Characteristics of the Middle Cervical Sympathetic Ganglion: A Systematic Review and Meta-Analysis
Authors: Baek Jung Hwan 
Published: October 2019

Background: Understanding the characteristics of the middle cervical sympathetic ganglion
(MCSG) may minimize procedure-related complications and maximize efficacy during surgery or
ultrasound (US)-guided procedures. The location and detection rate of the MCSG were variable
in small population studies. Therefore, a large population study or meta-analysis could give more
information about the MCSG.
Objectives: We aim to review the published literature and evaluate the anatomical features of
the MCSG, including the detection rate, location, size, and a normal variation, and to review the
clinical relevance of MCSG for procedures including, US-guided ganglion block, ethanol ablation
(EA), or radiofrequency ablation (RFA).
Study Design: A systematic review and meta-analysis. The Ovid-MEDLINE and EMBASE databases
were searched to find the detection rate, location, and other characteristics of the MCSG.
Setting: The pooled proportions for the detection rate of the MCSG were assessed using the
DerSimonian-Laird random-effects model.
Methods: Heterogeneity among the studies was determined using a chi-square analysis for the
pooled estimates and inconsistency index (I2
). In order to reduce the heterogeneity, sensitivity
analyses were performed.
Results: A review of 542 studies identified 8 eligible studies, with 273 MCSGs included in the
meta-analysis. The pooled proportion for the detection rate of the MCSG was 50.4% (95%
confidence interval [CI], 34.5–66.4%). Considerable heterogeneity among the studies was
observed (I2
= 94.9%). In the sensitivity analysis, when excluding one study, heterogeneity was
reduced with a recalculated pooled proportion of 44.2% (95% CI, 32.1–56.2%; I2
= 86.0%). The
location of the MCSG is usually posterior to the carotid sheath and anterior to the longus colli
muscle at the level of the C3–C7 vertebrae. There was a variant where the cervical sympathetic
trunk was located at the posterior wall of the carotid sheath and was adherent to the sheath. The
size of the MCSG is as follows: the width, length, and height ranges were 3.8–6.3 mm, 6.3–10.5
mm, and 1.7–2.1 mm, respectively. A specific type of MCSG, referred to as the “double middle
cervical ganglion”, consisting of 2 ganglia, was demonstrated in 3 studies with a detection rate
of 2.9–10%.
Limitations: This meta-analysis included a relatively small number of studies. Significant
heterogeneity was also present in the detection rate of MCSG in these studies. There was a lack of
concentrated information about the MCSG, because the majority of the included studies focused
on the entire cervical sympathetic chain, not only MCSG primarily. Improving complication rates
might be limited due to the approximate 50% detection rate.
Conclusion: Understanding the characteristics and variations of the MCSG could minimize
complications and maximize efficacy during surgery and US-guided procedures.
Key words: Middle cervical sympathetic ganglion, cervical sympathetic trunk, cervical
sympathetic chain, ultrasound, nerve block, ethanol ablation, radiofrequency ablation, thyroid,
Horner syndrome, meta-analysis