Verbal learning deficits following severe head injury: heterogeneity in recovery over 1 year

✓ A total of 40 severely head-injured patients were selected from the Traumatic Coma Data Bank, supported by the National Institute of Neurological Disorders and Stroke, to analyze the recovery of verbal learning across baseline and 6- and 12-month evaluations postinjury. During the initial 6 months, the group demonstrated marked recovery, followed by an absence of improvement over the latter part of the year. Analysis of this recovery curve on a case by case basis revealed three recovery subtypes: namely, a flat curve, a peak-drop curve, or an improvement curve. These three subtypes proved to have concurrent validity when compared with another memory test. Adding 19 new patients to the sample cross-validated the subtypes. However, the memory performance of the 59 patients was dissociated from other neuropsychological tests which showed recovery at more equivalent rates across the subtypes. Analysis of the demographic and neurological characteristics disclosed that the group with a peak-drop recovery curve was less well educated and the group with a flat curve demonstrated a trend toward higher levels of hypoxia. Moreover, the three subgroups were rated by their relatives to have equivalent levels of depression at baseline and at 6 months, but only the improved subgroup demonstrated reduced depression at 1 year. The clinical relevancy of these differential recovery curves is discussed.