Perhaps you should try some spelling variations:
"motor neuron disease" » "motor neutron disease", "motor neuro disease"
"motor neurons disease" » "motor neutrons disease", "motor neuros disease"
"motor neuronal disease" » "motor neutronal disease", "motor neuroal disease", "motor neural disease"
"motor neutronal disease" » "motor neutral disease", "motor neutron 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 neuron disease") OR ("motor neurons disease"))) or ((("motor neuronal disease") or ("motor neutronal disease"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("motor neuron disease") OR ("motor neurons disease"))) OR ((("motor neuronal disease") OR ("motor neutronal disease")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"motor neuron disease\") OR (\"motor neurons disease\"))) or (((\"motor neuronal disease\") or (\"motor neutronal disease\"))))".
• Removing quotes may allow a broader search: (((( motor neuron disease ) OR ( motor neurons disease ))) or ((( motor neuronal disease ) or ( motor neutronal disease )))).
• Adding a wildcard symbol may retrieve word variants: (((("motor neuron disease") OR ("motor neurons disease"))) or ((("motor neuronal disease") or ("motor neutronal disease"))))*.