Dermoid sinus and bone defects of the fifth thoracic vertebrae in a shih-tzu



Recently, we encountered a five year old, neutered, male shih-tzu presented with an acute onset of ataxia of the pelvic limbs after a tuft of hair, protruding from a dermoid sinus on the dorsal midline of the cranial thoracic region, had been pulled by the groomer. Radiographs showed a defect of the spinous process and the vertebral body of T5. The spinous process was found to be separated into two sections forming an opening on the dorsal aspect of the vertebral body. Myelography showed that the dermoid sinus was tethered to the spinal cord, classified as a type IV dermoid sinus. A dorsal approach was performed to remove the dermoid sinus. The sinus was found to exist between a bone defect of the spinous process and the vertebral body of T5. A dorsal laminectomy was also performed at the level of T5. One month postoperatively, the dog was still mildly ataxic with subtle conscious propioceptive deficits in the pelvic limbs. At a telephone interview two months later, the owners reported great improvement in the dog, and no noticeable ataxia.

There are many reports in Rhodesian ridgebacks (Mann & Stratton 1996) but a dermoid sinus has been reported only once previously in a shih-tzu (Selcer and others 1984). Reports have shown that neurological signs with dermoid sinuses are most often caused by infection of the sinus with dissemination to the spinal cord or brain (that is, myelitis, encephalitis). We report this case to encourage clinicians to consider this type of trauma to the spinal cord when assessing an animal with a dermoid sinus and neurological signs. Clinicians should educate their clients in exercising caution with pets with a dermoid sinus.