The lower motor neuron homunculus

Ravits, John; Stack, Julia

doi:10.1093/brain/awac310

Cited by 8 publications

(3 citation statements)

References 10 publications

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“…The topographic organization of the motor cortex and the spinal cord might be responsible for this difference in directionality of disease progression, reflecting somatotopic features of the upper and the recently proposed lower motor homunculus. 31 Moreover, while the abovementioned study relied on qualitative assessment of clinical signs, our work used semiquantitative scales to quantify the burden of UMN and LMN involvement.…”

Section: Discussionmentioning

confidence: 99%

Regional spreading pattern is associated with clinical phenotype in amyotrophic lateral sclerosis

Silani

Verde

Colombo

et al. 2023

Brain

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Increasing evidence shows that disease spreading in amyotrophic lateral sclerosis (ALS) follows a preferential pattern with more frequent involvement of contiguous regions from the site of symptom onset. Aim of our study is to assess if: 1) burden of upper (UMN) and lower motor neuron (LMN) involvement influences directionality of disease spreading; 2) specific patterns of disease progression are associated with motor and neuropsychological features of different ALS subtypes (classic, bulbar, primary lateral sclerosis, UMN-predominant, progressive muscular atrophy, flail arm, flail leg); 3) specific clinical features may help identify ALS subtypes which remain localized to site of onset for a prolonged time (regionally entrenching ALS, re-ALS). A single-center, retrospective cohort of 913 Italian ALS patients was evaluated to assess correlations between directionality of the disease process after symptom onset and motor/neuropsychological phenotype. All patients underwent an extensive evaluation including the following clinical scales: Penn Upper Motor Neuron Score (PUMNS), MRC scale for muscle strength and Edinburgh Cognitive and Behavioural ALS Screen (ECAS). The most frequent initial spreading pattern was that towards adjacent horizontal regions (77.3%), which occurred preferentially in patients with lower MRC scores (p = 0.038), while vertical diffusion (21.1%) was associated with higher PUMNS (p < 0.001) and with reduced survival (p < 0.001). Non-contiguous disease spreading was associated with more severe UMN impairment (p = 0.003), while contiguous disease pattern with lower MRC scores. Furthermore, non-contiguous disease spreading was associated with more severe cognitive impairment in both executive and visuo-spatial ECAS domains. Individuals with re-ALS were more frequently women (45.6% vs 36.9%; p = 0.028) and had higher frequencies of symmetric disease onset (40.3% vs 19.7%; p < 0.001) and bulbar phenotype (38.5% vs 16.4%; p < 0.001). Our study suggests that motor phenotypes characterized by a predominant UMN involvement are associated with a vertical pattern of disease progression reflecting ipsilateral spreading within the motor cortex while those with predominant LMN involvement display more frequently a horizontal spreading from one side of the spinal cord to the other. These observations raise the hypothesis that one of the mechanisms underlying disease spreading in ALS pathology is represented by diffusion of toxic factors in the neuron microenvironment. Finally, it is possible that in our cohort, re-ALS forms are mainly observed in patients with atypical bulbar phenotypes, characterized by a slowly progressive course and relatively benign prognosis.

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Section: Discussionmentioning

confidence: 99%

Regional spreading pattern is associated with clinical phenotype in amyotrophic lateral sclerosis

Silani

Verde

Colombo

et al. 2023

Brain

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“…The heterogeneity of ALS adds complexity to the interpretation of neurofilament as a prognostic biomarker. The clinical spectrum of ALS is mainly caused by phenotypes that result from the variable involvement of upper and lower motor neurons, as well as the region of onset and propagation pattern throughout the body regions [ 35 , 36 , 46 ]. Although the correlation between NfL and ALS progression has been demonstrated in previous studies, the effect of phenotypes on sNfL was uncertain [ 23 ].…”

Section: Discussionmentioning

confidence: 99%

Serum neurofilament light chain in distinct phenotypes of amyotrophic lateral sclerosis: A longitudinal, multicenter study

Meyer,

Dreger,

Grehl

et al. 2024

Euro J of Neurology

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ObjectiveTo assess the performance of serum neurofilament light chain (sNfL) in clinical phenotypes of amyotrophic lateral sclerosis (ALS).MethodsIn 2949 ALS patients at 16 ALS centers in Germany and Austria, clinical characteristics and sNfL were assessed. Phenotypes were differentiated for two anatomical determinants: (1) upper and/or lower motor involvement (typical, typMN; upper/lower motor neuron predominant, UMNp/LMNp; primary lateral sclerosis, PLS) and (2) region of onset and propagation of motor neuron dysfunction (bulbar, limb, flail‐arm, flail‐leg, thoracic onset). Phenotypes were correlated to sNfL, progression, and survival.ResultsMean sNfL was ‐ compared to typMN (75.7 pg/mL, n = 1791) ‐ significantly lower in LMNp (45.1 pg/mL, n = 413), UMNp (58.7 pg/mL n = 206), and PLS (37.6 pg/mL, n = 84). Also, sNfL significantly differed in the bulbar (92.7 pg/mL, n = 669), limb (64.1 pg/mL, n = 1305), flail‐arm (46.4 pg/mL, n = 283), flail‐leg (53.6 pg/mL, n = 141), and thoracic (74.5 pg/mL, n = 96) phenotypes. Binary logistic regression analysis showed highest contribution to sNfL elevation for faster progression (odds ratio [OR] 3.24) and for the bulbar onset phenotype (OR 1.94). In contrast, PLS (OR 0.20), LMNp (OR 0.45), and thoracic onset (OR 0.43) showed reduced contributions to sNfL. Longitudinal sNfL (median 12 months, n = 2862) showed minor monthly changes (<0.2%) across all phenotypes. Correlation of sNfL with survival was confirmed (p < 0.001).ConclusionsThis study underscored the correlation of ALS phenotypes – differentiated for motor neuron involvement and region of onset/propagation – with sNfL, progression, and survival. These phenotypes demonstrated a significant effect on sNfL and should be recognized as independent confounders of sNfL analyses in ALS trials and clinical practice.

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“…There are specific areas in the brain associated with the hands and mouth and the more they are used, the more development in these brain areas is possible. Areas located in the sensory cortex that are innervated by fibers from skin stimulation on body parts make up the structure called Penfield's Homunculus or Motor Homunculus; from each area the innervation proceeds to the motor cortex and participates in the motor activation of the corresponding parts of the body 1 .…”

Section: Introductionmentioning

confidence: 99%

Brain activity corresponding to swallowing and hands activity: narrative review

Leão,

Lobo Neto,

Gonçalves

et al. 2024

Rev Neurocienc

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Objective. To analyse the relationship between the level of brain activity during the hand motor act and swallowing in studies that used Functional Magnetic Resonance Imaging (FMRI). Method. A narrative literature review was carried out, and the data sources were obtained from Pubmed, BVS, and Google Scholar platforms. Results. Few studies were found that investigated the neurological activation correlated to the movement of hands and swallowing through FMRI, but all studies show a topographic relationship between the main areas for activity of hands and swallowing, as well as some studies showing some neurofunctional relationship between both concurrent activities. Conclusion. It is known that the precentral gyrus has significant areas innervating the hands and oral cavity, which are in nearby areas, being subject to questions about function interactions. The findings already described may encourage studies and discussions, but more research is needed to describe and measure the relationship between the motor areas of the hands and swallowing.

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The lower motor neuron homunculus

Abstract: Penfield’s motor homunculus anthropomorphizes the cerebral level of motor control, the upper motor neuron. However, it leaves the cranial and spinal motor neurons unrepresented. Here Ravits and Stack redress the imbalance by presenting a lower motor neuron homunculus.

Cited by 8 publications

References 10 publications

Regional spreading pattern is associated with clinical phenotype in amyotrophic lateral sclerosis

Regional spreading pattern is associated with clinical phenotype in amyotrophic lateral sclerosis

Serum neurofilament light chain in distinct phenotypes of amyotrophic lateral sclerosis: A longitudinal, multicenter study

Brain activity corresponding to swallowing and hands activity: narrative review

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