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Meningitis: Meningitis is an inflammation of the meninges, which are the membranes that cover the brain and spinal cord. It is usually caused by bacteria or viruses, but can also be caused by certain medications or other organisms (such as fungi). Many of the bacteria and viruses that cause meningitis are fairly common and may be associated with other routine illnesses. Bacteria and viruses that infect the skin, urinary system, and gastrointestinal or respiratory tract can spread via the bloodstream to the meninges through cerebrospinal fluid, the fluid that circulates in and around the spinal cord. Many different types of bacteria can cause bacterial meningitis. In newborns, the most common causes are Group B streptococcus, Escherichia coli, and Listeria monocytogenes. In older children, Streptococcus pneumoniae (pneumococcus) and Neisseria meningitidis (meningococcus) are often the causes. In some cases of bacterial meningitis, the bacteria may spread to the meninges from a severe head trauma or a local infection, such as a serious ear infection (otitis media) or nasal sinus infection (sinusitis). Bacterial meningitis can be caused by Haemophilus influenza type b (Hib) but, because of widespread childhood vaccinations, these cases are now becoming rarer. Vaccination against Hib is given to all infants. Because the disease is rare in children ages five and up, the vaccination is generally not given after age five. Many viruses can lead to viral meningitis, including enteroviruses (such as coxsackievirus, poliovirus, and hepatitis A) and the herpes viruses. There are vaccinations for these viruses.
Encephalitis: Encephalitis is an inflammation (swelling) of the brain. Encephalitis typically occurs in one of three ways: through infections by herpes viruses, through tick or mosquito bites, or through viruses that cause childhood infections.
The herpes viruses are one group and include chickenpox (Varicella zoster), Epstein-Barr virus (EBV), and herpes simplex (the virus that causes cold sores and genital herpes). Viruses like the West Nile virus, which is transmitted through a mosquito bite, and bacteria that cause Lyme disease and Rocky Mountain spotted fever, which are transmitted through tick bites, can also cause encephalitis. Viruses that cause measles, mumps, and German measles (rubella) may cause meningitis. These forms of meningitis are rare today because of widespread immunizations Some cases of encephalitis are mild, and symptoms only last for a short time. However, it is possible to develop severe cases of encephalitis that may even be life-threatening. Being exposed to a virus or bacterium that can cause encephalitis does not mean that the individual will automatically develop encephalitis. In fact, it is rare for infections to develop into encephalitis. One form of encephalitis, called ethylmalonic encephalopathy, is a rare inherited disorder that affects several body systems. About 30 individuals with this condition have been identified worldwide, mostly in Mediterranean and Arab populations. Although ethylmalonic encephalopathy appears to be very rare, researchers suggest that some cases have been misdiagnosed as other neurologic disorders.
Traumatic brain injury: Traumatic brain injury (TBI), also called acquired brain injury or head injury, occurs when a sudden trauma causes damage to the brain. TBI may result when the head suddenly and violently hits an object or when an object pierces the skull and enters brain tissue. Symptoms of a TBI can be mild, moderate, or severe, depending on the extent of the damage to the brain. A person with a mild TBI may remain conscious or may lose consciousness for a few seconds or minutes. Other symptoms of mild TBI include headache, confusion, lightheadedness, dizziness, blurred vision or tired eyes, ringing in the ears, bad taste in the mouth, fatigue or lethargy, a change in sleep patterns, behavioral or mood changes, and trouble with memory, concentration, attention, or thinking. An individual with a moderate or severe TBI may display these symptoms, but may also have a headache that gets worse or does not improve, repeated vomiting or nausea, convulsions or seizures, an inability to awaken from sleep, dilation of one or both pupils of the eyes, slurred speech, weakness or numbness in the extremities, loss of coordination, and increased confusion, restlessness, or agitation. TBI is a major public health problem, especially among males aged 15-24 and among elderly men and women 75 years and older. Children aged five and younger are also at high risk for TBI. Males account for two thirds of childhood and adolescent head trauma cases. Each year in the United States, approximately one million people are treated for head injuries in hospital emergency rooms and approximately 270,000 people experience a moderate or severe TBI. Approximately 50,000 people die from head injury annually, and approximately 80,000 of these survivors live with significant disabilities as a result of the injury. Half of all TBIs are due to transportation accidents involving automobiles, motorcycles, bicycles, and pedestrians. These accidents are the major cause of TBI in people under age 75. For those aged 75 and older, falls cause the majority of TBIs. Approximately 20% of TBIs are due to violence, such as firearm assaults and child abuse, and about 3% are due to sports injuries. Half of TBI incidents involve alcohol use. Traumatic brain injury is a frequent cause of major long-term disability in individuals surviving head injuries sustained in war zones. Outcome for patients with head injury depends heavily on the cause. In the US, for example, patients with TBIs from falls have an 89% survival rate, while only 9% of patients with firearm-related TBIs survive. TBI is classified as either closed or open (penetrating). A closed head injury means the individual received a hard blow to the head from striking an object. An open, or penetrating, head injury means the individual was hit with an object that broke the skull and entered the brain. This usually happens when moving at high speed, such as going through the windshield during a car accident. It can also happen from a gunshot to the head. There are several types of traumatic brain injuries, including concussions and contusions, which are bruises (hematomas) on the brain. A subdural hematoma is a collection of blood on the surface of the brain. Cerebral contusions are bruises on the brain, usually caused by a direct, strong blow to the head. Cerebral lacerations are tears in brain tissue, which often accompany visible head wounds and skull fractures. Cerebral contusions and lacerations are usually more serious than concussions. Contusions may be caused by the sudden acceleration of the brain that follows a jolt, which may be delivered by a forceful blow to the head, or by the sudden deceleration that occurs when a moving head strikes an immovable object. The brain can be damaged at the point of impact and on the opposite side by striking the inside of the skull. Contusions and lacerations may cause only minimal physical damage to the brain and few symptoms. However, if swelling or bleeding is severe, these injuries can lead to a severe headache, dizziness, and vomiting. Depending on which area of the brain is damaged, the ability to think, control emotions, move, feel, speak, see, hear, and remember may be impaired. The person may become irritable, restless, or agitated. One side of the body may become weak or feel numb. Confusion may develop. A more severe injury causes swelling within the brain, damaging brain tissue further. Severe brain damage is often accompanied by other injuries, especially scalp injuries, skull fractures, and injuries of the chest and spine.
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