IMAGING AND ELECTROPHYSIOLOGIC TESTING IN MILD HEAD-INJURY

Increasingly sophisticated neural imaging and electrophysiologic techn iques are beginning to demonstrate abnormalities in some patients who have the sequelae of mild head injury (MHI). Although the exact basis of many features of postconcussive syndrome remains elusive, these new er techniques are beginning to provide an anatomic and physiologic exp lanation for this disorder. Study of MHI suffers from several methodol ogic weaknesses. First, definitions vary between studies.1 The most co mmonly used and simplest definition is a Glasgow Coma Scale (GCS) scor e of 13 to 15. The GCS, which grades patients on a scale of 3 to 15 (u sing a simple clinical examination), has been criticized for not measu ring behavior. Moderate head injury (HI) is usually defined as a GCS o f 9 to 12 on initial examination. A GCS of 8 or lower is interpreted a s indicating severe HI. Some authors refine the definition of MHI, req uiring loss of consciousness (LOC) of less than 20 minutes and an abse nce of focal findings on examination in addition to a GCS of 13 to 15; however, the older literature relies more heavily on the duration of LOC or retrograde amnesia in defining MHI. Second, most imaging studie s do not limit themselves to MHI. Studies are usually performed on hos pitalized patients; those who are discharged from emergency rooms or w ho fail to seek immediate medical attention are underrespresented. Thi rd, the timing of the study has an influence on the findings. Studies are obtained at various times after injury, and this variable is not a lways analyzed.