EXPRESS: Diagnosis and surgical management of a type IVb dermoid sinus between the parietal and occipital bones in a young cat

Case summary

A dermoid sinus is a congenital, tubular skin defect caused by incomplete separation of the skin and nervous system during embryonic development. It is more common in dogs and usually located along the spine. Intranasal or superficial cranial forms have been occasionally reported. This case describes a dermoid sinus on the head of a cat with intracranial extension, illustrating diagnostic and surgical challenges.

A 1.5-year-old female British Shorthair cat was evaluated for a recurring, previously superficially resected cutaneous mass on the head with an abnormal pattern of hair growth. MRI and CT revealed an extra axial mass extending in a tubular fashion through a midline defect between the parietal and occipital bones, continuing caudally along a malformed tentorium. Mild focal cerebellar compression and suspected secondary meningitis, more evident on the right side, were also identified.

Surgery was performed via a combined caudotentorial and limited right-sided rostrotentorial craniectomy. Careful dissection along the lesion margins and durectomy of focally attached thickened meninges allowed complete resection. No post-operative complications or further neurological deficits occurred. Histopathology confirmed a dermoid sinus. Follow up after 28 months revealed no recurrence.

Relevance and novel information

To the authors’ knowledge, this is the first reported case of a type IVb dermoid sinus in a cat, successfully managed surgically. This case provides important clinical information regarding the diagnosis, imaging features, and surgical management of complex intracranially extending dermoid sinuses in feline patients.