OVERVIEW

What is intracranial infection?

Intracranial infection, also known as central nervous system infectious disease, is one of the most common neurological disorders. It is caused by pathogenic microorganisms invading the parenchyma, meninges, or blood vessels of the central nervous system.

What causes intracranial infection?

It occurs when pathogenic microorganisms invade the parenchyma, meninges, or blood vessels of the central nervous system. These pathogens include viruses, bacteria, fungi, spirochetes, parasites, rickettsiae, and prions.

What are the causes of intracranial infection?

Central nervous system infectious diseases have multiple etiologies.

What are the consequences of intracranial infection?

Early clinical manifestations vary, but severe cases can lead to death or leave serious sequelae.

Can intracranial infection be cured?

However, with early and aggressive treatment, most cases can be cured.

Is intracranial infection common?

In recent years, the incidence of intracranial infections has increased due to the rising prevalence of neurosyphilis, AIDS, prion diseases, etc.

Which type of intracranial infection is most common?

Among various intracranial infections, viral encephalitis is a relatively common type, with herpes simplex virus encephalitis being the most frequent.

What are the types of intracranial infection?

• Clinically, central nervous system infectious diseases are classified into three major categories based on the anatomical site of infection:

• Encephalitis, myelitis, or encephalomyelitis: primarily affecting the brain and/or spinal cord parenchyma;

• Meningitis, spinal meningitis, or meningomyelitis: primarily affecting the meninges of the brain and/or spinal cord;

• Meningoencephalitis: involving both the brain parenchyma and meninges.

• Based on etiology, they can be divided into five types: viral infections, bacterial infections, fungal infections, prion diseases, and parasitic infections.

SYMPTOMS

What are the common manifestations of intracranial infections?

The clinical manifestations vary depending on the affected site:

• Meningitis:

  • Fever, neck stiffness, and altered mental status are classic symptoms of meningitis, though they do not always occur simultaneously. Other associated symptoms may include nausea, vomiting, cranial nerve abnormalities, rash, and seizures.

  • Infants may exhibit nonspecific symptoms like lethargy or irritability, while adults often experience headaches, nausea, vomiting, and neck pain.

• Encephalitis:

  • Encephalitis should be considered if there is evidence of focal neurological deficits or seizures involving brain parenchyma.

  • The clinical presentation correlates with the function of the affected brain region. For example, temporal lobe involvement may lead to personality changes, psychiatric symptoms, or olfactory/gustatory hallucinations, potentially misdiagnosed as mental disorders.

  • Certain viruses, such as West Nile virus and Eastern equine encephalitis virus, preferentially target the basal ganglia and thalamus, leading to tremors or movement disorders.

  • Many bacteria and viruses, including *Bartonella henselae*, *Mycobacterium tuberculosis*, EV71, flaviviruses (e.g., West Nile virus, Japanese encephalitis virus), and alphaviruses (e.g., Eastern equine encephalitis virus), can cause brainstem encephalitis, manifesting as autonomic dysfunction, cranial nerve involvement, or respiratory drive impairment.

• Brain abscess:

  • The classic "triad" of headache, fever, and focal neurological deficits occurs in only 20% of patients with brain abscesses.

  • Neurological symptoms may be mild or absent, developing over days to weeks, and include hemiparesis, cranial nerve palsies, gait disturbances, or signs of increased intracranial pressure (e.g., nausea, vomiting, papilledema, altered mental status).

  • Up to 25% of patients may experience focal or generalized seizures.

  • Frontal lobe abscesses may present with headaches and behavioral changes, while occipital/cerebellar abscesses or those with meningeal/ventricular rupture can cause neck stiffness.

• In many cases, isolated headache may be the sole initial symptom of a brain abscess, especially in early stages.

How does intracranial infection progress?

The progression includes acute, subacute, and chronic infections, with the course varying based on the causative pathogen and affected site.

What are the potential risks of intracranial infections?

Untreated intracranial infections may lead to complications such as intellectual disability, epilepsy, paralysis, dementia, or hydrocephalus.

CAUSES

What are the pathways of intracranial infection?

The main routes of central nervous system infection include the following three:

• Hematogenous spread: Pathogens enter the bloodstream through insect bites, animal bites damaging the skin/mucosa, or directly via contaminated syringes, blood transfusions, etc. Facial infections may also allow pathogens to travel retrogradely through veins into the skull. Infected pregnant women can transmit pathogens to the fetus through the placenta.

• Direct infection: Pathogens spread intracranially through penetrating trauma or adjacent infected structures.

• Retrograde neuronal infection: Neurotropic viruses (e.g., herpes simplex virus, rabies virus) first infect the skin, respiratory tract, or gastrointestinal mucosa, then enter nerve endings, travel along nerve fibers, and finally spread retrogradely into the skull.

Is intracranial infection hereditary?

No.

DIAGNOSIS

How is intracranial infection diagnosed?

When diagnosing intracranial infection, doctors primarily rely on the patient's medical history, clinical manifestations, and laboratory tests. Among these, cerebrospinal fluid analysis and etiological examinations are crucial for a definitive diagnosis.

What tests are needed for intracranial infection?

• Routine laboratory tests (e.g., complete blood count, erythrocyte sedimentation rate, liver and kidney function tests): Assess the patient's general condition and evaluate medication safety.

• Cerebrospinal fluid examination: Measure cerebrospinal fluid pressure, observe its appearance, and collect samples for testing.

• Etiological tests: Cerebrospinal fluid culture, staining microscopy, etc., for diagnosis and differential diagnosis.

• Serological tests: Assist in diagnosis.

• Cranial CT and MRI: Help observe the size and location of lesions.

• Electroencephalogram (EEG): Certain central nervous system infections may show characteristic EEG changes.

• Brain biopsy: Performed for diagnosis and differential diagnosis.

What precautions should intracranial infection patients take before and after lumbar puncture?

Before lumbar puncture, the patient should empty their bladder and lie on their side on a firm bed with their back perpendicular to the bed surface. The head should be bent forward toward the chest, and the knees should be hugged tightly to the abdomen, arching the torso to widen the intervertebral spaces. During the procedure, the patient should cooperate with the doctor, avoid moving, and stay relaxed. After the puncture, the patient should lie flat (or prone if possible) without a pillow for 4–6 hours to prevent post-puncture low intracranial pressure headaches.

Is lumbar puncture mandatory for intracranial infection patients?

Local anesthesia is administered before lumbar puncture, so the patient will not experience significant pain—only mild soreness or numbness when the nerve is stimulated, which is normal. This is a routine clinical procedure and relatively safe. To identify the pathogen and provide targeted treatment, lumbar puncture is essential unless there are clear contraindications.

Which diseases are easily confused with intracranial infection?

Intracranial infection is a broad category of diseases that must be differentiated not only from intracranial space-occupying lesions and epilepsy but also among themselves. Doctors rely on cranial imaging, cerebrospinal fluid analysis, and etiological tests for accurate distinction.

TREATMENT

Which department should I visit for intracranial infection?

Neurology, emergency department, or infectious diseases department.

Can intracranial infection heal on its own?

A few intracranial infections are self-limiting, but most require hospitalization and standardized treatment.

How is intracranial infection treated?

Treatment for intracranial infection includes the following aspects:

• Pathogen-targeted medication: Depending on the causative pathogen, antiviral drugs, antibiotics, or antifungal drugs are used. Close monitoring of blood tests, liver/kidney function, and biochemical indicators is necessary.

• Corticosteroids: To control inflammation and reduce edema.

• Symptomatic treatment: Fever reduction, antiepileptic therapy, sedation, dehydration to lower intracranial pressure, etc.; maintaining airway patency and fluid/electrolyte balance; acupuncture and rehabilitation therapy during recovery.

• Surgical treatment: If imaging shows hydrocephalus, the patient exhibits delayed responses or coma, and dehydration therapy is ineffective, a ventriculoperitoneal shunt should be performed.

Does intracranial infection require hospitalization?

Most cases require hospitalization.

Can intracranial infection be cured completely?

Central nervous system infections have diverse causes and varying early clinical manifestations. Severe cases may lead to death or significant sequelae, but most cases can be cured with early and aggressive treatment.

DIET & LIFESTYLE

What should patients with intracranial infection pay attention to in their diet?

Provide a high-calorie, high-protein, and high-vitamin diet. Depending on the condition, nasogastric feeding or enteral nutritional support may be given.

What should patients with intracranial infection pay attention to in daily life?

Maintain a regular schedule, avoid fatigue, and quit smoking and alcohol. Strengthen physical exercise to improve overall health. If symptoms such as headache or fever occur, seek timely diagnosis and treatment at a qualified hospital.

Is follow-up examination necessary for intracranial infection?

Yes, regular hematological, cranial imaging, and cerebrospinal fluid tests should be performed as directed by the doctor.

PREVENTION

How to prevent recurrence of intracranial infection?

Follow medical advice for regular check-ups, eliminate the cause, and improve your immunity.

How can patients with intracranial infection prevent more serious consequences?

Early detection, early diagnosis, early treatment, and regular check-ups.