What is the primary characteristic of encephalitis?

The primary characteristic of encephalitis is the infection of the brain parenchyma. Encephalitis refers specifically to the inflammation of the brain tissue itself, often caused by viral infections, but can also arise from bacterial infections, autoimmune processes, or other factors. This leads to a direct impact on brain function, as the inflammation can disrupt neural activities, prompting symptoms such as seizures, confusion, fever, and neurological deficits.

Understanding this definition helps clarify why the other options do not represent the core feature of encephalitis. While swelling of the spinal cord pertains to myelitis, acute kidney injury is related to renal function and is not associated with brain inflammation, and inflammation of the meninges describes meningitis rather than encephalitis. Thus, the defining aspect of encephalitis is indeed the infection and inflammation occurring within the brain parenchyma.