The Mary Walker effect: Mary Broadfoot Walker.

Mary Broadfoot Walker (1888-1974) was the first to demonstrate the 'Mary Walker effect' describing the weakness of other muscle groups following release of the arteriovenous occlusion of an unrelated exercising muscle group in patients with myasthenia gravis, which led to the search for a circulating causative agent for myasthenia gravis. She was the first to clearly demonstrate that strength temporarily improved in patients with myasthenia gravis with physostigmine or Prostigmin (neostigmine). This dramatic treatment response has been erroneously termed the 'Mary Walker effect'. Further, she noted hypokalaemia during attacks of weakness in familial periodic paralysis, pioneering treatment with potassium chloride. Although Mary Walker practiced in a nonacademic setting and trained at a time when women were not allowed to train alongside men, she was the first to convincingly demonstrate three life-changing treatments in the field of neuromuscular medicine, a feat that few physicians of any era can claim.

The contribution of Dr. Mary Walker towards myasthenia gravis and periodic paralysis whilst working in poor law hospitals in London.

Dr. Mary Walker discovered in 1934 that physostigmine and Prostigmin temporarily restored muscle function in patients with myasthenia gravis. In the next five years, Dr. Walker and colleagues provided clinical evidence for the weakness of myasthenia gravis being caused by a "disturbance of transmission of excitation from motor nerve to voluntary muscle presumably caused by a deficiency of acetylcholine. Physostigmine (or Prostigmin) compensated for the lack of acetylcholine by delaying its destruction." Dr. Walker and colleagues also described the association between familial periodic paralysis and hypokalaemia.