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Medulla oblongata

The medulla oblongata is a crucial structure in the brainstem, connecting the pons above to the spinal cord below. It controls vital autonomic functions such as respiration, heart rate, and blood pressure, and acts as a major conduit for nerve tracts between the brain and spinal cord. The medulla also houses essential cranial nerve nuclei and regulates several reflexes fundamental for life. Understanding its anatomy, blood supply, drainage, and imaging characteristics is vital for clinical and radiological practice.

Synonyms

  • Bulb

  • Medulla

  • Myelencephalon (embryologic term)

  • Lower brainstem

Arterial Supply

  • Anterior spinal artery: Supplies the medial medulla.

  • Posterior inferior cerebellar artery (PICA): Supplies the lateral medulla.

  • Vertebral arteries: Supply ventrolateral and paramedian regions.

  • Direct branches of vertebral arteries also contribute.

Venous Drainage

  • Primarily via the anterior and posterior spinal veins.

  • Drainage continues into the vertebral venous plexus.

  • Additional drainage through inferior petrosal sinus and adjacent dural venous sinuses.

Functions

  • Regulation of cardiovascular and respiratory systems (cardiac, vasomotor, respiratory centers)

  • Control of reflexes such as swallowing, coughing, sneezing, vomiting, and gag reflex

  • Relay for ascending sensory and descending motor tracts between the brain and spinal cord

  • Contains nuclei for cranial nerves IX, X, XI, XII (glossopharyngeal, vagus, accessory, hypoglossal)

  • Plays a role in balance and coordination (vestibular nuclei)

  • Regulates autonomic functions critical for survival

MRI Appearance

  • T1-weighted:

    • Medulla appears as a structure of intermediate (isointense to slightly hypointense) signal compared to surrounding brainstem.

    • Gray and white matter differentiation is poor in normal scans.

  • T2-weighted:

    • Medulla shows intermediate to slightly hyperintense signal.

    • Cerebrospinal fluid (CSF) around the medulla is hyperintense, aiding anatomical delineation.

  • FLAIR:

    • Medulla is isointense to slightly hypointense relative to brain parenchyma.

    • Abnormal signals (from pathology) are more conspicuous due to CSF suppression.

CT Appearance

  • Medulla oblongata is iso- to slightly hypoattenuating relative to adjacent brainstem structures.

  • Normal gray-white differentiation is not readily visualized.

MRI images

Medulla oblongata mri 3t axial image