Sense of a presence and suicidal ideation following traumatic brain injury: indications of right-hemispheric intrusions from neuropsychological profiles.

50 patients who had sustained a traumatic brain injury were given complete neuropsychological assessments between 0.5 and 4.0 years after the incident; 62% of these patients reported that episodes of a "sensed presence" (left side: 71%; right side: 19%; both: 10%) had occurred. Sensed presences along the left side were primarily (82%) associated with anxiety or fear while those which occurred along the right side were more pleasant (83%). The neuropsychological profiles of patients who reported these experiences suggested elevated complex partial epileptic-like signs and a pattern of mild dysfunction within the right prefrontal and temporoparietal lobes which would promote brief hypermetabolic periods within the latter region. Patients who displayed this profile in conjunction with fragmentation of the self-concept and concomitantly lowered left-hemispheric linguistic functions reported more frequent suicidal impulses. The results are compatible with the hypothesis that the "sense of a presence" is an intrusion of the right-hemispheric homologue of the sense of self into left-hemispheric awareness.