A thorough clinical examination includes all systems, but with a special focus on the central and peripheral nervous systems. The level of consciousness must also be assessed and accurately documented using the Glasgow Coma Scale, which allows clinicians to place a numerical value upon the level of consciousness so that any deterioration or improvement can be measured and quantified.
The Glasgow Coma Scale was proposed in 1974 and is now widely accepted throughout the world. There is a total score of 15 points, such that 15/15 indicates that the patient is alert and fully oriented, whereas 3/15 indicates a severe and deep coma. The points score comprises a best motor response (total of 6 points), best verbal response (total of 5 points), and best eye movement response (total of 4 points).
In the clinic
Treatment of head injury
Treatment of primary brain injury is extremely limited. Axonal disruption and cellular death are generally irrecoverable. Whenever the brain is injured, like most tissues, it swells. Because the brain is encased within a fixed space (the skull), swelling impairs cerebral function and has two other important effects.
First, the swelling compresses the blood supply into the skull, resulting in a physiologically dramatic increase in blood pressure.
Second, the cerebral swelling may be diffuse, eventually squeezing the brain and brainstem through the foramen magnum (coning). This compression and disruption of the brainstem may lead to a loss of basic cardiorespiratory function, and death will ensue. Focal cerebral edema may cause one side of the brain to herniate beneath the falx cerebri (falcine herniation).
Simple measures to prevent the swelling include hyperventilation (which alters the intracerebral acid–base balance and decreases swelling) and intravenous corticosteroids (though their action is often delayed).
Extracerebral hematoma may be removed surgically.
The outcome of patients with head injury depends on how the secondary injury is managed. Even with a severe primary injury, patients may recover to lead a normal life.
In the clinic
The skull is a closed bony compartment, and the brain and cerebrospinal fluid are maintained physiologically within a narrow intracranial pressure range. Any new space-occupying lesion, such as a hematoma, an injury that leads to brain swelling, or a brain tumor, can increase intracranial pressure and compress the brain. In severe cases, the brain may be squeezed down into the foramen magnum, giving it a cone shape, termed cerebral herniation, or “coning.” This may in turn compress the brainstem and upper cervical spinal cord, which can be fatal.
Congenital herniation or coning of the cerebellar tonsils through the foramen magnum can also occur if the posterior fossa is too small, a condition known as Chiari I malformation (Fig. 8.52). This often causes no problems in childhood and may only start causing symptoms in adulthood.
In the clinic
In the clinic
Overview of cranial nerves
Afferent—Trigeminal nerve (CN V)
Efferent—Facial nerve (CN VII)
Afferent—Glossopharyngeal nerve (CN IX)
Efferent—Vagus nerve (CN X)
Afferent—optic nerve (CN II)
Efferent—oculomotor nerve (CN III)
Fig. 8.55 Overview of cranial nerves.