Dermoid sinus type IV associated with spina bifida in a young Victorian bulldog

DERMOID sinus (also termed pilonidal sinus, pilonidal cyst or dermoid cyst) is a developmental anomaly characterised by incomplete separation of the skin from the neural tube during embryonic development (Lord and others 1957, Mann and Stratton 1966, Antin 1970). Six different types of dermoid sinus exist and classification is based on their relationship to the supraspinous ligament (Mann and Stratton 1966, Kiviranta and others 2011). This short communication describes the clinical, MRI and histopathological features of a type IV dermoid sinus and spina bifida in a young Victorian bulldog. An 11-month-old male Victorian bulldog was referred for investigation of progressive paraparesis, moderate hindlimb ataxia and moderate proprioceptive deficits in both hindlimbs. At physical examination, it was noted that the hair was growing in a spiral fashion on the dorsal midline in the mid-thoracic region. A small, fluctuating mass was palpable subcutaneously and evoked considerable pain for the dog; the mass was continuous with a firm fistulous cord attached to the underlying tissues. A round-shaped opening in the skin (diameter 0.5 cm) containing no exudates was found after clipping of the hair. Radiographs of the thoracic and thoracolumbar spine were unremarkable. MRI scans (Vet-MR Grande; Esaote) of the dog's thoracic region were obtained in three planes of orientation before and after the intravenous administration of 0.1 mmol/kg gadolinium (Magnevist; Schering). Transverse T1-weighted and T2-weighted images revealed an invagination of the epidermal and dermal tissues towards the spinous process of T8. A fistular tract was visible connecting the spinal cord with the opened skin layers. The normal morphology of T8 was lost: this vertebra lacked a normal vertebral arch and the spinous process …