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Bacterial and viral meningitis
Otherwise healthy patients within age extremes present with clinically obvious acute bacterial meningitis. In contrast, most patients with subacute bacterial meningitis present a diagnostic challenge. Systemic examination occasionally reveals a pulmonary or otitis media co-infection. Signs of meningeal irritation include the following:
Papilledema is present in only one third of meningitis patients with increased ICP; it takes at least several hours to develop. Focal neurologic signs include the following:
Systemic findings can also be present. Extracranial infection (eg, sinusitis, otitis media, mastoiditis, pneumonia, urinary tract infection) may be noted. Arthritis is seen with N meningitidis but is found less commonly with other bacterial species. Nonblanching petechiae and cutaneous hemorrhages are seen classically with N meningitidis; however, these also can occur with other bacterial and viral infections. Endotoxic shock with vascular collapse is characteristic of severe N meningitidis infection. Altered mental status, from irritability to somnolence, delirium, and coma, can develop. Infants may have the following:
Approximately 25% of patients with bacterial meningitis present acutely, well within 24 hours of onset of symptoms. In contrast, patients with subacute bacterial meningitis and most patients with viral meningitis present with neurologic symptoms developing over 1-7 days. Chronic symptoms lasting longer than 1 week suggest the presence of meningitis caused by certain viruses or by tuberculosis, syphilis, fungi (especially cryptococci), or carcinomatosis. About 85% of adults and children with bacterial meningitis exhibit the classic triad of symptoms (ie, fever, headache, and neck stiffness).[14] These symptoms can develop over several hours or over 1-2 days. Fever is the most common manifestation (95%), while the other 2 symptoms are less common. However, in a meta-analysis of 845 patients, the sensitivity and specificity of these classic symptoms were poor. Even so, the negative predictive value of these symptoms is high (ie, the absence of fever, neck stiffness, or altered mental status eliminates the diagnosis of meningitis in 99-100% of cases). Other symptoms can include the following:
Increased blood pressure with bradycardia can also be present. Vomiting occurs in 35% of patients. Occasionally, if a patient has been taking antibiotics for another infection, meningitis symptoms can take longer to develop or may be less intense. On physical examination, a skin rash caused by meningococcal meningitis (50%), H influenzae, pneumococcal meningitis, echovirus type 9, or Staphylococcus aureus may be present.[18] Other neurologic signs include the following:
One quarter of affected patients have a fulminant onset within 24 hours of infection, and there may be a history of a respiratory illness within the preceding 7 days (50%). Patients with meningitis caused by the mumps virus usually present with the triad of fever, vomiting, and headache. It follows the onset of parotitis (salivary gland enlargement occurs in 50% of patients), which clinically resolves in 7-10 days. As bacterial meningitis progresses, patients of any age may have seizures (30% of adults and children; 40% of newborns and infants). As many as 40% of patients with acute or subacute bacterial meningitis have previously been treated with oral antibiotics (presumably due to misdiagnosis at time of initial presentation); in patients with partially treated meningitis, seizures may be the sole presenting symptom. Fever and changes in level of alertness or mental status occur less commonly than in untreated meningitis. Atypical presentation may be observed in certain groups. Elderly individuals, especially those with underlying comorbidities (eg, diabetes, renal and liver disease), may present with lethargy and an absence of meningeal symptoms. Patients with neutropenia may present with subtle symptoms of meningeal irritation. Other immunocompromised hosts, including organ and tissue transplant recipients and patients with HIV and AIDS, may also have an atypical presentation. Immunosuppressed patients may not show dramatic signs of fever or meningeal inflammation. A less dramatic presentation―headache, nausea, minimal fever, and malaise―may be found in patients with low-grade ventriculitis associated with a ventriculoperitoneal shunt. Newborns and small infants also may not present with the classic symptoms, or the symptoms may be difficult to detect. An infant may appear only to be slow or inactive, or he or she may be irritable, vomiting, or feeding poorly. Other symptoms in this age group include temperature instability, high-pitched crying, respiratory distress, and/or bulging fontanelles (late sign in one third of neonates). Approximately half of affected adults show signs of meningeal irritation, such as nuchal and/or spinal rigidity and a positive Kernig and/or Brudzinski sign.[18] The Kernig sign is determined in a supine patient by flexing the hip to 90° while the knee is flexed at 90°; an attempt to further extend the knee produces pain in the hamstrings and resistance to further extension. The Brudzinski sign is determined by passively flexing the neck while the patient is in a supine position with extremities extended; this maneuver produces flexion of the hips in patients with meningeal irritation. Resistance to passive flexion of the neck is also a sign. Exacerbation of existing headache by repeated horizontal movement of the head, at a rate of 2-3 times per second, may also suggest meningeal irritation. Systemic findings on physical examination may provide clues to the etiology of a patient’s meningitis. Morbilliform rash with pharyngitis and adenopathy may suggest a viral etiology (eg, EBV, CMV, adenovirus, HIV). Macules and petechiae that rapidly evolve into purpura suggest meningococcemia (with or without meningitis). Vesicular lesions in a dermatomal distribution suggest varicella-zoster virus. Genital vesicles suggest HSV-2 meningitis. Sinusitis or otitis suggests direct extension into the meninges, usually with S pneumoniae and H influenzae. Rhinorrhea or otorrhea suggests a CSF leak from a basilar skull fracture, with meningitis most commonly caused by S pneumoniae. Hepatosplenomegaly and lymphadenopathy suggest a systemic disease, including viral (eg, mononucleosis-like syndrome in EBV, CMV, and HIV) and fungal (eg, disseminated histoplasmosis). The presence of a murmur suggests infective endocarditis with secondary bacterial seeding of the meninges. General physical findings in viral meningitis are common to all causative agents, but some viruses produce unique clinical manifestations that help in focusing the diagnostic approach. The classically taught triad of meningitis consists of fever, nuchal rigidity, and altered mental status, but not all patients have all 3 symptoms, and almost all patients have headache. The examination reveals no focal neurologic deficits in the majority of cases. Дата добавления: 2015-09-18 | Просмотры: 714 | Нарушение авторских прав |