Implicit olfactory abilities in traumatic brain injured patients

Abstract

To investigate implicit olfactory abilities in a group of anosmic traumatic brain injured (TBI) patients, an olfactomotor priming paradigm was administered. A group of matched normosmic/mildly microsmic TBI patients and a group of neurologically healthy participants served as controls. For all the groups, an interference effect was evident on the peak velocity of grip aperture when participants grasped a large target preceded by a "small" odor. The present results suggest that some form of implicit olfactory processing is preserved in TBI patients even when diagnosed as anosmic on the basis of explicit olfactory testing.

Traumatic Brain Injury and Olfaction: A Systematic Review

“…Table 1 provides a brief overview of the main goals and findings of each of the 25 studies that we examined in detail (4–28) and the subsequent Tables 2–8 provide further detail regarding aspects of the methodology, sample characteristics, etc. The studies ranged broadly in terms of their principal focus (Table 1).…”

“…The studies ranged broadly in terms of their principal focus (Table 1). Most of the studies included individuals who had sustained a TBI, regardless of the presence or otherwise of olfactory problems (5, 6, 9–12, 14–17, 19, 21–24, 26, 27) while in eight studies participants with TBI were selected for the presence of olfactory complaints or established olfactory impairment (4, 7, 8, 13, 18, 20, 25, 28). While most of the studies were cross sectional in design, several had an important longitudinal aspect (7, 9, 18, 26).…”

“…Traumatic brain injury severity was variously defined by the Glasgow Coma Score (GCS) (5, 6, 9, 15, 16, 19, 24, 25, 27), the duration of post-traumatic amnesia (PTA) (5, 6, 9, 15, 19, 25), the occurrence (and/or duration) of LOC (5, 6, 14, 19, 22, 23) – measures available to the clinician early following TBI or by functional outcomes (e.g., neuropsychological test performance (4, 9, 15, 17, 19, 21, 22, 24, 26), behavioral tests, or other functional questionnaires (5, 6, 9, 10, 22, 26) (Tables 3 and 4). One study focused solely on severe TBI (4), while three were concerned with mild TBI only (6, 10, 16).…”

“…One study focused solely on severe TBI (4), while three were concerned with mild TBI only (6, 10, 16). Structural brain imaging was examined in relation to olfactory outcomes in a number of studies (12–14, 18, 24, 27) (Table 4).…”

“…In other studies, a significant mean reduction in olfactory performance in the post-TBI group relative to appropriate controls was reported, indicating impairment in some individuals. The University of Pennsylvania Smell Identification Test (UPSIT) was the olfactory instrument most commonly used (4, 8, 11, 17, 20–23, 28) followed by the Sniffin’ Sticks (6, 7, 10, 12) (Tables 5–8). …”