Meningitis

Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. Meningitis may develop in response to a number of causes, most prominently bacteria, viruses and other infectious agents, but also physical injury, cancer, or certain drugs. While some forms of meningitis are mild and resolve on their own, meningitis is a potentially serious condition due to the proximity of the inflammation to the brain and spinal cord. The potential for serious neurological damage or even death necessitates prompt medical attention and evaluation. Infectious meningitis, the most common form, is typically treated with antibiotics and requires close observation. Some forms of meningitis (such as those associated with meningococcus, mumps virus or pneumococcus infections) may be prevented with immunization.

Diagnosis
Investigations
Suspicion of meningitis is generally based on the nature of the symptoms and findings on physical examination. Meningitis is a medical emergency, and referral to hospital is indicated. If meningitis is suspected based on clinical examination, early administration of antibiotics is recommended, as the condition may deteriorate rapidly. In the hospital setting, initial management consists of stabilization (e.g. securing the airway in a depressed level of consciousness, administration of intravenous fluids in hypotension or shock), followed by antibiotics if not already administered.
Investigations include blood tests (electrolytes, liver and kidney function, inflammatory markers and a complete blood count) and usually X-ray examination of the chest. The most important test in identifying or ruling out meningitis is analysis of the cerebrospinal fluid (fluid that envelops the brain and the spinal cord) through lumbar puncture (LP). However, if the patient is at risk for a cerebral mass lesion or elevated intracranial pressure (recent head injury, a known immune system problem, localizing neurological signs, or evidence on examination of a raised ICP), a lumbar puncture may be contraindicated because of the possibility of fatal brain herniation. In such cases a CT or MRI scan is generally performed prior to the lumbar puncture to exclude this possibility. Otherwise, the CT or MRI should be performed after the LP, with MRI preferred over CT due to its superiority in demonstrating areas of cerebral edema, ischemia, and meningeal inflammation.
During the lumbar puncture procedure, the opening pressure is measured. A pressure of over 180 mm H2O is indicative of bacterial meningitis.
The cerebrospinal fluid (CSF) sample is examined for white blood cells (and which subtypes), red blood cells, protein content and glucose level. Gram staining of the sample may demonstrate bacteria in bacterial meningitis, but absence of bacteria does not exclude bacterial meningitis; microbiological culture of the sample may still yield a causative organism. The type of white blood cell predominantly present predicts whether meningitis is due to bacterial or viral infection. Other tests performed on the CSF sample include latex agglutination test, limulus lysates, or polymerase chain reaction (PCR) for bacterial or viral DNA. If the patient is immunocompromised, testing the CSF for toxoplasmosis, Epstein-Barr virus, cytomegalovirus, JC virus and fungal infection may be performed.

Epilepsy

Epilepsy is one of the most common of the serious neurological disorders. Genetic, congenital, and developmental conditions are mostly associated with it among younger patients; tumors are more likely over age 40; head trauma and central nervous system infections may occur at any age. The prevalence of active epilepsy is roughly in the range 5–10 per 1000 people. Up to 50 per 1000 people experience nonfebrile seizures at some point in life; epilepsy's lifetime prevalence is relatively high because most patients either stop having seizures or (less commonly) die of it. Epilepsy's approximate annual incidence rate is 40–70 per 100,000 in industrialized countries and 100–190 per 100,000 in resource-poor countries; socioeconomically deprived people are at higher risk. In industrialized countries the incidence rate decreased in children but increased among the elderly during the three decades prior to 2003, for reasons not fully understood.
Children with epilepsy are three to nine times more likely to have mental health problems than healthy children. Although the search for risk factors has often produced inconsistent results, there is evidence that the development of mental health problems in children with epilepsy is moderated and mediated by family risk factors. Attention-deficit/hyperactivity disorder (ADHD) affects three to five times more children with epilepsy than children in the general population, and children with epilepsy also have significantly higher rates of depression and anxiety. There is a strikingly higher prevalence of epilepsy in children with autism, and evidence suggests that epilepsy is a risk factor for autism, independent of other central nervous system problems.

Classification
Epilepsies are classified in five ways:
1. By their first cause (or etiology).
2. By the observable manifestations of the seizures, known as semiology.
3. By the location in the brain where the seizures originate.
4. As a part of discrete, identifiable medical syndromes.
5. By the event that triggers the seizures, as in primary reading epilepsy.
In 1981, the International League Against Epilepsy (ILAE) proposed a classification scheme for individual seizures that remains in common use.This classification is based on observation (clinical and EEG) rather than the underlying pathophysiology or anatomy and is outlined later on in this article. In 1989, the ILAE proposed a classification scheme for epilepsies and epileptic syndromes. This can be broadly described as a two-axis scheme having the cause on one axis and the extent of localisation within the brain on the other. Since 1997, the ILAE have been working on a new scheme that has five axes: ictal phenomenon, seizure type, syndrome, etiology and impairment.

Diagnosis
The diagnosis of epilepsy requires the presence of recurrent, unprovoked seizures; accordingly, it is usually made based on the medical history. EEG, brain MRI, SPECT, PET, and magnetoencephalography may be useful to discover an etiology for the epilepsy, discover the affected brain region, or classify the epileptic syndrome, but these studies are not useful in making the initial diagnosis.
Long-term video-EEG monitoring for epilepsy is the gold standard for diagnosis, but it is not routinely employed owing to its high cost, low availability and inconvenience.
Convulsive or other seizure-like activity, non-epileptic in origin, can be observed in many other medical conditions. These non-epileptic seizures can be hard to differentiate and may lead to misdiagnosis.
Epilepsy covers conditions with different aetiologies, natural histories and prognoses, each requiring different management strategies. A full medical diagnosis requires a definite categorisation of seizure and syndrome types.