Arzhang Cyrus Javan, Andrea Censullo You must consider the diagnosis of acute bacterial meningitis. Patients with acute bacterial meningitis usually present with some combination of headache, fever, nuchal rigidity, and altered mental status. Nuchal rigidity (i.e., stiff neck) is the hallmark sign of irritated meninges and can be demonstrated when the neck resists passive flexion. This patient is presenting with three of the four aforementioned signs and symptoms, therefore favoring a diagnosis of acute meningitis. Nausea, vomiting, and photophobia are other common components of the presentation. Keep in mind that a higher level of suspicion is required to diagnose bacterial meningitis in elderly and immunocompromised patients. These patients can have an atypical presentation, with lethargy and confusion serving as the main clinical manifestations. The list of organisms that can cause meningitis is long and can be daunting, but conducting a thorough history can sometimes help narrow the differential diagnosis. Assessing the patient’s immune status is paramount, as certain immunodeficiencies can predispose patients to distinct opportunistic pathogens. For example, the elderly (considered age 50 or older), diabetics, alcoholics, pregnant patients, patients on immunosuppressive medications, and those with impaired cell-mediated immunity are more susceptible to Listeria monocytogenes meningitis. Patients with human immunodeficiency virus (HIV) have a significantly increased risk of Cryptococcus neoformans meningitis. Patients with deficiencies in terminal complement are predisposed to recurrent N. meningitidis bacteremia (i.e., meningococcemia) and, rarely, meningitis. Step 2/3 Clinical Pearl A rash occurs in about 50% of patients with meningococcemia, independent of the presence or absence of meningitis, beginning as a diffuse macular rash that rapidly evolves into petechiae and purpura. Lesions can occur on the trunk, lower extremities, mucous membranes, and occasionally on the palms and soles (see Fig. 14.1). The presence of other risk factors, independent of the patient’s immune status, can also assist with the evaluation. For example, patients with recent head trauma or neurosurgical procedures are at greater risk for infection with Staphylococcal spp., H. influenzae, and nosocomial gram-negative rods. Certain elements from the history of present illness or the past medical history can also help elucidate the cause. A clinical picture of recent or active pneumonia, otitis media, or sinusitis can point towards a diagnosis of S. pneumoniae. A history of herpes may place herpes simplex virus (HSV) meningitis or encephalitis higher on the differential. Recent constitutional symptoms suggesting upper respiratory tract infection (URI) or a viral gastroenteritis should prompt one to think of other, more common causes of viral meningitis such as enteroviruses. Certain elements of the social history can be very helpful. High-risk sexual behavior should prompt one to consider syphilis or acute HIV infection in the differential diagnosis. Recent tick exposure should alert one to the possibility of Lyme disease, human granulocytic anaplasmosis (HGA), ehrlichiosis, or Rocky Mountain spotted fever (RMSF). Recent mosquito bites can be a clue for meningitis or encephalitis from arboviruses such as West Nile virus. Recent contact with sick children makes enterovirus meningitis a real possibility. Coccidioidal meningitis should be considered in patients with recent travel to certain regions of the southwestern United States with high endemicity for this soil-dwelling fungus. There have been outbreaks of N. meningitidis in crowded living conditions such as college dormitories and military barracks. Kernig’s and Brudzinski’s signs are used to test for meningeal irritation. To elicit Kernig’s sign, while the patient is supine, the practitioner passively flexes the patient’s hip 90 degrees and passively extends the knee from a 90-degree flexed position. The test is considered positive when the patient resists the straightening of the knee due to pain. Brudzinski’s sign involves flexing the neck of a patient who is supine. The test is considered positive if the patient reflexively flexes the hips and/or knees due to pain. A positive Kernig’s or Brudzinski’s sign can help point toward meningitis, but a negative test does not rule it out, as the sensitivity of these maneuvers is only roughly 5%. The clinical presentation of acute onset of headache, fever, and symptoms of meningeal irritation, along with neck stiffness and photophobia, is most concerning for meningitis. When considering meningitis, it is helpful to break it down further into two categories: acute bacterial meningitis and aseptic meningitis. Viral encephalitis is also on the differential but less likely. Other diseases to consider, though less likely in this patient with no focal neurologic findings, are a focal infection of the central nervous system such as a brain abscess, epidural empyema, or subdural empyema. One critical noninfectious diagnosis to keep in mind is subarachnoid hemorrhage. As described previously, acute bacterial meningitis is a medical emergency with an overall mortality around 25%. The mortality rate is even higher in patients with pneumococcal meningitis. The most common bacterial causes of meningitis in this patient’s age group (>50 years old) include S. pneumoniae, which is the most common cause of meningitis in adults overall, followed by N. meningitidis and L. monocytogenes. H. influenzae has become an exceedingly rare cause of meningitis in adults because of the widespread use of the H. influenzae type B vaccine, although it can still be seen in adults with predisposing factors such as cerebrospinal fluid (CSF) leak, recent neurosurgery, trauma, or mastoiditis. Common bacteria that cause meningitis in specific age groups and populations are displayed in Table 14.1. TABLE 14.1 Common Bacterial Pathogens in Meningitis and Recommended Empiric Antibiotic Therapy Based on Age and Risk Factors Aseptic meningitis is a term used to categorize any meningitis that has a negative CSF bacterial Gram stain and culture. The differential diagnosis is comprised of a broad range of both infectious and noninfectious etiologies, many of which can lead to an acute clinical picture that very closely resembles acute bacterial meningitis. Table 14.2 reviews many of the etiologies of aseptic meningitis.
A 60-Year-Old Male With Acute Headache and Fever
What medical emergency must you consider in this patient based solely on these initial symptoms?
What factors should be considered when evaluating the cause of a patient’s suspected meningitis?
What are Kernig’s and Brudzinski’s signs, and how reassuring is it that they are normal in this patient?
What is your differential diagnosis at this point?
Predisposing Factor
Common Bacterial Pathogens
Empiric Antimicrobial Therapy
Age 16-50 years old
S. pneumoniae, N. meningitidis
Vancomycin + third-generation cephalosporin
Age >50 years old or alcoholism
S. pneumoniae, N. meningitides, L. monocytogenes, aerobic gram-negative bacilli
Vancomycin + third-generation cephalosporin + ampicillin
Immunocompromised (i.e., HIV, immunosuppressive medication)
S. pneumoniae, N. meningitides, L. monocytogenes, aerobic gram-negative bacilli (including pseudomonas)
Vancomycin + ampicillin + cefepime or meropenem
Basilar skull fracture
S. pneumoniae, H. influenzae, Group A strep
Vancomycin + third-generation cephalosporin
Postneurosurgery, cerebrospinal shunt, or penetrating head trauma
S. aureus, coagulase negative staph, aerobic gram-negative bacilli including Pseudomonas spp., Propionibacterium acnes
Vancomycin + cefepime or ceftazidime or meropenem
14 A 60-Year-Old Male With Acute Headache and Fever
Case 14
