1. Introduction

It is a well-known fact that a head injury (Latin: trauma capitis) is a serious matter, as the skull contains the brain, which is the centre of our entire intellectual life. Because from a mechanical point of view the brain is a soft mass and therefore easily compressed by mechanical force, nature protected it with a hard bone casing: the skull. Head injuries can therefore affect the skull, the brain, or both. However, the concept that the degree of severity of a skull injury corresponds to that of the damage to the brain is not entirely correct. For example, in injuries where the skull is locally pierced by a sharp object, the brain is damaged only at the place of penetration where the bone splinters are pressed in, while the remainder is unaffected. This can be compared to the crumple zone of a car. Part of the energy is absorbed by the skull bones and is not transmitted to the brain. On the other hand, in injuries that exercise a great deal of force on the entire head, for example in high speed collisions, the skull often remains entirely sound, while the brain inside is very seriously damaged - this is referred to as a closed skull injury. We will look at skull and brain injuries separately.

2. Skull injuries

Linear skull fractures or cracks, simple fractures. The mildest form of skull damage is a cranial bone crack or a simple fracture. It can be represented on an X-ray of the skull when it is perpendicular to the viewing direction; cracks or fractures that are diagonal to the viewing direction are sometimes not visible. In such cases, CT scans can be used. In itself, the presence of this type of injury does not provide any information on the condition of the brain, but normally there will be no damage and the patient will be conscious. The risk in connection with a cracked skull is the development of an epidural haematoma if an artery of the dura mater is pierced by a bone splinter. Therefore, patients having suffered a skull fracture should be regularly monitored for the appearance of this problem. As such, simple fractures require no treatment: the bones heal within a short period of time.

In children, the growing cranium can cause what is referred to as a 'growing fracture'. Whenever the dura mater is torn under the crack in the skull, there is a possibility that scar tissue may form between the bone edges. Thus the fracture cannot heal and the crack increases in size as the cranium grows. Surgery may become necessary to correct the situation.

Basilar skull fractures. These are simple fractures at the base of the skull. When the fracture passes through the roof of the eye sockets, patients present heavily swollen "black eyes" due to the extravasation of blood in the orbits: this sign is also known as 'raccoon eyes'. It mostly disappears within a few days without residual problems. A frontal basilary skull fracture can also take place in the roof of the nasal cavity, which can cause an open connection between the cavity and the contents of the skull: in such cases, patients lose cerebrospinal fluid (liquor) through the nose. This liquor leakage involves the risk that bacteria may enter the cerebrospinal fluid from the nose, causing an inflammation of the membrane that covers the brain (meningitis), especially if the liquor leakage continues over time. For this reason, in such cases it is necessary to find the leak by means of a surgically practiced opening in the skull and to cover it up with meninges or a replacement tissue.

Even if the liquor leakage stops spontaneously, the opening, which is often filled only by soft scar tissue, can reopen and, once again, even years later, give rise to meningitis or a brain abscess. A fracture through the roof of the nasal cavity can also damage the olfactory nerve, causing the patient to lose his or her sense of smell (see Illustration). A more serious scenario occurs when a basilary skull fracture affects the opening providing passage for the optic nerve and damages the nerve, resulting in blindness of that eye. In a posterior basilar fracture running through the petrous bone, which houses the hearing apparatus, the patient can suffer damage to his hearing, and liquor may leak out of the ears. In such cases, the liquor leakage usually heals spontaneously. A basilar skull fracture as such does not require treatment unless long-term liquor leakage ensues. Unfortunately, there is no remedy for the damage to the optic or olfactory nerves.

Schematic drawing of basilary skull fractures

Illustration: Schematic drawing of basilary skull fractures: One frontal orbital and nasal cavity roof fracture and one posterior fracture through the petrous bone. The frontal fracture causes a blood extravasation in both eye sockets, originating the 'raccoon eyes' sign in the patient; in addition, liquor leaks out through the nose because the fracture in the roof of the nasal cavity represents an open connection between the contents of the skull and the outside world.

Depressed skull fractures. They are caused by a strong localised force that dents the skull over a certain area (see Illustration). Embedded bone splinters can damage both the underlying brain membranes and the brain tissue itself. Brain damage is usually very limited. Sometimes the skin is also damaged and the fracture as well as the underlying brain tissue are open, creating a risk of infection (see Illustration).

Therefore, such open or complex depressed fractures require surgery. Contamination and debris are removed from the wound, and bleeding in the bruised brain is staunched. The torn brain membrane is closed, and any lost sections are replaced with an artificial brain membrane (see Illustration). Bone fragments are restored to their original place to the greatest extent possible. If any pieces of bone are lost, there remains what is termed a 'bone defect'. This bone defect can be remedied in two ways: either by immediate placement of a titanium mesh (see Illustration), or, at a later date, by making up a piece of bone to measure to fill in the vacant area. Such made-to-measure pieces of cranium can consist of hydroxyapatite (which has the same composition as the skull itself and excellent assimilation), or of a plastic material such as PEEK or of titanium.

Schematic drawing of an open impression fracture

If the depressed fracture is not open, it does not need to be treated for as long as the depression in the skull is less than the thickness of the skull itself. However, if the depression is more significant, the bone fragments that damage the brain must be restored to their proper place, as otherwise scarring that could lead to epilepsy could occur in the brain.

Illustration: Schematic drawing of an open impression fracture. The impressed bone fragments are clearly visible through the open wound.

3. Brain injuries

Concussion. This is the mildest form of brain damage. Its signs are that after a fall or a blow to the head the patient briefly loses consciousness, and then appears unable to recall the accident and what happened shortly before (also known as retrograde amnesia). As the severity of the concussion increases, the periods of loss of consciousness and retrograde amnesia also become longer.

Brain contusion. This term is used when the loss of consciousness is longer and deeper and if neurological disorders such as paralysis appear. The clinical picture of brain bruising comprises a series of brain injuries, ranging from mild lesions that resolve quickly and spontaneously, via more severe lesions causing longer periods of unconsciousness and then resolving with varying degrees of residual neurological symptoms and disabilities, to very severe situations where patients remain in a coma that will, sooner or later, lead to death. Because loss of consciousness is a good yardstick for brain damage, it is assessed by means of the Glasgow Coma Scale (GCS). The patient is assigned a score determined on the basis of whether or not he/she opens his/her eyes, moves his/her arms, makes sounds in response to pain stimuli, being addressed, or spontaneously. The minimum score is 3, the maximum is 15 points. Very severe brain injury is involved at GCS scores 3-8, moderately severe at GCS scores of 8-14, and mild at GCS scores above 14.

4. Treatment of severe brain damage

Treatment is based on the principle that brain damage can be classified as being either primary or secondary.

Primary damage results directly from the injury and no further action is possible. Often the injury is so serious and the primary brain cell damage so extensive that the patient does not survive. But it is also possible that the injury is not so serious and that the primary damage becomes fatal not directly, but only later, once secondary damage has occurred. Damaged brain tissue is very sensitive as concerns lack of oxygen and reduced blood supply, while healthy brain tissue has many compensation mechanisms to deal with these situations.

Secondary brain damage can occur when due to blood loss at the time of the accident the blood pressure becomes too low, leading to inadequate blood supply to the brain, or when there is an oxygen deficit as a result of the airway being blocked by blood and mucus.

The treatment aims at preventing secondary damage. Therefore, the patient is treated and monitored in an Intensive Care Unit. Because he/she can usually not eat or drink independently, all food, but especially the required fluids, are given by intravenous infusion. To ensure good breathing, the patient's respiration is usually also aided by means of a tube in the airway. The tube can be inserted in the airway via the mouth (intubation), but for longer term needs it is introduced into the airway by means of an opening in the trachea (tracheotomy), with the breathing function being performed by a respirator. To monitor whether the artificial respiration is functioning correctly, blood oxygen and CO2 contents, as well as the blood's acidity, are measured on a regular basis. The number of red blood cells is also regularly measured to ensure that it is adequate and is not falling (indicating continuing bleeding) and whether the fluid intake is sufficient, which can be determined by means of the salt contents (electrolytes) in the blood. The patient is also primarily monitored for the first signs of complications, so that they can be reported and treated. There are specific and general complications. Monitoring can also include direct measurement of the pressure in the brain (see below).

General complications can occur in patients with any injury, not just head injuries, but as is often the case, these patients will also have sustained other injuries (multiple trauma or polytrauma). General complications include pneumonia, which is important with brain injuries because pneumonia can negatively affect the oxygen supply. In addition, injuries lead to an increased risk of thrombosis, which may need to be treated with an anticoagulant. Through being bedridden, the patient can also develop urinary infections, bedsores, and stiffening or locking of certain joints (contractures), which the care procedures seek to prevent.

5. Specific complications of brain damage are:

Bleeding: We already mentioned epidural haematomas in linear fractures. However, (usually acute) subdural and intracerebral haematomas as well as subarachnoid bleeding can occur with brain injuries when blood vessels in the brain are severed in the injury. The blood thus released takes up place in the skull, which causes the pressure inside (intracranial pressure) to rise, and significant portions of the brainstem that are responsible for regulating breathing, circulation and consciousness can become pinched (this is called cerebral herniation). If bleeding is suspected, a CT scan will be performed, with which the haematoma can be identified and then surgically removed.

Brain oedema. In the bruised portions of the brain, the effects of the injury can cause the walls of the very fine (capillary) blood vessels in the brain to ooze plasma. The plasma that leaks into the brain tissue, causing an excess of fluid in the brain, constitutes a brain oedema.

Het hersenweefsel gaat dan zwellen, precies zoals een gekneusde enkel gaat zwellen. In het geval van de hersenen heeft de zwelling kwalijke gevolgen, omdat de hersenen binnen een starre onuitzetbare schedel zitten, en de zwelling een verhoging van de intracraniële druk tot gevolg heeft en tenslotte ook een inklemming van vitale hersenstamgedeelten.

pressure measuring device

For this reason, a pressure measuring device is placed into the skull of patients with serious brain injury in whom brain oedema is suspected, in order to record the intracranial pressure. This type of pressure gauge is a tube that has a sensor at one end and which is introduced into the skull by means of a small opening. Brain pressure increases due to brain oedema are treated primarily by relieving the patient from excess fluids by means of diuretics, medication that encourages urination. Some diuretics, like concentrated mannitol or glycerol solutions, which draw the fluid from the brain, can be administered by intravenous infusion.

Lately, surgical treatment has also been applied; in these procedures, large pieces of skull bone are removed, and the dura mater is opened. Currently, evidence from studies has not yet demonstrated whether this treatment is effective. The strongly bruised portions of the brain can also be surgically removed. In this procedure, the irretrievably damaged brain tissue is removed in order to create more space for the remainder of the brain. Nonetheless, with serious brain injuries, in spite of all measures taken the patient may still die, because the primary brain damage was so severe that the brain cells have been destroyed. Usually, in such cases, brain governed functions such as breathing and circulation will also have collapsed. However, it is possible that the heart will continue to beat, while all brain functions such as consciousness, motoricity, speech, and all other intellectual activity are absent. Whether the brain has died (the patient is brain dead) can be confirmed by the absence of electrical brain activity by means of an EEG (electroencephalogram). Other signs are wide pupils that no longer contract under the stimulus of light, and the absence of reflexes upon neurological examination. In such cases, breathing is usually only present in the form of artificial respiration produced by a respirator, and the patient is unable to take over the breathing movements on his or her own if the machine is disconnected.

6. Early consequences of brain injury

As described above, the common feature of all brain injuries is a loss of consciousness. This is what is usually referred to as 'coma', but this term comprises such a broad range of loss of consciousness that it is not used in medical practice. The Glasgow Coma Score provides a much clearer picture of the depth of a coma, but its usefulness is reduced after approximately one week. At that time, many patients may open their eyes, but their underlying condition may not improve. Often, it only becomes clear after a certain period of time whether any concomitant neurological damage, such as speech disorders or paralysis, has also taken place.

7. Later consequences of brain injury

There is a clear connection between the Glasgow Coma Score on admission and the long-term outcome. Most patients with a score of 13 or more will recover more or less completely, while the prognosis is fairly poor for patients with a score of less than 8. Late consequences can consist of memory and concentration disorders, personality changes, neurological deficit (e.g. paralysis or speech disorders) and epilepsy. With very serious injuries, a vegetative coma can occur. The patient's eyes are open and he/she may seem to be looking at his/her surroundings, while there is no reaction at all to external stimuli. This condition is almost always permanent. Situations in which someone opens their eyes after months or years and suddenly asks 'Where am I?' is exclusively the stuff of movies.

8. Conclusion

As stated at the beginning, a brain injury as a result of an accident is a serious matter. However, in many cases everything will be all right. Factors determining a negative outcome are primarily (older) age and (low) Glasgow Coma Score at admission. This information enables the doctor to develop an approximate prognosis for the patient.