Discussion
The vast majority of lymphatic injury during spine surgery occurs in the thoracic and lumbar regions. Injury due to the close proximity of the thoracic duct and the cisterna chyli to the vertebral column results in chylothorax or chyloretroperitoneum.  The incidence of thoracic duct injury following cervical spine surgery is substantially lower in than in thoracolumbar surgery. This may be due to the longer anatomic course of the thoracic duct in the thoracolumbar area as compared to the cervical spine.  The height of the arch of the thoracic duct in the root of the neck also varies, and can be inferior to, at, or superior to the clavicle.1 Langford et al reported that a thoracic duct can extend as much as 5 cm above the clavicle2, and Hart et al described a case in which the arch was situated 7 to 8 cm above the clavicle.3 Also, there is significant deviation in the termination pattern of the thoracic duct as it joins the systemic circulation. It may end as single or multiple outlets into the left internal jugular vein, the left subclavian vein, the left external jugular vein, the left brachiocephalic vein, the left transverse cervical vein, or the right internal jugular vein.1,3-5
Intraoperative identification of lymphatic injury can be difficult due to the usual fasting state of patients prior to surgery, which diminishes lymphatic production and transport. Thus cloudy lymphatic material may not be visible in the wound even if an injury exists. Valsalva administration or placing the patient in the Trendelenburg position may assist in identifying an intraoperative leak.
During head and neck surgery, chyle leak from iatrogenic thoracic duct injury is a rare but serious complication that occurs in 0.5–1.4% of thyroidectomies6-10 and 2–8% of neck dissections2, 6, 11-13. However, it has only been reported postoperatively twice before following an anterior cervical disc fusion (ACDF). 14 Our case is the third case of chyle leak after cervical spine surgery.
Of the 3 reported cases of iatrogenic thoracic duct injury from ACDF (Table 1), 2 were male and 1 was female. All three of the patients were undergoing surgery focused on level C5-6 and were approached from the left side.
The patients were relatively healthy, with patient 1 being in an MVA, patient 2 having no comorbidities and patient 3 having hypertension. None of the patients were obese. The size of the postoperative chyle collection on imaging was 2.3 cm for Patient 2 and 4 cm for Patient 3. One of the 3 leaks was noted intraoperatively and was repaired immediately with clips. One of the leaks was noted after 2 months and was treated with needle aspiration. The third leak was noted 4 months after the initial surgery and required intrathoracic ligation of the thoracic duct. In the 2 patients with delayed leaks, there was no noted direct sizeable injury to the thoracic duct intraoperatively during initial surgery. Given the delayed presentation and return after 2 and 4 months following ACDF, the differential diagnosis before imaging and exploration was the formation of a post-op hematoma, seroma, or chyloma. Following imaging, drainage, and surgery, the suspicion of a chyloma was confirmed. We believe the chyloma likely occurred secondary to a retraction injury on a portion of her thoracic duct. There was a small leak that over time created a cystic capsule which contained the leak. Patient 3 had immediate release of significant chyle (after a drain had already collected 1000 mL) once this capsule was opened during subsequent repair, but Patient 2 was able to heal after a simple needle aspiration of 3.5 mL. These 3 patients show the range of leak severity after injury during ACDF.
Two patients were discharged the day after their initial ACDF, and one was discharged the same day as ACDF. As the ACDF surgery is trending towards an outpatient procedure, postoperative chyle leaks will often more likely be discovered in a delayed manner during an office visit, like Patients 2 and 3.
Presenting symptoms of the delayed leaks were nontender, mobile neck mass in Patient 2 and neck pain and swelling in Patient 3. No patient had postoperative fever, dysphagia, hoarseness, shortness of breath, or electrolyte abnormalities.
The 3 patients are doing well with follow up periods of 80 days, 3.5 years, and 5 years. Patient 3 who underwent thoracic duct ligation had no subsequent nutrition deficiency, as has been reported previously.15 After being addressed, patients may recover completely from this complication. None of these 3 patient has long-term side effects.