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Abstract
An attack on the central nervous system can be life-threatening. Whether a patient is facing meningitis or encephalitis, both emergencies demand immediate identification and appropriate intervention. We'll help you understand what causes these infections, how to pinpoint which type your patient has, and what you can do to help her to a full recovery.
JESSICA BURTON is a 22-year-old college student home on winter break. Her mother brought her into the emergency department because she has been running a fever for the past 2 days, is complaining of a severe headache, and screams in pain when she tries to move her neck.
As you assess Jessica, you notice some unusual findings when checking her neurologic status. Her pupils are equal and reactive to light, but she reports increased headache pain when you shine the penlight into her eyes. She can follow simple commands, but she seems drowsy and can't tell you the correct date. She can grip both of your hands with equal strength, but her grips are somewhat weak.
What's going on with this patient?
You quickly collaborate with the health care provider on call and discuss your assessment findings. You suspect that Jessica has bacterial meningitis, as evidenced by the classic symptom triad—fever, neck stiffness, and changes in level of consciousness (LOC)—and the fact that she's recently spent time in a college dormitory.
But how do you know she doesn't have viral encephalitis? Or maybe she's really exhibiting signs and symptoms of aseptic, not bacterial, meningitis. Perhaps she's even experiencing a mixture of both meningitis and encephalitis, known as meningoencephalitis. Knowing the subtle differences between meningitis and encephalitis is one of the keys to determining which type of infection your patient is experiencing.
In this article, I'll explain the ins and outs of meningitis and encephalitis, discuss signs and symptoms and important diagnostic tests to help differentiate between the two, and review treatment options and nursing interventions for both infections.
Let's start by sorting out the definitions of meningitis and encephalitis in more detail.
Two hotheads
Meningitis is an inflammation of the membranes that surround the brain (meninges); encephalitis is an inflammation of the brain itself. A patient with meningitis will experience many of the same symptoms as a patient with encephalitis. Both inflammations can cause the classic symptoms of fever, stiff neck, and altered LOC, with accompanying headache. Because encephalitis involves the brain directly, you may think that seizures would be a clear sign to help you distinguish between the two. Unfortunately, it's not that simple—both inflammations can cause seizures.
So how can you tell these conditions apart? Let's look at each disorder more closely.
Mind on meningitis
Meningitis is classified into two types: bacterial or septic, which is more common, and aseptic or viral. Let's take a look at the pathophysiology, potential causes, and signs and symptoms of bacterial meningitis first.
Bacterial meningitis
One of the 10 most common infectious causes of death, bacterial meningitis is responsible for about 135,000 deaths each year worldwide. According to the Centers for Disease Control and Prevention, 3,000 cases of bacterial meningitis occur in the United States each year, with a mortality rate of 10% to 12%.
In bacterial meningitis, infection causes inflammation of one or more of the meningeal membranes that surround the brain: the pia mater, arachnoid, and the dura mater (see Picturing the cranial meninges). The invading organism typically enters the central nervous system (CNS) through the blood, but may also gain entrance through a direct opening between cerebrospinal fluid (CSF) and the environment as a result of trauma, along cranial and peripheral nerves, or through the mouth or nose. Once inside the body, the invading organism triggers an inflammatory response, which usually begins in the pia-arachnoid tissue.
Neutrophils gather in the area of inflammation and produce an exudate in the subarachnoid space in an attempt to ward off the invasion, causing the CSF to thicken. The thickened CSF, which flows less readily around the brain and spinal cord, can block the arachnoid villi, further obstructing the flow. The exudate also exacerbates the inflammatory response, which increases pressure in the brain and irritates the meninges, which causes edema. Exudate can also extend to the cranial and peripheral nerves, triggering additional inflammation.
All of this can result in elevated intracranial pressure (ICP) from disrupted cerebral blood supply, thrombus or rupture, and encephalitis. If not reduced, increased ICP can lead to cerebral infarction, brain herniation, and death.
Bacterial meningitis may be a complication of bacteremia (presence of bacteria in the blood), especially from pneumonia, empyema (collection of pus in the pleural space), osteomyelitis, or endocarditis. Other infections that can cause bacterial meningitis include sinusitis, otitis media, encephalitis, myelitis, and brain abscess caused by Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae, or Escherichia coli.
Patients of any age can develop bacterial meningitis. Risk factors include:
[black small square] living in a dormitory (for example, college students or military personnel)
[black small square] serious drug allergies
[black small square] recent exposure to someone with bacterial meningitis
[black small square] recent travel to areas known for meningococcal disease, such as sub-Saharan Africa
[black small square] history of injected drug use
[black small square] recent head trauma
[black small square] otorrhea or rhinorrhea
[black small square] HIV infection or other immunocompromising conditions.
Our patient, Jessica, experienced the classic symptom triad of bacterial meningitis—fever, neck stiffness (nuchal rigidity), and changes in LOC. Many patients don't have all three symptoms, but almost every patient has at least one. Other signs and symptoms include:
[black small square] headache
[black small square] nausea
[black small square] vomiting
[black small square] chills
[black small square] malaise
[black small square] back, abdominal, and extremity pain
[black small square] irritability from increasing ICP
[black small square] seizures
[black small square] photophobia, diplopia, or other visual problems from cranial nerve irritation
[black small square] sinus arrhythmias from irritation of the autonomic nerves
[black small square] exaggerated and symmetrical deep tendon reflexes
[black small square] positive Brudzinski's and Kernig's signs (see Testing formeningeal irritation)
[black small square] delirium, deep stupor, or coma from increased ICP and cerebral edema
[black small square] progressive petechial or ecchymotic rash (occurs in half the patients with bacterial meningitis caused by N. meningitidis)
[black small square] papilledema (inflammation and edema of the optic nerve; rare)
[black small square] opisthotonos (a spasm more common in infants and children in which the back and extremities arch backward so that the body rests on the head and heels).
Because bacteremia usually accompanies bacterial meningitis, your patient may also exhibit systemic complications, such as septic shock, disseminated intravascular coagulation, acute respiratory distress syndrome, and septic or reactive arthritis.
Now, let's take a look at how aseptic meningitis compares.
Aseptic meningitis
In aseptic (viral) meningitis, lymphocytes infiltrate the pia-arachnoid tissue, but usually not as severely as in bacterial meningitis. The patient will have the clinical and lab evidence of meningeal inflammation, but the bacterial cultures will be negative. Because no exudate forms, aseptic meningitis is self-limiting and usually requires only symptomatic treatment.
Aseptic meningitis may result from a virus or other organism, but sometimes identifying the source is difficult or impossible. Common causes of aseptic meningitis include enteroviruses, including coxsackievirus, echovirus, and poliovirus; arboviruses; herpes simplex virus type 2 (HSV-2); mumps virus; Epstein-Barr virus; and West Nile virus.
Taking a thorough patient history of recent illness and having knowledge of seasonal epidemics can help you differentiate the many causes of aseptic meningitis. Assessment findings may reveal some clues about the source; for example, swollen lymph nodes in the neck may suggest mumps as the cause in a patient who hasn't been vaccinated, genital lesions may suggest HSV-2 infection as the culprit, and flaccid paralysis may point to West Nile virus.
Aseptic meningitis starts with the sudden onset of fever (up to 104° F [40° C]), changes in LOC (drowsiness, confusion, or stupor), and neck or spine stiffness when bending forward. Other signs and symptoms include:
[black small square] headache
[black small square] nausea
[black small square] vomiting
[black small square] abdominal pain
[black small square] sore throat.
Now that you have a better understanding of the two types of meningitis, let's take a look at encephalitis next.
Testing for meningeal irritation
Positive Brudzinski's and Kernig's signs indicate meningeal irritation, a sign of meningitis.
Have your patient lie in the supine position. Then place your hand under his neck and flex it forward, chin to chest. The test is positive if he flexes his ankles, knees, and hips bilaterally. The patient will typically complain of pain when his neck is flexed.
Have your patient lie in the supine position. Flex his hip and knee to form a 90-degree angle. Then attempt to extend his leg. If he exhibits pain or resistance to extension and spasm of the hamstring, the test is positive.
Lumbar puncture basics
During lumbar puncture, the patient is placed in a side-lying position and a needle is inserted into the arachnoid space of the spinal canal, usually between the third and fourth lumbar vertebrae.
After the procedure, assess the patient for possible complications. The most common complication of lumbar puncture is headache; the patient may also experience temporary paresthesia. Rarely, serious complications, such as spinal or epidural bleeding or nerve root trauma, may occur. Watch for weakness, loss of sensation, or paraplegia.
Eye on encephalitis
Like meningitis, encephalitis is classified into two types: viral and bacterial. With this disorder, however, the viral type is more common. Let's review the pathophysiology, potential causes, and signs and symptoms of each.
Viral encephalitis
A severe inflammation of the brain itself, viral encephalitis can be life-threatening and cause lifelong neurologic problems, such as learning disabilities, epilepsy, and memory or fine motor deficits.
In viral encephalitis, a virus causes intense lymphocytic infiltration of the brain tissue and leptomeninges, leading to cerebral edema, degeneration of the brain's ganglion cells, and diffuse nerve cell destruction. The invading organism typically enters the body through a mosquito or tick bite, but it can also enter the body through ingestion or inhalation, or in some cases via an animal bite (such as in rabies infection). Immunocompromised patients are particularly vulnerable to viral encephalitis after contracting a viral infection.
Viral encephalitis generally results from arboviruses, specific to rural areas, or enteroviruses, such as coxsackievirus, echovirus, and poliovirus, in urban areas. Other causes include mumps virus, HIV infection, adenoviruses, and demyelinating diseases after contracting measles, varicella, or rubella or after vaccination. The most common cause of viral encephalitis in western countries is herpes simplex virus type 1; viral encephalitis of this type has a 50% to 75% mortality rate if not treated immediately.
Signs and symptoms that signal the beginning of viral encephalitis include high fever (102° F to 105° F [38.9° C to 40.6° C]), severe headache, and vomiting. The illness can progress to include signs and symptoms of meningeal irritation, such as a stiff neck and back. Other signs and symptoms include neurologic disturbances, such as:
[black small square] drowsiness
[black small square] disorientation
[black small square] seizures
[black small square] paralysis
[black small square] delirium
[black small square] coma.
Many patients with viral encephalitis will exhibit only mild symptoms, such as headache, irritability, and lethargy.
Bacterial encephalitis
Rarely, encephalitis is caused by bacteria. The same patients who are at risk for bacterial meningitis are at risk for contracting bacterial encephalitis, as are those with syphilis or toxoplasmosis.
Signs and symptoms of bacterial encephalitis include the classic triad—fever, nuchal rigidity, and changes in LOC—and may also include headache and motor or sensory deficits. Remember, though, that the cause of encephalitis is more likely to be viral than bacterial.
memory jogger
To remember the order of the meningeal membranes, think of them as a PAD for the brain:
Pia mater (closest to the brain)
Arachnoid
Dura mater.
All mixed up
And just when you think you've got it all straight, consider this: A patient can experience meningitis and encephalitis at the same time. In meningoencephalitis, the signs and symptoms of meningitis and encephalitis are similar and overlapping. Additional tests must be performed to clarify which type of CNS inflammation the patient is experiencing so an appropriate treatment plan can be developed.
No need for eeny, meeny, miny, or moe
So, how can you tell which of the above your patient is experiencing? Apart from the obvious differences in the definitions of these diseases, you can identify more subtle differences through a bedside neurologic assessment (see A quick check of mental status). Knowing and recognizing these differences will help you put together the pieces of the puzzle and plan the best care for your patient.
A patient with meningitis and a patient with encephalitis will both experience an altered mental status; however, changes in LOC are usually more severe with encephalitis. As a general rule, a patient with meningitis may be lethargic and have trouble answering questions about her history due to headache pain. A patient with encephalitis, on the other hand, may experience more extensive mental status changes, such as motor or sensory deficits, behavior and personality changes, difficulties with speech, partial paralysis on one side of the body, paresthesias (pins-and-needles sensation in the extremities), and other symptoms that mimic a stroke or transient ischemic attack.
To assess for motor or sensory deficits, have the patient grip both of your hands at the same time and assess for equal strength. Then have her push against your hands with her feet to assess equal strength in the lower extremities.
Besides noting changes in your patient's LOC, monitor the results of lab tests, including two sets of blood cultures and a complete blood cell count with differential.
The health care provider will perform a lumbar puncture to collect samples of the CSF for bacterial culture and Gram staining. Normal CSF values in an adult are as follows: volume, 90 to 150 mL; pressure, 90 to 180 mm H2O; appearance, clear and colorless; total cell count, essentially free of cells. See Lumbar puncture basics for what you need to know about caring for a patient who has had a lumbar puncture.
Culture results may not be available for 24 to 48 hours. Because bacterial meningitis is so dangerous, the health care provider will start the patient on empiric antibiotic therapy until he can rule out a bacterial cause. This also applies to patients who are immunocompromised, younger than age 1, and elderly patients.
Let's check in with our patient.
After assessing Jessica, the health care provider ordered a lumbar puncture and sent samples of her CSF to be cultured, and Jessica was admitted to the hospital. Empiric intravenous (I.V.) antibiotic therapy with ceftriaxone and vancomycin was started immediately, and Jessica's neurologic status, fluid volume, and pain level were closely monitored.
Now, let's dig into the treatment options for each diagnosis.
A quick check of mental status
To quickly screen your patient for disordered thought processes, ask these questions. An incorrect answer to any question may indicate the need for a complete mental status exam.
The right drug for the right bug
Bacterial meningitis is treated with a 2-week course of high-dose I.V. antibiotics that cross the blood-brain barrier and careful fluid management. Dexamethasone may also be used as an adjunct therapy. Let's take a closer look.
The health care provider will prescribe the first antibiotic based on patient assessment and known risk factors, until he receives the results of the CSF culture. Empiric antibiotics of choice include penicillin, such as ampicillin and piperacillin, and third-generation cephalosporins, such as cefotaxime and ceftriaxone. Vancomycin is an option if resistant strains of bacteria are identified.
Empiric therapy is only a best guess. Once the CSF culture results are available, the health care provider will prescribe an antibiotic targeted at the patient's identified bacterial invader.
The health care provider may consider adding I.V. dexamethasone as adjunct therapy in the treatment of acute bacterial meningitis or pneumococcal meningitis. Dexamethasone is effective in improving outcomes and reducing neurologic complications if given 15 to 20 minutes before the first dose of antibiotic, then every 6 hours for the next 4 days.
Closely monitor your patient's fluid and electrolyte balance. As ordered, treat dehydration with volume expanders, but take care to avoid fluid overload, which can exacerbate cerebral edema. Meticulously record fluid intake and output and monitor electrolyte values. An electrolyte imbalance that shifts fluid into the brain could be catastrophic, given the patient's already inflamed meninges and potentially elevated ICP.
Aseptic meningitis is treated with supportive measures, such as bed rest, maintenance of fluid and electrolyte balance, analgesics for pain, and exercises to combat residual weakness.
Viral encephalitis is treated with the antiviral drug acyclovir, which is effective against the herpes simplex virus strain. If the patient has a concurrent bacterial infection, antibiotics are indicated. Anticonvulsants and corticosteroids may be used to reduce cerebral inflammation and edema. Furosemide or mannitol may be ordered to reduce cerebral swelling; closely monitor the patient's fluid and electrolyte balance to prevent dehydration. Sedatives may be given to alleviate restlessness, and acetaminophen can be used to relieve headache and reduce fever.
Bacterial encephalitis is treated in much the same way as bacterial meningitis, with third-generation cephalosporins or vancomycin. The goal of treatment is to administer the first dose of the appropriate antibiotic as soon as possible. Supportive measures include managing fever and pain, controlling coughing and straining to reduce the risk of increased ICP, providing airway protection, and initiating seizure precautions.
What can you do to help your patient to a full recovery? That's up next.
Support is the name of the game
Here's what you need to do when caring for a patient with meningitis:
[black small square] Ensure that droplet precautions are followed for the first 24 hours after initiation of antibiotic therapy.
[black small square] Assess your patient's neurologic function often and watch for deterioration. Be alert for a temperature increase up to 102° F (38.9° C), deteriorating LOC, onset of seizures, and altered respirations, all of which may signal an impending crisis.
[black small square] Continually monitor her vital signs, pulse oximetry value, and arterial blood gas values, which can help identify the need for respiratory support if ICP increases. Also monitor arterial blood pressure and central venous pressure.
[black small square] Monitor your patient's fluid balance. Make sure she consumes enough fluids to prevent dehydration without triggering fluid overload. Also monitor her body weight, serum electrolyte level, and urine volume, specific gravity, and osmolality.
[black small square] Assess your patient's pain level. If treatment is succeeding, she should be pain free.
[black small square] Position her carefully to prevent joint stiffness and neck pain. Turn and reposition her often and help with range-of-motion (ROM) exercises. Also remember to protect her from injury if she's experiencing seizures or a severely altered LOC.
[black small square] Maintain a quiet, comfortable environment.
[black small square] Provide emotional support and reassure your patient and her family.
When caring for a patient with encephalitis, follow these steps:
[black small square] Frequently assess your patient's neurologic function. Check for changes in LOC and signs of increasing ICP, and watch for signs and symptoms of cranial nerve involvement, such as ptosis (drooping eyelids), strabismus (misalignment of the eyes), diplopia (double vision), abnormal sleep patterns, and behavior changes.
[black small square] Monitor her intake and output carefully to maintain fluid balance. Avoid fluid overload to prevent cerebral edema.
[black small square] Position your patient carefully and turn her often to prevent joint stiffness and neck pain. Also perform ROM exercises.
[black small square] Provide a quiet, darkened room to ease headache and photophobia.
[black small square] Maintain adequate nutrition by giving small, frequent meals.
[black small square] If your patient is disoriented or confused, attempt to reorient her frequently.
So, how's our patient doing?
Jessica's CSF cultures identified S. pneumoniae as the infecting organism. Her health care provider discontinued the vancomycin because the organism wasn't resistant to cephalosporins. The ceftriaxone was continued for a total of 14 days. Jessica's condition improved significantly during her hospital stay—her fever resolved, her neurologic status returned to normal, and her neck and headache pain were brought under control. Due to her move toward recovery, Jessica was discharged home with instructions to finish the course of antibiotics.
On the Web
These online resources may be helpful to your patients and their families:
Encephalitis Society's encephalitis information resource: http://www.encephalitis.info
Centers for Disease Control and Prevention's arboviral encephalitis fact sheet: http://www.cdc.gov/ncidod/dvbid/arbor/arbofact.htm
Centers for Disease Control and Prevention's meningococcal disease fact sheet: http://www.cdc.gov/ncidod/dbmd/diseaseinfo/meningococcal_g.htm
Meningitis Foundation of America: http://www.musa.org
National Institute of Neurological Disorders and Stroke's meningitis and encephalitis fact sheet: http://www.ninds.nih.gov/disorders/encephalitis_meningitis/detail_encephalitis_meningitis.htm
National Meningitis Association: http://www.nmaus.org .
What about an ounce of prevention?
Prophylactic antibiotic therapy for family and friends in close contact with a patient with bacterial meningitis may be recommended to destroy the causative bacteria that may have colonized in the nasopharynx.
Some forms of bacterial meningitis can be prevented by vaccination. The pneumococcal vaccine may be given to adults age 65 and older and other high-risk adults. The meningococcal vaccine is effective against N. meningitidis bacteria and is recommended for patients ages 11 to 12 and college freshmen living in dormitories. The H. influenzae vaccine has significantly decreased meningitis caused by this organism in children.
The most effective way to prevent viral encephalitis is to try to prevent the illnesses that can cause it. Keeping immunizations current for common childhood illnesses, such as measles, mumps, and chicken pox, will give children a head start on prevention.
You've got it all in your head
You play a key role in the team that identifies and plans the care for patients experiencing meningitis or encephalitis. Now that you have a better understanding of what causes these attacks, the assessments you'll assist with and perform, and what you can do to help your patients, you've got all the information you need to make a huge difference!
Learn more about it
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