Where is the medulla oblongata located?

Update Date: 2024-06-06 Source: Network

The medulla oblongata is located directly in front of the cerebellum and at the lowermost end of the brainstem. It is shaped like an inverted cone, with its lower boundary connecting to the spinal cord at the level of the occipital foramen. The ventral surface of its upper boundary is separated from the pons by a transverse groove, while the dorsal surface forms the lower half of the rhomboid fossa.

The medulla oblongata resembles the spinal cord in appearance, and its sulci and fissures are extensions of those found in the spinal cord. On the ventral surface, there are two longitudinal ridges on either side of the anterior median fissure, called the pyramids, which are formed by fibers of the corticospinal tract. Below the pyramids, 70-90% of the fibers cross from left to right or vice versa, forming the decussation of the pyramids.

Outside the pyramids, there is a pair of oval-shaped ridges called the olives, separated by the anterolateral sulcus. The hypoglossal nerve exits the brain through this sulcus. Within the longitudinal sulcus outside the olives, the glossopharyngeal nerve, vagus nerve, and accessory nerve exit the brain from top to bottom.

On the dorsal surface, there are a pair of protrusions on either side of the posterior median sulcus called the gracilis nuclei (club-shaped bodies), which are enlarged extensions of the gracilis fasciculus. Deep to these nuclei are the gracilis nuclei themselves. Outside the gracilis nuclei, there is another pair of protrusions called the cuneate nuclei, which are enlarged extensions of the cuneate fasciculus. Deep to these nuclei are the cuneate nuclei.

Above and to the outer side of the cuneate nuclei, there is a pair of inferior cerebellar peduncles or ropes, which are bundles of fibers entering the cerebellum. Because the blood supply to the medulla oblongata is richer than other parts of the brainstem, the incidence of infarction in the medulla oblongata is lower than in the pons or midbrain. Infarction in the medulla oblongata accounts for less than 5% of posterior circulation infarctions.

Medial infarction of the medulla oblongata is often associated with vertebral artery occlusion, while bilateral medial infarction of the medulla oblongata is often caused by occlusion of one vertebral artery combined with vascular variation. The main symptoms and signs include weakness of the limbs, choking and coughing when drinking, difficulty swallowing, and dysphasia, abnormal sensations of depth and superficiality, hemiplegia, dyspnea, and disturbances of consciousness.

Magnetic resonance imaging shows long T1 and T2 signals in the bilateral medial medulla oblongata, and diffusion-weighted imaging reveals a characteristic "heart-shaped" appearance with high signal intensity.