Do you have a weakness in any of your arms/legs with/without pain in spine/back?
Do you have difficulty in using your upper limbs (hands) or your lower limbs (legs) or all 4 limbs without pain? Do you have difficulty getting up from a low chair or squatting position or toilet seat? These may be symptoms of a primary muscle disease called myopathy which also runs in family. Or there can be one or all 4 limbs weakness with wasting of muscles called Motor Neurone Disease. When muscle diseases /weaknesses are accompanied by pain, tenderness of muscles , then an inflammatory muscle diseases called polymyositis should be suspected investigated and treated with success.
When such weakness is accompanied by radiating- (spreading from back to lower portion of hand or heel ) pain in a limb or a band like pain across trunk or chest with alteration in sensation below a particular level and bladder symptoms then a spinal cord disease is suspected like transverse myelitis , demyelinating disease or a spinal cord tumour or infection over spinal cord or traumatic injury of spinal cord.
Similar weakness may occur, wherein weakness need not be continuously permanently present but fluctuates between morning and evening also and rest improves weakness and exertion brings out again weakness of muscles. This easy fatigability more towards evening hours reversed or minimized by taking rest can also occur in myasthenia, which require specific NCV and blood test to confirm it. It has gratifying treatment schedule available.