Central Nervous System Infections



Central Nervous System Infections





I. Bacterial Meningitis



  • Cause varies by age and immune status.








    Cause of Meningitis by Age























    Neonate (<1 mo)

    Child (1 mo-15 yr)

    Adult (15-60 yr)

    Older Persons (>60 yr)


    Gram-negative rods (50%-60%)

    Haemophilus influenza (50%)

    Pneumococcus (50%)

    Pneumococcus


    Group B streptococcus (30%)

    Meningococcus (30%)

    Meningococcus (25%)

    Gram-negative rods


    Listeria (2%-10%)

    Pneumococcus (20%)

    Staphylococcus (15%)

    Listeria (5%)


    Bacteria reach the meninges by hematogenous spread, direct extension from the sinuses or the ears, penetrating trauma, surgery, shunt, ruptured abscess, or sinus tracts. Once the bacteria have crossed the blood-brain barrier, they flourish. This results in an aggressive immune response.

    Factors predisposing to pneumococcal meningitis include pneumonia, otitis media, head injury, alcoholism, sickle cell disease.


  • Clinical Presentation



    • Symptoms include fever, headache, photophobia, seizures, nausea, vomiting, altered consciousness, and neck stiffness.


    • In children, vomiting, irritability, and seizures are most common.


    • In older persons, low-grade fever and altered consciousness predominate.


    • Signs include meningismus, positive Kernig sign, positive Brudzinski sign.


    • Petechial rashes suggest meningococcal meningitis (palpable purpura).


  • Diagnostic Procedures



    • Complete blood count, computed tomographic (CT) scan of head, lumbar puncture (LP), blood cultures, serum and cerebrospinal fluid (CSF) antigen studies.


  • Treatment



    • Begin treatment immediately.


    • Waiting for test results causes increased morbidity and mortality risk.


    • Ceftriaxone 2 g every 12 hours or cefotaxime 2 g every 4 hours


    • Add ampicillin for suspected listeria (<3 months or >50 years)


    • Add vancomycin if staphylococcus is suspected.


    • Add aminoglycosides if Gram-negative rods are suspected.



    • Dexamethasone 15 mg/kg per day should be used in children.


    • Rifampin prophylaxis should be given to those exposed to meningococcus.


    • Add acyclovir for herpes coverage.


  • Complications



    • Stroke—usually secondary to thrombophlebitis


    • Hydrocephalus—secondary to occlusion of arachnoid villi or adhesions between meninges and brain


    • Cranial nerve dysfunction


    • Seizures


    • Disseminated intravascular coagulation—most common with meningococcus and Gram-negative rods


    • Syndrome of inappropriate antidiuretic hormone secretion


    • Abscess or subdural empyema


    • Ventriculitis—usually in neonates


II. Subdural Empyema



  • A subdural empyema is a pyogenic exudate in the subdural space.



    • Subdural empyemas are typically secondary to direct extension from sinuses, osteomyelitis, brain abscess, or neurosurgic procedures.


  • Clinical Presentation



    • Symptoms include headache, fever, nausea, vomiting, and altered mental status.


    • Signs are usually focal (aphasia, hemiplegia) including focal seizures.


  • Diagnostic Procedures



    • CT Head


    • Do not LP—risk of herniation.


  • Treatment



    • Surgical drainage is required.


    • Appropriate antibiotic coverage


III. Brain Abscess



  • A brain abscess is a localized area of pyogenic exudate in the brain parenchyma.



    • They arise from hematogenous spread, direct extension from sinuses or otitis media (the most common cause), trauma, or rarely from meningitis.


  • Clinical Presentation

    Symptoms include headache, nausea, vomiting, fever, altered mental status, and progressive neurologic deficits. In many cases, the patient has a progressive neurologic deficit with no signs or symptoms of infection. Physical examination often reveals focal neurologic deficits and evidence of increased intracerebral pressure (papilledema).


  • Diagnostic Procedures



    • Do not LP—may rupture abscess resulting in ventriculitis or arachnoiditis.


    • Head CT with and without contrast shows an enhancing lesion at the grey-white junction.


  • Treatment



    • Superficial abscesses should be surgically drained.


    • Drainage is followed by intravenous (IV) antibiotics (PenG+flagyl+cephalosporin).


    • Decadron should be used in lesions with appreciable mass effect.


IV. Viral Meningitis



  • Viral meningitis is frequently referred to as aseptic meningitis.



  • May have a wide variety of causes including enterovirus (coxsackie, echo, polio), paramyxovirus (mumps), herpesvirus (Epstein-Barr, cytomegalovirus, herpes simplex), and HIV. Nonviral causes of aseptic meningitis include partially treated bacterial meningitis, tuberculosis, Lyme, syphilis, amoeba, fungus, rickettsia, sarcoid, subarachnoid hemorrhage, systemic lupus erythematosus, and demyelinating diseases.


  • Clinical Presentation



    • Viral meningitis is often preceded by a flulike illness.


    • Symptoms include headache, fever, seizures, nausea, vomiting, and stiff neck.


    • Signs include positive Kernig and Brudzinski signs.


  • Diagnostic Testing



    • LP reveals abnormal CSF with slightly increased glucose and increased protein.


    • There is a CSF pleocytosis (initially neutrophils, followed by lymphocytes).


    • Viral cultures and polymerase chain reaction (PCR) are only occasionally positive.


  • Treatment



    • Supportive


Atypical Bacterial Infections


I. Tuberculosis



  • Cause: Mycobacterium tuberculosis


  • Incidence: risk factors include HIV and ethyl alcohol.


  • Disease (neurologic)



    • Basilar meningitis with multiple cranial neuropathies


    • Tubercle formation


    • Parenchymal invasion


  • Pathologic Findings



    • Basilar meningitis with lower cranial nerve palsies


    • Caseating granulomas


    • CSF—acid fast bacilli-positive occasionally, very low glucose


  • Treatment: three-drug antitubercular therapy


II. Leprosy



  • Cause: Mycobacterium leprae


  • Incidence: transmitted by prolonged direct contact


  • Disease (neurologic)



    • Cutaneous and peripheral nerve lesions


    • Infected nerve nodules


    • Repeated attacks of neuralgic pain precede anesthesia


  • Pathologic Findings



    • Affected nerves are nodular and thickened.


    • Bacilli are present in the perineurium.


    • 33% have false-positive rapid plasma reagin.


  • Treatment: dapsone, rifampin, and clofazimine for 2 years


III. Mycoplasma



  • Cause: Mycoplasma pneumoniae


  • Incidence: respiratory aerial transmission



  • Disease (neurologic)



    • Meningitis


    • Encephalitis


    • Transverse myelitis


    • Acute cerebellar ataxia


    • Postinfectious leukoencephalitis


  • Pathologic Findings



    • CSF—normal glucose and protein. Polymorphonuclear neutrophils and monocytes


    • Cold agglutinins positive in 50%


    • Cultures usually negative


    • Antimycoplasma antibodies usually become positive.


  • Treatment: erythromycin, azithromycin


IV. Legionella



  • Cause: Legionella pneumophila


  • Incidence: epidemic. Contaminated air, water, or soil.


  • Disease (neurologic)



    • Acute encephalomyelitis


    • Acute cerebellar ataxia


    • Chorea


    • Peripheral neuropathy


  • Pathologic Findings: Myoglobinuria. Antibodies become positive.


  • Treatment: erythromycin IV for 14 to 21 days, azithromycin


Spirochete Infections


I. Syphilis



  • Cause: Treponema pallidum


  • Incidence: increasing with HIV infection


  • Transmission: sexual


  • Disease



    • “The Great Pretender”


    • Spirochetes invade the CSF within 3 to 8 months.


    • Meningitis occurs in 25%, occasionally becoming chronic.


    • Granuloma or gumma formation—focal signs.


    • Stroke secondary to endarteritis


    • Tabes dorsalis



      • Dorsal roots, dorsal columns, brainstem


    • Optic neuritis


    • General paresis of the insane


  • Pathologic Findings



    • CSF—mononuclear and lymphocytic infiltrate VDRL, positive. Increased protein. Increased IgG index.


    • Microhemagglutination assay-T. pallidum, fluorescent treponemal antibody absorption, positive. VDRL/rapid plasma reagin may be negative in tertiary syphilis.



  • Treatment



    • Penicillin-G 4 million units IV every 4 hours.


    • CSF at 6 weeks, 3 months, 6 months, 12 months, and 24 months


II. Lyme



  • Cause: Borrelia burgdorferi


  • Incidence: early summer transmission most common


  • Transmission: ixodid nymph tick vector


  • Disease



    • Erythema chronicum migrans


    • Headache


    • Myalgia


    • Meningismus


    • Cranial nerve palsies—Bell palsy most common


    • Mononeuritis multiplex, peripheral neuropathy, myopathy


    • Demyelinating disease


    • Guillain-Barré syndrome


    • Pseudotumor cerebri


  • Pathologic Findings: CSF—oligoclonal bands, positive; PCR, positive


  • Treatment: azithromycin, ceftriaxone


Viral Diseases


I. Poliomyelitis



  • Cause: enterovirus (picorna virus); polio, coxsackie, echovirus


  • Incidence: rare in United States with widespread use of the vaccine


  • Transmission: fecal-oral


  • Disease: broad spectrum of disease



    • Mild flulike illness in 95% with no CNS involvement.


    • Nonparalytic poliomyelitis



      • Flulike illness


      • Muscle pain (hamstrings)


      • Back pain


      • Aseptic meningitis


      • May or may not progress to paralytic poliomyelitis


    • Paralytic poliomyelitis



      • Rapid limb and bulbar weakness


      • Fasciculations


      • Reflexes are initially brisk but are eventually lost.


      • Most patients recover completely.


      • Some patients have residual weakness (atrophied limb).


      • Bulbar function recovers completely.


      • Mortality rate is 5% to 10%.


      • Postpolio syndrome occurs with late recurrence of weakness, pain, and fatigue in 20% to 30% of patients who initially recovered from paralytic polio.



  • Pathologic Findings



    • Neuronophagia


    • Immune response in the thalamus, hypothalamus, CN (Cranial nerve), motor nuclei, anterior horn, cerebellar nuclei


    • Cowdry B inclusions in the anterior horn cells


    • Coxsackie and echovirus can be isolated from the CSF.


  • Treatment: supportive. Vaccination with Salk (intramuscularly), Sabin (orally)


II. Herpes Zoster (varicella-zoster, shingles)



  • Cause: varicella-zoster virus


  • Incidence: 5/1,000 and increases with increasing age and with immunosuppression.


  • Transmission: acute infection by respiratory route, and shingles occurs by spontaneous reactivation of latent varicella-zoster virus.


  • Shingles Disease



    • T5-T10 dermatomes most common (66%)


    • Radicular pain with a vesicular eruption in the dermatome


    • The eruption may follow the onset of pain by several days.


    • Ramsay Hunt syndrome is a lower seventh nerve palsy associated with vesicular eruption in the auditory canal.


    • Postherpetic neuralgia occurs in 10% to 40% of cases


  • CNS complications occur in 1-3/10,000 cases



    • Cerebellar ataxia (most common complication)


    • Encephalitis


    • Transverse myelitis


    • Stroke (caused by vasculitis)


  • Pathologic Findings



    • CSF pleocytosis and increased protein


    • Inflammatory cells in the dorsal root ganglion


    • Tzanck prep, positive—multinucleated giant cells


  • Treatment



    • Acyclovir 800 mg 5 times per day for 7 days


    • Acyclovir shortens the duration of illness.


    • Acyclovir decreases postherpetic neuralgia.


    • Zoster ophthalmica—IV acyclovir


    • Pain management with gabapentin, oxcarbazepine, or topical lidocaine.


III. Herpes Encephalitis

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Sep 8, 2016 | Posted by in NEUROLOGY | Comments Off on Central Nervous System Infections

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