The human pyramidal syndrome Redux

Damage to the pyramidal tracts is necessary and sufficient for the production of the pyramidal syndrome in man

The causal role played by damage to the pyramidal tracts in the production of spastic hemiplegia in man has been hotly debated over the past hundred years. Two broad streams of thought have emerged from this dispute. The first, which is grounded on the clinicopathological schools of Jean-Martin Charcot (1825-1893) and Paul Flechsig (1847-1929), claimed that the four cardinal signs of hemiplegia, namely (i) paralysis, (ii) spasticity, (iii) hyperactive phasic muscle reflexes ("tendon jerks") and (iv) the sign of Babinski, are caused by injury or dysfunction of the pyramidal tracts. The second school, championed by John Farquhar Fulton (1899-1960) and Derek Denny-Brown (1901-1981), reflects the increasing influence of experimental neurology on clinicopathological concepts after World War II. According to this school, most elements of the pyramidal syndrome are caused by the added release or injury of extrapyramidal structures at different levels of the forebrain and brainstem. Most symptoms of spastic hemiplegia were thus interpreted as signs of extrapyramidal (e.g., reticulospinal) release or damage. However, consensus on which symptoms of spastic hemiplegia were due to pyramidal or extrapyramidal changes was never reached. To add to this uncertainty, a number of clinicopathological cases that supported the old view were sporadically published over the same period. The purpose of the present essay is to provide clinicoanatomic perspective to the neurological literature in support of the hypothesis that damage to the pyramidal tracts is a necessary and sufficient condition for the production of the complete pyramidal syndrome in man.

Diffuse and focal corticospinal tract disease and its impact on patient disability in multiple sclerosis

BACKGROUND AND PURPOSE

We investigated the impact of focal and diffuse corticospinal tracts damage on sensory-motor disability in multiple sclerosis (MS) patients.

METHODS

Twenty-five MS patients underwent 3.0 Tesla (3T) magnetic resonance imaging with diffusion tensor imaging (DTI). The Expanded Disability Status Scale (EDSS) and the Timed 25-Foot Walk test (T25FW) quantified patient physical disability. Fractional anisotropy (FA) and mean diffusivity (MD) of the corticospinal tracts, whole brain and corticospinal tracts lesion volume were also computed. Spearman rank correlation analyses measured the associations between DTI-derived metrics and other measures of disease. Partial correlation analyses between DTI and disability measures were performed and corrected for lesion volumes as appropriate.

RESULTS

Significant associations were seen between FA of the corticospinal tracts and EDSS (r = -.500, P = .0011), motor-EDSS (r = -.519, P = .008), and T25WF (r = -.637, P = .001) scores and MD of the corticospinal tracts and motor-EDSS (r = .469, P = .018) and T25WF (r = .428, P = .033) scores. When correcting for lesion volumes, only the association between FA of the corticospinal tracts and EDSS (r ≤ -.516, p ≤ .01) or motor-EDSS score (r ≤ -.516, p ≤ .01) persisted.

CONCLUSIONS

DTI at 3T shows that the impact of diffuse corticospinal tracts disease on sensory-motor disability is greatly mediated by focal lesions in MS.

The unbearable lightness of the extrapyramidal system

The concept of the extrapyramidal system comprises an amalgam of disparate and often conflicting ideas with a tortuous history. To the theoretical neuroscientist or practicing clinician, it promptly evokes semantic associations that are hardly reminiscent of its original meaning. The purpose of this article is to revisit the sources of the extrapyramidal concept and to examine the transformations that it went through from its inception, in the late 1890s, up to the neuroimaging revolution of the 1980s. Our review shows that the use of "extrapyramidal" as a surrogate for the basal ganglia, disorders of movement, or certain manifestations of spastic hemiplegia does not apply to humans; rather, it represents the historical product of the unwarranted translation of results of animal experimentation into the interpretation of clinical findings on human patients, misguided clinico-anatomic deductions, and fanciful phylogenetic notions. We conclude that the extrapyramidal concept is a valid and robust anatomic concept as long as it strictly refers to the collection of descending fibers originating in a few discrete brainstem tegmental motor nuclei that project to the spinal cord.