anatomy of the skull

the anterior fontanelle closes functionally between 9 and 26 weeks after birth, though it is not tightly sealed until about 18 months

the posterior fontanelle closes between birth and 8 weeks of age

suture lines close by interdigitation during childhood and osseous fusion occurs irregularly at variable dates adult life

the average frontal and parietal thickness in a young male is between 6 and 10mm

Fontanelle

"soft spot" on a baby's head

What is the most sensitive spot on the skull?

the pterion is the most sensitive and prone to damage spot on the skull

• the thickness of bone is the lowest

• suture for 3 connecting bones

• a major vessel lies underneath

Fractures of the skull - presence

the presence of a skull fracture is an indication of the severity of the force applied to the head and it is uncommon for a head injury that is sufficiently severe to crack the skull not to cause some intracranial effect

What is struck hoop analogy?

the adult skull is incompressible - due to incompressibility of skull and the inward bend caused by focal impact, the skull undergoes compensatory mechanism wherein there occurs bulging if other area

Fractures of the skull - linear fractures

when the frontal area is struck, the usual course for a linear fracture is vertically down the forehead, turning around the orbital margin to run backwards across the floor of the anterior fossa

a blow or fall onto the occiput may produce a fracture that typically passes vertically or obliquely downwards just to the side of the midline of the posterior fossa

in addition, the countercoup element of an occipital fall may cause fractures of the orbital plates in the anterior fossa

Cribriform plate

the cribriform plate is a portion of the ethmoid bone located at the base of the skull for the passage of the olfactory nerves

Sutures

in children and young adults, a linear fracture may pass into a suture line and cause a "diastasis" or opening of the weaker seam between the bones

this is most often seen in the sagittal suture between the two parietal bones

Fractures of the skull - spider web pattern

when severe local impact causes focal and general deformation, a combination of depressed fractures and radial fracture lines may form a spiders web pattern

Puppe's rule

where two or more separate fractures occur from successive impacts and meet each other, the sequence of injuries may be determined by Puppe's rule

Types of skull fractures - linear fractures

these are straight or curved fracture lines, often of considerable length

they either radiate out from a depressed zone, or arise under or at a distance from the impact area, from bulging deformation

they may involve the inner or outer table, but commonly traverse both

Types of skull fracture - ring fractures

these occur in the posterior fossa around the foramen magnum and are most often caused by a fall from a height onto the feet

if the kinetic energy of the fall is not absorbed by fractures of the legs, pelvis, or spine, the impact is transmitted up the cervical spine - this may be rammed into the skull, carrying a circle of occipital bone with it

Types of skull fractures - depressed fractures

focal impact causes the other table to be driven inwards and, the inner table will also usually be intruded into the cranial cavity with all the dangers of direct damage to the contents

Size of skull

the adult head weighs between 3-6 kg (7-14 lb), averaging 4-5 kg (10 lb)