An intracranial infection means germs have reached the brain or its coverings. The immune system sounds an urgent alarm, and symptoms climb quickly.

Fever is usually first. Temperature spikes to 38–40 °C (100–104 °F) and can swing from chills to sweats within an hour.

Headache follows fast. It feels like steady pressure or a band tightening around the skull and grows worse when you move your head or bend forward.

Neck stiffness appears early. Tilting the chin toward the chest feels like a pulled muscle, and bright light may make the pain spike.

Nausea and vomiting hit without stomach upset. The urge comes on quickly and may repeat, often bringing short-lived relief.

Thinking clouds over. You pause mid-sentence, forget where you are, or answer questions slowly. Family often notice the fog first.

Seizures can appear even in adults with no prior history. A blank stare, jerking limb, or full blackout are common forms.

Some people hear an inside “whoosh” matching their pulse. Raising the head on two pillows may quiet the noise.

If pressure rises, vision blurs at the edges or doubles for seconds. Closing one eye does not clear it.