What is the crossing of spinal cord tracts from one side body to other in brainstem.?

The crossing of spinal cord tracts from one side of the body to the other in the brainstem is known as decussation. Decussation occurs at specific levels of the brainstem and involves various sensory and motor tracts that transmit information between the brain and the spinal cord.

Examples of Decussations in the Brainstem:

1. Motor Decussations:

- Pyramidal Decussation (Motor Decussation): The pyramidal tracts, responsible for voluntary motor control, undergo partial decussation in the medulla oblongata. The majority of fibers (about 80%-90%) cross to the opposite side, forming the lateral corticospinal tract, while the remaining fibers continue on the same side as the corticospinal tract.

2. Sensory Decussations:

- Sensory (Lemniscal) Decussation: In the medulla oblongata, sensory pathways involved in touch, conscious proprioception (awareness of body position), and two-point discrimination cross to the opposite side. This includes the medial lemniscus, which transmits sensory information from the body to the thalamus and cerebral cortex.

- Spinothalamic Decussation: The spinothalamic tracts, which carry signals related to pain, temperature, and crude touch, undergo decussation in the spinal cord at various levels. The majority of fibers cross to the opposite side within a few segments of their entry into the spinal cord.

3. Visual (Optic) Decussation:

- Optic Chiasm: The optic nerves from both eyes partially cross at the optic chiasm, located at the base of the brain. The nasal fibers (from the inner half of each retina) decussate to the opposite side, while the temporal fibers (from the outer half) remain on the same side. This arrangement allows for binocular vision and the merging of visual fields from both eyes in the brain's visual cortex.

4. Vestibular Decussation:

- Medial Longitudinal Fasciculus Decussation: This decussation involves the medial longitudinal fasciculus, a brainstem pathway that coordinates eye movements, head position, and balance. It exchanges fibers between the left and right sides of the brainstem to control coordinated head and eye movements.

These are some of the key examples of decussations in the brainstem, where spinal cord tracts and other neural pathways cross from one side of the body to the other, ensuring proper communication and coordination between the left and right sides of the body and brain.