Alisa D. Gean MD, Presenter: Medical Advisory Board, NeuroLogica Corp

Robert C. Cantu MA, MD, Abstract Co-Author: Nothing to Disclose

To identify the imaging characteristics of the "second impact syndrome" (SIS) and draw parallels to non-accidental trauma.

We conducted a review of the current sports literature on SIS and combined it with 10 new cases of our own.  We defined SIS as a clinical scenario consisting of an initial concussion (without LOC), followed by persistent post-concussive symptoms, followed by a subsequent impact (also without LOC) that resulted in a catastophic outcome. Cases were analyzed with regard to sex, age, sport, Glasgow Coma Scale (GCS), and duration of symptoms before the second injury. CT and MR (when available) examinations were assessed for: maximal SDH thickness, SDH heterogeneity, midline shift, effacement of basal cisterns, brainstem distortion, presence of intra-axial hemorrhage (e.g., contusions, DAI), hemispheric “asymmetry” (defined as the thickness of hemisphere measured at the level of the lateral ventricles), preservation of hemispheric gray-white differentiation, and post-traumatic ischemic infarction.

There are 8 prior published cases of a thin acute SDH in association with unilateral hemispheric swelling in patients who returned to play before the symptoms of a prior head injury had resolved.  We add 10 new patients with a similar clinical scenario who suffered a catastrophic outcome.  Nine of the 10 patients were young males playing American football; the 10th patient was a 10 y/o girl playing pee-wee football. ALL of our patients demonstrated: 1) maximal SDH thickness <1cm, 2) SDH heterogeneity, 3) completely effaced basal cisterns and convexity sulci , 4) brainstem compression due to uncal and diencephalic herniation, 5) no evidence of intra-axial hemorrhage (e.g., contusions, DAI), 6) preserved gray-white matter differentiation within the cerebral hemispheres on admission CT, 7) “hemispheric asymmetry”, and 8) multifocal post-traumatic ischemic infarction on follow-up imaging (if the patient survived).

Isolated acute hyperemic hemispheric swelling in association with a small acute SDH in athletes receiving a second head injury while still symptomatic from a prior head injury is characteristic of the SIS.  Parallels between victims of non-accidental trauma and our cohort of patients will be presented.

The SIS is characterized by a distinct and ominous clinical scenario as well as a unique imaging appearance. 

Gean, A, Cantu, R, The "Second Impact Syndrome": An Uncommon Catastrophic Result of Repetitive Head Injury with a Characteristic Imaging Appearance.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9001463.html