Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder that profoundly damages the brain by causing rapid and severe neurodegeneration. It belongs to a group of diseases called transmissible spongiform encephalopathies, which are characterized by the brain tissue developing a sponge-like appearance due to widespread neuronal loss and the formation of microscopic holes.
At the core of how CJD affects the brain is an abnormal protein called a prion. Normally, prions are harmless proteins found in the brain, but in CJD, these proteins misfold into a harmful shape. These misfolded prions then induce other normal prion proteins to also misfold, creating a chain reaction. This accumulation of abnormal prions disrupts the normal function of brain cells, leading to their death and the breakdown of brain tissue.
The damage caused by prions is widespread but particularly affects areas responsible for cognition, movement, and sensory processing. Early in the disease, people may experience subtle psychiatric symptoms such as depression, anxiety, or behavioral changes. As the disease progresses, the brain’s ability to process thoughts, memories, and language deteriorates rapidly, leading to severe dementia. This cognitive decline is accompanied by motor symptoms including involuntary jerking movements (myoclonus), problems with coordination and balance (ataxia), muscle stiffness or rigidity, and difficulties with speech and swallowing.
On a microscopic level, the brain tissue in CJD shows a characteristic spongy degeneration. This means that neurons (brain cells) die off, leaving behind tiny holes that give the brain a porous, sponge-like texture. Alongside this, there is often an abnormal buildup of prion proteins forming clumps, which further disrupts normal brain function. The loss of neurons and the damage to the brain’s structure cause the brain to shrink and lose its normal architecture.
Different forms of CJD affect the brain in slightly different ways but share this core pattern of rapid neurodegeneration. Sporadic CJD, the most common form, typically presents with rapidly progressive dementia and neurological decline that leads to death within about a year. Variant CJD, linked to exposure to prions from infected beef (mad cow disease), often begins with psychiatric symptoms and sensory disturbances before progressing to more classic neurological signs. Familial forms, caused by inherited mutations, also lead to similar brain damage but may have a slower progression.
As the disease advances, the brain’s control over basic functions deteriorates. Patients may become mute and immobile, entering a state called akinetic mutism, where they are awake but unable to move or communicate. Eventually, the extensive brain damage leads to coma and death.
In summary, Creutzfeldt-Jakob disease affects the brain by introducing misfolded prion proteins that propagate and accumulate, causing widespread neuronal death, spongy degeneration of brain tissue, and severe disruption of cognitive and motor functions. This relentless destruction of brain cells leads to rapid mental decline, movement disorders, and ultimately, fatal brain failure.
