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Hippocampal volume in adult burn patients with and without posttraumatic stress disorder.

OBJECTIVE
Increasing evidence suggests that posttraumatic stress disorder (PTSD) is associated with small hippocampal size. The authors compared trauma-exposed subjects with PTSD and trauma-exposed subjects without PTSD to clarify whether small hippocampal size is related to PTSD or to mere trauma exposure.


METHOD
Three-dimensional structural magnetic resonance imaging was used to assess hippocampal volumes in 30 men who had recently been exposed to a severe burn trauma and 15 matched healthy comparison subjects.


RESULTS
Relative to the comparison subjects, the trauma-exposed subjects with PTSD (N=15) as well as the trauma-exposed subjects without PTSD (N=15) had significantly smaller volumes of the right hippocampus (subjects with PTSD: -12%; subjects without PTSD: -13%). Larger total areas of burned body surface were significantly related to smaller left hippocampal volumes. Use of analgesic/sedative treatment with the N-methyl-d-aspartic acid (NMDA) antagonist ketamine was significantly related to larger right hippocampal volumes and to stronger PTSD symptoms.


CONCLUSIONS
PTSD is not a necessary condition for small hippocampal size in trauma-exposed individuals. Rather, the results provide evidence that smaller hippocampal size in trauma-exposed individuals is a result of traumatic stress. The posttraumatic application of NMDA antagonists may protect against hippocampal damage induced by traumatic stressors but increases the patient's risk of developing PTSD symptoms.