[5] Although the pattern of inflammation is similar to other neuropathological conditions, resembling CNS inflammatory diseases which produces lesions alike to those that occur in NME, a definitive diagnosis can be made solely based on by histopathological examination through a necropsy.
[6] After a short amount of time vestibulo-cerebellar symptoms will rapidly progress, leaving the animal in a state of depressed consciousness having seizures, amaurosis and ataxia.
[3] When examining the transversal sections, the non-suppurative (lymphoplasmacytic and histiocytic) inflammation of both the meninges and encephalitis have characteristic histopathologic changes of necrotizing nature in the corona radiata (white matter), the thalamus and the cerebrocortical area.
[6][8] The meninges itself is focally thickened by dense aggregations of lymphocytes, plasma cells and macrophages infiltrating due to the reinforced immune answer (perivascular cuffing).
[9][10] Several multifocal encephalic lesions in corona radiata are erasing the border in the cerebral hemispheres between white and grey matter, exposing an asymmetrical ventricular enlargement.
[4] They can be divided into three phases: Additionally, temporal lobes with dense mononuclear cells can be observed infiltrating the meninges, and cerebellar herniation through the foramen magnum,[3] which leads to neurological symptoms like continuous circling or stroke-like seizures.