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Infectious Disease and Microbiology – Neurological Symptoms and Signs with Fever
Overview and Definitions
Clouding of consciousness refers to mild inattentiveness and slightly reduced wakefulness. Obtundation describes slowed responses to external stimuli with decreased alertness and increased sleepiness. Coma is a state of unarousable unconsciousness with no purposeful response to pain. Encephalitis is inflammation of the brain associated with neurologic or mental status changes. Meningitis is inflammation of the meninges surrounding the central nervous system and may be acute, presenting over hours, or chronic, lasting longer than four weeks.
Clinical Approach
Fever with neurologic symptoms requires urgent evaluation for central nervous system infection, systemic infection, or noninfectious neurologic pathology. History should include onset and progression of neurologic symptoms, medication and substance use, trauma, travel, animal exposures, immunocompromised states, and past medical history, with collateral history when available. A complete physical examination should be performed with emphasis on dermatologic, head and neck, cardiopulmonary, and a comprehensive neurologic assessment including mental status, cranial nerves, funduscopy, gait, tone, power, reflexes, sensation, and cerebellar function. Level of consciousness should be documented using the Glasgow Coma Scale. Examination for meningitis includes assessment of neck stiffness, Kernig and Brudzinski signs, and jolt accentuation of headache. Funduscopic examination is important to detect papilledema, subarachnoid hemorrhage, or hypertensive encephalopathy.
Epidemiology
Herpes simplex virus type 1 accounts for approximately 10% of encephalitis cases. In regions where tuberculosis is endemic, tuberculomas are a frequent cause of intracranial mass lesions. The annual incidence of bacterial meningitis in the United States is approximately 1.5 per 100,000 population. In adults, the most common pathogens are Streptococcus pneumoniae, Neisseria meningitidis, and Listeria monocytogenes, with Staphylococcus aureus, including methicillin-resistant strains, increasingly recognized.
Etiology
Acute fever with neurologic signs suggests bacterial meningitis, encephalitis, or infectious intracranial lesions, all of which are medical emergencies. CNS granulomas may be caused by syphilis, cysticercosis, tuberculoma, fungal infections, or sarcoidosis. Enteroviruses are the most common cause of aseptic meningitis. Opportunistic infections are common in advanced HIV infection. Listeria rhombencephalitis presents with brainstem and cranial nerve involvement and is best identified on MRI. Parasitic causes include Echinococcus granulosus, schistosomiasis, amebiasis, and paragonimiasis. Fungal causes include Cryptococcus neoformans, Histoplasma, Coccidioides, Blastomyces, Aspergillus, mucormycosis, and Pseudallescheria. Viral cerebellar encephalitis may follow measles, varicella, Lyme disease, rabies, or legionellosis. Free-living amoebae such as Naegleria fowleri cause acute fulminant meningitis, while Acanthamoeba and Balamuthia cause chronic meningoencephalitis. Noninfectious causes include drug intoxication or withdrawal, malignancy, and subarachnoid hemorrhage.
Clinical Features
Bacterial meningitis typically presents with acute onset of fever, headache, neck stiffness, photophobia, nausea, and vomiting. Absence of headache and jolt accentuation makes bacterial meningitis unlikely, although individual clinical features lack sensitivity. Central nervous system tuberculosis is commonly associated with fever. Brucellosis may cause chronic granulomatous meningitis with constitutional symptoms and relevant animal exposure.
Diagnostic Evaluation
Initial investigations include complete blood count, electrolytes, renal and liver function tests, and blood cultures. Lumbar puncture is essential unless contraindicated by raised intracranial pressure or coagulopathy and should include opening pressure, cell count with differential, protein, glucose, Gram stain, culture, mycobacterial and fungal studies, cryptococcal antigen, syphilis testing, and PCR for herpes simplex or varicella zoster virus. Neuroimaging with CT or MRI is required to exclude space-occupying lesions, with MRI offering superior sensitivity for encephalitis and brainstem disease. In bacterial meningitis, cerebrospinal fluid typically shows elevated opening pressure, neutrophilic pleocytosis, high protein, and low or normal glucose. Viral meningitis usually demonstrates lower white cell counts with lymphocytic predominance and moderately elevated protein.
Management
Empiric treatment for suspected bacterial meningitis includes a third- or fourth-generation cephalosporin combined with vancomycin, with ampicillin added in patients over 50 years of age or immunocompromised to cover Listeria. Dexamethasone should be administered early when pneumococcal meningitis is suspected. Acyclovir should be initiated if herpes simplex encephalitis is a consideration. Antimicrobial therapy must not be delayed for imaging or lumbar puncture when meningitis is suspected.
Additional Care
Management often requires a multidisciplinary approach, with involvement of physiotherapy, occupational therapy, and speech and language pathology during recovery.
Follow-Up and Prognosis
Early recognition and prompt treatment are critical to reducing morbidity and mortality associated with infectious neurologic syndromes.
Complications
Complications include death, deafness, visual impairment, seizures, stroke, cognitive impairment, and increased intracranial pressure.
Overview and Definitions
Clouding of consciousness refers to mild inattentiveness and slightly reduced wakefulness. Obtundation describes slowed responses to external stimuli with decreased alertness and increased sleepiness. Coma is a state of unarousable unconsciousness with no purposeful response to pain. Encephalitis is inflammation of the brain associated with neurologic or mental status changes. Meningitis is inflammation of the meninges surrounding the central nervous system and may be acute, presenting over hours, or chronic, lasting longer than four weeks.
Clinical Approach
Fever with neurologic symptoms requires urgent evaluation for central nervous system infection, systemic infection, or noninfectious neurologic pathology. History should include onset and progression of neurologic symptoms, medication and substance use, trauma, travel, animal exposures, immunocompromised states, and past medical history, with collateral history when available. A complete physical examination should be performed with emphasis on dermatologic, head and neck, cardiopulmonary, and a comprehensive neurologic assessment including mental status, cranial nerves, funduscopy, gait, tone, power, reflexes, sensation, and cerebellar function. Level of consciousness should be documented using the Glasgow Coma Scale. Examination for meningitis includes assessment of neck stiffness, Kernig and Brudzinski signs, and jolt accentuation of headache. Funduscopic examination is important to detect papilledema, subarachnoid hemorrhage, or hypertensive encephalopathy.
Epidemiology
Herpes simplex virus type 1 accounts for approximately 10% of encephalitis cases. In regions where tuberculosis is endemic, tuberculomas are a frequent cause of intracranial mass lesions. The annual incidence of bacterial meningitis in the United States is approximately 1.5 per 100,000 population. In adults, the most common pathogens are Streptococcus pneumoniae, Neisseria meningitidis, and Listeria monocytogenes, with Staphylococcus aureus, including methicillin-resistant strains, increasingly recognized.
Etiology
Acute fever with neurologic signs suggests bacterial meningitis, encephalitis, or infectious intracranial lesions, all of which are medical emergencies. CNS granulomas may be caused by syphilis, cysticercosis, tuberculoma, fungal infections, or sarcoidosis. Enteroviruses are the most common cause of aseptic meningitis. Opportunistic infections are common in advanced HIV infection. Listeria rhombencephalitis presents with brainstem and cranial nerve involvement and is best identified on MRI. Parasitic causes include Echinococcus granulosus, schistosomiasis, amebiasis, and paragonimiasis. Fungal causes include Cryptococcus neoformans, Histoplasma, Coccidioides, Blastomyces, Aspergillus, mucormycosis, and Pseudallescheria. Viral cerebellar encephalitis may follow measles, varicella, Lyme disease, rabies, or legionellosis. Free-living amoebae such as Naegleria fowleri cause acute fulminant meningitis, while Acanthamoeba and Balamuthia cause chronic meningoencephalitis. Noninfectious causes include drug intoxication or withdrawal, malignancy, and subarachnoid hemorrhage.
Clinical Features
Bacterial meningitis typically presents with acute onset of fever, headache, neck stiffness, photophobia, nausea, and vomiting. Absence of headache and jolt accentuation makes bacterial meningitis unlikely, although individual clinical features lack sensitivity. Central nervous system tuberculosis is commonly associated with fever. Brucellosis may cause chronic granulomatous meningitis with constitutional symptoms and relevant animal exposure.
Diagnostic Evaluation
Initial investigations include complete blood count, electrolytes, renal and liver function tests, and blood cultures. Lumbar puncture is essential unless contraindicated by raised intracranial pressure or coagulopathy and should include opening pressure, cell count with differential, protein, glucose, Gram stain, culture, mycobacterial and fungal studies, cryptococcal antigen, syphilis testing, and PCR for herpes simplex or varicella zoster virus. Neuroimaging with CT or MRI is required to exclude space-occupying lesions, with MRI offering superior sensitivity for encephalitis and brainstem disease. In bacterial meningitis, cerebrospinal fluid typically shows elevated opening pressure, neutrophilic pleocytosis, high protein, and low or normal glucose. Viral meningitis usually demonstrates lower white cell counts with lymphocytic predominance and moderately elevated protein.
Management
Empiric treatment for suspected bacterial meningitis includes a third- or fourth-generation cephalosporin combined with vancomycin, with ampicillin added in patients over 50 years of age or immunocompromised to cover Listeria. Dexamethasone should be administered early when pneumococcal meningitis is suspected. Acyclovir should be initiated if herpes simplex encephalitis is a consideration. Antimicrobial therapy must not be delayed for imaging or lumbar puncture when meningitis is suspected.
Additional Care
Management often requires a multidisciplinary approach, with involvement of physiotherapy, occupational therapy, and speech and language pathology during recovery.
Follow-Up and Prognosis
Early recognition and prompt treatment are critical to reducing morbidity and mortality associated with infectious neurologic syndromes.
Complications
Complications include death, deafness, visual impairment, seizures, stroke, cognitive impairment, and increased intracranial pressure.
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