Vagal nerve stimulator

Case contributed by Dr Ashesh Ishwarlal Ranchod

Presentation

The patient presented for a routine mammogram and wellness check-up. There is a known history of epilepsy.

Patient Data

Age: 50 years
Gender: Female
Mammography

The mammogram is unremarkable.

There is a benign intramammary lesion within the right breast 9 o'clock axis.

There is a known left-sided vagal nerve stimulator (VNS) with dual leads.

There is scattered deodorant artefact (artefact persisted even though the patient was requested to cleanse prior to mammogram once she confirmed the use of deodorant).

Ultrasound

Breast ultrasound confirmed an intramammary benign lymph node at the 9 o'clock axis.

Ultrasound was otherwise normal.

X-ray

X-rays reveal a typical left-sided vagal nerve stimulator.

The pulse generator and battery are implanted subcutaneously within the left chest wall.

The non-fragmented dual leads ascend to the mid-cervical soft tissues where the terminal electrodes are placed adjacent to or on the left vagal nerve.

There are focal C5/C6 degenerative changes with degenerative grade I retrolisthesis of C5 on C6, decreased disc space, and anterior and posterior osteophytosis with mild loss of normal lordosis.

The chest X-ray is unremarkable except for the vagal nerve stimulator(VNS).

 

Personal magnet

Photo

The patients are given two therapy magnets to activate or deactivate their vagal nerve stimulators manually. The magnet can either be worn like a watch by the use of a wristband. Alternatively, a belt buckle is provided so that the device may be worn like a pager. The device can also be kept loose in a pocket or handbag etc.

The device is swiped over the pulse generator to provide an extra dose of therapy on demand to stop/shorten/decrease the intensity or improve recovery during breakthrough seizures. It does this by activating or deactivating a sensor (called a Reed switch).

During singing, public speaking or exercising, patients may experience side effects and hence they can manually temporarily suspend therapy by using the therapy magnet.

Always remember to ask the patient to remove these magnets prior to imaging to prevent a potentially harmful projectile incident.

Note: this patient has given permission to upload these images of her used wristband device and her spare device.

Disclosure: I, Ashesh I Ranchod, have no actual or potential ethical or financial conflict of interest in relation to this device. This case is not intended to be a personal endorsement or recommendation of this product.

Case Discussion

Vagal nerve stimulation is indicated in patients with intractable epilepsy, treatment-resistant depression, drug-refractory hypertension and cardiac failure. This patient had intractable epilepsy, with poor control on four different anti-epileptic medications. Her initial VNS lasted 10 years and was recently replaced. She had a significantly improved lifestyle once she had a VNS implanted.

There is ongoing research to treat chronic headaches and intractable pain, rheumatoid arthritis, inflammatory bowel disease, bipolar disorder, obesity and Alzheimer's disease.

The pulse generator (which also houses the battery) is implanted within the left-sided infraclavicular subcutaneous soft tissues. A single or dual lead then ascends to the mid-left neck, with terminal electrodes that are placed on or near the left vagus nerve.

The right vagal nerve is not usually utilized due to its greater number of cardiac efferent fibers whose stimulation may result in more frequent adverse cardiac complications.

When treating drug-refractory hypertension and cardiac failure the VNS may be implanted within the right anterior chest wall soft tissues, with one lead tip within the right ventricle(sensing electrode) and the second lead (stimulating electrode) around the right vagal nerve.

So assessing the position of the leads may allude to the nature of the treatment between cardiac and non-cardiac.

Newer VNS devices are nowadays MRI conditional and limitations need to be strictly followed to avoid disasters and adverse events. Always inquire fully about the device prior to any MRI scan examination especially if it's an "old" device that may not be MRI conditional. Device settings are usually recorded and the device is usually interrogated and programmed by the treating clinicians prior to and after MRI studies.

Warning:

VNS patients often carry a small clip-on magnet to activate and deactivate their devices. Should this be inadvertently taken into the MR scanning room, it may result in an unexpected and potentially harmful projectile incident. (Images of the therapy magnet have been uploaded above).

Disclosure: I, Ashesh I Ranchod, have no actual or potential ethical or financial conflict of interest in relation to this device. This case is not intended to be a personal endorsement or recommendation of this product

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