NeuroImaging Radiological Interpretation System (NIRIS) for acute traumatic brain injury

Last revised by Muhammad Shoyab on 9 Jun 2021

The NeuroImaging Radiological Interpretation System (NIRIS) is a scheme for structured contextual reporting of CT head examinations of suspected head injuries.

The NIRIS was proposed 1 in 2018 by a multi-institute group of neuroradiologists based at Stanford University. Its unique objective is to enable the CT report to guide patient management towards specific and mutually exclusive action categories, an aim envisioned by Marshall et al. 2 when they proposed the Marshall classification back in 1991. This is where it also differs from the other existing systems like Rotterdam scoring, Helsinki scoring etc., whose principal focus is on making proper predictions on prognosis 1.

The presence of any one of the points promotes the patient into a higher category.

NIRIS presently applies only to plain CT in head injury patients. Further research can enable these action categories to be aligned with MRI findings.

While NIRIS remains to be validated by international or regulatory bodies, it is already being adopted by authors 3 working on contextual/disease-specific reporting templates. Further, since it utilizes the common data elements (CDE) defined by the National Institute of Health (NIH), this classification may find some place in the HIRADS categorizations under development by the American College of Radiology (ACR).

The authors have not specified a category for when a patient of clinically suspected diffuse axonal injury gets a normal CT image. Since a normal CT does not rule out diffuse axonal injury, such a patient requires MRI and/or close observation. This should have been included under NIRIS 1, but now it may be wrongly classified as NIRIS 0 based on “no abnormal findings”.

There is also no specific category for diffuse cerebral edema, although it may be the only finding in some cases, thus requiring further imaging and/or close observation.

Mild, moderate and severe hydrocephalus need to be clearly defined for the purpose of this classification since it is one of the discriminating features of the higher grades (NIRIS 2 to 4) that require aggressive management.

When compared against the already existing Rotterdam and Marshall classifications, NIRIS performed satisfactorily 1. Interobserver agreement in identifying the category discriminators, i.e. fracture, hemorrhage, mass effect etc. was also found to be high 4.

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