Hypodipsic hypernatremia after long-standing polydipsia in a cat with suspect neonatal head trauma.

A 16-month-old neutered male domestic shorthair cat weighing 2.7 kg was referred for further evaluation of acute generalized muscle weakness and paraparesis after a long-standing history of polyuria-polydipsia. The diagnosis of hypodipsic/adipsic hypernatremia relied on the key findings of absent spontaneous drinking despite hypernatremia and a hyperosmolar state (444.8 mOsm/kg, reference interval 280 to 310 mOsm/kg). Brain MRI revealed severe multifocal anatomic anomalies of the rostral calvarium and the forebrain, suggestive of encephaloclastic porencephaly. Involvement of the thalamic and hypothalamic regions could have been responsible for the cat's adipsic hypernatremia. The unique aspects of this case were the rare description of central nervous system disease leading to hypodipsia, and the history of chronic polydipsia before the acute onset of hypodipsia. Key clinical message: Multifocal abnormalities of the forebrain can present with polyuria-polydipsia syndrome, hypodipsia/adipsia, or both, depending on the stage of the disease. This likely happens when the hypothalamic and thalamic regions are affected, since they regulate antidiuretic hormone release and thirst, respectively.