We recently had a debate during one of our weekly Neuro meetings on the “standard of care” for work-up of a patient with new onset seizures. As a neuroradiologist I insisted that all patients with such a history undergo an MR of the brain, and that if a CT head is done through the ER, and it is negative, the conclusion in the report should read something like “an MR of the brain should be considered for further work up of seizures.” The non-neuroradiologists in the group argued that the burden of getting an MR or not should fall upon the ordering clinician, and us radiologists should not recommend an MR in light of a negative CT.
What are your thoughts? Thanks.
New Onset Seizure Work-Up
I think it may help to review the literature prior to formulating a policy – and consider the prevalence of CT and MR abnormalities in the various epilepsy groups. The literature clearly demonstrates what everyone knows – that MR is better than CT for “epilepsy”. This is also true for patients with a new onset seizure. In patients presenting with first-onset seizure in either the pediatric or adult age group, epileptogenic abnormalities occurred on MRI in 14% (38/263 in King et al Lancet 352:66-67, 1998) and 16% of 518 (in Berg et al. Brain in press). In King’s study, 28 of the 38 patients with MRI abnormalities had CT scans performed; CT was able to detect abnormalities in only 12 (43%) of those 28 and there were no cases where CT was positive with a negative MR. No lesions occurred in patients with idiopathic generalized epilepsies. In the more restrictive group of patients with intractable epilepsy undergoing surgjcal treatment, sensitivities for detecting abnormalities were 95% (104/109 in Bronen et al Radiology 201:97-105, 1996) for MRI versus 32% (35/109) for CT; CT was able to detect 34% (35/104) of those 104 abnormalities detected by MRI.
Based on this data, it’s fair to conclude that there is a small but significant prevalence of abnormalities that will be found by MR in new onset seizures (about 15%) and that MR is 2-3x more sensitive than CT. And since the recommendations/guidelines by a number of organizations is to obtain an MRI for all seizures except febrile or those due to idiopathic generalized epilepsies, I generally recommend an MRI exam with the following caveat: I suggest that MRI is more sensitive than CT and that an MRI may be helpful if the seizure may be due to a focal or partial seizure.