Hydrocephalus in Ziggy Star the Northern Fur Seal

Ziggy Star is a Northern fur seal who lives at the Mystic Aquarium in Connecticut. She was found stranded on a California beach about four years ago and was very emaciated. The aquarium staff soon discovered that she had neurological problems. She was deemed unreleasable by the federal government.

Over time, Ziggy developed worsening neurological symptoms, including seizures. Eventually it was decided that something had to be done in order to improve her quality of life, even if the procedure involved risk. Ziggy has recently recovered from a type of surgery never before performed on a Northern fur seal and perhaps never performed on a pinniped (a group consisting of seals, sea lions, and the walrus).

Northern fur seal male (in front) and females (behind); M. Boylan,
public domain license

The Northern Fur Seal

The scientific name of the Northern fur seal is Callorhinus ursinus. It’s an eared seal that lives in and around the North Pacific Ocean. The animal feeds chiefly on fish but also catches squid. Males are much larger and bulkier than females. The adult males are black, dark brown, or medium grey in colour. Adult females tend to be a mixture of colours. Young pups are black.

During the winter, northern fur seals move further southwards and may reach as far south as Baja California. In May, the animals form breeding rookeries. A male maintains a harem consisting of as many as fifty females.

Hydrocephalus

Ziggy Star had hydrocephalus, a condition that also occurs in humans and other mammals. Cerebrospinal fluid collects in the ventricles, or spaces, inside the brain. It’s normal for the ventricles to contain the fluid, but in hydrocephalus an excessive amount collects inside them. The pressure exerted by the fluid pushes the brain against the skull and damages the organ.

In humans, a shunt (tube) is often placed in the brain to drain the fluid to another part of the body, which then gets rid of the fluid. In Ziggy’s case, the shunt was implanted through her skull and extended down her neck into her abdomen.

Ziggy’s Surgery

One problem with Ziggy’s surgery was positioning the shunt correctly. Since Northern fur seals are mammals like us they have the same basic body structure and function. They have some differences from us, however, such as the size and proportion of each body part. The shape of the skull, brain, and ventricles is different in humans and seals, for example. A hole was drilled through Ziggy’s skull so that the shunt could be inserted into the correct place. It was vital that the location of the opening was correct.

Another potential problem with Ziggy’s surgery was the use of an anesthetic. Marine mammals have a “dive reflex”. This causes changes in their physiology when they dive so that they can survive for an extended time underwater. Heart rate slows, for example, and peripheral blood vessels (those near the surface of the body) constrict. A general anesthetic can cause problems in an animal if it activates the dive reflex.

The veterinarians that operated on Ziggy came from Cummings School of Medicine at Tufts University. Other specialists were added to the surgical team to increase the chance of success, including one with experience in giving anesthetics to marine mammals.

The Result

The surgery appears to have been successful. The operation took place on November 30th, 2017. Ziggy took four days to wake up from the anesthetic, so the attention that she got from an anesthetic specialist was probably very valuable. The latest report about her condition that I’ve read was published on January 15th, 2018. At that point she was recovering nicely. Her behaviour was more normal, her weight was increasing, and she was entering the water occasionally. I hope her recovery continues and that her life is soon much better than it was before the surgery.

References

Ziggy Star information from the Mystic Aquarium

Information about Ziggy's surgery from Tufts University

Facts about Ziggy's treatment and recovery from Gizmodo