A 37 year old male came to with a history of frequent falls and difficulty in grasping objects since 1 year. He was a security guard but found that he could not stand up easily from the past year. He also had difficulty in writing and picking up objects. He also gave history of difficulty in rising from sleeping position.
On examination, he was found to have normal higher mental functions, though there was slight slurring of speech. Gait was high stepping with a lot of instability. Patient had to use both hands to support himself to rise from bed. Bulk of all the muscles was reduced. On asking to grip the hand, it was not easily released. Frontal balding was observed. Sensory system and reflexes were normal. All other systems were normal. What could the diagnosis be?