Abstract

Ultrasound-guided sampling of cerebrospinal fluid (CSF) is a rapid, safe technique described in horses, cows, dogs, cats, and rabbits.^1–6 Antemortem CSF sampling was recently reported in a bottlenose dolphin (Tursiops truncatus) using radiographic guidance. Real-time imaging of needle placement into the subarachnoid space, however, was not performed.⁷

An adult female Tursiops truncatus in human care died acutely. Twelve hours postmortem, longitudinal ultrasonography of the atlantooccipital region on dorsal midline was performed (C60 5-2 MHz, Sonosite M-Turbo®, Bothell, WA). The anechoic, well-defined, triangular cisterna magna was readily identified between the external occipital crest and the fused atlas-axis, dorsal to the cervical spinal cord. Cervical ventroflexion markedly increased conspicuity and size of the cisterna (1.8 cm depth x 2.5 cm length). The ultrasonographic distance between the skin and the center of the cisterna was ∼9 cm. A 17 g 6.8 cm coaxial introducer needle (Argon Medical Devices®, Athens, TX) was advanced with ultrasound-guidance through the blubber and dorsal musculature to the cisterna. The stylet was removed and a 20 g 5.5” spinal needle passed through the introducer. The needle tip was seen entering the cisterna, the stylet removed, and 10 mL CSF collected. The resultant sample was grossly colorless, and on cytological evaluation, minimally cellular and minimally hemodilute, with protein 152 mg/dL, RBC 430/µL, and WBC 2/µL.

Given (1) the increased risk of fatal spinal cord puncture when performing cervical centesis without needle tip visualization, (2) the increased risk of hemorrhage from the spinal rete mirabilis in this species, and (3) that the caudal skull and cervical spine are not palpable in T. truncatus, ultrasound-guided needle placement for CSF sampling is advised in antemortem cases.

Acknowledgments

The author kindly thanks the phenomenal veterinary and animal care staff, as well as the leadership of Clearwater Marine Aquarium, in particular Dr. Shelly Marquardt. Dr. Carolina Le-Bert of the U.S. Navy Marine Mammal Program, Dr. Dean Hendrickson of Colorado State University College of Veterinary Medicine, and Drs. Mike Walsh and Nicole Stacy of the University of Florida are also acknowledged for their clinical excellence and scientific contributions.

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