Picture this scenario: it’s the day after you gave a patient an anesthetic injection to work comfortably, and they call you up, saying, “Doctor, my tongue is still numb from yesterday!” Instantly, anxiety kicks in, for both you and your patient. This specific issue is medically termed Lingual Nerve Paresthesia.
The short, direct answer is that this problem usually stems from one of two main reasons: either the anesthetic needle directly touched the lingual nerve, or the anesthetic solution itself had a toxic effect on the nerve. The good news is there are plenty of strategies we can use to significantly reduce the risk of this happening, and we’re going to dive into them in detail.
Why It Happens: Causes of Post-Anesthetic Lingual Numbness
When a patient complains about tongue numbness after an anesthetic, there are primarily two underlying causes we should consider:
1. Direct Trauma to the Lingual Nerve by the Needle (Needle Trauma):
The lingual nerve lies in very close proximity to the Inferior Alveolar Nerve during injection. In some instances, the needle might inadvertently strike the nerve, causing a minor physical trauma.
Why Does This Occur?
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Anatomical Variations: The exact position of the lingual nerve isn’t fixed in every individual. Some patients have it exceptionally close to the injection site, which inherently elevates the risk of injury.
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Sudden Patient Movement: If the patient makes an unexpected, sudden movement while you’re administering the injection, the needle could accidentally hit the nerve.
2. Neurotoxic Effect of the Local Anesthesia on the Nerve:
Some theories suggest that certain types of local anesthetics might exert a neurotoxic effect on nerves, especially if injected in high concentrations very close to the nerve itself.
Who’s the Main Suspect?
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Articaine 4%: Numerous studies have linked the use of Articaine in Inferior Alveolar Nerve Blocks (IANB) to an increased risk of lingual nerve paresthesia. However, it’s crucial to understand that there isn’t definitive scientific evidence to conclusively confirm this.
Why Articaine in Particular?
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High Concentration: Articaine 4% is double the concentration of Lidocaine 2%.
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Enhanced Diffusion: Articaine is known to diffuse more extensively through tissues. This increased spread could potentially allow it to reach the lingual nerve in higher concentrations, even if the injection site was slightly further away.
How to Prevent Lingual Numbness After Anesthesia (Prevention is Key)
Although this issue isn’t entirely predictable, there are many proactive steps we can take to minimize its occurrence to the greatest extent possible.
1. Injecting Anesthesia Higher: “Higher is Better”
This is arguably the most critical rule in IANB. The higher your injection site, the better and safer it generally is.
The Correct Technique:
During an IANB, try to position your needle at least 6 mm above the Occlusal Plane. Personally, I prefer to inject around 10 mm above the occlusal plane.
Why Does This Make a Difference?
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Improved Accuracy: When you inject higher, you’re getting closer to the Mandibular Foramen, which significantly increases the success rate of your anesthesia.
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Enhanced Safety: More importantly, you move further away from the lingual nerve, which typically runs close to the Lingula. In this specific region, the nerve is often unifascicular, meaning all nerve fibers are bundled together in a single fascicle. If you strike this single fascicle with the needle, the potential damage is substantial. However, as you move higher, these fascicles tend to separate, so even if you happen to contact a smaller fascicle, the resulting damage is considerably less (2).
2. Using a Sharp Needle:
A dull needle creates a larger wound in the tissues, which undeniably increases the risk of nerve injury.
The Correct Technique:
Replace your anesthetic needle as soon as you feel it becoming barbed or dull. If it has penetrated tissue once or twice, it’s generally best to swap it out for a fresh one.
3. Injecting Anesthesia Slowly: “Slow is Pro”
Rapid injection creates high pressure within the tissues, which can unfortunately harm surrounding nerves.
The Correct Technique:
Don’t rush when injecting the anesthetic! A standard carpule should ideally be injected over at least 60 seconds—that’s roughly two drops per second.
“The Patient Felt an Electric Shock, Doctor!” – What Happened?
If your patient experiences a sudden “electric shock” or “stinging” sensation during an IANB injection, it usually indicates that the needle has briefly contacted either the Lingual Nerve or the Inferior Alveolar Nerve.
Does This Definitely Mean the Tongue Will Be Numb?
Not necessarily! In most cases, this is merely a transient electric shock, and the nerve typically returns to normal function without any lasting issues.
What Should You Do If This Occurs?
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Withdraw the Needle 1 mm: If the patient feels an electric shock, gently pull the needle back about 1 mm to move it away from the nerve.
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Continue Injecting Slowly: After repositioning away from the nerve, continue the injection very slowly.
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Reassure the Patient: Inform the patient that this can sometimes happen and that it’s not generally serious.
What If the Numbness Persists? (Post-Anesthetic Paresthesia Management)
If a patient calls you the next day and their tongue is still numb, the most crucial thing to do is reassure them and take their complaint seriously.
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Reassure the Patient: Explain that this is a rare complication and, in about 90% of cases, it is temporary and will resolve on its own within 8 weeks.
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Document the Case: It’s imperative to document everything in the patient’s file: the type of anesthetic used, the injection site, and any events that occurred during the injection (like an electric shock).
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Follow-Up: Schedule follow-up appointments for the patient to visit your clinic every two weeks to assess the condition and monitor for any improvement.
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Nerve Vitamins: You might consider prescribing a Vitamin B Complex, as it can aid in nerve regeneration.
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Referral to a Specialist: If the numbness persists for more than two months without any noticeable improvement, it’s best to refer the patient to an Oral and Maxillofacial Surgeon for a more in-depth evaluation of their condition.
Conclusion: Prevention is the Key to Safety
Lingual numbness after anesthesia is a rare but certainly very bothersome complication if it occurs. By diligently following these straightforward steps—especially the “Higher is Better” rule for IANB—we can significantly reduce its risk. Always remember: slow injection, a sharp needle, and clear communication with your patient are the cornerstones of safe practice in dentistry.
