Bacterial Infections

Cause

WBC

GLU

PRO

Opening Pressure

Bacterial meningitis

200-10,000

(90% polyps)

<40

>100

200-300

Viral meningoencephalitis

10-1,000

(lymph predom)

nl/inc

inc

Tuberculous meningitis

50-500

(lymph predom)

<40

>100

inc

Cryptococcal meningitis

20-200

(lymph predom)

<20-40

>100

inc

Parameningeal infection

10-100

(mixed)

nl/inc

Meningitis – most often H. flu, S. pneumo, Neisseria

Newborn to 29 days – usually group B strep (usually associated with pneumonia; 50% mortality) or E. coli, listeria
Infants 1-2 months – strep pneumonia
Young children 3 months-9 years

H. influenzae (b subtype) – nasopharyngeal colonization leading to sepsis (blood cultures usually positive); bilateral subdural effusion (culture negative); steroids can prevent deafness; frequently have long-term seizures
N. meningitides
S. pneumoniae

Older children/young adults 10-29 years

N. meningitides – nasopharyngeal colonization leading to sepsis; most have petichiae; Waterhouse-Friederischen syndrome (shock, hemorrhage especially in adrenals)
S. pneumoniae
H. influenzae

Adults 30-59 years

S. pneumoniae
N. meningitides
H. influenzae

Elderly above 60 years or alcoholics

S. pneumoniae
N. meningitides
Gram negative bacilli

Immunocompromised

L. monocytongenes
Enterobacteriaceae
S. pneumoniae
H. influenzae
Nocardia asteroids
M. tuberculosis

Shunt infections

S. epidemidis
S. aureus
Enterobacteriaceae
Corynebacterium sp.

Penetrating injury or depressed fx

S. aureus
Enterobacteriaceae

Skull fx with CSF leak

S. pneumoniae

Abscess – usually direct connection from ear or sinus infection although can be hematogenous spread (MCA, GWJ) – 5% mortality

Increased risk with cyanotic heart disease or pulmonary AVM (5% of these patients get cerebral abscesses); accounts for 60% of abscesses in children
Acute bacterial endocarditis
NOT Subacute bacterial endocarditis – this causes strokes not abscesses (although 10% get mycotic aneurysms)
Hx: HA, lethargy, ± focal neurologic deficit, ± fever
Dx: Leukocytosis, increased ESR
Contrasted head CT shows ring-enhancing lesion with marked surrounding edema
Etiology:

Parameningeal (sinusitis, otitis) – Streptococcus, Haemophilus, Staphylococcus, gram negative anaerobes
Penetrating injury – Staphylococcus
Hematogenous (pneumonia, endocarditis) – various organisms including Nocardia
Post-surgical – Staphylococcus

Rapid decompensation if rupture into ventricular system occurs
Stages in the development of a brain abscess:

Early cerebritis (days 1-3)

Necrotic center with inflammatory PMNs and marked edema
No gliosis or capsule formation

Late cerebritis (days 4-9)

Necrotic center at maximum with inflammatory PMNs and macrophages, reticulin appears, edema at maximum, gliosis and new vessel formation begin

Early capsule formation (days 10-14)

Necrotic center is decreasing with inflammatory macrophages, collagen appears, edema is decreasing, gliosis is increasing, new vessel formation at maximum

Late capsule formation (>14 days)

Necrotic center continues to decrease with mainly fibroblasts present, collagen is increasing, gliosis at maximum, edema continues to decrease

Treatment: Surgical debridement and abx

Encephalitis – usually due to legionella, mycoplasma, listeria, viral
Subdural empyema – often strep from adjacent infection
Epidural abscess – staph aureus, strep, gram negative, TB; usually associated with osteomyelitis in spine
Osteomyelitis – moth-eaten bone with poor margins; similar radiographic appearance to metastasis

Gradenigo’s syndrome – CN VI palsy and retroorbital pain caused by osteomyelitis

Tuberculosis – 2/3 of patients with CNS tuberculomas have tuberculosis elsewhere (hematogenous spread); mortality 30%; caseating necrosis with giant cells

CSF – increased lymphocytes/protein, decreased glucose (not as low as bacterial meningitis)

Leprosy

Lepromatous – lepra cells (histiocytes filled with organisms); in cold parts of body; leprosin test negative
Tuberculoid – less severe; caseating granulomas; hypesthetic skin; lepromin test positive

Whipple’s disease – trephonema whipilli – foamy macrophages with PAS+ granules (the organisms); weight loss, abdominal pain, diarrhea, lymphadenopathy, arthralgia
Actinomycosis – branching, like fungus, sulfur granules, AFB-
Nocardia – usually in lung, multiple abscesses, weakly AFB+
Syphilis – 25% with CNS symptoms (years after untreated primary infection)

Congenital – notched tooth, deafness, interstitial keratitis (Hutchinson’s triad)
CNS

Meningovascular (lues) – 7 years after infection; subacute meningitis with perivascular lymphocytes, Huebner’s arteritis (intimal proliferation), strokes of basal ganglia and MCA
General paresis of the insane – 15 years after infection; encephalitis, gummas, atrophy, necrosis, Argyll-Robinson pupils
Tabes dorsalis – 20 years after infection; myelopathy with demyelination of thoracic spine, meningeal fibrosis; lightning pains, sensory ataxia, urinary incontinence, decreased tendon reflexes, decreased proprioception and vibration sense, Argyll-Robinson pupils, optic atrophy, charcot joints in hip/knee/ankle

Lyme – May to July, immune complex mediated, associated with skin rash (erethyma migrans); can cause aseptic meningitis with cranial nerve involvement (esp. CN VII), myopathy, radiculopathy, myopathy
Tetanus – inhibits renshaw cells; can be generalized (more common) or local; similar to strinchnine, black widow, Stiffman syndrome; EMG shows loss of silent period after contraction; treat with antitoxin, penicillin, dilantin
Diphtheria – pharyngeal; causes tracheal inflammatory exudate; exotoxin causes ascending paralysis, cardiomyopathy; delayed symmetric sensormotor polyneuropathy with demyelination

Bacterial Toxins

Tetanus

Caused by Claustridium tetani
Bacterial enters through a cut and travels to the CNS via peripheral nerves
Causes presynaptic excitation of agonist and antagonist muscles (especially the massater) by inhibiting the release if inhibitory neurotransmitters (especially from Renshaw cells)
Generalized tetanus has a 50% mortality
EMG shows a loss of the silent period after contractions with a continuous discharge of normal motor unit
Differential includes strychnine poisoning, black widow spider bite, and stiff-man syndrome
Treat with antitoxin, penicillin, and wound debridement

Diptheria

From Corynebacterium diphtheriae
Causes throat and tracheal inflammation with pseudomembrane
Affects the heart and nerves, causing ascending paralysis and cardiomyopathy, early bulbar and ciliary dysfunction, delayed symmetric sensorimotor peripheral polyneuropathy with demyelination
Treat with antitoxin

Botulism

Caused by Clostridium botulinim
Exotoxin causes presynaptic inhibition at the NMJ by decreasing ACh release
Symptoms include blurred vision, unreactive pupils, diplopia, bulbar paralysis, respiratory suspension, descending quadriparesis
EMG shows incremental response (similar to Eaton-Lambert syndrome)
Treat with antiserum, guanidine, and supportive respiratory case
decreased presynaptic acetylcholine like Lambert-Eaton; 2-4 days; descending paralysis; incremental EMG; extraocular muscles affected first; pupils affected

Cholera

Inhibits G-protein