Transient unilateral brachial plexus block following landmark-guided superficial cervical plexus block: A case report

Abstract

We report a case of a 61-year-old male patient with impaired function of the contralateral brachial plexus after right parathyroidectomy. The symptoms appeared directly after emerging from general anaesthesia and disappeared completely within 24 h after surgery. The follow-up check after 6 weeks was unremarkable. The patient suffered from asthma, osteoporotic degenerative changes of the spine and a chronic impingement of the left shoulder. He showed no signs of pain or limitations while reclining his neck during pre-operative airway assessment. Before surgery, a bilateral superficial cervical plexus block was performed by the surgeon using the landmark technique. We discuss the positioning of the neck and cervical spine in preparation for surgery and pre-operative superficial cervical plexus block as possible causes for the impaired function of the brachial plexus observed in this patient. We conclude that the latter was the most likely cause in this patient and recommend considering ultrasound guidance for the performance of superficial cervical plexus block.

Introduction

Parathyroidectomy is a common surgical procedure and is generally performed under general anaesthesia with a slight extension of the neck and an additional superficial cervical plexus block (SCPB) to reduce intraoperative and post-operative opioid use.^1,2 SCBP is a peripheral nerve block that targets the nerve roots of C2–C4 and is a suitable technique for providing analgesia after superficial surgery in the neck area. ² This block can be performed either by using anatomical landmarks or by ultrasound guidance. ¹ We report a post-operative transient upper limb weakness and discuss SCPB as well as extension of the neck for optimal surgical exposure as possible causes for this uncommon complication.

Case

A 61-year-old man was scheduled for parathyroidectomy on the right side due to primary hyperparathyroidism caused by a parathyroid adenoma. He had a medical history of asthma and had developed severe osteoporosis affecting the whole spine because of a long-lasting inhalational steroid therapy. In addition, left shoulder mobility was affected by chronic impingement and he exhibited a limitation in his elbow extension related to an accident a few years ago. The anaesthetic pre-operative assessment showed no evidence of a potentially difficult airway with a Mallampati Score of I and no restrictions or pain during neck extension. With a body weight of 64 kg, the patient had a BMI of 19.8 kg/m² and there was no history of hypertension, diabetes, smoking or any cardiovascular problems. The patient was classified as American Society of Anesthesiologist (ASA) physical status class II. An extra note was made to extend the neck carefully due to osteoporosis. Anaesthesia was induced and maintained with fentanyl, propofol, and remifentanil to avoid the use of neuromuscular blocking agents interfering with the neurostimulation of the recurrent laryngeal nerve during surgery. Intubation of the trachea was performed with a conventional laryngoscope without extensive hyperextension, revealing a Cormack–Lehane grade II view during intubation. The patient was in a supine position with a small pillow beneath the shoulder blades to allow for a slight neck extension and arms alongside the body as per standard protocol at our institution to allow for an optimal surgical exposure. A bilateral SCPB was performed by the surgeon using the landmark technique with 10 mL of Ropivacaine 0.5%, 5 mL (=25 mg) on each side. The surgical procedure lasted 103 min without any intraoperative complications. Vital signs were always within a normal range with a mean arterial pressure between 70 and 80 mmHg. The patient was extubated immediately after the procedure and transferred to the post-operative recovery room. Shortly after the transfer a painless weakness of the patient’s left arm was noticed. Neurological examination 3.5 h after the beginning of surgery showed muscular strength grade 2/5 for lifting the arm, 4/5 for flexion and extension in the elbow, and 4/5 for spreading of the fingers and extension of the wrist. Fist closure was unaffected with preserved muscular strength. There was no headache, change of consciousness, dysarthria, or weakness of the ipsilateral leg and vital signs were normal. Due to the present mild symptoms and the absence of any signs suspicious of a stroke or complications related to the cervical spine requiring immediate action, we chose an expectative approach, and therefore no CT or MRI imaging was performed. Twelve hours after surgery the weakness was still noticeable, however, the next morning, approximately 24 h after surgery, the patient showed a complete recovery of the muscular strength in his left arm and left the hospital two days after surgery. In the follow-up check six weeks later there were no neurological deficits detectable.

Discussion

We have described a case of transient, incomplete post-operative loss of motor function in the left arm after focussed parathyroidectomy on the right side. There were two possible mechanisms for our patient’s symptoms. The most likely cause was a transient nerve block of the brachial plexus as a complication of the bilateral SCPB due to a spread of the local anaesthetic drug towards deeper layers of the neck. However, we could not completely rule out temporary nerve damage through a slight extension of the cervical spine during intubation and surgery.

As a standard procedure in our institution, parathyroidectomy is performed under general anaesthesia with a bilateral SCPB applied shortly before the surgical incision. SCPB has been shown to reduce the use of opioids and to increase the time until first request of analgesia. By blocking the four superficial sensory branches of the anterior rami of C2–C4 (lesser occipital, great auricular, transverse cervical and supraclavicular nerves) anaesthesia in the anterior traingle of the neck is achieved. These superficial branches travel through the prevertebral fascia and then pass between the sternocleidomastoid muscle (SCM) and the prevertebral muscles before reaching the skin. The mid-portion of the posterior border of the SCM is the point of interest for the SCPB. It is possible to perform this nerve block using either a landmark technique or an ultrasound-guided technique. Senapathi et al. showed that the ultrasound-guided technique is more effective in reducing intraoperative as well as post-operative opioid use compared to the conventional landmark technique, as the spread of the local anaesthetic can be visualised and incorrect puncture into deeper layers can be prevented. ¹ However, in our institution the bilateral SCPB for thyroidectomy and parathyroidectomy is performed using the landmark technique due to its simplicity and effectivity. There are only a few studies focusing on complications from SCPB, most reviewing its use for thyroidectomy or carotid endarterectomy. SCPB shows significantly fewer complications than deep cervical plexus block.^2,3 There are only two published cases of transient brachial plexus block after thyroidectomy with SCPB, both patients were slim as was the case with our patient, and it was assumed that the injection of the local anaesthetic drug was deeper than intended^2,4 or that the drug spread through tissue planes towards the roots of C5–T1 ⁴ which form the brachial plexus and provide sensory and motor function to the upper extremity. These roots merge into three trunks and cross the interscalene triangle spatially very close to the injection point of the landmark-guided SCPB, so it is easy to imagine the above-mentioned spread of local anaesthetic drugs. In addition, there is evidence that only about 50% of people show ‘classical’ anatomy of the brachial plexus branching variants, others display various variations, with either the plexus also containing the C4 root or the superior trunk piercing through or even crossing anterior to the anterior scalene muscle instead of lying in between the anterior and the middle scalene muscles. ⁵ Interestingly, these variations were detected almost exclusively unilaterally on the left side, ⁵ which was also the side affected in our patient. Therefore, an anatomical variation of the brachial plexus could have facilitated the spread of the local anaesthetic drug towards the roots and trunks that were clinically affected.

As a differential diagnosis, another possible cause for our patient’s loss of motor function could have been a compression and therefore transient damage of the anterior rami of the spinal nerves C5–T1. Compared to the two published case reports on this topic our case was unique in that the patient’s spine was affected by severe osteoporosis. The overall incidence of cervical spondylotic myelopathy increases significantly with age and is higher in the male population.^6,7 Even in asymptomatic subjects, MRI imaging showed posterior disc protrusion with compression of the spinal cord in 7.6%, mostly in elderly individuals aged 50 and older. ⁸ Therefore, it is important to maintain awareness towards this common and often asymptomatic condition during surgeries where extension of the neck is required. During general anaesthesia patients do not have wilful control of their neck position and compression of their spinal cord or longitudinal vessels could occur, even if the pre-operative airway and neck examinations show no signs of limitations, as in our case. Literature shows previously reported cases of even tetraplegia after surgeries with prolonged neck extension, including thyroidectomies and parathyroidectomies.^9,10 It is therefore possible that the brachial plexus could have suffered a compression during neck extension facilitated by cervical spondylosis. However, the distinct pattern of muscle weakness in our patient could not be assigned to an exact location of possible damage along the course of the brachial plexus, neither at the level of the roots nor at the level of the trunks. Also, knowing that our patient suffered from bony spine disease, we paid particular attention to the cautious positioning of his cervical spine before and during surgery and adjusted the procedure to limit extension of the neck. It is therefore rather unlikely that a compression of the nerves was the cause for our patient’s weakness, and we argue that the patient experienced a mild complication of the bilateral SCPB with a distribution of the local anaesthetic drug towards the brachial plexus.

Conclusion

A transient brachial plexus block after parathyroidectomy with SCPB is a very rare complication. Most importantly, mechanical causes due to perioperative manipulation of the cervical spine have to be ruled out. Every anaesthetist should keep in mind that even a seemingly superficial nerve block can affect deeper-lying nerves—and although very rare—this complication should be mentioned during pre-operative discussions with the patient. Ultrasound guidance reduces the risk of an unwanted distribution of the local anaesthetic when performing SCPB and should therefore be strongly considered.