The sympathetic nervous system plays an important role in cancer progression and other diseases. Surgical sympathectomy is a valuable method for studying these processes by inducing complete unilateral adrenergic ablation. This technique avoids the side effects associated with pharmacologic inhibition of the sympathetic nervous system.
Additionally, it is less invasive than previously described methods because it avoids dissection of the carotid artery. When performing this technique, it may be difficult to enter the right space where the ganglion resides and differentiate it from the fat. Identifying the landmark and practice is therefore essential.
The anatomy appears slightly different when in motion and undissected, so visual demonstration provides a better guide on how to identify the anatomical landmark which is key for this technique. Begin by applying topical ophthalmic ointment to the anesthetized mouse to prevent ocular injuries and dryness. Place the mouse under a dissecting microscope on its dorsal side and maintain inhalation anesthesia using a precision vaporizer and nose cone.
Secure both forelimbs with hypoallergenic tape. Clean the shaved ventral aspect of the neck with povidone iodine and then wipe with 70%alcohol. After repeating the cleaning process two more times, place a sterile drape over the surgical site.
Then use small scissors and make a 1.5 centimeter midline skin incision on the ventral aspect of the neck from approximately two millimeters below the chin to two millimeters above the sternal notch. Separate the skin from the underlying fascia by inserting pointed scissors under the skin on each side and spreading. Then retract the edges of the skin laterally with forceps to expose the underlying fascia and submandibular salivary glands.
Pull the submandibular glands caudally with forceps to reveal the underlying muscles. Next, locate the junction of the posterior belly of the digastric muscle and omohyoid muscle. Insert the tip of 45 degree angled forceps at this junction lateral to the anterior jugular vein to pierce and spread an opening in the overlying deep cervical fascia.
Keep this window open with the 45 degree angled forceps and expand this opening wider by performing spreading maneuvers with a pair of curved forceps in the other hand. Locate the superior cervical ganglion or SCG on the lateral wall of the revealed space. While maintaining the opening with forceps with the other hand, gently grasp the SCG with forceps and pull it out of the opening to bring it into better view.
Once the SCG is in view, grasp the lateral base of the SCG where it is still attached to the surrounding tissues. Using the other hand, slowly and gently retract the SCG in a ventral and caudal direction multiple times to gradually avulse the ganglion little by little. Keep the ganglion intact during this maneuver to ensure no residual ganglion remnants are left behind.
Slowly release the base of the ganglion and check for bleeding by looking for blood pooling. Once done, move the salivary glands back to their normal anatomic positions. Approximate and close the skin using simple interrupted 5-0 nylon sutures.
During the dissection, the right anterior jugular vein coursed alongside the trachea's lateral border. When P0 tdTomato transgenic mouse with red fluorescent neurons was examined under a fluorescent microscope, the fluorescent vagus nerve was observed coursing laterally to the common carotid artery and the fluorescent SCG was observed at the bifurcation of the common carotid artery lateral to the anterior jugular vein. The resected SCG in a transgenic mouse was confirmed by its red fluorescence compared to the non-fluorescent SCG control.
The immunofluorescent staining confirmed a tyrosine hydroxylase, a marker for adrenergic nerves. After superior cervical ganglionectomy, ptosis, that is the drooping of the eyelid, was observed, which is a sign of Horner syndrome. Immunofluorescence staining for a tyrosine hydroxylase on the right submandibular salivary gland following right superior cervical ganglionectomy confirmed the successful ablation of the adrenergic signaling with absent tyrosine hydroxylase nerve staining.
In contrast, the left control submandibular gland maintained its adrenergic input and intact a tyrosine hydroxylase nerve staining which was also confirmed by quantification. ELISA quantification of norepinephrine in the salivary gland confirmed a significant reduction in norepinephrine expression in the submandibular gland on the side of superior cervical ganglionectomy in contrast to the control sham surgery side. Be patient and gentle when removing the SCG.
Avulse it slowly in a piecemeal fashion. Otherwise, the carotid artery connected to the SCG may easily be injured resulting in bleeding.
