Quiz

What is the nerve that is the most likely to be mistaken for the cervical vagus nerve?

Ansa cervicalis profunda (aka ansa cervicalis or ansa hypoglossi)
Ansa cervicalis superficialis
Superior cardiac ramus
Phrenic nerve
Hypoglossal nerve

In the most common configuration, at the usual site of implantation, the vagus nerve within the carotid sheath is located?

Behind the carotid artery
Behind the internal jugular vein
Between the vessels but posteriorly
Between the vessels but anteriorly
Lateral to the internal jugular vein

Regarding the following statements concerning the recurrent (inferior) laryngeal nerve on the left side, which are correct:

It is sometimes identified during VNS primary implant.
Never identified during VNS primary implant.
The location of its fibers within the cervical vagus nerve is highly variable.
The position of its fibers within the nerve are posteromedial as the nerve will branch off medially in the upper thoracic region
Its fiber are central within the nerve.
The organization of fibers within the nerve are poorly known and unpredictable.

The choice of the internal coil lead diameter of the lead has no impact on the rate of complication in univariate analysis?

True
False

Not performing the strain relief bend and lead fixation with the silicon tether has been associated with an increased rate of lead breakage?

True
False

Regarding the fixation of the pulse generator before wound closure, which statements are right?

It is recommended by Livanova.
It is not mandatory since the pocket is small and the generator will be rapidly engulfed within scar tissue and stabilized into fibrosis.
It is a way of preventing twiddler syndrome
It enables to completely rule out the risk of twiddler syndrome.

Bradycardia or asystolia induced by vagal nerve stimulation is reported to occur in which percentage of cases?

0.5 %
5%
0.1%
0.001%
20%

Regarding the lead itself, which statements are right?

The anchor tether is green in color.
The anode (+ electrode) is white in color.
The cathode (- electrode) is green in color.
Electrical current flows from the negative to the positive electrode.
Action Potentials are generated in both direction (upward/downward or ortho/antidromically) at the level of the negative (cathode) electrode.
Implanting upside/down the lead (anchor tether proximally) does not impair the clinical result since there will still be action potential generated and flowing in both directions.

Regarding anatomical variations and possible surgical findings that may hinder the procedure, which are likely and worth being aware of?

Low take-off of superior cardiac ramus may cause difficulties during VNS surgery.
The main sympathetic trunk is usually exposed and may give rise to postoperative Horner’s syndrome in case of injury.
The superior and inferior laryngeal nerve are not exposed.
A prominent external jugular vein can be encountered immediately below the platysma.
The ansa cervicalis (profunda) provide innervation to the infra-hyoid muscles.
If two nerves are encountered within the carotid sheath, the one with the biggest caliber usually corresponds to the vagus nerve.
Twiching of the cervical muscle upon testing is commonly encountered and should not be a source for concern.

Regarding the site of implantation of the electrode around the cervical vagus nerve trunk, which statements are right?

Livanova recommends to implant below where the superior and inferior cervical cardiac branches separate from the vagus nerve.
There are no recommendation given by Livanova with respect to the site of implantation.
The site of implantation may be left at the discretion of the surgeon depending of the intraoperative findings.
2 cm section is usually sufficient to perform electrode wrapping.

If one encounters trouble and struggles during the wrapping step, it may be ascribable to the following reasons:

A sufficient length of the cervical nerve was not exposed.
There may be adhesions remaining around the nerve
An efficient method to lift up the nerve was not resorted to.
The electrode is quite stiff and arrives almost at a 90 degree angle with regard to the nerve plane.
The inner diameter of the coil that was chosen is too small with regard to the nerve diameter.

Regarding the non-recurrent inferior laryngeal nerve, which statements are right?

It is truly exceptional on the left side and will practically never be encountered.
Its prevalence is much higher on the right side.
The existence of a right non recurrent laryngeal nerve is classically between 0.3% and 1.6% but was reported to reach up to 1.9% by Yetisir and al.
It is reported to be 0.04% on the left side.
It is related to embryologic developmental anomaly of the aortic arch and associated with the presence of an aberrant subclavian artery (arteria lusoria, on the right).

Regarding the anatomic variations that may be encountered during VNS, in the rare event of finding a duplicated trunk within the carotid sheath, the following possibilities should be considered:

Aberrant position of the phrenic nerve
Non recurrent inferior laryngeal nerve
Aberrant course or root of the ansa cervicalis
Truly duplicated vagal trunk
Aberrant cervical sympathetic trunk.
Thick superior cardiac ramus

Regarding the ansa cervicalis, which statements are right?

It is also known as ansa cervicalis profunda or ansa genioglossi.
It contains motor fibers that supply the sternocleidomastoid muscle.
It provides innervation to the infrahyoid muscle expect the thyro-hyoid and genio-hyoid muscles.
Its contributors may be identified intra-operatively by their position outside the carotid sheath.
Its contributors may be identified intra-operatively by low current bipolar electrical stimulation that will induce muscle twitching.
The ansa cervicalis or its contributors could have inadvertently been included into the coils if there is muscle twitching upon testing VNS.
Muscle twitching during the surgery is related to current spread and should not be a source of concern.

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