Trauma to the brain can be devastating. The CNS (brain) may suffer trauma as a part of polytrauma (for example in motor vehicle accidents one may suffer apart from head injury, injuries to other organs such as fractures of the long bones and pelvis, splenic laceration, puncture wounds to the lungs etc) or solitary trauma to the brain ( for example gunshot wound to the head etc).
The human brain is thankfully quite well protected by a rigid unyielding bony skull, thus most of the times with minor head trauma such as a blow to the head or in a fall, the underlying brain escapes significant injury.
The rigid skull can be both a blessing as well as a curse. Let me explain this a little more. The rigid skull does a great job in protecting the underlying brain, but when someone does suffer head trauma say a big bleed in the brain, the rigid skull does not allow the swollen brain to expand. Thus the pressure inside the brain rises (pressure inside the brain is referred to as intracranial pressure or ICP). As the ICP goes up higher and higher it diminishes the blood supply to the brain and can cause secondary ischemic changes. This concept forms the basis to understanding the pathophysiology of head trauma. It is called Monro-Kellie Doctrine. In 1783 Alexander Monro said that the skull was like a rigid box filled with a nearly incompressible brain and that its total volume tends to remain constant. So any increase in the volume of the cranial contents (e.g. brain, blood or cerebrospinal fluid), will elevate intracranial pressure. Further, if one of these three elements increase in volume, it must occur at the expense of volume of the other two elements. So if the blood inside the brain rises due to a big bleed (from head trauma) either the brain has to shrink to accomodate it or the cerebro-spinal fluid volume has to decrease.
Trauma to the brain commonly occurs during motor vehicle accidents (MVA). Head injury has become the signature injury of the Iraq war and numerous soldiers and civilians have suffered trauma to the brain from IEDs (improvised explosive devices). Let us discuss some of the common forms of head injury.
I shall start with bleeding into the brain.
Bleeding can occur into different compartments of the brain and each of these presents in a slighly different way. Bleeding can occur into the epidural space (this is the space between the dura and the cranial bone). When bleeding occurs into the epidural space it is called an epidural hematome (EDH). Epidural hematomas are usually associated with a skull fracture and the bleeding is either from the middle meningeal artery or from one of its branches.
Bleeding can occur into the subdural space (space between the dural and the arachnoid membrane). This is referred to as a sub-dural hematoma (SDH). Sub-dural hematomas usually occur due to breakage of small bridging veins that traverse that space.
Bleeding can occur into the sub-arachnoid space. This is referred to as sub-arachnoid hemorrhage (SAH). SAH commonly occurs when an intracranial aneurysm ruptures in the brain.
Bleeding can also occur into the substance of the brain itself. This is referred to an intracranial hemorrhage (ICH). Sometimes the ICH may rupture into the ventricles of the brain. Then this hemorrhage is referred to as an intraventricular hemorrhage (IVH).
So how do patients who have bleeding into the brain due to trauma like fall or a MVA present. Usually patients who have sustained a head injury are somolent and difficult to arouse. At times the reverse may be true and thay may be agitated and aggressive. Depending on the site (location) of bleeding in the brain and the amount of blood in the brain, they may be weak on one side. Another common presentation is with a seizure. these seizures which occur after a head injury indicate that there is blood in the brain which is irritating the brain. Later some of these head injury patients may develop a seizure disorder (epilepsy). This kind of epilepsy which usually develops 6 months to 18 months after a significant head injury is called post traumatic epilepsy.
Management of the head injury patients: Head injury patients should ideally be managed in a specialized center equipped with a neurological intensive care unit and having neuro-surgical facilities. Rapid triage is the need of the hour because time is brain. Once these patients reach the hospital a quick assessment is done to make sure that vitals are stable. By vitals I mean that they have a stable blood pressure (a low blood pressure may be a sign that they are losing blood somewhere like into the gut. Remember in an accident, patients just do not suffer head injury, they may also have injury to other organs such as the lungs, liver and spleen), stable heart rate, stable respiration (if they are not breathing for some reason, they may need to have a tube inserted down the throat-this is called endotracheal intubation), and stable temperature.
Once the vitals are noted to be stable , then begins the process of trying to localize the site or sites of injury. A quick bedside neurological examination may give the doctor a pretty good idea of the location and kind of hemorrhage in the brain. A non-contrast (without any dye or contrast) head CT scan is then done to localize the site of hemorrhage.
