Red neuron

Red neuron refers to a morphological state of a neuron that has undergone certain changes indicative of injury or death. This condition is typically observed in neurons that have been subjected to ischemia (lack of blood supply) or hypoxia (lack of oxygen). The term "red neuron" is derived from the eosinophilic (red-staining) appearance of the neuron's cytoplasm when stained with eosin, a common histological stain. This change is considered one of the earliest signs of neuronal injury and is a critical indicator in neuropathological examinations.

Characteristics

Red neurons exhibit several distinctive morphological changes including:

• Shrinkage of the cell body: The neuron's cell body becomes smaller and more rounded.
• Eosinophilic cytoplasm: The cytoplasm stains more intensely with eosin, giving the neuron a distinct red appearance under a light microscope.
• Pyknosis of the nucleus: The neuron's nucleus becomes dark, condensed, and often eccentrically located due to the clumping of chromatin.
• Loss of Nissl substance: The rough endoplasmic reticulum and ribosomes, collectively known as Nissl substance, disperse or disappear, contributing to the eosinophilic appearance of the cytoplasm.

Pathophysiology

The transformation into a red neuron is a result of the neuron's inability to maintain its normal functions due to the stress of ischemia or hypoxia. This condition leads to a cascade of cellular events including energy failure, calcium influx, activation of destructive enzymes, and ultimately, cell death. The morphological changes associated with red neurons are a manifestation of these underlying pathological processes.

Clinical Significance

The presence of red neurons is a crucial diagnostic feature in forensic pathology and neuropathology, indicating that neuronal injury or death occurred at least 12-24 hours prior to examination. This can help in determining the timing of ischemic events, such as strokes or other forms of brain injury. However, it is important to note that the appearance of red neurons alone does not provide information about the cause of the ischemia or hypoxia.

Related Conditions

Several neurological conditions can lead to the formation of red neurons, including:

• Stroke: Interruption of blood supply to part of the brain.
• Traumatic brain injury (TBI): Physical trauma to the brain.
• Epilepsy: Severe or prolonged seizures can cause hypoxia in brain tissue.
• Cardiac arrest: Can lead to global brain ischemia due to lack of blood flow.

See Also

• Neuron
• Ischemia
• Hypoxia (medical)
• Neuropathology

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