Non-Surgical Cord Lateralization Using Botulinum Injection for Bilateral Abductor Cord Palsy in Patients of Papillary Thyroid Carcinoma

Abstract

Bilateral abductor cord palsy occurs in up to 7% of patients undergoing total thyroidectomy. Surgical management using tracheostomy is the treatment of choice for patients with severe respiratory distress but has poor psychosocial acceptance and results in permanent changes in anatomy. Other surgical techniques have poor voice outcomes. We present a case series of patients of bilateral abductor cord palsy post total thyroidectomy for papillary thyroid carcinoma who underwent Botulinum injection into the adductor muscles (Cricothyroid ± Lateral cricoarytenoid) and were able to manage without tracheostomy. Botulinum paralytic toxin could help as a temporary non-surgical measure or as a bridge till spontaneous recovery of nerve function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-025-05435-2.

Introduction

Surgery in the form of total thyroidectomy is the mainstay of treatment for differentiated thyroid cancer [1]. The postoperative complications of thyroidectomy include nerve injuries in the form of unilateral or bilateral vocal fold paralysis. Bilateral abductor cord palsy has an incidence of 1.3–6.6% [2]. It is a life-threatening condition that may require an emergency surgical procedure (tracheostomy) for maintenance of the airway. The use of intraoperative monitoring has improved the identification and functional monitoring of the recurrent laryngeal nerve. However, their benefit is not universal [2].

New treatment modalities are available for bilateral vocal cord paralysis which prevent the need for emergency tracheostomy. Surgical techniques include cord lateralization, arytenoidectomy, cordotomy, and laryngeal pacing and medical techniques include positive pressure ventilation (CPAP, BiPAP), gene therapy, injection Botulinum toxin (BTX), and stem cell therapy [3, 4]. Surgical procedures are ablative and could result in long-term decline in voice outcomes and permanent changes to anatomy. Medical treatment with gene, stem cell therapy is still developing [3]. Management with positive airway pressure (BiPAP or CPAP) has poor compliance and provides temporary relief till a definitive procedure is planned [5].

We attempted to manage bilateral abductor cord palsy in papillary thyroid carcinoma patients without tracheotomy.

Cases Reports

Case #1

Forty-six-year-old female with Papillary thyroid carcinoma T3aN1bM0 underwent Total Thyroidectomy, central compartment neck dissection and right posterolateral neck dissection (Level 2–5). Intraoperative findings showed a 5 cm nodule encasing the right recurrent laryngeal nerve (RLN) which had to be shaved off the nerve. The left RLN was preserved. Postoperatively she developed respiratory distress (stridor) and hoarseness on day 1. Fibre optic laryngoscopy showed edematous larynx with right vocal fold immobility and left abductor cord palsy. She was started on CPAP which was tapered subsequently and used only intermittently. Repeat laryngoscopy on postoperative day 11 showed resolution of laryngeal edema however the cord immobility persisted. She continued to have dyspnea on minimal exertion (MRC grade 2).

BTX (6IU) was injected into the right lateral cricoarytenoid and cricothyroid muscle under EMG guidance on day 12. The patient had no periprocedural complications. Her functional status and dyspnea on exertion improved from day 13. At 6 weeks post-procedure she was able to climb two flights of stairs and her airway on endoscopy is shown in Fig. 1.

Fig. 1.

Fibreoptic laryngoscopy at 4 weeks post-surgery showing adequate airway chink

Case #2

Fifty-five-year-old female of Papillary thyroid carcinoma T3aN0 underwent Total thyroidectomy. Both nerves were structurally preserved. She had stridor and noisy breathing on the day of surgery. Fibreoptic laryngoscopy showed bilateral abductor cord palsy with threatened airway chink. She was managed with CPAP during initial 3 days. She underwent BTX injection (6U) in the ipsilateral cricothyroid muscle under USG guidance on day 3 of surgery. She had no periprocedural complications. She was discharged on day 10. On subsequent weekly follow-ups, she had improved functional status. At 8 weeks post-surgery, she regained abduction of the left cord and had good exercise tolerance (able to climb 1 flight of stairs).

Technique of Injection

Botulinum toxin injection preparation – 50IU lyophilized BTX powder is reconstituted in 10mL NS. It is then loaded in an Insulin syringe with a 26G needle. Two to four syringes are then loaded with 0.6mL of reconstituted BTX. (BTX should be used within 24 h of reconstitution)

EMG - The machine used was a Nicolet Viking Quest, utilizing hollow needle electrodes for simultaneous EMG assessment and injection of botulinum to target muscle. The technique of EMG needs to be altered to isolate individual muscles for injection [6] Fig 2.

Fig. 2.

(a) and 1(b): LCA injection in 1 (a): Midline entry just below the thyroid cartilage. Angulated as depicted and inserted 10–15 mm. EMG activity will increase and rapidly drop during phonation. Entry 5 mm lateral to the midline, tangential to the cricothyroid membrane; inserted 15–20 mm deep. EMG activity increases by gradually increasing the pitch of voice

Interpretation- Laryngeal EMG is evaluated in four parts, during insertion, at rest, during minimal voluntary contraction, and maximal voluntary contraction (Fig 3). The normal waveform morphology expected is a biphasic wave with an amplitude of 200 to 500 microvolts and a 5–6 millisecond duration. Early in injury, it produces waves having small amplitudes, long durations, and polyphasic shapes. As healing progresses, the waves produced have greater amplitudes than normal, are polyphasic and with a prolonged duration. The recruitment pattern of motor units which occurs during voluntary contractions is lost in nerve injuries [7].

Fig. 3.

(a), 2(b): EMG Recording of case #1. 3(a) shows different phases of lateral cricoarytenoid; and (b) shows EMG of cricothyroid (CT) with the left CT (upper) showing decreased amplitude than right CT (lower)

Ultrasound – Sonosite ultrasound was used with an 8–13 Hz linear transducer probe. The CT muscle is identified as a flat muscle 1.5–2 cm away from the midline superficial to the hypoechoic thyroid and cricoid cartilages and between the two [8] (Fig 4).

Fig. 4.

EMG-guided botulinum toxin injection using a hollow needle core

Injection technique – Under Ultrasound or EMG guidance, the needles are inserted through the cricothyroid space. More than one point of injection is chosen in the identified muscle to maximize the number of motor units to which the paralytic agent is delivered. Maximum delivery of 1.2mL to each of the adductor muscles is intended (1.2mL = 6IU). A summary of BTX injections used in our cases is mentioned in Table 1.

Table 1.

Summary of Botulinum injection in the two patients

	Case #1	Case#2
EMG finding	Right CT – Polyphasic with decreased MUAP. B/ LLCA – Polyphasic, normal MUAP	CT – Polyphasic, MUAP (Right > Left) LCA – Polyphasic, normal
Muscles targeted	Rt CT, LCA	CT
Technique	EMG guided	USG guided
Dose per muscle	6 IU	3 IU
Total dose	12	6

CT – Cricothyroid muscle, LCA – lateral cricoarytenoid, MUAP – Motor unit action potential, IU – international units

Discussion

Despite meticulous dissection, improved precision of surgical ablative instruments, and intraoperative nerve monitoring, up to 6% of cases could be affected by bilateral abductor cord palsy post total thyroidectomy. Drawbacks of tracheostomy include – lack of phonation, continual need for tube care, risk of tube block, multiple hospital visits, and poor social acceptance [3, 9]. Hence, the gold standard treatment of bilateral vocal fold immobility continues to evolve.

In abductor cord palsy, there is an imbalance of forces between the abductors (PCA) and adductors (CT and LCA). As per Semon’s law and Wagner Grossman’s laws, the paramedian position is due to the unopposed action of the phylogenetically older (and sturdier) adductor - cricothyroid muscle [10]. Botulinum toxin is a paralytic agent that inhibits presynaptic release of the neurotransmitter Acetylcholine in motor neurons. BTX when aimed at the adductors, rebalances the forces and results in an improved airway and avoiding tracheostomy [11]. Chemo denervation has been used extensively for overactive or synkinetic laryngeal muscle activity successfully [12, 13]. In our cases, it results in improved airway chink by cord lateralization. BTX has a limited period of action ranging from 4 to 12 weeks. Neuropraxia of the recurrent laryngeal nerve recovers generally in 6–8 weeks [14]. Hence, its use is justified as a temporary bridge till a definitive procedure or spontaneous recovery [4, 15]. Both the cases described had spontaneous recovery of at least one of the nerves.

No significant adverse effects were encountered apart from mild local site pain during EMG recording or injection of toxin. In both the cases described above, we could achieve near-normal functional status (mMRC dyspnea grade ≤ 2) at a follow-up of 2.5 years for case#1 and 1.25 years for case#2. Both cases received 30mCi I¹³¹ RAIU post-diagnostic scan. Both patients tolerated radioiodine treatment well. There was no further decompensation post-iodine treatment as mentioned in a few cases in literature [16–18].

Multiple studies have shown the effectiveness and safety of botulinum toxin. Ekbom et al. reported success in 10 of the 11 patients treated with Botulinum toxin used in a dose of 2.5IU. Sahin et al. reported a series of 24 patients who received 9IU of Bt toxin in each CT muscle at a mean duration of 11 months post palsy. They objectively reported limited success in airway parameters on spirometry. Results were better when the dose to injection duration was shorter. In our patients, the time from palsy to injection was 12 days in Case #1 and 3 days in Case #2. A dose of 2.5–9 units per muscle seems appropriate [15].

In conclusion, Botulinum toxin injection (2.5IU – 9IU) could be used in cases when acute bilateral abductor cord palsy is encountered despite structural preservation of at least one recurrent laryngeal nerve during thyroidectomy along with mild to moderate signs and symptoms of respiratory distress. Cricothyroid and/or lateral cricoarytenoid muscle should be targeted. Early injection post palsy would have a better outcome in avoiding tracheotomy. The optimal dose of injection needs to be studied with larger samples and prospective studies. Botulinum toxin should be injected under EMG or USG guidance with multiple injection sites within the muscle to maximize motor unit paralysis.

Electronic Supplementary Material

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Author Contributions

AK: Data collection, Manuscript writing, Critical analysis of scientific content. DB: Data collection, Manuscript writing, Proof reading. SP: Analysis of scientific content, Proof reading. AT: Conceived the idea, Proof reading, Provided and cared for study patients.

Funding

No funding was received for this study.

Declarations

Ethical approval

No ethical approval needed as per Institute Ethics Committee. Informed written consent was taken from the patient for publishing.

Consent to publish

The participants have consented to the submission of the case report to the journal.

Competing interests

There were no competing interests.