Probabilistic mapping of the cervical sympathetic trunk ganglia

Activating PV-positive neurons in ventral thalamic reticular nucleus reduces pain sensitivity in mice

Previous studies have demonstrated that thalamic reticular nucleus (TRN) and the sub-nuclei play important roles in pain sensation. Our previous findings showed that activating parvalbumin-positive (PV+) neurons in dorsal sector of TRN (dTRN) could reduce the pain threshold and consequently increase the pain sensitivity of mice. Recent studies have shown that activation of GABAergic projection of TRN to ventrobasal thalamus (VB) alleviated pathological pain. GABAergic neurons in TRN are mainly PV+ neurons. However, the exact roles of ventral TRN (vTRN) PV+ neurons in pain sensation remain unclear. In this study, the designer receptors exclusively activated by designer drugs (DREADD) method was used to activate the PV+ neurons in vTRN of PV-Cre transgenic mice, and the mechanical threshold and thermal latency were measured to investigate the regulatory effects of vTRN on pain sensitivity in mice. Thereafter, PV-Cre transgenic mice, conditional anterograde axonal tract tracing, and immunohistochemistry were used to investigate the distribution of PV+ neurons fibers in vTRN. The results showed that the activation of PV+ neurons in vTRN increased the mechanical threshold and thermal latency, which indicated reduction of pain sensitivity. The fibers of these neurons mainly projected to ventral posterolateral thalamic nucleus (VPL), ventral posteromedial thalamic nucleus (VPM), ventrolateral thalamic nucleus (VL), centrolateral thalamic nucleus (CL) and various other brain regions. These findings indicated that activation of PV+ neurons in the vTRN decreased pain sensitivity in mice, which provided additional evidence on the mechanisms of PV+ neurons of TRN in regulating neuralgia.

Radiological evaluation of the localization of sympathetic ganglia in the cervical region

PURPOSE

To determine local variations of cervical sympathetic ganglia (CSG) according to vertebral levels on preoperative neck magnetic resonance imaging (MRI) by designating carotid artery (CA) as the standard landmark at the center, in attempts to prevent injury to CSG in the anterior-anterolateral approaches performed in the cervical spinal region.

MATERIALS AND METHODS

The retrospective study reviewed neck MRI images of 281 patients, of which the images of 231 patients were excluded from the study based on the exclusion criteria. As a result, the MRI images of the remaining 50 patients were included in the study. The circumference of carotid artery (CA) was divided into eight equal zones with CA defined as the standard landmark at the center. High-risk zones were determined based on the anterior-anterolateral approaches.

RESULTS

At C1 level, a superior ganglion was located on the right side in 32 (64%) and on the left side in 30 (60%) patients. At this level, it was most commonly located in Zone 6. Middle ganglion was observed most frequently at C3 level, which was detected on the right side in 17 (34%) and on the left side in 17 (34%) patients. At this level, it was most commonly located in Zone 2.

CONCLUSION

Variations in the localizations of superior and middle cervical ganglia should be taken into consideration prior to surgical procedures planned for this region. This study sheds light on high-risk zones in the surgical site and could guide surgeons to better understand the location of cervical sympathetic ganglia before surgical planning.

Superior Cervical Sympathetic Ganglion: Normal Imaging Appearance on 3T-MRI

Objective

To identify superior cervical sympathetic ganglion (SCSG) and describe their characteristic MR appearance using 3T-MRI.

Materials and Methods

In this prospective study, we recruited 53 consecutive patients without history of head and neck irradiation. Using anatomic location based on literature review, both sides of the neck were evaluated to identify SCSGs in consensus. SCSGs were divided into definite (medial to internal carotid artery [ICA] and lateral to longus capitis muscle [LCM]) and probable SCSGs based on relative location to ICA and LCM. Two readers evaluated signal characteristics including intraganglionic hypointensity of all SCSGs and relative location of probable SCSGs. Interrater and intrarater agreements were quantified using unweighted kappa.

Results

Ninety-one neck sites in 53 patients were evaluated after exclusion of 15 neck sites with pathology. Definite SCSGs were identified at 66 (73%) sites, and probable SCSGs were found in 25 (27%). Probable SCSGs were located anterior to LCM in 16 (18%), lateral to ICA in 6 (7%), and posterior to ICA in 3 (3%). Intraganglionic hypointensity was identified in 82 (90%) on contrast-enhanced fat-suppressed T1-weighted images. There was no statistical difference in the relative location between definite and probable SCSGs of the right and left sides with intragnalionic hypointensity on difference pulse sequences. Interrater and intrarater agreements on the location and intraganglionic hypointensity were excellent (κ-value, 0.749–1.000).

Conclusion

3T-MRI identified definite SCSGs at 73% of neck sites and varied location of the remaining SCSGs. Intraganglionic hypointensity was a characteristic feature of SCSGs.