Central Nervous System Viral Diseases

The nervous system has multiple intrinsic defenses against viral infection, including the blood-brain barrier. Yet, the postmitotic nature of neurons creates a uniquely vulnerable environment susceptible to irreversible damage. Various viruses can infect the different cell types within the central nervous system, neurons, oligodendrocytes, astrocytes, and microglia. Infections can cause acute and chronic infections. While there are a large number of well-defined viral-mediated diseases of the nervous system, there are an equal number of diseases that may have an as of yet unproven viral etiology. Damage to the cells can happen via cytopathic and nonlytic mechanisms. Clearance of viruses can occur via cell-mediated and antibody-mediated processes. In some cases, viruses are never cleared from the nervous system completely, and can episodically reactivate. Understanding the potential pathways and outcomes of viral infections is necessary for determining the possible role viruses may play in a variety of diseases.