Adults have head injuries more frequently than any age group resulting from falls, motor vehicle crashes, colliding or being struck by an object, or assaults.

Children, however, may experience head injuries from accidental falls or intentional causes (such as being struck or shaken) leading to hospitalization.

In the case of an open head injury, the skull is cracked and broken by an object that makes contact with the brain.

The person may become sleepy, behave abnormally, lose consciousness, vomit, develop a severe headache, have mismatched pupil sizes, and/or be unable to move certain parts of the body.

A penetrating head injury occurs when an object pierces the skull and breaches the dura mater.

If the impact causes the head to move, the injury may be worsened, because the brain may ricochet inside the skull causing additional impacts, or the brain may stay relatively still (due to inertia) but be hit by the moving skull (both are contrecoup injuries).

This injury is a result due to a blow to the head that could make the person's physical, cognitive, and emotional behaviors irregular.

In all cases, the patients develop post concussion syndrome, which includes memory problems, dizziness, tiredness, sickness and depression.

The hemorrhage is considered a focal brain injury; that is, it occurs in a localized spot rather than causing diffuse damage over a wider area.

Diffuse axonal injury, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact.

Overlying scalp laceration and soft tissue disruption in continuity with a skull fracture constitutes "compound head injury", and has higher rates of infection, unfavorable neurologic outcome, delayed seizures, mortality, and duration of hospital stay.

Symptoms of a mild brain injury include headaches, confusion, ringing ears, fatigue, changes in sleep patterns, mood or behavior.

[citation needed] Cognitive symptoms include confusion, aggression, abnormal behavior, slurred speech, and coma or other disorders of consciousness.

Physical symptoms include headaches that do not go away or worsen, vomiting or nausea, convulsions or seizures, abnormal dilation of the eyes, inability to awaken from sleep, weakness in the extremities, and a loss of coordination.

Common symptoms of head injury include coma, confusion, drowsiness, personality change, seizures, nausea and vomiting, headache and a lucid interval, during which a patient appears conscious only to deteriorate later.

The widely used PECARN Pediatric Head Injury/Trauma Algorithm helps physicians weigh risk-benefit of imaging in a clinical setting given multiple factors about the patient—including mechanism/location of the injury, age of the patient, and GCS score.

[26] Lesions to the parietal lobes may result in agnosia, an inability to recognize complex objects, smells, or shapes, or amorphosynthesis, a loss of perception on the opposite side of the body.

A CT is an imaging technique that allows physicians to see inside the head without surgery in order to determine if there is internal bleeding or swelling in the brain.

[31] Computed tomography (CT) has become the diagnostic modality of choice for head trauma due to its accuracy, reliability, safety, and wide availability.

[33] Glasgow Coma Scale (GCS) is the most widely used scoring system used to assess the level of severity of a brain injury.

Due to the high risk of even minor brain injuries, close monitoring for potential complications such as intracranial bleeding.

Second-line alternatives include decompressive craniectomy (Jagannathan et al. found a net 65% favorable outcomes rate in pediatric patients), barbiturate coma, hypertonic saline, and hypothermia.

Rules like these are usually studied in depth by multiple research groups with large patient cohorts to ensure accuracy given the risk of adverse events in this area.

In children with uncomplicated minor head injuries the risk of intracranial bleeding over the next year is rare at 2 cases per 1 million.

Malignant post traumatic cerebral swelling can develop unexpectedly in stable patients after an injury, as can post-traumatic seizures.

However, persons who sustain head trauma resulting in unconsciousness for an hour or more have twice the risk of developing Alzheimer's disease later in life.

To combat overuse of head CT scans yielding negative intracranial hemorrhage results, which unnecessarily exposes patients to radiation and increase time in the hospital and cost of the visit, multiple clinical decision support rules have been developed to help clinicians weigh the option to scan a patient with a head injury.

In 1848, Phineas Gage was paving way for a new railroad line when he encountered an accidental explosion of a tamping iron straight through his frontal lobe.

[39] Ten years later, Paul Broca examined two patients exhibiting impaired speech due to frontal lobe injuries.

It wasn't until Leborgne, formally known as "tan", died when Broca confirmed the frontal lobe lesion from an autopsy.