Nerve Injury caused by Dermal Filler

Dr Tim Pearce

March 11, 2020

Nerve injury in facial aesthetics is a rare complication, but it is also severely disruptive and upsetting for patients and clinicians alike.

It’s vital to understand what can cause this problem & how to effectively diagnose it.

Types of Nerve Injury

Any type of nerve injury is going to be painful & traumatic experience for your clients.

Nerve injury can be broken down into 3 sections and they are (in order of least to most severe):

• Neuropraxia

This is the most common type of nerve damage you will see in Medical Aesthetics.

It is caused by dysfunction of the myelin layer.

You could think of this as an electrical wire that has its sheath damaged halfway along and the current is leaking out to earth instead of carrying on to the end of the wire.

• Axonotmesis

In this type of nerve injury, there is not only demyelination but also loss of a section of the axon.

Crucially the endoneurium is preserved, which means the neuron can regenerate.

• Neurotmesis

In this type of injury we have myelin sheath damage plus axonal loss and then one of three other variations of injury:

1. Damage to the endoneurium, which means growth is possible but slower.
2. Damage to the perineurium, which means growth is possible but poor.
3. Finally damage to the epineurium, which means no regrowth.

Diagnosis of Nerve Injury

To effectively diagnose a nerve injury you will need to have a face to face consultation with the client.

Upon meeting the patient you should notice weakness, paralysis or tingling in the muscles on the face.

If it was caused by the procedure you would expect this to occur either immediately, or within 24 to 48 hours on average during which time inflammation peaks.

Ruling out Stroke

In your initial assessment, you should rapidly check for other symptoms so that you can rule out this cause.

In the UK we use the FAST algorithm and your patient may already have the signs. FAST is broken down into:

1. Face drooping.
2. Arm weakness
3. Speech difficulty.
4. Time to call an ambulance.

The simplest way to differentiate a stroke from a facial nerve palsy is to look at the forehead.

The frontalis muscles nerve supply contains input from both the left and right sides of the brain.

Therefore if the cause is a stroke, the forehead will still move on both sides.

The result is facial paralysis from the forehead down on one side.

Of course, some of our patients may have had botulinum toxin in their forehead which may complicate assessment.

If in any doubt it’s always best to initiate treatment for the most threatening of the likely differential diagnosis.

Nerve Injury: Confirm the Diagnosis

The use of video is invaluable in the situation.

By carefully documenting facial movement you can monitor progress in much more detail.

It’s important to examine muscular function across the whole face including the ocular and periocular muscles.

The facial nerve also includes sensory and parasympathetic functions in its terminal branches.

It can be very difficult to be certain that the nerve symptoms your patients’ report are due to the procedure that you carried out.

The two most obvious connection is the time at which symptoms occurred relative to the procedure and the area treated.

1. In the case of a neuropraxia, you would expect symptoms to arise in a matter of hours but not immediately.
2. In the case of axonotmesis, you would expect a much more rapid onset of symptoms as the axon itself has been damaged.

Similarly, you would expect neurotmesis to occur immediately, as much of the nerve has been severed.

It is vital you are always on the lookout for signs of viral infection more consistent with classical Bell’s palsy.

To Conclude

Nerve injuries are a rare but important side effect.

Consenting your patients is vital, but an awareness of the anatomy and your injection technique is really the key to limiting the chances of being confronted with this problem.

If it ever does occur, you should from history, be able to initiate the correct management and appropriately reassure your patients.