Use of the phrase 'pyramidal weakness' within the past 100 years.

The concept of 'pyramidal weakness' denotes that neurological examination findings can be localised to the central nervous system (CNS), and implying a specific pattern of motor weakness involving upper limb extensors and lower limb flexors. However, other weakness patterns have been observed in CNS lesions. We aim to investigate the pattern of weakness observed in CNS lesions and explore the use of the phrase 'pyramidal weakness' over time. We searched Medline, PubMed, and Google Scholar up to January 1st, 2022, using keywords such as 'distal weakness,' 'upper limb flexion,' 'lower limb extension,' 'pyramidal weakness,' and related terms. The inclusion criteria were papers relating to brain or spinal cord lesions and terms inferring their presence or the description of a motor weakness pattern. We identified 117 studies since 1889, of which 29.9% of publications described weakness in upper limb extensors and lower limb flexors, and 26.5% reported distal weakness. We found an early reference to 'pyramidal weakness' in 1922 in the context of unilateral weakness in encephalitis with no description of the upper limb extensor and lower limb flexor pattern. Since 1988, 'pyramidal weakness' has become associated with weakness in upper limb extensors and lower limb flexors. The phrase 'pyramidal weakness', used in its current format, has been more frequent since the 1980s. Distal weakness and upper limb extensor and lower limb flexor weakness have been associated with CNS lesions.