Hernia and 
General Surgeon  
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Why Choose Parathyroid and Thyroid Surgery with Us?


Continuous intra-operative nerve monitoring - cIONM

The recurrent laryngeal nerve (RLN) is at risk on each side of the trachea that the thyroid gland and parathyroid glands are draped over. The nerves supply the vocal folds (we have one each side). If damaged the vocal fold will not move normally. It can remain either open or closed or somewhere in-between. This weakens the strength and refinement of your voice. The voice box works harder to make you heard and tires more quickly than it should, so you can lose your voice during the day. It also protects the airways from food, secretions and fluids. If these get into the airway, they can make you cough and splutter. It is called aspiration and leads to recurrent chest infections and altered swallow sensation.

So being able to monitor the function of the RLN during surgery seems like a good idea! Nerve monitoring started to be introduced between 2000 and 2010 in thyroid surgery, but its uptake has been slow in the UK and the NHS due to the additional expense of the machine and consumables used with each case. There was not enough evidence at the time to prove its efficacy and the technology was in early stages of development.

Fast forward to today. The technology has advanced to the point that we can see the wave signal of the RLN throughout the operation and note if it changes, beat to beat. This wave signal changes long before the function of the nerve is lost. Because we now better understand how the signal change is warning us of possible ensuing loss of function, we can change what we are doing before the wave signal changes become a loss of function. It has become so reliable that we no longer need to routinely check for vocal cord function before and after surgery. 

There are 2 kinds of nerve monitoring: Intermittent and Continuous

Intermittent nerve monitoring is using a probe that initiates a nerve signal in the RLN if it is touched by the stimulating probe. If the nerve is working between where the nerve is stimulated and the muscle it moves, it creates a detectable signal in the circuit we set up at the start of surgery. The limitation is you do not know if the nerve is becoming damaged until it has lost function. It still reduces temporary and permanent nerve injury rates, but it is not perfect.

In continuous nerve monitoring, the circuit we set up at surgery creates a continuous 'beat to beat' assessment of the nerves function. We set this up on the vagus nerve that the RLN is a branch of so we can get warned of damage occurring out of our direct line of site. It has helped us understand the mechanisms of injury. The most common injuries are due to unseen traction on the RLN– continuous monitoring warns us of this before the damage is done. More rare is a crush injury of the nerve. Again, we get warned immediately if we have done this. If we can remove the crushing force quickly the nerve loss of function is more likely to be temporary. It means we have to dissect the nerve less (which increases risk of injury itself) and even if we don't find the nerve we still know it is working. 

We used to check the nerve function by examining the vocal fold. We did this by putting a flexible camera all the way up the nose and around and down into the back of the throat to examine the cords. In my practice we no longer need to do this unless there is a serious and persistent change in RLN function during surgery or a change of voice suggestive of RLN injury noted after surgery.

Recurrent Chest infection from RLN damage

This fact was little known about until a few years ago. If you permanently lost the function of the RLN you could get recurrent chest infections. People with a RLN palsy from any cause had an average reduction in their life span of 10 years because of this injury due to chronic chest disease. cIONM can prevent this.

Reducing RLN injury

In the past temporary loss of RLN function after this kind of surgery was around 12-15%. It was permanent in 1-3%.  Observational outcome data now shows that cIONM significantly reduces RLN palsy compared to using no nerve monitoring or even intermittent nerve monitoring. With cIONM it is falling further and with time and embracing innovative technology we hope to make this surgical complication a thing of the past.

Voice change

There is a second nerve often damaged in thyroid surgery called the external branch of the superior laryngeal nerve. It is tiny. The cIONM can be used to monitor and help us find this nerve too. The impact of damage to this nerve only ever really impacted singers. But sparing it is still a bonus and loss of minor voice refinement will improve as a result in all patients.