Hello BethThere are a lot of posts about unilateral injections in the archives. Click on 'Archives' near the top left of this page and then enter the phrase 'unilateral injection'.
I'll repeat a previous post of mine in here for your convenience. This method certainly works for me and some others - has the double benefit of lasting longer than bilateral injections and with less of the breathy voice. I get 10 units in the same cord each time and it lasts 6/8 months.
Good luck and please let us know how you get on!
David Barton (AD/SD, Auckland, NZ)
Interesting question about the difference between bilateral and unilateral Botox injections for AD/SD.
I dug up some material from the archives which I've included in here rather than type it afresh. All comments based on my personal patient experience only. To answer your specific question - what you are experiencing is fairly typical I think, but the voice should settle down a bit soon. Probably I'd leave it at least 10-14 days before coming to a definite conclusion about the success of the shot. I've had occasions where I thought the right spot had been missed, but my voice settled down later.
Your concern about the dosage level could be justified - usually a significantly higher dose is needed with unilateral injections compared to bilateral to produce a significant benefit.
A good starting point in discussing methods of injection is to note that we have 2 vocal cords - like many systems/organs in the human body - eg kidneys, legs, nostrils etc - we have these on both sides. The vocal cords produce 'voice' by moving across to the midline so that breath rising from the abdomen vibrates across the edge of the cords. In AD/SD this process goes wrong - the cords over-close inappropriately and cause the breaks and straining to force words out that we are familiar with.
In SD it is debatable as to whether the laryngeal dystonia (that's the underlying disorder that produces the voice we know as spasmodic dysphonia) affects the control of one vocal cord only, or both. It would make a good research study. However, in this answer I'll try to focus on approaches to treating the symptoms.
When Botox was first administered to patients the physicians injected both cords (this is termed 'bilateral' injections) to induce the deliberate semi-paralysis which helps minimise the spasms. Later on, some doctors noticed that a similar effect could be produced by only injecting one vocal cord (termed a 'unilateral' injection.
In a sizable number of AD/SD patients the effect of Botox given bilaterally is quite severe, and results in a lengthy period of aphonia (voicelessness) or close. Many patients describe this effect as 'breathiness' but it can be worse than that, as you have experienced, and as I did previously. In contrast to aphonia, breathiness is a soft, smooth, husky voice - difficult to project with any volume, especially over noise, and often a patient can only manage a few words before they have used up all their breath support, and have to breathe in to replace the wasted air. Hence the term 'breathiness' - it means needing frequent intakes of breath rather than difficulty in breathing when not talking.
Back to injection methods .....
In a unilateral injection what seems to happen is that by giving the shot in one cord only, the uninjected cord can still move across to the midline (so some volume) and the injected cord remains flaccid (so no spasms).
Some other points:
Another way of adjusting Botox injections to avoid aphonia or reduce breathiness is to lower the dose. Usually a first Botox shot is 2.5 units bilateral. This can be reduced down as far as 0.33 or 0.5 units - but in some cases (mine and others) there was still aphonia/breathiness, and the low dose meant the spasms returned too quickly - in weeks rather than months.
With unilateral injections the dose is higher (5, 7.5, 10, 12.5 units are typical - I get 10 and am thinking of reducing it to 7.5 next time)
Which cord is injected? It depends. I suppose a really expert doctor could analyze whether the SD is more apparent in one cord than the other, but usually it depends more on the anatomy (the vocal cords are not symmetrical in that one muscle is on top of the other near the front). I think most patients who get unilateral injections in the same cord each time have the right cord injected.
Should unilateral injections alternate between cords? Again, it depends. In my case I found doing left-right-left-right etc over a period of time meant that both cords were weakened and I was still too breathy - so I stick to one cord only - the right one.
My doctor spreads the Botox around ... injecting two sites in the one cord. This increases the chance of hitting the right spot.
Hang in there, and keep trying - there is a wide variation between patients, and even over time the underlying disorder can change, so it's not easy arriving at, and sticking with, the perfect Botox SD treatment method - in fact it doesn't exist - the SD is still there and so Botox produces, at its best, a serviceable and functional voice, not a flawless voice where you are never aware of difficulties.
David Barton (AD/SD, Auckland, New Zealand)
