| "Meningitis" and "encephalitis" are two words that pop | | | | infecting organism, and guiding successful treatment. |
| onto most people's radar screens from time to time, | | | | While an imaging test like a CT scan or an MRI scan is |
| and usually in some scary context, like hearing of a | | | | often included as part of the evaluation, they do not |
| cluster of cases in their child's school, or reading media | | | | replace the lumbar puncture in identifying the essential |
| reports of epidemics occurring nationally or | | | | features of the infection. |
| internationally. While most people understand that these | | | | A lumbar puncture is usually performed with the patient |
| words mean there is some sort of infection of the | | | | lying on one side, curled into a fetal position. The doctor |
| nervous system, other distinctions and implications are | | | | preps and drapes the patient's lower back to create a |
| often left unstated and, as a result, can be vague or | | | | sterile field in which to work. After numbing the skin of |
| confusing. | | | | the lower back the doctor inserts a needle in the |
| The basic concepts are built into the words | | | | middle of the spine, puncturing the meninges. In the |
| themselves. Starting at the ends of the words and | | | | lower back there is no spinal cord, so there is no risk |
| working forwards, "-itis" is the medical suffix meaning | | | | of puncturing it, too. Watery fluid is collected into tubes |
| inflammation. Although it's possible for inflammation to | | | | as it drips out of the back of the needle. Then the |
| occur without an infection being present, as a practical | | | | needle is withdrawn. |
| matter, in most cases of meningitis or encephalitis the | | | | This watery fluid is called CSF--short for cerebrospinal |
| inflammation is indeed due to an infection. | | | | fluid--and because it resides within the meninges (and |
| The next step in understanding these concepts is to | | | | outside of the brain and spinal cord) it holds some of |
| analyze the first parts of the words. "Mening-" refers | | | | the keys to diagnosing the infection. Laboratory |
| to the meninges which are the membranous coverings | | | | personnel can perform several tests on the fluid right |
| of the brain and spinal cord. So "meningitis" means | | | | away, like measuring the concentrations of red and |
| inflammation or infection of these membranous | | | | white blood cells, as well as the concentrations of |
| coverings. By contrast, "encephal-" refers to the | | | | protein and sugar. An increase in concentration of |
| encephalon or brain (originating from the Greek word | | | | white blood ("pus") cells and an increase in protein |
| "enkephalos"), so "encephalitis" means inflammation or | | | | concentration are expected findings when the |
| infection of the brain itself. | | | | meninges are infected by either bacteria or viruses, |
| Although no case of meningitis or encephalitis is trivial, | | | | with the changes more pronounced in bacterial |
| depending on the particulars, some cases end up as | | | | infections than in viral infections. Reductions in sugar |
| temporary illnesses from which there is full recovery, | | | | concentration are common in bacterial but not viral |
| while others can be severely damaging or even lethal. | | | | infections. Other tests on the CSF involve inherent |
| In a nutshell, cases of meningitis caused by viruses are | | | | delays, like trying to grow bacteria from the CSF in |
| usually associated with good outcomes (even without | | | | Petri dishes or other culture media. |
| treatment), while cases of meningitis involving bacteria | | | | In truth, cases of encephalitis also usually involve |
| are very serious and require emergency treatment | | | | inflammation of the meninges, so a stickler for linguistic |
| with powerful antibiotics. All cases of | | | | accuracy could rightly maintain that they should be |
| encephalitis--usually caused by viruses and not by | | | | called "meningo-encephalitis" to reflect the |
| bacteria--are serious, and antiviral treatment is available | | | | involvements of both meninges and brain. But in |
| for some of the viruses involved, but not all. | | | | common usage, the "meningo-" prefix is often dropped. |
| Most cases of either meningitis or encephalitis start | | | | So because CSF changes occur in cases of both |
| fairly abruptly, sometimes following an obvious infection | | | | meningitis and encephalitis, the main clinical feature that |
| elsewhere in the body and sometimes not. As with | | | | separates the two is the patient's mental state, with |
| most infections, a fever is usually present in meningitis | | | | confusion or decreased level of consciousness making |
| or encephalitis, but is not necessarily striking. In both | | | | a strong case for encephalitis. |
| cases the patient feels miserable in general and often | | | | Once the CSF has been collected, the doctor can |
| complains of pain in the head, neck, or both. | | | | begin treatment without risk of obscuring the fluid's |
| Because encephalitis involves infection of the brain | | | | diagnostic features. So long as there is any likelihood of |
| itself, symptoms of altered brain function--like confusion | | | | bacterial infection, the doctor administers one or more |
| or decreased alertness--are usually present, while in | | | | antibiotic drugs, usually via an intravenous catheter. If |
| cases of meningitis the patient is initially alert and, | | | | the clinical findings could also be interpreted as due to |
| though understandably distracted by pain and misery, | | | | a treatable virus, the doctor concurrently administers |
| still in command of their mental processes. | | | | an antiviral drug. With the seriousness of these |
| In either case, prompt medical assessment is important. | | | | illnesses, the benefits of over-treatment exceed its |
| In both meningitis and encephalitis a lumbar puncture | | | | risks, and once the dust settles and the diagnosis is |
| (also known as a spinal tap) is usually crucial in | | | | clarified, needless treatment can be discontinued |
| detecting the presence of an infection, identifying the | | | | without harm. |