Sir , 1 year ago my mothers right side leg...

How to treat  in ability to move right leg

the cause may be due to herniated disc in the vertebral column which compress the nerves that emerges our from the spinal cord and the treatment in this case is by surgical intervention or intervention by endoscopy to remove the herniated disc that compress the nerves . other suggestive causes of this problem is the presence of stroke in the brain area that control the leg which can be treated by drugs like aspirin or clopidogrel after exclusion of the presence of bleeding and in case of stroke it will take months for leg to improve and should  also has physiotheraby . other cause may be multiple sclerosis which can be treated by cortisone and interferon beta 

How to diagnose  in ability to move right leg

MRI can be done to diagnose herniated disc in the back and it can be done on the brain and spine to exclude multiple sclerosis which can be also diagnosed by analysis of cerebrospinal fluid , also ultrasound of the neck arteries should be done to exclude and lesion in it also nerve conduction study of the leg nerve can be done to help in the diagnosis

what are the possible causes of in ability to move right leg

herniated disc in the vertebral column
stroke
multiple sclerosis
carotid artery stenosis

advise

you should follow up with the neurologist to assess the case and provide the treatment