The Brain - Physiology of deterioration

Two causes of altered consciousness

Structural and Metabolic

Structural causes

Trauma, Vascular disease, Infection and Neoplasms

Trauma casuses

• concussion

• cerebral contusion

• diffuse axonal injury

• haematomas (subdural/extradural),

• intracranial haemorrhages, 

• cerebral oedema

• cerebral laceration

What is a concussion?

Mild traumatic brain injury caused by a bump, blow or jolt to the head.

What is a cerebral contusion?

Bruise on the brain tissue. It involves bleeding and swelling (edema) inside the brain caused by a direct, forceful impact to the head. It is a serious form of a TBI.

What is a diffuse axonal brain injury (DAI)?

It is a severe type of brain injury that occurs when the brain rapidly shifts and rotates inside the skull. This violent motion causes the brain's long, connecting nerve fibers (axons) to stretch and tear, destroying communication between different areas of the brain. Because the damage is widespread rather than localized to one spot, DAI is one of the most devastating forms of head trauma and is a primary cause of prolonged comas and vegetative states

What is a hematoma (subdural/extradural)?

Localized collection of blood outside blood vessels, usually caused by trauma. Subdural and extradural hematomas refer to dangerous pools of blood that form in different layers of the surrounding brain.

• Extradural Hematoma (EDH) → blood pools between the skull and dura mater (epidural space)

• Subdural Hematoma (SDH) → Blood pools deeper, between the dura mater and the arachnoid mater (subdural space)

What is an intracranial hemorrhage?

Often called a brain bleed. Is any bleeding that occurs inside the skull. It is a life-threatening medical emergency that happens when a blood vessel ruptures or leaks, causing blood to pool in the skull and put dangerous pressure on the brain tissue. Because the brain requires a constant supply of oxygen to function, an intracranial bleed can quickly cause brain cells to die.

What are the 4 types of Intracranial Hemorrhages?

• Intracerebral Hemorrhage: Bleeding directly inside the brain tissue itself.

• Subarachnoid Hemorrhage: Bleeding in the area between the brain and the tissues covering it (the subarachnoid space).

• Subdural Hemorrhage: Bleeding that pools between the brain and the outermost layer of tissue (the dura mater).

• Epidural Hemorrhage: Bleeding that occurs between the skull bone and the dura mater.

What is cerebral edema?

Cerebral edema, commonly known as brain swelling, is the dangerous and potentially threatening buildup of excess fluid inside or outside the brain cells. Because the rigid, bony skull cannot expand to accommodate the swelling, this trapped fluid severely increases the pressure inside the head, restricting blood flow and oxygen

What is cerebral laceration?

A cerebral laceration is a severe type of TBI where the actual tissue of the brain is mechanically cut or torn. It is distinct from a brain contusion (a bruise) because it involves tearing both the brain tissue and the surrounding protective membranes (pia-arachnoid). Because tearing the brain causes direct bleeding and nerve damage, cerebral lacerations are treated as serious medical emergencies. [1]

Vascular causes

• cerebral infarction

• intracerebral haemorrhage

• subarachnoid haemorrhage

What is a cerebral infarction?

A cerebral infarction is a medical term for an ischemic stroke. It occurs when blood flow to an area of the brain is blocked or significantly reduced, depriving brain tissue of oxygen and vital nutrients. Without immediate blood supply, the affected brain cells die. Primary causes → thrombosis, embolism

What is a intracerebral haemorrhage?

An intracerebral hemorrhage (ICH) is a type of stroke that occurs when a diseased blood vessel bursts within the brain tissue. This medical emergency allows blood to leak into the brain, building up pressure and causing rapid damage to brain cells.

Primary causes → chronic hypertension, cerebral amyloid angopathy, other causes (blood thinners, tumors, head trauma, illicit stimulants.

What is a subarachnoid haemorrhage?

A subarachnoid hemorrhage is a life-threatening type of stroke caused by sudden bleeding into the subarachnoid space — the area between the brain and the tissues covering it. It requires immediate emergency medical attention.

Primary causes → ruptured aneurysm, head trauma, other vascular issues

Infection causes

• meningitis

• encephalitis

• subdural empyema (abscess).

What is meningitis?

The dangerous swelling of the membranes (meninges) that surround the brain and spinal cord. It is usually caused by viral or bacterial infections, though fungi and parasites can also be responsible. Bacterial cases are medical emergencies that require immediate treatment

What is encephalitis?

Encephalitis is a serious medical condition characterised by the inflammation of the brain tissue (the parenchyma). It is typically caused by viral infections or an autoimmune response where the body's immune system mistakenly attacks the brain. The swelling can lead to brain damage and life-threatening complications.

What is subdural empyema (abscess)?

A subdural empyema is a life-threatening, rapidly expanding collection of pus located in the space between the dura mater (the outer membrane of the brain) and the arachnoid mater (the middle membrane). It is considered a medical emergency requiring urgent neurosurgical drainage and heavy intravenous antibiotics.

Neoplasm causes

• primary brain tumours (e.g. meningiomas, gliomas, pituitary adenomas)

• metastatic tumours (originating outside the CNS)

What is a brain tumor?

A brain tumor is an abnormal mass or growth of cells in the brain or skull. These growths can be malignant (cancerous) or benign (non-cancerous). Because the brain is enclosed in a rigid skull, even benign tumors can cause dangerous pressure as they grow, impacting bodily functions, memory, and behavior.

What is a metastatic tumor?

A metastatic tumor is a cancerous growth that has spread from the part of the body where is first developed (the primary site) to a distant organ or tissue. It is also commonly referred to as Stage IV cancer.

Metabolic causes

Systemic metabolic disorders

Hypoxic encephalopathies

Toxicity

Body temperature extremes

Seizures

Systemic metabolic disorder casues

• hypoglycaemia

• diabetic ketoacidosis

• electrolyte imbalances (e.g. hypo/hypercalcaemia, hypo/hyponatraemia)

• metabolised end products from cardiac, renal, respiratory and hepatic failure.

Hypoxic encephalopathies causes

• hypertensive crisis

• severe hypotension (leading to decreased cerebral perfusion)

• cardiac failure (e.g. following hypovolaemia, MI or arrhythmias)

• respiratory failure 

• carbon-monoxide poisoning.

Toxicity causes

• poisons

• drug overdose

• alcohol intoxication.

Body temperature extreme causes

• heat stroke

• hypo and hyperthermia

Seizure causes

• epilepsy

•  non-epileptic seizures caused by physiological or psychological conditions