Perhaps you should try some spelling variations:
"motor neuronals disease" » "motor neurals disease", "motor neutronals disease", "motor neuroals disease"
"motor neuronal disease" » "motor neural disease", "motor neutronal disease", "motor neuroal disease"
"motor neurons disease" » "motor neutrons disease", "motor neuros disease"
"motor neuron disease" » "motor neutron disease", "motor neuro disease"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((("motor neurons disease") or ((("motor neuronals disease") OR ("motor neuronal disease"))))) or ("motor neuron disease"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("motor neurons disease") OR ((("motor neuronals disease") OR ("motor neuronal disease"))))) OR ("motor neuron disease")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"motor neurons disease\") or (((\"motor neuronals disease\") OR (\"motor neuronal disease\"))))) or (\"motor neuron disease\"))".
• Removing quotes may allow a broader search: (((( motor neurons disease ) or ((( motor neuronals disease ) OR ( motor neuronal disease ))))) or ( motor neuron disease )).
• Adding a wildcard symbol may retrieve word variants: (((("motor neurons disease") or ((("motor neuronals disease") OR ("motor neuronal disease"))))) or ("motor neuron disease"))*.