Infections Diseases
A.
Bacterial
1. Meningitis
a. Infection within the subarachnoid space
b. Usually caused by spread of an infectious agent via the bloodstream from an infective focus elsewhere in the body
1. In neonates, 50% are from things like E coli and H influenzae
2. In children, 50% are from H influenzae
3. In adults, 30% are from S pneumoniae
c. Clinical manifestations
1. Rapid onset over several days
2. Clinical symptoms include generalized headache, fever, vomiting. Lethargy, stiff neck, and confusion.
3. Malaise and backache are common
d. Treatment is with a high-dose of intravenous antibiotics that cross the blood-brain barrier
e. Neurologic Complications
1. Seizures
2. Focal cerebral signs
3. Acute cerebral edema
4. Dysfunction of cranial nerves 3, 4, 6, & 7 in about 15% of patients
5. Hearing loss
6. Hemiparesis
7. Dysphasia and hemianopsia in 15%
2. Brain Abscess
a. Causes
1. Infection spread from middle ear or sinus
2. In association with congenital heart disease
3. Spread of infection from a distant site
4. Direct introduction of bacteria following penetrating head injuries
b. Cardinal symptom is a relentless and progressive headache, which is usually followed by focal neurologic
manifestations
c. Fever is seen in only two thirds of patients
d. Early diagnosis is possible with CT
e. Lumbar puncture should be avoided to prevent herniation or rupture of the abscess into the ventricular system
f. Treatment with penicillin or the such may be successful such that surgery may not be necessary
3. Neurosyphilis
a. Paretic neurosyphilis is the late complication of syphilis occurring decades after the original infection (there are
other types of neurosyphilis)
b. Clinical presentation resembles meningoencephlitis
c. Early symptoms include fatigue, irritability, personality changes, forgetfulness, and tremor
d. Symptoms at late stage include impaired memory and judgment, confusion, disorientation, seizures, dysarthria,
myoclonus, and poor motor control
e. Treatment with penicillin is the antibiotic of choice for all forms of neurosyphilis
4. Cysticercosis
a. Infection with the larval form of the porcine tapeworm
b. Humans acquire the adult tapeworm by eating uncooked pork
c. Humans also may accidentally ingest tapeworm eggs, which hatch in the small intestince, burrow into venules,
and are carried to distant sites
d. The larvae are relatively large and may lodge in the subarachnoid space, ventricles, or brain tissue
e. Symptoms may not occur until 4-5 years later, when larvae die and provoke an inflammatory response
f. Cysts in the cerebrum may mimic a brain tumor
g. Cysts in the subarachnoid space may result in a chronic meningitis and arachnoiditis
h. Cysts in the ventricular system may cause obstructing hydrocephalus
THE FINE PRINT: Caveat emptor! These study materials have helped many people who have successfully completed the ABCN board
certification process, but there is no guarantee that they will work for you. The notes’ authors, web site host, and everyone else involved in the
creation and distribution of these study notes make no promises as to the complete accuracy of the material, and invite you to suggest changes.
5.
B.
Tetnus
a. Affects the motor unit of the peripheral nervous system
b. There are three type of bacteria-produced toxins known to affect humans
c. Clinical manifestations
1. Early symptoms include restlessness, localized stiffness and soreness, low-grade fever, and sometimes
hemorrhage at the wound site.
2. Initial symptoms of generalized tetanus are nonspecific, including irritability, insomnia, and headache
3. Eventually, tonic contractures appear, secondary to the continuous activity of multiple muscle groups (early
symptoms after an incubation period)
a. Nuchal rigidity
b. Lockjaw (trismus)
c. Risus sardonicus – facial expression seen as raised eyebrows and grinning distortion of the face,
resulting from spasm of face muscles
d. Dysphagia
4. Treatment is best with immunization starting at newborn, and continuing every 10 years
a. Penicillin or other antibiotics are used to treat active tetnus
5. Recuperative period may be 2-4 months, and mortaility is 25-75%
Viral (HIV/AIDS discussed elsewhere)
1. Meningitis
a. Referred to aseptic memingitis
b. Rarely fatal
c. Typically runs its course
d. Clinical syndrome consists of fever, headache, and other signs of meningeal irritation and a predominantly
lymphocytic pleocytosis with normal CSF glucose
e. Other symptoms may include lethargy, irritability, and drowsiness. Also may see photophobia, pain with eye
movements, or stiffness of the neck and spine on forward bending (meningeal irritation)
f. It’s rare to see confusion, stupor, or coma
2. Varicella-Zoster
a. Varicella-Zoster is an exclusively human herpesvirus that cause chickenpox (varicella), becomes latent in cranial
nerve and dorsal-root ganglia, and frequently reactivates decades later to produce shingles (zoster) and
postherpetic neuralgia
b. Associated with severe, sharp pain and characteristic rash
c. Occurs more often in immunocompromised patients or the elderly
d. Varicella occurs mostly in the spring, but zoster develops throughout the year
e. Common cranial nerve involvement are 5, 7, & 3
f. Treatment may include analgesics (e.g., acetaminophen, codeine) and antivirals (e.g., famciclovir, oral acyclovir)
3. Herpes simplex encephalitis
a. It’s the most common sporadic acute viral disease of the brain in the U.S.
b. It affects both sexes and all age groups in every season
c. Mortality is high (70%)
d. Survivors often have significant neuropsychiatric sequelae
e. Most greatly affects the medial temporal and frontal lobes
f. Common to see hemorrhagic necrosis, infammatory infiltrates, and cells containing intranuclear inclusions
g. Most common clinical findings are fever and alteration of consciousness
h. In majority, we see headache, personality changes, speech difficulties, and seizures
i. Mortality can be substantially reduced by early antiviral therapy (e.g., Acyclovir), although cognitive deficits are
permanent
4. Rabies
a. Acute viral disease of the central nervous system
b. Usually transmitted to humans through a wound contaminated by the saliva of a rabid animal
c. Rare airborne transmission has been noted in bat-infested caves
d. Dog and cat bites account for 90% of human rabies cases
e. The virus travels by nerve routes into the brain where it disseminates widely, then traveling to multiple organs
f. Incubation periods range from 15 days to 1 year
g. The disease begins with a prodrome of anxiety, fever, and headache, often with paresthesias at the bite site
h. 2-10 days later, we see delirium, seizures, nuchal rigidity, paralysis, and excitability
i. Stimulus-sensitive spasms of the pharynx, esophagus, or neck muscles may occur. Survival is not great at this
stage
j. Treatment with vaccine, but no known effective treatment once clinical illness develops
THE FINE PRINT: Caveat emptor! These study materials have helped many people who have successfully completed the ABCN board
certification process, but there is no guarantee that they will work for you. The notes’ authors, web site host, and everyone else involved in the
creation and distribution of these study notes make no promises as to the complete accuracy of the material, and invite you to suggest changes.