Abstracts

Rationale: To understand patterns of epilepsy care at the primary and tertiary level one must assess investigations and management at each level, and variables that determine clinician behavior. We analyzed prior and new investigations after a 1st visit at our epilepsy centre, and variables associated with these decisions. Methods: The Calgary Division of Neurology is the main tertiary referral centre for adults with epilepsy, serving 1.3 million people. We prospectively captured data on consecutive adults with the diagnosis of epilepsy at the 1st encounter in our outpatient epilepsy program, using a validated data capture and verification system, excluding patients with single seizures and children. We captured type and number of investigations done prior to referral and new investigations triggered by the 1st encounter in the epilepsy program and analyzed factors associated with these decisions. Results: In 687 consecutive patients (52% women) the mean age and duration of epilepsy was 40 and 12 years respectively, 64.1% had focal epilepsy, 23% had idiopathic generalized epilepsy, and 21% were seizure free in the past year. At the time of the 1st visit, 83% and 61% already had an EEG and MRI, respectively. Video-EEG and neuropsychological tests had been done each in 7%. Patients with focal seizures, as compared to other seizures, were 20% more likely to have had an MRI (p0.005), but just as likely to have had a CT head (60%), and routine (80%) and sleep deprived (20%) EEG. New investigations were ordered in 70% of patients as follows: Scalp EEG (52%), MRI (38 %), video-EEG (7%), CT head (2%). The probability of new tests did not vary by type of seizure or epilepsy syndrome (60%-70%), but in pair-wise comparisons new tests were ordered in fewer patients with localization related epilepsy (RR=0.85, p=0.009), and in more patients with GTC seizures (CT, MRI, routine EEG) (RR=1.13, p=0.04). The most frequently repeated investigations were routine EEG (49%), MRI (27%) and video-EEG (26%). In contras CT was ordered in 2%. Seizure freedom in the past year did not influence the decision to order new tests. But previous findings strongly influenced the probability of repeating a test. A repeat MRI was ordered only in 23% of patients with a previously abnormal MRI, but in 53% with previously normal MRIs (p<0.001). Repeat EEG and MRI were more likely in patients with focal epilepsy and unknown seizure focus (64% for EEG, 45% for MRI). Conclusions: Up to 17% of patients have no EEG and 39% have no MRI prior to referral to tertiary care, and investigations are ordered in 70% after assessment. Patients with any GTCs get more outpatient investigations after the 1st visit than those with focal seizures. The causes remain to be determined. The most important predictor of new investigations is not lack of seizure control, but uncertainty of localization of seizure focus and previous findings on EEG and MRI. CT is used broadly by referring clinicians, but rarely by epilepsy specialists. There is a need for systematic studies assessing investigations for epilepsy and their yield in primary and in tertiary care settings.