Ascending infection is also thought to occur from the middle ear, ie ear base swellings are often associated with otitis media.A gradual build-up of bacteria and yeast may lead to otitis externa which is difficult to manage due to the stenosis of the ear canal.This can either continue to be a chronic wax-filled outpouching of the ear canal or may progress to infection with concurrent ear issues such as otitis media, otitis interna Otitis media/interna and otitis externa Otitis externa. ![]() Development of a diverticulum of the ear canal wall just behind the ‘kink’ present in lop-eared rabbit ears due to chronic cerumen build-up.Bite wounds in the area of the tympanic bulla may lead to ear base abscessation (rare).One study has shown that lop-eared rabbits show statistically significantly more frequent ear canal stenosis, higher scores of cerumen and erythema, and more frequent potential pain response during ear examination, compared with erect-eared rabbits.Anatomical predisposition for cerumen to build up just behind the ‘kink’ in lop-eared rabbits’ ears.Abscesses arising from osteomyelitic tympanic bulla and otitis media/interna may also be associated with ear base swellings.Primary abscessation may occur rarely due to a penetrating wound through the tympanic bulla, eg cat bite.Secondary infection (and inflammation, although the inflammatory response in such cases is often minimal) and abscessation may ensue, although it has been argued that this does not represent a true abscess as it does not represent infection within a tissue.The cerumen builds up behind the ‘kink’ and over time can cause an outpouching or diverticulum of the ear canal at this site.The ear canal may act like a kinked hose, not allowing movement of cerumen out of the ear.In lop-eared rabbits, the ear canal is deformed, with a ‘kink’ occurring at the level of the junction of the auditory meatus and tragus, ie the ears droop down at this point.Print off the Owner factsheet on Ear base abscesses to give to your clients. Any facial nerve damage is likely to be permanent. The prognosis will be more guarded if vestibular and middle ear signs are present. Secondary infection of the diverticulum is likely to require surgery to attempt a ‘cure’. It can be difficult to assess their level of pain or discomfort. Prognosis: many lop-eared rabbits appear to cope with long-term ear swellings, especially if there are no other associated clinical signs.May require treatment ranging from no treatment to simple manual expression of the diverticulum contents, to flushing, to surgery such as lateral wall resection, sometimes coupled with lateral bulla osteotomy, or partial or total ear canal ablation. Treatment: variable, depending on clinical signs and the severity of any concurrent ear issues.Ancillary tests such as diagnostic imaging and culture and sensitivity may be indicated to assess for concurrent ear disease and to assess what treatment is required. Diagnosis: generally pathognomonic when swelling is palpable or visible in this region.There may be other signs associated with concurrent otitis externa, media or interna such as aural discharge, head shaking, facial paralysis or neurological signs, eg head tilt. Signs: a palpable swelling at the base of one or both ears.Primary abscessation may occur rarely due to a penetrating wound through the tympanic bulla, eg cat bite. In addition to this non-infectious diverticulitis, ascending infection may occur from the middle ear, ie ear base swellings are often associated with otitis media or osteomyelitis of the tympanic bulla. A gradual build-up of bacteria and yeast may lead to otitis externa which is difficult to manage due to the stenosis of the ear canal. In lop-eared rabbits the ear canal at the level of the ‘kink’ is soft-walled and therefore likely to become distended to form a pouch or diverticulum. ![]() As a result, the ear canal becomes occluded and cerumen builds up behind the kink and cannot leave the ear.
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