Medial Medullary Syndrome

by Craig Canby, PhD

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    00:00 The first lesion that we are going to take a look at is that of medial medullary syndrome. This occurs within the medulla at the level of the olive and above the pyramidal decussation. This is a vascular lesion.

    00:25 We can see that the basilar artery could be involved in causing this lesion. This lesion could also be due to an issue with blood delivery through the vertebral artery. The anterior spinal artery could also be involved in decreasing the blood flow to the medial region of the medulla. Here we see the involved area of the medullary region. Here we have the medial aspect highlighted. Involved structures are going to involve the corticospinal tract, the pyramid. You’re also going to damage the medial lemniscus.

    01:18 The hypoglossal nucleus and its fibers are going to be lesioned. The pyramid is down here. Here, the medial lemniscus is in this area. Then your hypoglossal nucleus is in the upper portion of this medial image.

    01:37 Now, if you have damage to these three structures, then we have to think about what the symptoms would be for each one that’s damaged. If we begin with the corticospinal tract and symptoms that attend here, you’re going to be looking at contralateral hemiparesis in the upper and lower extremities. So again, you’re looking at a tract and the findings will be contralateral and this is the case. That was one of the pearls to keep in mind. Damage to the medial lemniscus component of this area is going to interfere with the posterior columns. As a result, you’re going to have contralateral loss of vibration, conscious proprioception as well as fine touch. Again, this is a spinal cord pathway, happens to be ascending but findings of a pathway are going to be on the contralateral side of where the lesion is. Now lastly, we’re going to involve a cranial nerve component. That is the hypoglossal nucleus and its fibers. When a cranial nerve nucleus or the fibers are damaged, you’re looking at ipsilateral findings. So, since the hypoglossal nerve innervates the tongue, you’ll have ipsilateral paralysis of the tongue. As a result, when you ask a patient to stick out their tongue, the tongue will deviate to the same side of the lesion.

    About the Lecture

    The lecture Medial Medullary Syndrome by Craig Canby, PhD is from the course Brain Stem.

    Included Quiz Questions

    1. Posterior inferior cerebellar artery (PICA)
    2. Anterior spinal artery (ASA)
    3. Basilar artery
    4. Left vertebral artery
    5. Right vertebral artery
    1. Deviation of the tongue toward the side of the lesion
    2. Ipsilateral paralysis of the face
    3. Dysphagia
    4. Nystagmus
    5. Loss of the gag reflex
    1. Ipsilateral hemiparesis in the upper and lower extremities
    2. Loss of contralateral proprioception
    3. Contralateral loss of vibration
    4. Contralateral loss of fine touch
    5. Ipsilateral hypoglossal dysfunction

    Author of lecture Medial Medullary Syndrome

     Craig Canby, PhD

    Craig Canby, PhD

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