Concurrent Type IVa Dermoid Sinus, Thoracic Meningomyelocele, and Spina Bifida in a Maltese Dog: CT and MRI Findings

Abstract

A 5-year-old neutered male Maltese weighing 3.8 kg was referred due to worsening hindlimb stiffness and urinary incontinence that progressed over three months. Physical examination revealed a focal skin depression along the dorsal midline of the mid-thoracic area. Neurological examination demonstrated decreased postural reactions in the hindlimbs, as determined by hopping and wheelbarrowing tests. Thoracic radiographs showed a split appearance of the T6 vertebral spinous process, and computed tomography confirmed a dorsal arch defect spanning the T2 to T9 vertebrae. Magnetic resonance imaging revealed a dermoid sinus extending ventrally from a cutaneous focal indentation to the dura mater through the vertebral defect, consistent with a Type IVa lesion. At the same level, focal dorsal tenting of the meninges was also observed, indicative of meningomyelocele. Adjacent to the dural connection from C5 to T13 vertebrae, syringomyelia was identified. Moreover, a well-defined structure within the subcutaneous tissue at the T5 level was connected to the supraspinous process by a thin strand, suggestive of a suspected Type I or Type II dermoid sinus. Based on these findings, a diagnosis of concurrent Type IVa dermoid sinus, meningomyelocele, and spina bifida was established. Surgical decompression of the spinal cord was performed to address suspected tethered cord syndrome and to prevent progression of neurological deficits. Following surgery, urinary incontinence improved and there were no post-operative complications. When neural tube defects are suspected through clinical and neurological evaluations, advanced imaging modalities such as CT and MRI are recommended for thorough assessment of spinal anomalies, for accurate classification, and to facilitate surgical planning.