He Used to Run Several Times a Week. Now He Could Barely Stand.


When Ahmed read that this previously healthy man was suddenly having trouble walking, the first thing that came to mind was Guillain-Barré syndrome (G.B.S.). This is an autoimmune disorder: Antibodies, usually triggered by an infection, mistakenly attack healthy cells, confusing them with the invaders they are there to control. In G.B.S., the targeted cells are those forming the protective shield around nerve fibers. Without this covering, the nerves are damaged and stop transmitting sensory information between the body and the brain.

But as soon as Ahmed read further and saw that the man was using whippets, another much more likely diagnosis sprang to mind. Nitrous oxide is considered a relatively safe drug — unless used frequently, when it can cause weakness and paralysis that can become permanent. The drug binds to the working part of vitamin B12, inactivating this key nutrient. The lack of functional B12 causes injury and eventually destruction of the protective sheath and the nerve below, causing symptoms similar to those seen in G.B.S. Once sufficient nerve tissue is destroyed, the weakness becomes irreversible.

“If [his weakness] is due to whippets, he needs to come to the ER to get IM vitamin B12,” Ahmed texted back. “Get him to an ER pronto!” Ahmed had seen this once before during his training in critical-care medicine in London. Even a brief delay can cause permanent damage. Maslyn immediately called his friend back with the urgent recommendation.

Dr. Matthew McIntosh was the doctor assigned to take care of the patient at Buffalo General Hospital. By the time he saw the man, blood tests to measure his B12 level had already been sent, and he’d got his first doses of the vitamin. McIntosh had heard of whippets; had heard it was a popular recreational drug. But he had never seen anyone in the hospital because of it and was completely unaware of the vitamin B12 deficiency that could come from its misuse. And so after hearing about this patient, McIntosh did what all doctors must do when confronted with something new — he went to the internet.

It doesn’t take much work to uncover the long and colorful history of nitrous oxide. It was first discovered in the late 18th century, and its recreational use and euphoric properties were identified decades before its utility as an anesthetic. The link between overuse and this kind of B12 deficiency wasn’t identified until 1978. But it has been well described in the medical literature since.

The blood tests revealed that although the man had normal levels of vitamin B12, it wasn’t doing its job. The nitrous oxide had made the vitamin he had in his system useless. Other blood tests and M.R.I.s of the man’s brain and spine showed no other abnormalities. The man got several doses of the vitamin over the next couple of days, and he improved rapidly. When he arrived at the hospital, he was too weak to stand. By the time he left, he could walk with the aid of a walker.

After a month of vitamin replacement and intense physical therapy, the patient is now able to walk on his own. His gait is a little awkward, but he finally feels certain he will get it all back. He was using whippets on and off for a decade. The drug is not considered addictive, but he will tell you that he was fully addicted to it. He quit using the drug many times over the years but frequently relapsed when stressed or depressed. But he is confident that this time he has quit for good. There is no amount of stress that would provoke him to risk permanent disability. He was lucky this time. He is entering rehab to make sure he’ll never have to be lucky again.

Lisa Sanders, M.D., is a contributing writer for the magazine. Her latest book is “Diagnosis: Solving the Most Baffling Medical Mysteries.” If you have a solved case to share, write her at Lisa.Sandersmd@gmail.com.


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