Clinicopathologic features of brain herniation in animals

SUMMARY Caudal transtentorial, foramen magnum, rostral transtentorial, and cingulate gyrus herniation were diagnosed alone or in combination in 14 dogs, 7 cats, 1 horse, and 1 goat. Eleven of the affected animals had encephalitis; others had various diseases, including brain neoplasms, cranial trauma, and hydrocephalus. Herniation followed anesthesia or csf aspiration, or both, in 7 of the animals. Clinical signs were attributable to herniation in 13 cases. Animals with caudal transtentorial herniation had initial clinical evidence of midbrain compression followed occasionally by deficits related to the pons and medulla oblongata. Tetraplegia, apnea, and coma developed most often in animals with foramen magnum herniation. Clinical signs directly related to rostral transtentorial or cingulate gyrus herniation did not develop. Treatment with corticosteroids and osmotic diuretics occasionally resulted in temporary alleviation of clinical signs in animals with caudal transtentorial or foramen magnum herniation. However, neurologic dysfunction progressed and resulted in death or necessitated euthanasia within 12 hours in most cases. Animals with rostral transtentorial or cingulate gyrus herniation were not treated. At necropsy, animals with caudal transtentorial herniation of the temporal cortex had resultant compression and caudal displacement of the midbrain. Foramen magnum herniation of the cerebellum resulted in compression of the displaced cerebellum and medulla oblongata. Flattening of the rostral cerebellar vermis against the tentorium cerebelli occurred in animals with rostral transtentorial herniation. Compression of the opposite cingulate gyrus was the only consistent pathologic feature in cases of cingulate gyrus herniation.