Infections – Diseases



  • Infection within the subarachnoid space
  • Usually caused by spread of an infectious agent via the bloodstream from an infective focus elsewhere in the body
    • In neonates, 50% are from things like E coli and H influenzae
    • In children, 50% are from H influenzae
    • In adults, 30% are from S pneumoniae
  • Clinical manifestations
    • Rapid onset over several days
    • Clinical symptoms include generalized headache, fever, vomiting. Lethargy, stiff neck, and confusion.
    • Malaise and backache are common
    • Treatment is with a high-dose of intravenous antibiotics that cross the blood-brain barrier
    • Neurologic Complications
      • Seizures
      • Focal cerebral signs
      • Acute cerebral edema
      • Dysfunction of cranial nerves 3, 4, 6, & 7 in about 15% of patients
      • Hearing loss
      • Hemiparesis
      • Dysphasia and hemianopsia in 15%

Brain Abscess

  • Causes
    • Infection spread from middle ear or sinus
    • In association with congenital heart disease
    • Spread of infection from a distant site
    • Direct introduction of bacteria following penetrating head injuries
  • Cardinal symptom is a relentless and progressive headache, which is usually followed by focal neurologic manifestations
  • Fever is seen in only two thirds of patients
  • Early diagnosis is possible with CT
  • Lumbar puncture should be avoided to prevent herniation or rupture of the abscess into the ventricular system
  • Treatment with penicillin or the such may be successful such that surgery may not be necessary


  • Paretic neurosyphilis is the late complication of syphilis occurring decades after the original infection (there are other types of neurosyphilis)
  • Clinical presentation resembles meningoencephlitis
  • Early symptoms include fatigue, irritability, personality changes, forgetfulness, and tremor
  • Symptoms at late stage include impaired memory and judgment, confusion, disorientation, seizures, dysarthria, myoclonus, and poor motor control
  • Treatment with penicillin is the antibiotic of choice for all forms of neurosyphilis


  • Infection with the larval form of the porcine tapeworm
  • Humans acquire the adult tapeworm by eating uncooked pork
  • Humans also may accidentally ingest tapeworm eggs, which hatch in the small intestince, burrow into venules, and are carried to distant sites
  • The larvae are relatively large and may lodge in the subarachnoid space, ventricles, or brain tissue
  • Symptoms may not occur until 4-5 years later, when larvae die and provoke an inflammatory response
  • Cysts in the cerebrum may mimic a brain tumor
  • Cysts in the subarachnoid space may result in a chronic meningitis and arachnoiditis
  • Cysts in the ventricular system may cause obstructing hydrocephalus


  • Affects the motor unit of the peripheral nervous system
  • There are three type of bacteria-produced toxins known to affect humans
  • Clinical manifestations
    • Early symptoms include restlessness, localized stiffness and soreness, low-grade fever, and sometimes hemorrhage at the wound site.
    • Initial symptoms of generalized tetanus are nonspecific, including irritability, insomnia, and headache
    • Eventually, tonic contractures appear, secondary to the continuous activity of multiple muscle groups (early symptoms after an incubation period)
      • Nuchal rigidity
      • Lockjaw (trismus)
      • Risus sardonicus – facial expression seen as raised eyebrows and grinning distortion of the face, resulting from spasm of face muscles
      • Dysphagia
    • Treatment is best with immunization starting at newborn, and continuing every 10 years
      • Penicillin or other antibiotics are used to treat active tetnus
    • Recuperative period may be 2-4 months, and mortality is 25-75%

Viral (HIV/AIDS discussed elsewhere)


  • Referred to aseptic memingitis
  • Rarely fatal
  • Typically runs its course
  • Clinical syndrome consists of fever, headache, and other signs of meningeal irritation and a predominantly lymphocytic pleocytosis with normal CSF glucose
  • 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)
  • It’s rare to see confusion, stupor, or coma


  • 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
  • Associated with severe, sharp pain and characteristic rash
  • Occurs more often in immunocompromised patients or the elderly
  • Varicella occurs mostly in the spring, but zoster develops throughout the year
  • Common cranial nerve involvement are 5, 7, & 3
  • Treatment may include analgesics (e.g., acetaminophen, codeine) and antivirals (e.g., famciclovir, oral acyclovir)

Herpes simplex encephalitis

  • It’s the most common sporadic acute viral disease of the brain in the U.S.
  • It affects both sexes and all age groups in every season
  • Mortality is high (70%)
  • Survivors often have significant neuropsychiatric sequelae
  • Most greatly affects the medial temporal and frontal lobes
  • Common to see hemorrhagic necrosis, infammatory infiltrates, and cells containing intranuclear inclusions
  • Most common clinical findings are fever and alteration of consciousness
  • In majority, we see headache, personality changes, speech difficulties, and seizures
  • Mortality can be substantially reduced by early antiviral therapy (e.g., Acyclovir), although cognitive deficits are permanent


  • Acute viral disease of the central nervous system
  • Usually transmitted to humans through a wound contaminated by the saliva of a rabid animal
  • Rare airborne transmission has been noted in bat-infested caves
  • Dog and cat bites account for 90% of human rabies cases
  • The virus travels by nerve routes into the brain where it disseminates widely, then traveling to multiple organs
  • Incubation periods range from 15 days to 1 year
  • The disease begins with a prodrome of anxiety, fever, and headache, often with paresthesias at the bite site
  • 2-10 days later, we see delirium, seizures, nuchal rigidity, paralysis, and excitability
  • Stimulus-sensitive spasms of the pharynx, esophagus, or neck muscles may occur. Survival is not great at this stage
  • Treatment with vaccine, but no known effective treatment once clinical illness develops