Structural and Functional Changes Relevant to Maxillary Arterial Flow Observed During Computed Tomography and Nonselective Digital Subtraction Angiography in Cats With the Mouth Closed and Opened

Abstract

Some cats develop blindness during procedures with mouth gags, which possibly relates to maxillary arterial occlusion by opening the mouth. Our first aim was to use computed tomography (CT) to describe how vascular compression is possible based on morphologic differences between mouth positions. Our second aim was to use nonselective digital subtraction angiography to assess whether opening the mouth induces collateral circulation. Six healthy cats were examined. During CT, the maxillary artery coursed between the angular process of the mandible and the rostrolateral wall of the tympanic bulla. The median distance between these structures was shorter when the mouth was opened (left, 4.3 mm; right, 3.6 mm) vs. closed (left, 6.9 mm; right, 7.1 mm). Additionally, the distance was shorter on the side ipsilateral to the gag (P = 0.03). During nonselective angiography, with the mouth closed, there was strong sequential opacification of the external carotid arteries, maxillary arteries, maxillary retia mirabilia, cerebral arterial circle, and basilar artery. Additionally, there was uniform opacification of the cerebrum and cerebellum. With the mouth opened, opacification of the maxillary arteries (rostral to the angular processes) was reduced in all cats, the cerebral arterial circle and basilar artery had simultaneous opacification in four of six (67%) cats, and the cerebrum had reduced opacification compared to the cerebellum in four of six (67%). In conclusion, the maxillary arteries are situated such that they can be compressed when opening the mouth. Opening the mouth did not consistently induce collateral circulation sufficient to produce comparable cerebral opacification as when the mouth was closed.

Late‐onset seizures in a domestic shorthaired cat with global brain ischaemia and cortical laminar necrosis

“…19 There have also been several reports of postanaesthesia cortical blindness in cats, 9,10 some of which have been associated with the use of a mouth gag causing com-promised flow through the maxillary artery. 11,[20][21][22] Other proposed causes of blindness in cats after anaesthesia included GBI secondary to periods of hypoperfusion and hypoxaemia under general anaesthesia. In human medicine, perioperative visual loss is rare, with an estimated incidence of 0.02%.…”

Bilateral fibrodysplasia ossificans affecting the masticatory muscles and causing irreversible trismus in a domestic shorthair cat

“…2,9,16 Additionally, prolonged trismus and muscle swelling may have impaired the blood supply of the maxillary arteries to the retinae and brain. 30–32…”

“…2,9,16 Additionally, prolonged trismus and muscle swelling may have impaired the blood supply of the maxillary arteries to the retinae and brain. [30][31][32] In people, FOP lesions may arise after a regional inflammatory process such as a viral infection, fatigue, or muscle trauma and strain. 1 No history of trauma was reported in our case.…”

Global cerebral ischemia with subsequent respiratory arrest in a cat after repeated use of a spring-loaded mouth gag

“… 1 , 2 , 3 , 7 Occlusion of the MB-ECA can cause cerebral hypoxia, resulting in global cerebral ischemia. 1 – 7 Further compounding ischemia, the use of anesthesia may cause a reduction in perfusion to vital structures. 1 , 2 , 3 , 4 , 6 Areas of the brain most vulnerable to ischemic damage are the cerebral cortex, hippocampus, caudal colliculi and thalamic nuclei.…”