The prime examples of incurable infections of the nervous system that lead to major morbidity and death are rabies, Creutzfeldt–Jakob disease (CJD) and human immunodeficiency virus (HIV). Other chronic and persistent viral infections of the central nervous system (CNS) that commonly lead to progressive deterioration and death include progressive multifocal leukoencephalopathy (PML) and subacute sclerosing panencephalitis. In these conditions, progressive cognitive impairment, seizures, myoclonus, ataxia and visual loss commonly proceed to a persistent vegetative state.

RABIES

Rabies is a uniformly fatal disease once clinical symptoms are manifest. The few who survive have received either pre-exposure prophylaxis or expeditious post-exposure prophylaxis after the rabid contact and before developing frank clinical disease. Therefore, there is a need to suspect the possibility of rabies early, and vaccinate promptly.

Rabies presents as either encephalitis or paralysis. Encephalitic or ‘furious’ rabies (most cases) has symptoms of hydrophobia, pharyngeal spasms and hyperactivity leading to paralysis, coma and death. The paralytic form, ‘dumb rabies’, is much less common.

Rabies progresses through five clinical stages with much variability, depending on extent of bites, amount of secretion encountered and proximity to the CNS; that is, disease transmitted through bites close to the brain will progress faster than disease transmitted through bites on the lower extremities.

The incubation period following the bite of an infected creature (dog, bat, etc.) ranges from 10 days to 1 year, with an average of 1–2 months.