Removal of a Presumed Peripheral Cerebral Cyst via Craniectomy in a Crested Pekin Duck ( Anas platyrhynchos f dom).

A juvenile, male crested pekin duck ( Anas platyrhynchos f dom) was presented for neurologic signs suggestive of cerebellar disease. Physical examination revealed microphthalmia, erratic head movements, and ataxia. Computed tomography scan of the head and neck regions revealed 2 full-thickness skull-bone defects within the caudal portion of the cranium. The cerebellum appeared to be ventrally compressed by a homogeneous, triangular, fluid-attenuating region (0-10 Hounsfield units). A craniectomy was performed, and a presumed peripheral cerebral cyst was removed with suction and gentle dissection. No postoperative complications occurred, and the patient showed clinical improvement for 5 months after surgery. However, after 5 months, the owners elected euthanasia because of poor prognosis after finding the duck minimally responsive in a water enclosure. At necropsy, a thin-walled, epithelial structure was present in meninges and was adhered to the skull at the presumed surgical site.

Syndrome of inappropriate antidiuretic hormone secretion in a cat with a putative Rathke's cleft cyst.

An 11-year-old spayed female domestic shorthair cat was evaluated for anorexia, lethargy and weight loss of 6 days' duration. Bilateral mydriasis, absent menace response, slow-to-absent pupillary light reflexes, bilateral retinal detachment, intermittent horizontal nystagmus, intermittent ventral strabismus and systemic hypertension were present. Biochemical analysis revealed severe hyponatremia, severe hypochloremia and mild hypokalemia. Multifocal central nervous system disease was suspected based on optic, trigeminal sensory (ophthalmic branch), vestibulocochlear and possible oculomotor nerve dysfunction. Thoracic radiographs showed mild cardiomegaly without evidence of congestive heart failure. Ultrasound revealed mild pleural and peritoneal effusion. A cause of the severe hyponatremia was not identified, and it persisted despite fluid therapy. Syndrome of inappropriate antidiuretic hormone secretion (SIADH) was suspected as the cause of hyponatremia. Humane euthanasia was elected owing to continued clinical decline. Serum hyposmolality, urine hyperosmolality, natriuresis and lack of confirmed renal, thyroid and pulmonary disease aided in the presumed diagnosis of SIADH. Post-mortem histopathology of the brain revealed degeneration of the hypothalamus and optic tracts, along with a prominent fluid-filled craniopharyngeal duct (putative Rathke's cleft cyst) separating the pars distalis and the pars intermedius. The hypothalamic degeneration, possibly secondary to a Rathke's cleft cyst, was hypothesized to be the cause of presumptive SIADH in the patient. Although rare in occurrence, Rathke's cleft cyst should be included as a differential diagnosis in dogs and cats with signs of pituitary dysfunction.

Intramedullary epidermoid cyst in the thoracic spine of a dog.

A 5 yr old female spayed mastiff was evaluated for a 3-4 mo history of paraparesis and 3 days of acutely worse paraparesis and incontinence. On magnetic resonance imaging, a spinal cord lesion was present at the ninth thoracic vertebra. The lesion was hyperintense on T2-weighted images (T2-W), and a hyperintense rim was present on T1-weighted postcontrast images. Histologic examination showed a cystic mass lined by squamous epithelial cells. Histopathologic diagnosis was an intramedullary epidermoid spinal cyst. Epidermoid cyst should be a differential diagnosis in young dogs with a myelopathy and an intramedullary spinal cord lesion on magnetic resonance imaging examination.

Ependymal cyst in the cerebrum of an African green monkey (Chlorocebus aethiops).

A focal lesion was detected by magnetic resonance imaging in the right caudal occipital lobe of the cerebrum in an African green monkey (Chlorocebus aethiops). Neurological signs were not observed in this animal. At necropsy examination, an 8mm wedge-shaped intracranial cavity was found, which apparently did not communicate with the ventricles. Microscopically, the inner surface of the cavity was lined by ciliated cuboidal epithelium with positive immunoreactivity for S100 protein, glial fibrillary acidic protein and cytokeratin. Based on the gross, microscopical and immunohistochemical findings the lesion was classified as an ependymal cyst. To the best of our knowledge, this is the first report of an ependymal cyst in an African green monkey.

Cerebellar ependymal cyst in a dog.

An 11-week-old, male, Staffordshire Bull Terrier had a history of generalized ataxia and falling since birth. The neurologic findings suggested a localization in the cerebellum. Magnetic resonance imaging of the brain was performed. In all sequences the area of the cerebellum was almost replaced by fluid isointense to cerebrospinal fluid. A complete necropsy was performed after euthanasia. Histologically, the lesion was characterized by extensive loss of cerebellar tissue in both hemispheres and vermis. Toward the surface of the cerebellar defect, the cavity was confined by ruptured and folded membranes consisting of a layer of glial fibrillary acidic (GFAP)-positive glial cells covered multifocally by epithelial cells. Some of these cells bore apical cilia and were cytokeratin and GFAP negative, supporting their ependymal origin. The histopathologic features of our case are consistent with the diagnosis of an ependymal cyst. Its glial and ependymal nature as demonstrated by histopathologic and immunohistochemical examination differs from arachnoid cysts, which have also been reported in dogs. The origin of these cysts remains controversial, but it has been suggested that they develop during embryogenesis subsequent to sequestration of developing neuroectoderm. We speculate that the cyst could have been the result of a pre- or perinatal, possibly traumatic, insult because hemorrhage, and tissue destruction had occurred. To our knowledge, this is the first description of an ependymal cyst in the veterinary literature.

Ependymal cyst in a cynomolgus macaque (Macaca fascicularis).

BACKGROUND: A focal hypointense intracranial lesion was detected by magnetic resonance imaging in the right caudal occipital lobe of the cerebrum in an asymptomatic cynomolgus macaque (Macaca fascicularis). RESULTS: Following euthanasia, gross evaluation of the lesion revealed a 1 cm diameter, wedge-shaped intracranial cavitation without apparent communication with the ventricles. Histologically, the lesion was lined by ciliated cuboidal to low columnar epithelium that showed immunopositivity for cytokeratin, S-100, and GFAP. CONCLUSION: Based upon the gross, histologic, and immunohistochemical findings, this lesion was classified as an ependymal cyst. In the human patients, ependymal cysts are benign, non-infectious, non-inflammatory lesions of the central nervous system that are believed to originate from aberrant migration of ependymal cells during development. To our knowledge, this is the first report of an ependymal cyst in a non-rodent veterinary species and the first report of a benign intracranial cyst of any classification in a non-human primate.

Imaging diagnosis--degenerative intraspinal cyst associated with an intervertebral disc.

A 6-year-old neutered male Rottweiler had chronic episodic signs of thoracolumbar pain and inability to stand that did not improve after rest and nonsteroidal antiinflammatory medication. In magnetic resonance images, an extradural mass was identified between the spinal cord and the T13/L1 intervertebral disc; the mass was compressing the cord in a dorsoventral direction. The lesion had a low signal intensity rim that enhanced slightly after gadolinium administration, and contents with similar signal intensity to cerebrospinal fluid. The lesion was removed surgically by severing its attachments to the annulus fibrosus. The histologic diagnosis was degenerative intraspinal cyst. The origin of such cysts, and their relationship to synovial and ganglion cysts is discussed.