Posttraumatic Stress Disorder: Perspectives for the Use of Deep Brain Stimulation

Posttraumatic stress disorder (PTSD) may develop after a person is exposed to one or more traumatic events, such as sexual assault, warfare, serious injury, or threats of imminent death.

The diagnosis may be given when a group of symptoms, such as disturbing recurring flashbacks, avoidance or numbing of memories of the event, and hyperarousal, continue for more than a month after the occurrence of a traumatic event.

Most people having experienced a traumatizing event will not develop PTSD. People who experience assault-based trauma are more likely to develop PTSD, as opposed to people who experience non-assault based trauma such as witnessing trauma, accidents, and fire events.

Children are less likely to experience PTSD after trauma than adults, especially if they are under ten years of age.

War veterans are commonly at risk for PTSD.


Mild traumatic brain injury (mTBI) contributes to development of affective disorders, including post-traumatic stress disorder (PTSD).

Psychiatric symptoms typically emerge in a tardive fashion post-TBI, with negative effects on recovery. Patients with PTSD, as well as rodent models of PTSD, demonstrate structural and functional changes in brain regions mediating fear learning, including prefrontal cortex (PFC), amygdala (AMYG), and hippocampus (HC). These changes may reflect loss of top-down control by which PFC normally exhibits inhibitory influence over AMYG reactivity to fearful stimuli, with HC contribution. Considering the susceptibility of these regions to injury, Schneider et al., examined fear conditioning (FC) in the delayed post-injury period, using a mouse model of mTBI. Mice with mTBI displayed enhanced acquisition and delayed extinction of FC. Using Proton magnetic resonance spectroscopic imaging ex vivo, they examined PFC, AMYG, and HC levels of gamma-aminobutyric acid (GABA) and glutamate as surrogate measures of inhibitory and excitatory neurotransmission, respectively. Eight days post-injury, GABA was increased in PFC, with no significant changes in AMYG. In animals receiving FC and mTBI, glutamate trended toward an increase and the GABA/glutamate ratio decreased in ventral HC at 25 days post-injury, whereas GABA decreased and GABA/glutamate decreased in dorsal HC. These neurochemical changes are consistent with early TBI-induced PFC hypoactivation facilitating the fear learning circuit and exacerbating behavioral fear responses. The latent emergence of overall increased excitatory tone in the HC, despite distinct plasticity in dorsal and ventral HC fields, may be associated with disordered memory function, manifested as incomplete extinction and enhanced FC recall 1).

Treatment

Although most patients often improve with medications and/or psychotherapy, approximately 20-30% are considered to be refractory to conventional treatments. In other psychiatric disorders, DBS has been investigated in treatment-refractory patients. To date, preclinical work suggests that stimulation at high frequency delivered at particular timeframes to different targets, including the amygdala, ventral striatum, hippocampus, and prefrontal cortex may improve fear extinction and anxiety-like behavior in rodents. In the only clinical report published so far, a patient implanted with electrodes in the amygdala has shown striking improvements in PTSD symptoms.

Neuroimaging, preclinical, and preliminary clinical data suggest that the use of DBS for the treatment of PTSD may be practical but the field requires further investigation 2).

1) Schneider BL, Ghoddoussi F, Charlton JL, Kohler RJ, Galloway MP, Perrine SA, Conti AC. Increased Cortical Gamma-Aminobutyric Acid Precedes Incomplete Extinction of Conditioned Fear and Increased Hippocampal Excitatory Tone in a Mouse Model of Mild Traumatic Brain Injury. J Neurotrauma. 2016 Sep 1;33(17):1614-24. doi: 10.1089/neu.2015.4190. Epub 2016 Mar 18. PubMed PMID: 26529240.
2) Reznikov R, Hamani C. Posttraumatic Stress Disorder: Perspectives for the Use of Deep Brain Stimulation. Neuromodulation. 2016 Dec 19. doi: 10.1111/ner.12551. [Epub ahead of print] Review. PubMed PMID: 27992092.

Leave a Reply