Neuropathology of Spontaneous Hypertensive Encephalopathy in Cats

Pathologic features of 12 cats with naturally acquired systemic hypertension and concomitant hypertensive encephalopathy were analyzed. All cats demonstrated acute onset of signs localized to the forebrain and/or brainstem, including stupor, coma, and seizures. All cats had systemic hypertension, ranging from 160 to 300 mm Hg. Gross lesions were identified in 4 of 12 cases, including caudal herniation of the cerebrum and cerebellum, sometimes with compression of the rostral colliculus and medulla. Histologically, all cases featured bilaterally symmetrical edema of the cerebral white matter. Associated vascular lesions, especially arteriolar hyalinosis, were also observed. Concurrent lesions were chronic tubulointerstitial nephritis (11/12 cases), adenomatous hyperplasia of the thyroid gland (4 cases), hypertensive choroidal arteriopathy (6 cases), and left ventricular hypertrophy (5 cases). This study demonstrates that the typical histologic manifestation of spontaneous hypertensive encephalopathy in cats is bilaterally symmetrical edema of the subcortical cerebral white matter.