Dermoid/Epidermoid Cyst (Cholesteatoma)
Epidermoid or dermoid cysts, which contain varying amounts of epidermal and dermal structures, result from congenitally displaced embryonic remnants that proliferate with age. During embryological invagination of neuroectoderm, portions of ectoderm destined to differentiate into skin become entrapped as the neural tube closes. Because the neural canal closes from a caudal to cranial direction beginning at the brains stem level, the fourth ventricle and cerebellomedullary and fourth ventricular region are common sites for these abnormalities to be present. Congenital epidermoid or dermoid cysts are sometimes thin walled and contain mucinous material, keratin, or desquamated epithelial cells. Abnormally displaced cells are likely present at birth; however, the onset of clinical signs usually occurs later in life. Some animals are not presented for evaluation until adulthood or middle age. Theoretically, these cysts can also occur iatrogenically due to laceration and inward displacement of a skin fragment during cerebrospinal fluid collection performed at the cisterna magna. Less likely, dermoid or epidermoid cysts may also occur in the spinal cord.
Age of Onset: Typically greater than 5 years of age, although any age of animal can be affected
Sex Predisposition: Any sex of animal can be affected
Clinical Course:
Variable - some dogs do not demonstrate clinical signs while others may develop progressive signs dependent on the location and severity of the dermoid or epidermoid cyst.
Variable - some dogs do not demonstrate clinical signs while others may develop progressive signs dependent on the location and severity of the dermoid or epidermoid cyst.
Clinical Signs:
Movement
Paresis
Ataxia
Proprioception
Proprioceptive deficits
Cranial Nerves
Cranial nerve deficits (vestibular, etc.)
Spinal Reflexes
Hyperreflexia
Other
May be associated with otogenic meningoencephalitis (Newman 2015)
Movement
Paresis
Ataxia
Proprioception
Proprioceptive deficits
Cranial Nerves
Cranial nerve deficits (vestibular, etc.)
Spinal Reflexes
Hyperreflexia
Other
May be associated with otogenic meningoencephalitis (Newman 2015)
Intracranial - fourth ventricle and cerebellomedullary regions are common
Spinal - variable
Spinal - variable
Unknown
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