Statistics from Altmetric.com
Charles Mark Wiles makes some excellent points about pyramidal weakness.1 What we observe is largely just the ‘normal’ pattern of asymmetry of strength in the upper and lower limbs, amplified by disease and sometimes spasticity, and can often be found in lower motor neurone syndromes as well as upper.
But there is one clinical scenario where I would argue it remains a useful signpost, that is the differentiation of limb weakness due to a functional versus a structural disorder. Patients with a functional hemiparesis typically have a global pattern of weakness in which the flexors and extensors are either equally weak (‘global’ weakness’), or where the flexors are actually disproportionately weak in the arms and the extensors disproportionately weak in the legs (a pattern I have described as ‘inverse pyramidal weakness’2). Neither global or inverse pyramidal patterns are usually demonstrated, at least at the elbow and knee, among patients with structural disease in the best of the studies cited by Wiles.3
Global weakness is, therefore, really a form of inverse pyramidal weakness since it must occur by selectively affecting upper limb flexors and lower limb extensors, something that had not properly dawned on me until I read this article.
I teach medical students that there are four main patterns of limb weakness: pyramidal (which perhaps should be renamed the ‘normal’ pattern), proximal, distal and global/inverse pyramidal (which perhaps could just be called ‘functional’, since it is rarely seen in other disorders). These categories are, I would argue, a useful starting point to combine with other basic clinical information in reaching a diagnosis. I notice it reduces the anxiety of students to ask them to focus on this more than whether the strength should be recorded as a 4 or a 4+, when such distinctions are usually meaningless.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.