Amyotrophic lateral sclerosis (ALS)
General description
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by both sporadic and progressive degeneration, leading to the loss of cell bodies of both upper and lower motor neurons. While the typical age of onset ranges from 10 to 80 years, the majority of cases are most commonly diagnosed between the ages of 50 and 60.
ALS with dementia
TDP-43 is a protein constituting inclusion body of neuronal cells commonly found in ALS and Frontotemporal lobar degeneration (FTLD) with ubiqutin-positive inclusions. ALS with dementia is categorized in between ALS and FTLD. While most ALS cases are related to TDP-43 proteinopathy, not all FTLD cases are related.
Corticospinal tract lesion
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Internal capsulePosterior limbCorticospinal tract
In ALS, degeneration of the corticospinal tract is most effectively detected within the posterior limb of the internal capsule. Absent degeneration in the internal capsule, lesions within other regions of the corticospinal tracts are typically not observed.
Motor cortex lesion
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CerebrumFrontal lobePrecentral gyrusCerebral cortex
On MRI, hypointense signal is observed on T2WI within the cerebral cortex of the precentral gyrus, corresponding to the primary motor cortex. This finding reflects deposition of iron in this region.
Precentral white matter hyperintensity
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CerebrumFrontal lobePrecentral gyrusCerebral white matter
In addition to the hypointense signal within the precentral cortex on T2WI, corresponding to iron deposition, hyperintense signal is also observed in the white matter of the precentral gyrus.
Corpus callosum lesion
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Corpus callosum
Although an uncommon finding, bilateral hyperintense signal may be observed in the corpus callosum on T2WI. However, when present in conjunction with hyperintense signal involving the corticospinal tracts, it may indicate the presence of degenerative changes.
ALS with dementia
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CerebrumFrontal lobe
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CerebrumTemporal lobe
In ALS with dementia, relatively symmetrical atrophy is observed bilaterally involving the frontal and temporal lobes. Additionally, hyperintense signal is present within the white matter on T2WI. In contrast, Frontotemporal lobar degeneration (FTLD) often exhibits an asymmetric pattern of atrophy, whereas in ALS with dementia, the lobar atrophy tends to be relatively symmetrical.