Hello. Sir I can understand your concern regarding your father health I think you should know that a person with motor neuron disease will have muscle weakness leading to easy tiredness, muscle aches, even vocal cord and tongue is made of muscles in the body so there might be difficulty in speech,there may be difficulty in breathing, swallowing, gripping objects etc.generally blood test is done to know about creatinine kinase level which will be abnormal in MND, MRI can also support in diagnosis. Nerve conduction studies and electromyography is very helpful in diagnosis. Kindly consult a neurologist for further queries.