Simple SummaryThis paper reports a case of suppurative meningoencephalitis byPseudomonas aeruginosafrom the direct extension of chronic otitis in a Gir cow. The direct extension of otitis media/interna results in secondary pyogranulomatous intracranial lesions occasionally. Clinical signs included forebrain, cerebellum, cranial nerve VII, VIII, and XII impairment. Pure cultures ofP. aeruginosawere obtained and identified in the suppurative central nervous system (CNS) lesions, meninges, and inner ear samples. The paucity of case reports of middle or inner ear infections evolving to suppurative processes in the CNS of adult cattle suggests underreporting or lack of diagnosis.AbstractThis paper aims to report clinical, laboratory and pathological features in a case of suppurative meningoencephalitis byP. aeruginosafrom the direct extension of chronic otitis in a Gir cow. The cow was recumbent during physical examination, and neurological examination revealed depression, absence of left eyelid and auricular motor reflex, and hypotonic tongue. Hematology revealed hemoconcentration, leukocytosis by neutrophilia, and hyperfibrinogenemia. Cerebrospinal fluid was slightly turbid, and presented polymorphonuclear pleocytosis, and hyperproteinorrachia. Grossly, the skull floor showed a purulent green–yellow exudate that drained from the left inner ear to the cisterna magna. There was diffuse congestion of the telencephalon, and meninges showed severe hyperemia, moderate thickening, and opacity with the deposition of fibrinosuppurative material ventrally, extending to the cerebellum and brainstem. The left cerebellar hemisphere showed an approximately 1.5 cm in diameter liquefaction area surrounded by a hemorrhagic halo. Histologically, cerebellar, mesencephalic, thalamic, and brain base meninges were intensely thickened and showed severe suppurative inflammation and fibrin deposition. Small multifocal suppurative areas were observed in the cerebellum and brainstem, characterized by a necrotic core, a number of neutrophils, and Gram-negative intralesional bacillary myriads. Pure cultures ofP. aeruginosawere obtained and identified in the suppurative CNS lesions, meninges, and inner ear samples. This report highlights an uncommon clinical evolution of secondaryP. aeruginosasuppurative meningoencephalitis, probably triggered by recurrent parasitic otitis in an adult Gir cow. Veterinarians, practitioners, and farmers must be aware of the risk of CNS infections after unresolved media and inner otitis, especially in cattle breeds more prone to developing parasitic otitis, such as the Gir and Indubrasil breeds.