Brainstem

This photo gallery presents the anatomy of brainstem by means of MRI (T1-weighted sagittal, axial and coronal views).

Brainstem = Midbrain + Pons + Medulla

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The Brainstem

The brainstem refers to the middle part of the brain(1). It consists of the medulla, pons, and midbrain.

The brainstem helps relay sensory information, such as pain, eye and mouth movement, involuntary muscle movements, consciousness, respirations, hunger, and cardiac function(2).

These functions are possible because of the brainstem’s unique anatomy(3). The brainstem houses cranial nerve nuclei and serves as a passageway for several essential neural pathways.

Moreover, the brainstem contains several crucial collections of white and grey matter(4). The grey matter within the brainstem contains nerve cell bodies and develops different vital brainstem nuclei.

Meanwhile, the white matter tracts of the brainstem include axons of nerves traversing their course to various structures(5). These axons come from cell bodies lying in the central nervous system. Some of these white matter tract cell bodies occupy the brainstem.

Equipped with a thorough knowledge of brainstem anatomy, clinicians can localize lesions of the brainstem.

Medulla

The medulla oblongata or medulla refers to the lowest part of the brainstem(6). It is usually divided into two parts(7).

The open or superior part is where the fourth ventricle forms the medulla’s dorsal surface. Meanwhile, the closed or inferior part is where the fourth ventricle’s metacoel or caudal part lies within the medulla.

The medulla is the most critical part of the brain(8). It contains the cardiac, respiratory, vomiting, and vasomotor centers(9). Moreover, it regulates autonomic, involuntary functions, including breathing, heart rate, and blood pressure.

Research showed that the cardiovascular and respiratory systems unite as one regulating system within a specific part of the medulla(10).

Pons

Pons refers to the deep part of the brain located in the brainstem(11). In particular, it lies between the medulla oblongata and the midbrain.

Pons consists of nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that manage sleep, respiration, bladder control, taste, hearing, eye movement, facial expressions, and posture(12).

Midbrain

The shortest segment of the brainstem is the midbrain(13). It contains several structures vital in maintaining various body functions.

For instance, the midbrain has the relay nuclei, responsible for processing auditory and visual information(14). Moreover, this part of the brainstem houses the nuclei of cranial nerves that control eye movement and facial sensation.

Brainstem Stroke

Brainstem stroke may be hard to diagnose and can have complex symptoms(15). Individuals with brainstem stroke may experience dizziness and vertigo without the hallmark of most strokes—the weakness on one side of the body.

For brainstem stroke resulting from a clot, the faster blood flow can be restored, the higher the chances for recovery.

More severe brainstem strokes can lead to a locked-in syndrome in which survivors can move their eyes only(16).

Brainstem stroke has similar risk factors to strokes in other areas of the brain. These include diabetes, high blood pressure, heart disease, and smoking.

Assessing Brainstem Stroke

Initial assessment of patients presenting with a suspected brainstem stroke includes vital signs, oxygen saturation, pulse rate, blood pressure, and fingerstick blood glucose levels(17). 

A non-contrast computed tomography (CT) scan of the head and brain magnetic resonance imaging (MRI) also help detect brainstem stroke.

Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) refers to a medical imaging technology that employs a magnetic field and computer-generated radio waves to form detailed pictures of the body’s internal organs and tissues(18). 

MRI machines are usually large, tube-shaped magnets. As the patient lies inside the MRI machine, the magnetic field temporarily realigns the body’s water molecules. Through radio waves, these aligned atoms create faint signals used to generate cross-sectional images or slices. 

Magnetic resonance imaging is the most sensitive medical imaging technique in evaluating the structure of the brain and spinal cord(19). Brain MRI diffusion-weighted images and fluid-attenuated inversion recovery images can detect brain tissue infarction as they are highly sensitive in the hyper-acute setting(20).

Computed Tomography

A computed tomography (CT) scan uses X-ray images from various angles around one’s body and computer processing to generate cross-sectional images or slices of the blood vessels, bones, and soft tissues inside the body(21).

Unlike the regular X-rays, CT scan images show more detailed information. 

Moreover, a non-contrast CT scan of the head is a quick and widely available imaging modality(22). A non-contrast CT scan does not use a substance taken by mouth or injected into an intravenous (IV) line to produce clearer images(23).

Before undergoing the procedure, patients should inform the doctor if they have allergies or illnesses to avoid possible adverse effects. Pregnant or lactating women should also inform their doctor to avoid harmful effects on the baby.

  1. Johns Hopkins Medicine. Magnetic Resonance Imaging (MRI) of the Spine and Brain. Retrieved from https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/magnetic-resonance-imaging-mri-of-the-spine-and-brain 
  2. Ibid. 
  3. Crumbie, L., MBBS. Brainstem. Retrieved from https://www.kenhub.com/en/library/anatomy/the-brainstem 
  4. Basinger H, Hogg JP. Neuroanatomy, Brainstem. [Updated 2020 May 23]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK544297/ 
  5. Ibid.
  6. Johns Hopkins Medicine. Op Cit.
  7. LibreTexts. Medulla Oblongata. Retrieved from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/11%3A_Central_Nervous_System/11.4%3A_The_Brain_Stem/11.4B%3A_Medulla_Oblongata 
  8. Johns Hopkins Medicine. Op Cit.
  9. LibreTexts. Op Cit.
  10. Iordanova R, Reddivari AKR. Neuroanatomy, Medulla Oblongata. [Updated 2020 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK551589/ 
  11. Johns Hopkins Medicine. Op Cit.
  12. LibreTexts. Functions of the Brain Stem. Retrieved from https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/11%3A_Central_Nervous_System/11.4%3A_The_Brain_Stem/11.4A%3A_Functions_of_the_Brain_Stem 
  13. Vasković, J. (2020, Oct. 29). Midbrain (Mesencephalon). Retrieved from https://www.kenhub.com/en/library/anatomy/midbrain-pons-gross-anatomy 
  14. Ibid
  15. American Stroke Association. Brain Stem Stroke. Retrieved from https://www.stroke.org/en/about-stroke/types-of-stroke/brain-stem-stroke 
  16. Ibid.
  17. Gowda SN, De Jesus O. Brainstem Infarction. [Updated 2020 Nov 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560896/ 
  18. Mayo Clinic. MRI. Retrieved from https://www.mayoclinic.org/tests-procedures/mri/about/pac-20384768 
  19. Vasković, J. (2020, Oct. 29). Normal brain MRI. Retrieved from https://www.kenhub.com/en/library/anatomy/normal-brain-mri 
  20. Gowda SN, (2020). Op Cit. 
  21. Ibid. 
  22. Mayo Clinic. CT scan. Retrieved from https://www.mayoclinic.org/tests-procedures/ct-scan/about/pac-20393675 
  23. Johns Hopkins Medicine. Computed Tomography (CT or CAT) Scan of the Abdomen. Retrieved from https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/computed-tomography-ct-or-cat-scan-of-the-abdomen 
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