The structure of the Brain
Source: Biology Diagrams
Having the constituency of jelly and appearance of a cauliflower the adult brain weighs approximately 1.5kg. The brain is contained within the cranium. Between the skull and brain are 3 membranes, identified collectively as the meninges. The dura mater is attached to the skull and is the toughest of the three. In the middle is the arachnoid mater and, closest to the brain, is the pia mater. Also protecting the brain and delivering nutrients is the cerebrospinal fluid. The fluid is created in the blood stream and contains proteins and glucose. It washes around the brain and returns to the bloodstream. It is renewed several times each day. Despite being around 2.5% of our body weight, the brain accounts for 20% energy consumption, even when resting. Therefore, when working it consumes fuel from oxygen we breathe and the carbohydrates we eat.
Observation reveals two hemispheres to the brain. The two spheres are connected by the corpus callosum (thicker in men). The two spheres are clamped around the brain stem. The brain stem is connected to the spinal cord which communicates with the body, sending messages to and from the brain. The stem controls breathing. At the top of the brain stem is the cerebellum. This is responsible for balance, muscle tone and coordination.
The cerebral cortex is the outer layer of the brain. The cortex is divided into four lobes-frontal, parietal, temporal and occipital. At the back of the skull is the occipital lobe, dealing with sight, hallucinations and loss of academic skills. Around each ear is the temporal lobe, addressing language, speech, concentration and memory. The parietal lobe sitting around the top of head deals with movement and spatial issues, including hand-eye coordination and poor visual perception. Finally, at the very front of the brain is the frontal lobe, which is responsible for our mood, word finding, perseveration, thought, planning and decisions.
The lobes do not work in isolation. The idea that the brain can be neatly split into compartments is completely wrong. The lobes and other areas communicate with each other by a series of electrical impulses. This comes from about 100 billion cells. These cells are made up of neurons and glial. The latter protect the former from various chemicals, stimulate the neuron and remove dead neurons. Every neuron is connected to around 10,000 additional neurons, fanning outwards, with dendrites and axons. The dendrites receive information from other neurons and the axons send messages. The axons are covered in myelin sheath. The messages are sent by an electrical charge, making a connection from one neuron to another. The gap between neurons is called the synapse.
The impulse between the neurons is achieved by neurotransmitters, called synaptic transmission. These messages tell our body what to do.
Three categories of brain injuries
There are three categories of injury, being crushed, open and closed head injury. A crushing injury arises when two hard surfaces come together. An open brain injury is penetration through the skull to the brain, eg a bullet. A closed head injury is where there is no penetration to the brain, but nonetheless, can be serious. Indeed, this is most common and frequently seen in road traffic accidents, either passengers being thrown forward into a windscreen or pedestrians being struck and thrown up on the bonnet.
The initial impact represents the first injury. Then one sees the potential for problems in the oxygen supply. Thirdly, there are issues of blood supply and the impact of chemical reactions.
At the moment of the first injury to the brain, also described as blancmange like, it is shaken. The neurons are pulled and the fragility of the connectors through the dendrites and axons can be broken, known as diffuse axonal damage. That damage means messages cannot be sent from the brain to the various body parts and thus the body does not properly function.
In fast moving impacts the brain is thrown about (contre coup) so that it comes into contact with the hard ridges of the brain, most notably the frontal lobe, the critical thought processing unit. These sharp ridges cause blood vessels to tear and bleed.
What follows is the risk of the blood supply being cut. With the blood carrying the oxygen, an interruption can lead to damage and death, a hypoxic injury.
Finally, further injury may arise perhaps days or weeks later, through a change in the chemical reaction, bruising or bleeding in the brain. This is why patients are giving advice at time of early discharge from hospital (because of risk of later injury). If there is a bleed, the blood will clot, causing a haematoma. This can lead to intracranial pressure, which must be released promptly to reduce the risk of further injury, as again the oxygen supply will be interrupted. Haematomas are clearly seen on MRI scans.
A transient ischaemic attack and stroke are other examples of ABI’s. The former is a temporary loss of brain function whereas the latter is long lasting. However, the causes are similar, ie a loss of blood supply to the brain, which thus means oxygen is not delivered to this vital organ. There are two main causes. First the blockage of an artery carrying blood. The second is a haemorrhage within the brain or between the membranes. If there is no oxygen that part of the brain affected will die and thus injury follows.
Making a compensation claim for a head or brain injury
If you want to enquire about making a head or brain injury claim following a car accident, fall, sporting injury or other incident, please contact one of our experienced brain injury solicitors on 0333 123 9099. Alternatively, you can send an email with your name and contact information and brief details as to the nature of the accident/clinical negligence and the injuries sustained to firstname.lastname@example.org and one of our team will be able to help you.