Something Fishy Going On

One afternoon a 52-year-old man, a recently retired military intelligence analyst, came to the Walter Reed neurology clinic complaining of the tingles. Scott had already seen several physicians, including two civilian neurologists, and gotten no answers. Lindsey, one of the residents, saw the patient first and presented the case to me. 

Scott looked ex-military: trim, short-haired, neatly dressed. He recounted additional unusual symptoms present for the past several months. Holding his hands out and spreading his fingers, he described having intermittent but frequent numbness and tingling all over, but especially in his hands and feet, as well as fatigue and aching pain in his muscles. He went on to describe a symptom that sounded a bit crazy. He apologized first.

“Sorry, I know this sounds nuts. But I have been having this numbness and tingling that runs up my face in a strip from my chin, up across my forehead, over the top of my head and down into my neck. Comes and goes. It’s really weird.” He held his thumb and forefinger about two inches apart and made a sweeping motion from his chin up over the top of his head. 

That kind of bizarre symptom, not typical of any organic neurological disorder, often elicits eye-rolling behavior in physicians, who immediately discount it as psychological. The possibility of a disorder I had read and heard about but never seen entered my mind, and I asked a critical question, "Have you had anything unusual happen with hot and cold things?"

He looked startled for a moment, then said, "Yes I have, but it sounds so crazy I haven't told anyone, even my wife. When I get in the shower, no matter how hot I turn the water it feels cold. And if I turn the water to cold to see if I can feel that, the cold seems to hurt and feel hot. My hot coffee never seems more than lukewarm. It's really strange."

I posed another critical question, "Do you like seafood?"

Scott related a particular fondness for seafood. He was not the sort of picky, reluctant seafood eater who stuck to lobster, shrimp and scallops, a crustaceanophile. No, he embraced all marine life as potentially edible. Yes, he had eaten grouper. Yes, he had eaten snapper. Were some unusual fish offered at a good seafood restaurant he would likely try it. Barracuda had never presented itself on a menu but if it did he would enjoy some. 

The travel history sometimes becomes important, particularly when faced with an unusual constellation of symptoms or findings. Diseases not endemic to a particular locale may show up unexpectedly because the patient has contracted the condition on a trip, then become symptomatic on returning home. In the age of jet travel, diseases can spread widely and quickly. Ebola virus has a restricted geographic distribution but American physicians had to treat several cases after infected travelers flew home. 

Scott had visited Florida in the past few months but could not recall having eaten seafood while there.

I told him, "I'm beginning to think you may have ciguatera intoxication."

I explained that ciguatoxin, a marine toxin that lurks in the plankton around coral reefs, causes ciguatera intoxication. The little fish eat the plankton, big fish eat the little fish, and so on up to the biggest fish. The ciguatoxin accumulates with each step up the food chain and is present in the highest amounts in large predator fish, such as barracuda, grouper, snapper and amberjack. These are some of the major offenders in a long list of fish that can harbor ciguatoxin. The toxin is tasteless, odorless and colorless. A fish containing ciguatoxin looks, smells and tastes perfectly fine. Cooking does not affect the heat stable toxin.  

Ciguatera intoxication occurs mostly in the tropics. A seafood-loving traveler to the Caribbean had best take care. Ciguatoxin-bearing barracuda became such a problem in south Florida at one point the city of Miami passed an ordinance forbidding restaurants from serving barracuda inside the city limits. Outside the city limits you were on your own. 

The patient does not even have to travel. Sometimes the disease comes to him because fish these days travel, too. Grouper caught off Saint Croix can arrive in Omaha the next day. 

Over several visits, after talking with his wife and perusing his memory banks, the story slowly emerged. He had eaten grouper in a restaurant in Arlington, Virginia. After ingestion, ciguatera typically causes abdominal pain, nausea, vomiting and diarrhea. Scott had developed the GI symptoms within a few hours of eating the grouper and the sensory symptoms began within the next couple of days. He had not made the connection. Why should he? Who expects to develop a tropical disease after eating out in Arlington? Except he did.

The CDC reported six outbreaks of ciguatera poisoning involving twenty-eight people in New York City between August 2010 and July 2011, thirteen from eating barracuda, fifteen from eating grouper. Avoiding consumption of all reef fish is the only sure-fire way to prevent ciguatera. Especially in the days of apparently widespread fish fraud, when what appears on a diner’s plate may not match what the restaurant prints on its menu, what should a seafood lover do? There are no good answers.

Ciguatera is a clinical diagnosis.1 There are no confirmatory tests. Testing the suspect fish source can sometimes confirm the diagnosis, but that opportunity had long since passed. Scott underwent blood tests and some electrical studies of his nerves and muscles—all normal.

Nerve cell membranes have channels through which the sodium and potassium ions that control membrane excitability pass. The flux of these ions controls the membrane potential. Gates control access to the ion channels. With depolarization of the membrane to threshold level, the sodium ion access gates fly open and sodium rushes into the cell, depolarizing the membrane and producing an action potential. 

Ciguatoxin paralyzes the sodium channel gates in the open position. The nerve cells become irritable, firing constantly, never able to rest because the toxin has rendered the cell membranes unstable and hyperexcitable, skittish and jittery, discharging with minimal provocation or firing spontaneously. It’s like having all your nerve endings exposed and constantly overstimulated. A miserable condition. 

Scott, a smart guy, started reading and concluded the symptoms of ciguatera he found sounded a lot like him. We began empiric treatments using agents that block the sodium channel in an attempt to stabilize the hyperexcitable membranes of his sensory nerve cells. He failed to respond to several different medications. There was not much else to do. 

Ciguatera usually causes an illness that resolves in a few days to a few weeks, but some cases become chronic and leave the affected patient suffering for months or years. It appeared Scott would fall into that latter group, doomed to endure cigua-aggravation for a long time.

He began to look for help elsewhere, seeking reassurance about the diagnosis and suggestions regarding treatment. Very few physicians in the world know much about ciguatera intoxication; most doctors have not even heard of it. 

Scott tracked down a tropical medicine specialist in Australia who had seen a lot of ciguatera and published on the topic. He managed to get in touch with the expert, who told Scott he absolutely agreed with the diagnosis of ciguatera intoxication but had nothing to offer in terms of therapeutic suggestions. The patient gradually improved a little but remained fairly symptomatic at followup. 

Daily rounds, or ward rounds, accomplish the work of patient care and involve literally walking around and seeing individual in-patients in the hospital. In a teaching hospital setting, ward rounds typically include the attending physician and the residents, interns and medical students who make up a ward team. 

Grand rounds is a weekly teaching conference, a sit-down affair, usually a lecture, for all the ward teams and others in the department. A visiting professor from out of town or another department often speaks at grand rounds as a subject matter expert. 

Scott, although not a professor, or even a physician, had become an expert on ciguatera intoxication and knew more about it than most doctors. Considering the impressive level of his autodidacticism and his personal insights into the condition, I asked him to give grand rounds. The idea of a patient lecturing to a roomful of doctors produced some blowback but curiosity won out. 

The grand rounds went well. The patient proved articulate, knowledgeable and organized. I stood by to provide backup but he needed no help. He gave a very good lecture, as good as any grand rounds. Never before or since have I attended a grand rounds with a patient as the guest speaker. Perhaps we should do it more often. 

In addition to the scientific content, he described the experience of living with ciguatera intoxication, the daily travails of dealing with the weird sensory symptoms, the fatigue and the muscle aches. Try to imagine, for just a moment, not being able, for the rest of your life, to enjoy a hot shower. He provided a personal perspective no physician or scientist could, and the audience was richer for it. 

I may have had grouper a few times before seeing Scott. Never again.