Viral encephalitides include acute viral encephalitis, post-infectious encephalomyelitis, viral infections of the central nervous system (CNS), and chronic degenerative diseases. This chapter presents the diagnostic and clinical challenges that accompany the management of seizures following CNS infection by the herpes viruses, RNA viruses, enteroviruses, and arenaviruses. Fever, headache, lethargy, nausea, and non-specific flu-like symptoms are often the first clinical signs of infection, with subsequent symptoms of leptomeningeal irritation becoming prominent. Specific viruses can now be detected in the cerebrospinal fluid (CSF) using polymerase chain reaction (PCR) where previously specific viral diagnoses could only be made by brain biopsy. Patients should therefore be treated with acyclovir if the clinical suspicion is high pending final herpes simplex virus (HSV)-1 PCR results, and repeat CSF testing should be considered. Wider applications of PCR may help to determine individual risks for some of the more common viral agents.

Rheumatoid arthritis (RA) is an autoimmune disease that is characterized by an inflammatory, symmetric polyarthritis. The mechanisms by which RA patients are predisposed to stroke are varied. The most common of these causes is atherosclerotic disease, which seems to be accelerated by the underlying RA. The role of systemic inflammation in mediating atherosclerotic disease is becoming clear and may be the underlying link between RA and vascular events. Systemic vasculitis in RA involves the vasa nervorum of the peripheral nervous system. Meningeal and brain biopsy remains the gold standard in confirming a diagnosis of vasculitis in RA patients. Although there is a theoretical risk of mechanical injury to the vertebral artery due to cervical arthritis and atlantoaxial subluxation in RA, this most often results in cervical myelopathy. Stroke due to vertebral dissection has been reported in RA, but the vertebral artery occlusion was sometimes associated with only minimal atlantoaxial subluxation.

This chapter deals with isolated angiitis of the central nervous system (CNS), and begins with an overview of the pathology and pathogenesis of the condition. The nonspecific pathological pattern of isolated CNS angiitis is characterized by infiltrations of the vascular walls with mononuclear cells including lymphocytes, macrophages, and histiocytes. The pathogenesis of isolated CNS angiitis is unknown and progress is slow because of the rarity of tissue samples acquired from carefully documented cases. Brain imaging, angiography, and brain biopsy are the diagnostic options investigated in the chapter. In patients with a unique focal presentation such as stroke, and with isolated CNS angiitis suspected on the basis of angiography alone, a course of several-weeks of high-dose corticosteroids associated with a calcium channel blocker and no immunosuppressor can be proposed. The diagnosis of reversible cerebral angiopathy should be carefully considered in these patients.