Blood is seen layering into the brain along sulci and fissures, or filling cisterns (most often the suprasellar cistern because of the presence of the vessels of the circle of Willis and their branch points within that space). The classic presentation of subarachnoid hemorrhage is the sudden onset of a severe headache (a thunderclap headache). This can be a very dangerous entity and requires emergent neurosurgical evaluation and sometimes urgent intervention. Cerebral contusion
Cerebral contusion is bruising of the brain tissue. The piamater is not breached in contusion in contrary to lacerations. The majority of contusions occur in the frontal and temporal lobes. Complications may include cerebral edema and transtentorial herniation. The goal of treatment should be to treat the increased intracranial pressure. The prognosis is guarded. Diffuse axonal injury
Diffuse axonal injury, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact. Axons are stretched and damaged when parts of the brain of differing density slide over one another. Prognoses vary widely depending on the extent of the damage. Compound head injury
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. Signs and symptoms
Three categories used for classifying the severity of brain injuries are mild, moderate or severe. Mild brain injuries
Symptoms of a mild brain injury include headaches, confusion, ringing ears, fatigue, changes in sleep patterns, mood or behavior.
An ulcer is a deeper breach of epithelium compared to an erosion or excoriation, and involves damage to both epithelium and lamina propria.An erosion is a superficial breach of the epithelium, with little damage to the underlying lamina propria. A mucosal erosion is an erosion which specifically occurs on a mucous membrane. Only the superficial epithelial cells of the epidermis or of the mucosa are lost, and the lesion can reach the depth of the basement membrane. Erosions heal without scar formation.Excoriation is a term sometimes used to describe a breach of the epithelium which is deeper than an erosion but shallower than an ulcer. This type of lesion is tangential to the rete pegs and shows punctiform (small pinhead spots) bleeding, caused by exposed capillary loops. Causes
Ulcers and erosions can be the result of a spectrum of conditions including:

Those causing auto-immune epithelial damage, damage because of an immune defect (e.g., HIV, leukemia)
Infections (e.g. herpes viruses)
Nutritional disorders (e.g., vitamin deficiencies). Chemicals such as SLS (a common ingredient in many toothpastes) have been linked to mouth ulcers, and have been recognized by public health agencies such as the NHS as a risk factor. Injuries (e.g. biting of the lip, tongue, and cheek, hard foods can scrape the oral tissues, hot foods can cause burns)
Stress: When the body is stressed, the immune symptom may trigger mouth sores

Pathophysiology
The exact pathogenesis is dependent upon the cause.