MRI reveals structural changes in shark

In December 2004, an atypical acute-onset scoliotic event, probably the result of trauma, occurred in a female sand tiger shark at The Deep, a sea-life center in Hull, U.K. Initial survey radiography indicated a likely scoliosis. Researchers used MRI to obtain information on neurological status and acquire detailed images of the spine. As far as we know, this is the first time an MR scan has been conducted on a live shark (see photo).

The practical and logistical challenges of maintaining a 2.4-meter-long, 120-kg live shark in a mobile MRI unit were considerable. Two hours and 12 minutes elapsed from the initial administration of anesthesia for capture until the shark's return to the exhibit, although the scanning process took only 44 minutes. The shark was under constant monitoring and gill irrigation. Aquarists from The Deep, veterinary surgeon Marc Geach, and scanning technicians performed the examination. The shark has remained stable for the past year.

The imaging results showed the early stages of dynamic remodeling of the affected region of the spine but did not reveal any neurologic abnormalities. The images were of high quality, and MRI is now considered appropriate for investigation of spinal abnormalities in this species. The procedure is being written up for submission to a peer-reviewed publication.

A number of aquariums worldwide have reported spinal deformities of the vertebral column in captive sand tiger sharks. Clinical presentations typically involve spinal curvature between the pectoral girdle and cranial dorsal fin. This condition is usually progressive and often has a poor prognosis. Researchers have used radiography and CT to study the vertebral columns of sand tiger sharks postmortem, which has provided valuable information on the structural changes that occur in scoliosis.

-By Graham Hill, science officer, The Deep, and Marc Geach, MRCVS, veterinary director, Zoolife International