Creutzfeldt-Jakob Disease

Excerpt

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive, rare, transmissible, and uniformly fatal neurodegenerative condition caused by prion proteins. This condition has a long incubation period. CJD was first described in 1920 by Hans Creutzfeldt and later in 1921 and 1923 by Alfons Jakob. Later, Clearance J. Gibbs began using the term "Creutzfeldt-Jakob disease" because the acronym "CJD" was similar to his initials.

CJD primarily affects the central nervous system (CNS). The primary functional unit of the CNS is the neuron, a unique cell type that can receive, store, and transmit information. CNS neurons do not regenerate, although some regions of the brain can heal to a limited extent due to the presence of stem cells. Attributes that make the CNS unique from other organ systems include the following:

1. Cerebral blood flow autoregulation

2. Having the cranium for bony protection

3. Unique metabolic substrate requirements

4. Absence of a true lymphatic system

5. Cerebrospinal fluid (CSF) circulation

6. Minimal immunologic surveillance

7. Distinct injury response and tissue repair mechanisms

Neurons in the brain are topographically organized, with functional domains existing in anatomically defined regions. For example, the cerebral cortex controls voluntary movements, while the hypothalamus plays a significant role in autonomic responses. The somatotopic organization of brain cells enables various areas of the body to receive sensory and motor input from the CNS, which is beneficial in localizing neurological lesions.

Neurons differ in structure and size. Synapses are formed by axons and dendrites that greatly differ in number from cell to cell. Nissl bodies, which also vary in number, play a crucial role in the synthesis of nerve cell proteins and neurotransmitters. Neurofilaments maintain the cytoskeleton and play an essential role in nerve conduction.

Glia are cells that support the neurons. They include the following:

1. Astrocytes are star-shaped glial cells that supply nutrients to the neurons, act as nerve detoxifiers, provide protection from harmful macromolecules, and contribute to CNS repair and scar formation.

2. Oligodendrocytes myelinate the CNS axons.

3. Ependymal cells line the ventricles and control CSF production and flow.

4. Microglia comprise the macrophage system of the CNS.

CJD neuronal inclusions damage brain neurons, manifesting with nonspecific prodromal symptoms early in the disease course and neurologic changes, such as myoclonus, in the later, advanced stages.