2973 Use of the phrase 'pyramidal weakness' within the past 100 years

Background/Objectives‘Pyramidal weakness’ implies that neurological examination findings can be localized to the central nervous system (CNS). Neurology trainees are taught that ‘pyramidal weakness’ infers upper limb extensor and lower limb flexor weakness. However, other weakness patterns are observed in CNS lesions and are not included in this teaching. We aim to investigate the pattern of weakness observed in CNS lesions and explore the use of the phrase ‘pyramidal weakness’ over time.MethodsWe searched Medline, PubMed, and Google Scholar up to 1/1/2022, using these terms: ‘distal weakness’, ‘upper limb flexion’, ‘lower limb extension’, pyramidal: ‘weakness’, ‘sign’, ‘tract sign’, ‘syndrome’, and sign of pyramidal: ‘lesion’, ‘disease’ and ‘involvement’. 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.ResultsWe 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 upper limb extensor and lower limb flexor weakness. Since 1988, ‘pyramidal weakness’ has become associated with weakness in upper limb extensors and lower limb flexors. ConclusionThe phrase ‘pyramidal weakness’, used in its current format, is more frequent since the 1980s. Distal weakness and upper limb extensor and lower limb flexor weakness have been associated with CNS lesions. ‘Pyramidal weakness’ should also infer a pattern of distal weakness.