Horner’s syndrome caused by the first rib fracture sustained during coronary artery bypass grafting: a case report and literature review

Background Horner’s syndrome is a rare complication of cardiovascular surgery. A bone fragment and hematoma due to rib fracture after cardiac surgery may cause injury to the brachial nerve plexus and sympathetic nerve trunk, leading to neurologic disorders and Horner’s syndrome. However, few reports have revealed the etiology of Horner’s syndrome after cardiovascular surgery based on imaging. Herein we present a case in which a plain CT scan confirmed the etiology of Horner’s syndrome after coronary artery bypass grafting (CABG), reviewing 139 CABG cases retrospectively in our hospital and 6 case reports of Horner’s syndrome associated with cardiovascular surgery. Case presentation A 69-year-old woman with a history of percutaneous coronary intervention and total abdominal hysterectomy with bilateral salpingo-oophorectomy had chest pain on exertion. Coronary angiography showed severe triple vessel disease. She underwent off-pump coronary artery bypass grafting (CABG). A median sternotomy was performed, and the split sternums were widened using a sternal retractor. The bilateral internal thoracic arteries were harvested. A triple CABG was performed. She had left shoulder pain after surgery. She complained of anhi-drosis involving the left face and hyperhidrosis involving the right face from postoperative day (POD) 6. Left ptosis and blurry vision appeared after discharge from the hospital, for which she saw a neurologist in our hospital on POD 48. Miosis could not be clearly confirmed. She was diagnosed with Horner’s syndrome. A plain CT scan revealed displaced fractures of the bilateral first ribs and left second rib. The bone fragment of the left first rib head was displaced 3 mm anteriorly compared to the left first rib head before surgery, which suggested that the fragment affected the stellate ganglion in the sympathetic trunk. The patient had regular follow-up evaluations. The anhidrosis persisted, but the ptosis improved, and the miosis was not confirmed at the 6-month follow-up evaluation. Conclusions We should recognize that Horner’s syndrome is one of the complications of cardiovascular surgery, especially CABG. Fracture of the first rib head with a displaced bone fracture was shown to be a contributor to ipsilateral Horner’s syndrome. When symptoms of Horner’s syndrome and other neurologic symptoms are noted after open heart surgery, a plain CT examination should be obtained.

median sternotomy is a remarkably forceful procedure, requiring forces from 150 to 300 N (kg・m/s 2 ) in corpses [2] and leading to rib fracture.A bone fragment and hematoma due to rib fracture may cause injury to the sympathetic nerve trunk and brachial nerve plexus [3,4], leading to Horner's syndrome and other neurologic disorders.However, few reports have revealed the etiology based on imaging.Herein we present a case in which a plain CT scan confirmed the etiology of Horner's syndrome after coronary artery bypass grafting (CABG), reviewing 139 CABG cases retrospectively in our hospital and 6 case reports of Horner's syndrome associated with cardiovascular surgery.

Case presentation
A 69-year-old woman with a history of percutaneous coronary intervention and a total abdominal hysterectomy with bilateral salpingo-oophorectomy had chest pain on exertion.Coronary angiography showed severe triple vessel disease.The SYNTAX score was 30, which favored CABG over percutaneous coronary intervention.She underwent off-pump CABG without anti-platelet respite.A pillow was placed under the back adjacent to the shoulder bones.A median sternotomy was performed, and the split sternums were widened using a sternal retractor (IMR15-710-J; Getinge, Gothenburg, Sweden) (Fig. 1A,  B).Bilateral internal thoracic arteries (ITAs) were harvested with a Harmonic ® scalpel (Johnson and Johnson, NJ, USA).A saphenous vein graft was also harvested.A triple CABG was performed.The respirator was withdrawn on postoperative day (POD) 1.Her recovery was uneventful, but she complained of left shoulder pain after the surgery.She also had anhidrosis involving the left face and hyperhidrosis involving the right face from POD 6.The pain persisted and was treated with acetaminophen.The patient had such a severe allergy to a contrast agent that myocardial scintigraphy was substituted for a postoperative coronary CT.A plain CT and MRI were not performed.The patient was discharged on POD 16.After discharge, in addition to anhidrosis involving the left face, left ptosis and blurry vision appeared, for which she saw a neurologist in our hospital on POD 48 (Fig. 2A).Miosis could not be clearly confirmed.She was diagnosed with Horner's syndrome.A head MRI revealed no lesions around the medulla oblongata.The symptoms persisted and a plain CT scan on POD 76 revealed displaced fractures of the bilateral first ribs and left second rib (Fig. 2B), which were thought to be caused by rib retraction during the CABG.The bone fragment of the left first rib head was displaced 3 mm anteriorly compared to the left first rib head before surgery (Fig. 2C), which suggested that the fragment affected the stellate ganglion in the sympathetic trunk.The patient had regular follow-up evaluations.At the 6-month follow-up evaluation, the anhidrosis persisted, but the ptosis and blurry vision improved, and the miosis was not confirmed.
To elucidate the relationship between Horner's syndrome and the first rib fracture due to CABG using ITA in our hospital, we retrospectively researched 139 patients who underwent CABG using an ITA from January 2022 to February 2024 who were followed by coronary or plain CT scans within 2 months after CABG (Table 1).In all cases, the same sternal retractor (IMR15-710-J) was used.The bilateral ITAs, LITA, and RITA were used in 91, 44, and 4 patients, respectively.The types of rib fractures were categorized as displaced or non-displaced (infraction fracture), and the sites of rib fractures were divided into the head, neck, tubercle, and body.Among all patients who sustained rib fractures, no patient sustained more than one fracture per rib.Among 95 patients in whom the RITA was used, 31 (32.6%)patients sustained a right first rib fracture, and among 135 patients in whom the LITA was used, 37 (27.4%)patients sustained a left first rib fracture.Of both ribs, a Fig. 1 Finding of LITA harvesting (These are pictures of reference and irrelevant to the patient described herein).A A median sternotomy was performed and the split sternums were widened using a sternal retractor (IMR15-710-J; Getinge, Gothenburg, Sweden).The maximum chest opening width of this retractor is 130 mm.This is a picture of reference and irrelevant to the patient described herein.B Rib retraction can be adjusted by a screw.The maximum movement range of the screw is 70 mm fracture of rib body was most frequent (right, 54.8%; left, 56.8%).Although 8 (5.8%) of 139 patients sustained the first rib head fracture, only the patient described herein (0.72%) developed Horner's syndrome.

Discussion
Horner's syndrome results from damage to the ipsilateral oculosympathetic pathway.Lung, breast, and mediastinum tumors, as well as neck injuries may cause the syndrome due to direct compression of the oculosympathetic pathway [5].However, cardiovascular surgery can also cause Horner's syndrome.Only six case reports [1,[6][7][8][9][10] of Horner's syndrome due to cardiovascular surgery were identified on a search of the literature (Table 2), which may in part be because the symptoms of Horner's syndrome do not always appear simultaneously and are sometimes too mild to be noticed.Leftsided Horner's syndrome was attributed to CABG in three cases [1,6,10] and the current case, and left lateral thoracotomy operation in two case [7,8].In most cases, the firstly recognized Horner's symptom was ptosis and the onset day was within 2 days after the operation.Generally speaking, Horner's syndrome caused by trauma is immediately diagnosed after a traumatic event, but the symptoms can be shown in a delayed manner [11], as in the current case.In some cases, the symptoms resolved spontaneously or with medication.
A sternal retractor, especially one for harvesting the ITAs, can cause rib fractures.Kimura [12] reported up to five fractures of the left upper rib after CABG using the left ITA (LITA).Rib retraction for harvesting ITAs after a median sternotomy exerts leverage on ribs like a nail puller.Specifically, the rib tubercle, split sternum, and rib head are the fulcrum, point of force, and point of action, respectively (Fig. 3).The rib head and neck are fixed by the costovertebral joint and costotransverse ligament, respectively.A sternal retractor for ITA harvesting is often placed at an upper position across the sternal angle.Forceful retraction during harvesting an ITA can exert excessive work according to the principle of leverage,  leading to fracture of the point of action (head of the first rib).If the rib is fragile, the power of excessive retraction may focus on the point of action, resulting in disruption of the principle of leverage and a fracture between the fulcrum (rib tubercle) and the point of force (split sternum).The rib fracture on CABG will incur more bleeding because perioperative anti-platelet drug therapy is a cornerstone of CABG.A displaced fracture and the ensuing bleeding could lead to injury of the surrounding organs and a hemothorax.A dislocation fracture of the costovertebral joint has been reported to cause injury to the intercostal artery and azygos vein, leading to a hematoma [13].In the same way, a bone fragment of the first rib and subsequent hematoma is considered to directly or indirectly compress brachial nerve plexus and stellate ganglion [3,4,12] (Fig. 4).The stellate ganglion, which is a second-order neuron of the oculosympathetic pathway, is located on the ventral surface of the first rib head [14] (Fig. 3).The left stellate ganglion is more densely surrounded than the right ganglion by the vertebral artery, esophagus, longus colli muscle, vertebral body, and left rib head, which might explain why Horner's syndrome occurs more often on the left side after open heart surgery.In addition, the LITA is used more frequently than the right ITA (RITA) during CABG for its good patency.
Horner's syndrome complicates all open heart surgery in 0.6-1.7% of cases [3,[16][17][18] and 0.2-7.7% of CABG cases [19][20][21].We retrospectively reviewed 139 CABG cases, among which 8 patients (5.8%) sustained the first rib head fracture (Table 1).Among those 8 patients, only the patient with displaced fracture described herein (0.72%) developed Horner's syndrome, and the other 7 patients with non-displaced fracture (infraction fracture) did not develop Horner's syndrome.This can not only graphically but also statistically prove that the displaced bone fracture of the first rib head and the ensuing inflammation and hematoma directly compress or injure the left stellate ganglion and lead to Horner's syndrome.
Horner syndrome after cardiovascular surgery may be a self-limiting complication based on the outcomes of 7 patients (Table 2), including the patient described herein.This finding can be in part because the inflammation and hematoma surrounding the fracture improved over time and the injured neuron recovered spontaneously.However, we should take Horner syndrome into account as a preventable complication.Minimum sternal widening and careful manipulation of a sternal retractor may prevent iatrogenic Horner's syndrome [6].The incidence of first rib fractures due to median sternotomy has been reported to decrease when the sternal retractor is placed at a lower position [3].From the viewpoints of the retraction blade, a sternal retractor for harvesting the ITAs is mainly divided into two types: Takedown pattern retractor and French pattern retractor (Fig. 5).There are no reports comparing the two retractors in the literature.A sternal retractor can be equipped with foil load sensors to measure the force distribution over the retractor blades [2].Therefore, further research for the relation among retraction force, chest opening width, harvesting time, and orthopedic and neurological complications for each retractor is expected, which may lead to a decrease in the complications by retractors.

Conclusion
We should recognize that Horner's syndrome is one of the complications of cardiovascular surgery, especially CABG.Fracture of the first rib head with a displaced bone fracture is a contributor to ipsilateral Horner's syndrome.When symptoms of Horner's syndrome and other neurologic symptoms are noted after cardiovascular surgery, a plain CT examination should be obtained.

Fig. 2
Fig. 2 Findings before and after CABG.A Left ptosis appeared after discharge and she was diagnosed with Horner's syndrome on postoperative day (POD) 48.B Plain CT scan on POD 76 revealed displaced fractures of the right first rib neck (blue arrow) and the left first rib head (red arrow).C Plain CT scan before CABG.Compared to this image, the bone fragment of the left first rib head (B, red arrow) was shown to be displaced 3 mm anteriorly, which suggested that the fragment affected the stellate ganglion in the sympathetic trunk

Fig. 3
Fig.3 Schema for the mechanism underlying rib fracture.Forceful retraction (blue arrow) can exert excessive work according to the principle of leverage (red arrow), leading to a fracture at the point of action (rib head).If the rib is fragile, the power of excessive retraction may be conducted to the point of action, resulting in disruption of the leverage principle and fracture between the fulcrum (rib tubercle) and point of force (split sternum)

Fig. 4 Fig. 5
Fig.4 Schema involving the mechanism underlying Horner's syndrome due to fracture of the first rib head.A bone fragment of the first rib head and subsequent hematoma can compress or injure the stellate ganglion (orange arrow), which is a second-order neuron of the oculosympathetic pathway, leading to Horner's syndrome.Copyright © 2011, Medic Media.Reproduced with permission from Institute for Health Care Information Sciences ed. Medical Disease: An Illustrated Reference Guide.vol.7 Neurology and Neurosurgery.1st ed.Tokyo, Japan: Medic Media; 2011[15]

Table 1
The first rib fracture after CABG using the ITA in our hospital (2022.1∼2024.2)