| Affiliation |
(AGL) Chairman, Department of Ophthalmology, The Methodist Hospital, Houston, Texas; Professor of Ophthalmology, Weill Cornell Medicine, New York City, New York; (YK) Class of 2021, Baylor College of Medicine, Houston, Texas |
| Transcript |
So this little violin looking thing is the medulla. It looks different than the mid-brain which has those mickey mouse ears and the pons which looks like an apple. The only reason an ophthalmologist would ever go to the medulla is because sometimes there's an infarct in the lateral portion of the medulla which we call the lateral medullary syndrome. It also goes by the name of the Wallenberg Syndrome. So the Wallenberg syndrome is something an ophthalmologist needs to know because there are a number of findings in the Wallenberg that show up to ophthalmology.; Everything from the cortex has to go to the spine and everything from the spine has to go back up to the cortex. So when we have a lateral medullary syndrome, we are involving structures that are both descending and ascending. So one of the pathways is from the hypothalamus descending down the posterior lateral portion of the brainstem to control the sympathetics for the eye. That oculosympathetic pathway produces a little bit of ptosis, upside-down ptosis, and an anisocoria that's greater in the dark. That is called a Horner's syndrome. So when we have a Horner's syndrome, we'd like to know if there are other features that might suggest that this is the Wallenberg. The other eye features include rotary nystagmus. And that nystagmus may be associated with symptoms of oscillopsia - the subjective motion in the environment, nausea, and vertigo. And this can result from involvement of the inferior cerebellar peduncle. So information from the cerebellum has to transmit to the brainstem and vice versa. Those afferent and efferent fibers can be destructed in the lateral medulla, producing the symptoms of gait ataxia, nausea, vomiting, vertigo, dizziness, and rotary nystagmus. The patient also might have diplopia from the skew deviation. A skew deviation is a vertical deviation that doesn't localize to a single muscle or muscle group. And it's from disruption of the otolith input at the level of the brainstem or cerebellum. And so when we have diplopia, it doesn't have to be from cranial nerves 4, 5, or 6 which live rostrally in the midbrain and the pons. It could be way down here in the medulla from skew deviation. The patient may also have involvement of trigeminal. As you know, the trigeminal nucleus is quite long. It has a mesencephalic portion in the midbrain, a descending portion that runs all the way down to the spinal nucleus. And that means it's got to pass this lateral medulla. So the patient might have pain or numbness in their face. And you heard from previous YouTube videos that the cranial neuropathies are ipsilateral. So it'll be have ipsilateral face numbness or pain. But because the spinothalamic tract which is ascending from your spine to the thalamus, is a contralateral finding, that'll produce a crossed sign. So in a lateral medullary infarct on the left, we might have a left face and a right body hemisensory loss. That combination of crossed signs - left face, right body, ataxia, diplopia, nystagmus, vertigo, oscillopsia, rotary nystagmus, and the Horner's syndrome, characterizes the key features of the Lateral Medullary syndrome, also known as the Wallenberg syndrome. The most common cause of the Wallenberg syndrome is an infarct from its blood supply, the posterior inferior cerebellar artery, PICA, so when we have an acute Wallenberg syndrome we should be looking for PICA occlusion and that can be from vertebral disease, basilar disease, cardioembolic disease, something that's occluded the PICA. The medial structures are spared in the Lateral Medulla syndrome. The medial structures are the vibration and the pain and temperature and the pyramids which control the corticospinal tract and so we don't usually have hemiparesis. And we don't normally have the other sensory modalities then that's in the lateral medulla because those are medial medullary syndromes. You should know therefore as an ophthalmologist, any patient with a Horner's, rotary nystagmus or skew, you still got to know a little about the medulla, Wallenberg. |
