PTSD is a psychiatric condition that can develop following exposure to a traumatic event that involved actual or threatened death or serious injury, where the response involved intense fear, helplessness, or horror. Symptoms include re-experiencing intrusive thoughts, flashbacks avoidance, arousal and impaired memory. Alterations in memory, motivation and mood have been associated with dysfunction of the central acetylcholinergic (ACh) system. Changes in the regional distribution of muscarinic ACh receptors (m-AChR) have been demonstrated in some disorders that exhibit similar neuropsychiatric symptoms, and I-123 iodo-dexetemide (IDEX) uptake corresponds to the known distribution of m-AChR. Therefore, it was postulated that IDEX could be used to investigate whether there were alterations in cerebral cholinergic binding activity in patients with PTSD.
SPECT brain imaging of 10 PTSD subjects (Clinician Administered PTSD Score 57-115) and 5 control subjects was performed using an IRIX triple-headed gammacamera after injection of 194 MBq of IDEX. Iterative reconstruction with attenuation correction was performed with OSEM. Spatial normalization to a standard anatomical space, global scaling and voxel-based statistical analysis was performed with SPM2.
In the PTSD group, deficits in IDEX binding were found in the right precuneus (corrected p = 0.0004), left insula (corrected p = 0.0005), and bilateral parahippocampi (left corrected p = 0.001; right corrected p = 0.00009) and an increase was demonstrated in the caudate (corrected p = 0.041).
Alterations in ACh binding in PTSD are evident in regions that can begin to explain a part of the altered cognitive symptomatology apparent in this condition.