Introduction The National Institute of Health Stroke Scale (NIHSS) is a neurological deficit scale originally designed for clinical trials and has become a required metric in stroke centers in the United States. The evolution of acute stroke therapy has validated the early treatment of large vessel occlusions, the diagnosis of which can accurately be made with CTA imaging. Therefore, many comprehensive stroke centers not unlike ours have adopted an initial screening CTA stroke protocol. Currently our institution utilizes a multi-phase CTA protocol for initial imaging in patients with suspected stroke. This protocol is fast and accurate at diagnosing proximal occlusions. However, it has been our observation that many of these cases do not have treatable lesions. In such cases, additional imaging with MRI is obtained for definitive diagnosis. Although NIHSS has been criticized for low Positive Predicative Value for Large vessel proximal occlusions (LVPO), it has been shown to be quite sensitive for post stroke prognosis. We postulate that NIHSS could be applied as a triage factor in the acute stroke settings. Patient’s with a low score (shown to have a good prognosis by NIHSS) could be initially imaged with MRI/MRA instead of CTA.

Methods We retrospectively reviewed Stroke patients with multiphasic CTA from 8/2016 through 4/2017. Inclusion criteria were; presentation with acute stroke signs after initial evaluation by ED staff or stroke neurologist with subsequent multiphase CTA imaging. NIHSS scores were collected from patient‘s charts calculated upon initial presentation through EPIC system.

Results 376 underwent multiphase CTA during the study period.

75 patients out of 376 (20%) had NIHSS of 4 or less.

Of these 75 patients, 7 (9%) had LVPO.

Overall, this yield a 90% Negative Predictive Value for LVPO.

Discussion The current standard of care within our system is obtaining CTA multiphase for every patient with suspected neurologic deficits concerning for stroke. A large number of those patient’s will undergo MRI evaluation for definitive diagnosis whether CTA examination is positive, negative or indeterminate. Based on our retrospective findings, only a small percentage of patients, with a NIHSS of 4 or less, would show evidence of large vessel occlusion on CTA. MR technology is ever evolving with faster imaging capabilities. In fact, we have created a rapid/stroke intervention protocol including a DWI, FLAIR, GRE and MRA head which can be performed in roughly 6 mins. Therefore, we postulate that patients with NIHSS of 4 or less could be triaged to MRI instead of CTA. This would increase diagnostic accuracy and efficiency, while reducing radiation exposure and well as reducing the number of negative CTAs.

Conclusion Based on our findings, we postulate that Initial imaging evaluation of stroke patients with NIHSS of 4 or less could be performed with rapid MRI/MRA imaging. This could be not only more definitive in diagnosis but also reduce the number of negative CTAs and eliminate any imaging redundancies for more directed patient care as compared to current practice.

Disclosures M. Alhasan: None. K. Alsomali: None. N. Emerson: None.