Magnetic resonance imaging findings in epileptic cats with a normal interictal neurological examination: 188 cases

Abstract

Epilepsy is a common neurological condition in dogs and cats. Although an increased likelihood of significant brain lesions with age has been identified in neurologically normal dogs with epileptic seizures, the underlying aetiology of epileptic seizures in cats that present with normal physical and neurological examinations remains unknown. In this cross‐sectional study, the authors examined MRI findings in a large population of cats with a normal interictal physical and neurological examination. They hypothesised that age would have an impact on the prevalence of detectable lesions. First, following the guidelines for dogs and in accordance with previous studies, the authors divided the cats into three age groups (aged one year or younger, between one and six, and older than six) and calculated the proportion of cats with a detectable lesion on MRI in these groups. In the first group, 3/32 cats (9.4 per cent) had significant MRI abnormalities that were all consistent with congenital malformation; in the second group, only 5/92 (5.4 per cent) MRI scans were abnormal and in the third group, 15/ 65 (23.1 per cent) cats showed abnormal findings that were predominantly lesions of neoplastic origin. Second, to investigate the impact of age further, data were investigated as a continuous variable using receiver operating characteristic analysis. This indicated an optimal cut‐off age of five years, above which MRI abnormalities were more likely, with an increase in the odds of a significant structural lesion increasing by 14 per cent per year.

Formation of a meningoencephalocele after removal of a frontal lobe meningioma by transfrontal craniotomy in a cat

“…15 Acquired meningoencephaloceles are rarely described in cats and can be of non-traumatic, traumatic and spontaneous origin following the human classification scheme. 16,17 In the present case an iatrogenic traumatic aetiology was obvious.…”

Recurrent seizures in cats: Diagnostic approach – when is it idiopathic epilepsy?

“…Raimondi et al recently reported that 23% of cats older than 6 years at seizure onset with a normal interictal neurologic examination had a significant structural abnormality on MRi causing their seizure disorder. 30 The most common causes of structural epilepsy in cats include neoplasia, inflamma-tory disorders, and vascular disorders such as infarcts or hemorrhage. 1,7,11,16,17,20 Congenital anomalies, degenerative disorders, storage diseases and thiamine deficiency have also been reported.…”

“…The diagnosis of IE (primary epilepsy or unknown epilepsy) is one of exclusion and in dogs and cats is traditionally made based on typical signalment and seizure history, unremarkable interictal physical and neurologic examination, exclusion of under lying metabolic and toxic causes, and inability to find an intracranial cause (Table 2). 1,3,5,6,10,14,23,29,30,61,62 These criteria for diagnosis have been problematic in cats, however, because until recently the published reports describing cats with IE have been very limited. Historically, iE was considered to be an uncommon cause of seizures in cats.…”

“…Although there is proven inheritance of iE in several dog breeds, and inheritance is suspected in many others based on high breed prevalence or familial occurrence, there is really very little evidence to support a genetic cause in most cats with iE. [6][7][8]14 Studies have reported iE in 22-57% of cats with recurrent seizures, 4,7,12,13,16,[28][29][30]61,62,64 suggesting that iE should be considered an important differential diagnosis in such cases. The diagnosis of iE in these studies was based on normal interictal physical and neurologic examinations, normal metabolic testing and, in most cases, unremarkable MRi or postmortem histopathology of the brain.…”

“…in several studies the mean age for seizure onset in cats with iE was between 3 and 5 years, while cats with intracranial disease did not usually start experiencing seizures until they were older than 8 years of age. 1,4,7,10,11,16,30,61,62,64,65 There are, of course, exceptions as congenital disorders, FiP, non-suppurative meningoencephalitis of unknown etiology and feline ischemic encephalopathy predominantly affect young cats, while neoplasia is more common in the older cat population. Although there is considerable overlap between groups, a young adult cat is more likely to have iE than structural intracranial disease.…”