Unilateral Facial Paresis Secondary to a Suspected Brainstem Arachnoid Cyst in a Maltese Dog

Abstract

ABSTRACT. An 8-year-old, intact female Maltese dog was presented with decreased tear production and unilateral loss of eye blinking. Neuro-ophthalmic examination and brain magnetic resonance imaging were performed to determine the origin of facial paresis. A cystic lesion in the left pontomedullary region which displayed equal intensity to cerebrospinal fluid was revealed. Hyposignality was noted on fluid attenuated inversion recovery sequences, and the lesion was suggestive of an arachnoid cyst. This report described unilateral facial nerve dysfunction that resulted from a suspected brainstem arachnoid cyst in an unusual anatomic location.KEY WORDS: arachnoid cysts, brainstem, canine, facial paresis.J. Vet. Med. Sci. 73(4): 459-462, 2011 Facial paresis and paralysis result in facial muscle dysfunction from cranial nerve diseases and injuries [26]. Intracranial and brainstem abnormalities including congenital and neoplastic space-occupying lesions can result in facial nerve dysfunction, which are classified as central in origin. Additionally, parasympathetic denervation to the lacrimal pathway of the facial nerve can also result in loss of tear production. Intracranial cysts are likely developmental in origin and can develop in cerebrum, cerebellum, and brainstem thus may cause cranial nerve dysfunction in human and dogs as well [5,21,29,31]. However, intracranial cysts located in the brainstem are extremely rare in both human and dogs [8,18,21,23,28,31,32]. We described a case of unilateral facial paresis concurrent with lacrimal loss, which was strongly suspected to be caused by a pontomedullary cystic lesion.An 8-year-old, intact female Maltese dog was admitted for evaluation of a unilateral blinking disorder. The patient had been diagnosed as keratoconjunctivitis sicca (KCS) by the referring animal hospital. Topical therapy for KCS including artificial tear, topical antibiotics and cyclosporine showed no improvement. Moreover, sudden onset of blepharoplegia of the left eye (OS) was detected a few days before visiting our referral hospital.The outer appearance of the face was symmetrical. However, the left nostril was drier and more narrowed than the right nostril (Fig. 1A). Marked blepharoedema and mild mucoid ocular discharge were observed bilaterally ( . A neuro-ophthalmic examination revealed a loss of palpebral and corneal reflexes (OS) and the menace response (OS). Direct and consensual pupillary light responses (PLR) and the results of other bilateral cranial nerve tests were normal. The patient was tentatively diagnosed as unilateral facial paresis. As the course of clinical signs was slow and progressive, the presence of primary cause of facial paresis was strongly suspected rather than idiopathic facial paresis which typically showed acute onset. Thus laboratory tests were performed to search the cause of KSC and facial paresis. Otoscopic examination and skull radiography showed no evidence of otitis. The results of routine laboratory test were not remarkable. Reverse transcriptase-polymerase cha...

Two different indications of ventriculoperitoneal and cystoperitoneal shunting in six dogs

“…Another type of intracranial cysts has been described in the veterinary literature. A brainstem AC causing unilateral facial paresis was found in an 8-year-old Maltese dog, and it was treated conservatively (Kim et al, 2011). There is no fundamental medical treatment which could reduce the size of an IAC.…”

A Recurrent Suprapituitary Ependymal Cyst Managed by Endoscopy-Assisted Transsphenoidal Surgery in a Canine: A Case Report

“…The most common sites of intracranial cysts in animals include the fourth ventricle and cerebellopontine angle (2, 6, 8, 10, 12, 14–16) and the area above the quadrigeminal plate (4–7, 9). There are individual reports of cysts located in the brainstem (6, 9, 11, 13); cerebellum (3); and frontal (11), diencephalic (1), and hypophyseal (31) regions. Lesions involving the cerebellar, medullary, and fourth ventricular regions can be best approached from the caudal direction (suboccipital approach, e.g., cystoperitoneal shunting).…”

“…The MRI findings and surgical management of a neuroendodermal cyst have also been described (8). Other reports involve a brainstem arachnoid cyst in the pontomedullary region that caused unilateral facial paresis in an 8-years-old female Maltese dog (9) and a caudal fossa respiratory epithelial cyst in the fourth ventricle that caused bilateral vestibular syndrome in an 11-months-old female Bloodhound (10). Meningioma is also a common intracranial tumor in dogs, although cystic meningioma is rare and has been described in only one study involving three dogs (11).…”