Botulinum toxin

Intralaryngeal injection of botulinum toxin has been a recognised treatment for Spasmodic Dysphonia (SD) for over 30 years (Watts et al., 2004). SD is a dystonia which affects voicing resulting in a strained, strangled voice (Adductor form-most common, about 90% ) or breathy phonatory breaks (Abductor form). ILO/VCD differs from SD because the abnormal adductor movements occur during breathing, whereas in SD these adductions occur during speech. However since ILO/VCD also involves abnormal adductor vocal cord movements it is reasonable to consider whether similar intralaryngeal injections may also be beneficial in ILO/VCD.

A Melbourne based clinic reported the results of their first 11 patients (24 injections) in 2014 (Baxter at al., 2014) and whilst realising that this was not a double blinded study the results were sufficiently encouraging to continue offering the treatment. Currently the clinic has injected 105 patients and are about to undertake a detailed analysis of their results.

Botulinum toxin treatment is offered to those patients with diagnosed ILO/VCD who have failed to respond to Laryngeal Retraining from a Speech Pathologist (for standardization the clinic insist the patient must have received treatment from the associated Speech Pathology group before considering injection).

In the clinic botulinum toxin type A as Botox  (Allergan) is used- the Melbourne based clinic have reported no experience of the Dysport product.

Botox in SD has usually been delivered by awake trans thyrohyoid membrane injections under EMG guidance or direct visual guidance using fibreoptic trans-nasal laryngoscopy. Initially  both techniques were used but operators found that it was difficult to “target” especially in patients who often have an irritable airway and had several failures to inject. The procedures were often quite time consuming in some patients, therefore a technique was developed of injecting using a flexible 23 G sclerotherapy needle via the injection port on a standard bronchoscope.

The image below depicts a 23g sclerotherapy needle and 1mL syringe containing 5 units of botulinum toxin. The following image shows the loaded sclerotherapy needle ready for deployment within a bronchoscope’s 2.0mm working channel. Note that the tip of the needle is visible in the second picture for demonstration purposes but the needle should always be fully retracted into the sheath before insertion into the bronchoscope to avoid damage.

This technique gives  an excellent view of the vocal cords and the needle can be easily placed transmucosally into the thyroarytenoid muscle at the junction of the anterior and middle thirds of the vocal cords.  The Melbourne based clinic report that they have never had a failure to localise the injection with this technique and the procedure is very quick-usually less than 5 in minutes total.

This technique requires that the patient has a day case bronchoscopy suite admission under short sedation. The procedure can also be performed by a non-laryngology trained Respiratory physician.

Botulinum toxin is compounded by the hospital pharmacist into 1ml sterile syringes (5 botulinum toxin units/1 mL) on the day of the procedure.

The optimal starting dose (adults) is 5 units unilaterally. If the patient has a sub optimal response a repeat treatment can be performed after 3 months. In some cases 5 units bilaterally may be required.

Side-effects of soft voice or minor dysphagia for days to a few weeks after treatment are common but usually well tolerated. One patient with an underlying neurological problem required inpatient care for 2-3 weeks.

The clinic offers repeat injections as necessary, and observes that the duration of effect is longer and the number of repeat injections less than with SD, which usually requires repeat injections, often 2-3 per year.