Localization of paralysis in stroke

What do you need to know about the paralysis of your patient to shorten the list of possible stroke locations?

  • Is the paralysis proportionately affecting arm and leg (brachiocrural) or more brachially or crurally or even a monoparesis?
  • Does it affect proximal or distal muscles or both?
  • How much and in what form is the face affected? Is the face afflicted during volontary and/or emotional innervation?
  • Is it purely motor? Is an associated sensory disturbance ipsi- or contralateral? Dissociated?
  • What cranial nerves are involved?

We discuss the anatomy of the corticospinal and corticobulbar (in particular the corticofacial) tracts, moving through the various levels

  • Cortical: primary motor cortex, sensory cortex, premotor cortex
  • Subcortical
  • Internal capsule
  • Cerebral peduncle
  • Pons
  • Medulla

We spend some time on the anatomy of the internal capsule – here, the centuries-old descriptions have been reconfirmed in tractography studies.

Some pearls

  • Monoparesis is rarely if ever capsular or subcapsular.
  • Pure motor proportionate paralysis tends to be capsular.

As for references, I highly recommend Brazis’ Localization book (the first chapter), complemented by the recently edited Stroke Syndromes book (aka the bible).

Dissociative facial paralysis

It is rare when thetraditional  New England Journal of Medicine forgets it’s past. Thus you have to conclude that the appearance of two “Images in Clinical Medicine” on our topic of yesterday within 12 years is intentional rather than careless:

What do you think?
Whatever, we explore the classic phenomenon of dissociative facial paralysis which led old textbooks  to infer a localizing value of volitional facial paralysis (e.g. has to be capsular or higher). Nowadays we know from case reports that emotional facial paralysis can appear in medullary, AICA, capsular and many more lesion locations, leaving the path of emotional facial innervation completely unclear and thus reducing the localizing value of dissociation.
So in my view, it is still one of the most fascinating physiological (and phylogenetic) facts that nature decided to devote so much energy intoproducing  emotional facial expression (also having to come up with quite a lot of machinery to recognize them). But it helps nada in the daily life of a Neurologist.

Gyri and Sulci of the lateral view of the brain

One of the most obvious core qualifications of a Neurologists is neuroanatomy knowledge. We are going to recap gyri, sulci and lobes. First we are filling in all annotations on the medical color book page, then compare it to the Sobotta atlas and finally (most importantly) try to identify the gyri on axial T1 images.

Added after the fact: It is easy to locate the frontal gyri on the mri once you identified the frontal end (which is not identical to the frontal pole!). For the temporal gyri start with the central sulcus (a problem in itself, but we covered this in a previous session), extend it into the temporal operculum, then take the highest gyrus there as the superior temporal gyrus. The most difficult one is the inferior parietal gyrus, since the intraparietal sulcus is hard to identify.