Table 2.
Key diagnostic differences between ALS, HSP, and PLS.
| Diagnostic Test | PLS | ALS | HSP |
|---|---|---|---|
| Denervation Potentials on EMG | +/- 1 | +++ | +/- |
| Abnormal SSEPs | +/- | - | ++ |
| Precentral Gyrus Atrophy (MRI) | ++ | + | - |
| Corticospinal Tract Hyperintensity on T2-weighted imaging | + (late) | + (early) 2 | + |
| FDG-PET Findings | Focal motor cortex hypometabolism (‘stripe sign’) | Motor cortex + diffuse frontal cortex hypometabolism | Heterogenous areas of cortical hypometabolism |
| TMS MEPs prolonged? (early/late) | +++/+++ | +/++ | -/- |
| Neurofilament light chain levels | ++ | +++ | + |
| Bunina Bodies | +/- | ++ | - |
| TDP-43 Inclusions | + 3 | ++ | - |
1 one to few muscles, non-progressive over time. 2 Identification in first 1–2 years of symptom onset may help distinguish UMNdALS from PLS. 3 TDP-43 NCI reported in primary motor cortex of PLS patients but rarely found in LMNs as compared to ALS.