Outer ear infection

Disease Description (Causes and Symptoms)

• Definition and pathophysiology: An inflammatory disease of the brain parenchyma, classified according to cause as primary (directly caused by an acute viral infection) or secondary (spreading to the brain after an infection in another area or an immune response). Inflammation may remain localized to one area or may progress diffusely.
• Main causes
  • Viruses: Herpes simplex virus (HSV‑1), arboviruses (mosquito-borne, including Japanese encephalitis), varicella-zoster virus (VZV), Epstein–Barr virus (EBV), cytomegalovirus (CMV), enteroviruses, etc.
  • Bacterial causes (mainly in the form of meningitis or secondary infection): Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, etc. Neonates: Escherichia coli, group B Streptococcus, etc. Older adults and immunocompromised individuals: Listeria, etc.
  • Other causes: Mycobacterium tuberculosis, fungi, HIV, autoimmune causes (e.g., NMDA receptor antibody encephalitis), mechanical factors (after head trauma or surgery), parasites, etc.
  • Secondary encephalitis may often appear 2–3 weeks after the onset of the primary infection.
• Main symptoms
  • Fever, headache, chills, vomiting
  • Altered mental status (stupor, drowsiness, confusion, decreased consciousness)
  • Seizures, focal neurological deficits (motor weakness, speech disturbance, changes in vision or hearing)
  • Neck stiffness, photophobia
  • Children (infants): bulging fontanelle, decreased feeding, tremors, etc.
  • The severity of symptoms varies depending on the cause and lesion location; some may be mild or temporary

Treatment Methods

• General principles
  • Hospitalization and prompt diagnostic testing (brain MRI, cerebrospinal fluid testing, etc.) are required immediately when encephalitis is suspected, with empiric treatment started when the cause is unknown.
  • When intensive care is required (e.g., decreased consciousness, recurrent seizures, respiratory failure), active life-support treatment (airway maintenance and mechanical ventilation) is provided.
• Drug treatment
  • When HSV is suspected: Start empiric intravenous acyclovir immediately (adults: 10 mg/kg IV q8h; dose adjustment according to renal function is required). Do not discontinue until HSV has been ruled out.
  • When a bacterial cause is suspected: Administer empiric antibiotics (selection depends on age, region, and risk factors). In older adults and immunocompromised individuals, add ampicillin to cover Listeria.
  • Anticonvulsants: Start promptly to control seizures (levetiracetam, phenytoin, etc.). EEG is required to assess for nonconvulsive status epilepticus.
  • Immune-mediated encephalitis: Immunosuppressive and immunomodulatory treatment with high-dose steroids, IVIG, plasma exchange, and, when necessary, rituximab, etc.
  • Treatment according to specific etiology: Tuberculous, fungal, and parasitic causes are treated with appropriate antituberculous, antifungal, and antiparasitic agents.
• Surgery/procedures
  • If a brain abscess is present, drainage or surgical treatment may be considered.
  • Decompressive surgery may be considered in cases of severe cerebral edema or increased intracranial pressure.
• Supportive treatment and interventions
  • Fluid and electrolyte correction, antipyretics and analgesics, and pulmonary and hemodynamic support
  • Intracranial pressure management: elevating the head, sedation, and use of hypertonic solutions (hypertonic saline, mannitol)
  • Early referral for rehabilitation (motor, speech, and cognitive therapy) when necessary
• Lifestyle management and precautions
  • Rest, sleep, nutrition, and fluid replacement are recommended
  • If there is a history of seizures, driving and operating machinery are prohibited (follow the doctor's instructions)
  • Renal function, liver function, and medication adverse effects must be monitored during treatment

Checklist Before an Outpatient Visit (Including Preparation Items and Example Questions)

• Items to prepare (for an outpatient or emergency visit)
  • A list of all medications and supplements currently being taken (including doses and administration times)
  • Past medical and surgical history, and whether the person is immunocompromised (use of immunosuppressants, HIV, etc.)
  • The time of recent onset and pattern of symptom progression (timeline or notes)
  • Copies or summaries of recent test results (blood tests, chest imaging, brain MRI/CT, and CSF test results)
  • Videos of seizures, if available, and records of seizure duration and frequency
  • Vaccination history (varicella, MMR, Japanese encephalitis, etc.)
• Information to record for oneself before the outpatient visit
  • A diary of changes in body temperature and major symptoms (headache severity, changes in consciousness, vomiting, and whether seizures occurred)
  • Adverse effects or changes in symptoms after taking medications
• Example questions before the outpatient visit (items for the patient to ask)
  • If sudden changes in consciousness or seizures occur, should I go to the emergency room immediately?
  • What points should be monitored for adverse effects of my current medications (e.g., anticonvulsants and antivirals)?

General Example Questions to Ask the Doctor

• What are the possible causes of this disease, and what additional tests are needed?
• How will the adverse effects and monitoring of the currently prescribed medication (or planned treatment) be managed?
• I had a seizure. How long should I take anticonvulsants?
• When can I resume daily activities (driving, returning to work, exercising, etc.)?
• What is the prognosis (likelihood of recovery and risk of sequelae)?

Disease-Specific Example Questions

• How many days does it usually take to receive the results of a CSF PCR test (e.g., HSV‑1/2 PCR)? How long will treatment be continued depending on the results?
• If autoimmune encephalitis (e.g., NMDA antibody encephalitis) is suspected, when should immunotherapy (steroids, IVIG, plasma exchange, etc.) be started? How likely is it that additional immunosuppressants will be needed?

Additional Emergency Guidance

• When an immediate emergency room visit is needed: Visit immediately if acute stupor or decreased consciousness with a high fever, recurrent or prolonged seizures (seizure lasting >5 minutes), difficulty breathing, or acute neurological deficits (hemiplegia, speech disturbance, etc.) occur.

Prevention Summary

• If possible, keep relevant vaccinations up to date (Japanese encephalitis when living in an endemic area, varicella, MMR, etc.) and follow infection-prevention practices such as avoiding mosquitoes and insects and washing hands.
• Immunocompromised individuals should consult healthcare professionals to consider additional preventive measures (prophylactic antibiotics, vaccine timing, etc.).

Caution: This material is intended to provide general information. If you have symptoms or suspect this condition, seek medical attention from a healthcare professional immediately.