They used to be rare and quite deleterious, which is due to the fact that most of the pathologically relevant medial medullary infarctions (MMI) that have been described by the Neurologists of old were actually quite large in comparison to what we often find in MRI-proven small rostral medial medullary strokes. We use the particular instance of MMI to review brainstem anatomy along the lines of the 4m4s-rule, try to sketch a brainstem section at the level of the lower and upper medulla and step by step place all the relevant structures in it (corticospinal tract, vestibular centers, medial lemniscus, spinothalamic tract, motor nerves, trigeminal tracts and so on).
So why is MMI underrecognized? Because it might hide under the cloak of the simple lacunar syndrome of sensorimotor stroke. Here are hints at the brainstem localization:
- The face is spared in hemiparesis.
- The sensory disturbance is dissociated, affecting mostly medial lemniscal qualities
If more dorsal structures are affected, some more brainstemmy features can appear (vertigo, XII palsy, …). Quite fascinating is ocular lateropulsion, which we also review.
All what I know about this topic is from Caplan’s Stroke Syndromes, where JS Kim has written the chapter on medullary strokes, on which the Koreans seem to know more than anyone else in the world…