Case summary: A 6-month-old female domestic shorthair cat was presented with acute onset non-ambulatory right hemiparesis and horizontal nystagmus following an injection attempt in the neck, during which the cat did not cooperate. Magnetic resonance imaging (MRI) revealed a well-defined intra-axial lesion on the right side of the myelencephalon. The lesion was T2-weighted hypointense and T1-weighted hypointense to isointense to grey matter, non-contrast enhancing, with perilesional oedema and signal void on T2*-weighted images. A linear hyperintense lesion in the muscles of the right dorsolateral aspect of the neck on short tau inversion recovery images was also observed. These MRI findings were consistent with iatrogenic brainstem haemorrhage and a muscle needle tract. The cat made a good recovery with just mild residual neurological deficits 6 weeks after the injury.
Relevance and novel information: To our knowledge, this is the first report of an iatrogenic brainstem needle injury in a cat and the first report of a central nervous system iatrogenic trauma after a parenteral injection. Care should be taken with neck parenteral injections, especially in the cranial cervical area.