The scalp is often, though by no means invariably, dam- aged in trauma that causes injury to the underlying skull
and brain. The usual range of abrasions, contusions and lacerations may be inflicted, though a modifying factor is the presence of hair, which may deflect a tangential blow or partly cushion a direct impact.
When an injury is visible on the forehead, the back of the neck, the lower temple or on a bald area, the examin- ation is no different from elsewhere on the body. 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 sus- pected, the hair must be carefully shaved away to expose the scalp for further examination and photography.
Forensic anatomy of the scalp
Superficially, the skin carries hair follicles, sebaceous glands and sweat glands. The skin is attached to the aponeurosis (see below) by vertical strands of fibrous tissue that break up the subcutaneous layer into pockets filled with fat. The blood vessels and nerves lie in this layer, above the epicra- nial aponeurosis (formerly called the ‘galea aponeurotica’).
This is a dense sheet of fibrous tissue that lies in the deep
Head and spinal injuries
■ Injury to the scalp 174
■ Facial injuries 178
■ Falls 180
■ Fractures of the skull 181
■ Forensic anatomy of the brain membranes 189
■ Extradural haemorrhage 190
■ Heat haematoma 192
■ Subdural haemorrhage 192
■ Subarachnoid haemorrhage 196
■ Forensic implications of brain membrane 198 haemorrhage
■ Ruptured berry aneurysm and trauma 198
■ Subarachnoid haemorrhage and alcohol 199
■ The rapidity of death in subarachnoid 199 haemorrhage
■ Rotational trauma to the head and upper neck: 200 basilovertebral artery injury
■ Head injuries in boxers 204
■ Cerebral injuries 204
■ Histological diagnosis of early cerebral hypoxia 212
■ Secondary brainstem lesions 213
■ Spinal injuries 214
■ References and further reading 216
layer of the scalp over the whole cranium. It is really a flat- tened tendon uniting the frontal and occipital bellies of the occipitofrontalis muscle.
Deep to the aponeurosis is a thin layer of loose connect- ive tissue that separates it from the pericranium, which is the exterior periosteum of the skull, the dura being the internal counterpart. Some veins traverse all the layers from the superficial fascia to the pericranium, and go on to penetrate the skull and communicate with the intracranial venous sinuses, thus forming a route for meningitis and sinus thrombosis from infected injuries of the scalp.
Abrasion of the scalp
Brush abrasions are less common than in other sites because of the protective effect of the hair, which also tends to pre- vent or blur the patterned effect of less severe impacts.
Impact abrasions from a perpendicular force are imprinted as usual on to the scalp, though again the intervening hair may reduce the severity. Unless the hair is carefully removed
at autopsy, with a sharp scalpel or razor, and care taken not to cause artefactual cuts, lesser degrees of abrasion will inevitably be missed.
Bruising of the scalp
Bruising may be difficult to detect until the hair has been removed. Marked swelling is a common feature of exten- sive bruising, as the liberated blood cannot extend down- ward because of the rigidity of the underlying skull.
However, this subsides, or at least diffuses, after death.
Commonly, a severe head injury leads to a thick, swollen, indurated layer of blood beneath the scalp, which may extend over a wide area. The blood is sometimes below the aponeurosis, the tough fascial layer of the scalp, but is more often between this and the epidermis.
Blood may also be present beneath the pericranium, the periosteum that is closely applied to the outer surface of the skull. This is often seen in head injuries in infants, usually in association with skull fractures, as the source of the blood is from the fracture line itself. The close attachment of the pericranium to the suture lines in infants may sharply cir- cumscribe the extent of the bleeding.
In addition to frank bleeding beneath the scalp, marked oedema may occur after injury and the layers of the scalp may be greatly swollen and thickened by a jelly-like infiltra- tion of tissue fluid.
As will be discussed under ‘black eye’, bleeding under the scalp may be mobile, especially under gravity. Thus a bruise or haematoma under the anterior scalp may slide down- wards within hours – even minutes – to appear in the orbit,
Injury to the scalp
Epidermis Dermis
Subcutaneous tissue with septa Superficial fascia
Epicranial aponeurosis Loose connective tissue Pericranium (periosteum) Skull diploë
FIGURE5.1 Anatomy of the scalp.
FIGURE5.2 A laceration of the scalp caused by a blow from an iron bar. The edges are crushed and bruised, with strands of connective tissue and hairs crossing the gap, indicating that it was not caused by a sharp-edged weapon.
simulating a black eye from direct trauma. Similarly, 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 post-mortem phenomenon. They may first become evident, or much more prominent, some hours – or even a day or so – after death. This is caused either by movement of the
liberated blood through tissue planes or by haemolysis spreading outwards to stain the subcutaneous tissues, making it always advisable to return to examine the body a day or two following the autopsy.
The 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, as in the upper forehead or bald areas, 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
Lacerations of the scalp bleed profusely, and dangerous and even fatal blood loss can occur from an extensive scalp injury if it is 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 aponeurosis or skull. This may happen if the hair becomes entangled in machinery, as was formerly not uncommon in women working in factories.
A more common cause nowadays is a traffic accident, where a rotating vehicle tyre comes into contact with the head, caus- ing a ‘flaying’ injury similar to that seen on limbs.
Scalp injuries may bleed profusely even after death, espe- cially if the head is in a dependent position. A post-mortem injury to the head may bleed considerably if inflicted soon after death and these facts may sometimes cause confusion about the ante-mortem or post-mortem nature of the wound, or about the length of time of survival following the injury. There is no reliable way of resolving this difficulty.
Lacerations of the scalp may reproduce the pattern of the inflicting object, even though a random splitting is so com- mon. Severe blows from shaped objects such as hammers or heavy tools may reproduce the profile of the weapon totally FIGURE5.3 Lacerations of the scalp from an iron bar. The margins
are bruised and the scalp tissue is extruding in places. The generally parallel direction of the five wounds indicates that the assailant probably delivered the blows in rapid succession with little change of orientation between weapon and head.
FIGURE5.4 Stellate laceration of the scalp caused by a heavy blow with a piece of timber. The support of the underlying skull has caused the tissues to split widely. At autopsy, full clearance of the hair must be made to allow detailed examination and photography.
FIGURE5.5 Wounds from a metal poker superficially resembling incised cuts, but having edges and tissue bridges within the wounds.
Injury to the scalp
or in part. A circular-faced hammer may punch a circle in the scalp, but more often only an arc of a circle is seen. In such cases, the position of the edge that digs in most deeply may give an indication of the angle of the blow. There may be a depressed fracture of the underlying skull of the same shape and size, though the interposition of the dense scalp may cause the skull defect to be slightly larger than the weapon. A depressed fracture in these circumstances is not inevitable, however, and one or more linear fractures may radiate from the impact site.
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, which may appear remarkably like a slash from a sharp instrument. Close examination, using a lens if necessary, will show that this 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
It is vital for the pathologist to appreciate that falls on to a flat surface, or a blow from a wide, flat object such as a plank or paving stone, may sometimes leave no external mark whatsoever on the exterior of the head, but commonly such an injury will cause a ragged split which may be linear, stellate or quite irregular.
Such injuries on the back point of the head are com- monly caused by falling, especially in inebriated victims.
Falls backwards against a ridge, such as a wall or pavement kerb, 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 protruberance, the fore- head or the parietotemporal areas. Injuries on the vertex
FIGURE5.7 Sliced incised wound of the scalp, from a large knife. The wound is markedly undercut, turning a wide flap of scalp. The clean edges, with a lack of any abrasion or bruising, indicate the sharpness of the weapon.
FIGURE5.6 Deep linear incised wounds due to a heavy, sharp cleaver. The depth of penetration varies, the large wound overlying extensive skull fractures. The wounds on the neck are due to light contact with the edge of the same blade.
should always raise the suspicion of assault, as it is unusual to fall upon the top of the head, even from a considerable height. Occasionally, a fall backwards that just happens to reach a vertical surface, such as a wall or piece of furniture, can cause damage to the top of the head, but there is then usually an obvious grazing component to the lesion.