How do I manage paresthesia caused by a needle injury?

This question was submitted by a general dentist: How do I manage paresthesia caused by a needle injury? The patient felt an electric shock on his tongue while I was inserting the needle for the block.  I had not injected anything yet.  Is there a different way to manage the paresthesia if you know it is from trauma or from anesthetic toxicity?

Dr. Dan Haas, Dean of the Faculty of Dentistry at the University of Toronto and Dr. Suham Alexander provided this quick initial response

Paresthesia is defined as a persistent anesthesia or altered sensation that extends beyond the expected duration of anesthesia. It is usually an unpreventable complication in patients undergoing oral surgical procedures including implant placement; however, it is also a common issue cited in dental malpractice litigation.

The sensation of the “electric shock” is caused by needle contact with the nerve, and may be all that is required to produce paresthesia. It is uncommon for nerves to be severed during local anesthetic injection given the small gauge needles used in dentistry. The definitive cause of paresthesia following local anesthetic injection is not known with certainty, but there has been the suggestion that it is more common following blocks using 4% local anesthetic solutions. Most cases of paresthesia will spontaneously resolve within days, weeks, or months. Those that last beyond 6 to 9 months are considered permanent.

If it is determined that paresthesia is due to surgical trauma, then consultation with an oral and maxillofacial surgeon should be considered to help determine if a surgical approach to repair is warranted. If it is determined that paresthesia is due to local anesthetic injection, then consider the following.

Patient Management  

1. Reassure patient

• Practitioner should speak to the patient personally
• Explain how paresthesia occurs and expected timeframe for resolution
• Book an examination appointment with the patient
• Record incident in the dental record

2. Patient examination

• Discuss phenomenon of paresthesia with patient
• Explain paresthesia may take time to resolve and can take months, although rarely it may persist indefinitely
• Determine degree and extent of paresthesia patient is experiencing
• Record examination findings in the chart

3. Follow-up with patient

• Re-examine patient within one month, and then in 1 – 2 month intervals, or more often if appropriate, for as long as the paresthesia persists. An improvement in the signs and symptoms, however gradual, is often a promising sign of eventual complete resolution.
• If paresthesia persists at this first follow-up appointment, offer to refer the patient to an oral and maxillofacial surgeon or other appropriate specialist for an assessment.

4. Dental Treatment

• Dental treatment may continue in other areas of the mouth
• If further treatment is required in the area of the sensory deficit, avoid injecting local anesthetic into this region – consider alternative techniques to deliver anesthetic

References 

1. Malamed SF. Handbook of Local Anesthesia. 2013. Elsevier Mosby. St. Louis, Missouri.
2. Moore PA and Haas DA. Paresthesias in Dentistry, Dental Clinics of North America 2010;54(4): 715-730