Self-limiting myoclonus following supraclavicular brachial plexus block with Ropivacaine: A rare incidence

Noor Mohamed Eliyas^1*, K Senthil Kumar¹, Khaja Mohideen¹, S Skandha², M Muralidhasan²

¹Department of Anaesthesiology, Kauvery Hospital, Cantonment, Trichy

²Department of Plastic and Reconstructive surgery, Kauvery Hospital, Cantonment, Trichy

Abstract

A 42-year-old male with no previous known comorbidity came with a history of assault and injury to the left thumb causing near total amputation and was posted for wound exploration and replant of thumb. The surgical procedure was done under Ultrasound-guided left supraclavicular brachial plexus block. The procedure lasted for 3 hr which was uneventful. The patient had undergone emergency re-exploration of the wound after 6 hr again under the same anaesthetic technique with reduced dosage. Intraoperatively patient had a self-limiting myoclonic activity of the left thumb which was not responding to medications and disappeared in 6 hr.

Keywords: Peripheral Nerve block; Supraclavicular approach of Brachial plexus; Myoclonus; Self-limiting.

Background

Myoclonus is a brief shock-like involuntary arrhythmic movement or twitching of a muscle or group of muscles lasting less than 200 milliseconds in electromyography. Although myoclonus following spinal anaesthesia has been reported many times, its occurrence after peripheral nerve blocks especially done under ultrasound guidance is very rare. In our case, it was noted that the site to be operated had repeated twitching movement even after a good dense Supra clavicular block and was a real challenge for the surgeon to operate under microscope where an absolute immobility is required to operate under microscope.

Case Presentation

A 42-year-old male with no previous known comorbidities came with a history of assault and injury to the left thumb. He was complaining of severe pain over the base of the left thumb, inability to use, loss of sensation distally and thumb hanging with skin support. On examination, near total amputation of left thumb at the proximal phalangeal level with thumb hanging with the skin at the dorsal side was noted. The distal part of the thumb was not viable.

Fig (1): Near total traumatic amputation of left thumb

On clinical assessment

Height	Weight	BP	Pulse Rate	SPO2%	Temperature	Respiratory Rate	GCS
175 Cm	76 kg	130/70 mmHg	106/Min	99% at Room air	97.6⁰F	20/Min	15/15

The patient was posted for wound exploration and replant of thumb under supraclavicular brachial plexus block. To allay the anxiety and pain Inj. Midazolam 2mg IV and Inj.Fentanyl 100 mcg IV was given. In the pre-operative anaesthesia induction room, after following WHO surgical safety check list and with standard monitoring facilities USG guided Left side Supra clavicular brachial plexus block was given with 20 ml of 0.75% Ropivacaine. After 20 minutes, complete sensory and motor blockade were achieved. The patient was shifted to the operation theatre and standard monitors were applied. The Surgical procedure lasted for 3 hours and the intra-operative period was uneventful. In that duration the tourniquet time was 1 hour and 45 minutes. The patient was shifted to the post-operative ward in stable condition.

Fig (2): Post reconstruction of the left thumb

Five hours later the patient was again posted for Re-exploration of the left thumb. As prolonged duration of the procedure was anticipated, Ultrasound-guided left supraclavicular brachial plexus block with 15 ml of 0.75% of Ropivacaine was repeated. The patient was shifted to the operating room and standard monitors were put. Intraoperatively, 30 min after the nerve block, we noticed a jerky movement of the left thumb. The patient was unaware of the abnormal movements and there was no change in the patient’s mental status. The abnormal movement involving the left thenar region and thumb was arrhythmic, shock-like, involuntary twitching lasting for few seconds and self-limiting in nature and recurred after a periodic pause. It was not responding to medications like intravenous midazolam and propofol. We couldn’t identify any aggravating or relieving factors. Surgical team managed to proceed with the surgery in spite of occasional rhythmic movement of the thumb as patient had absolutely no pain

A provisional diagnosis of self-limiting peripheral myoclonus was made. The myoclonic movement appeared throughout the intraoperative period which lasted for 2 hr and 30 min and continued in the postoperative ward. Myoclonus gradually decreased and disappeared 6 hours after the surgical procedure without any intervention.

Discussion

Regional anaesthetic techniques are gaining popularity in recent years despite general anaesthesia being used for the majority of surgical procedures to avoid complications of general anaesthesia. Although considered safe, effective and feasible, regional anaesthesia rarely has its adverse effects and complications. With the use of ultrasound-guided techniques complications are very rare. Supraclavicular brachial plexus block is a commonly used technique for surgeries involving upper extremities below elbow level.

Advantages of Regional Anaesthesia are:

Reduced incidence of nausea and vomiting
Smooth transition to pain control
Avoids polypharmacy
Increased blood flow to the extremity
Less drowsiness
Helps in early ambulation
Tracheal intubation and its response could be avoided.

Myoclonus is a brief arrhythmic movement or twitching of a muscle or group of muscles which is involuntary. There are various classifications available for myoclonus. The most accepted one is based on the neuroanatomic origin of electrical discharge which is classified as follows^[1]:

Cortical
Subcortical
Spinal
Peripheral

Myoclonus appearing after spinal anaesthesia is a recognised phenomenon ^[2]. But very few cases have been reported after peripheral nerve block. Peripheral myoclonus is believed to be caused by lesions in the peripheral nerve or injury or entrapment which alters the sensory input and central reorganisation occurs over some time ^[3]. The most commonly occurring peripheral myoclonus is a hemifacial spasm.

In our patient, Peripheral myoclonus was noticed with involuntary, arrhythmic movement or twitching involving the left thenar and thumb region after reconstruction of thumb and supraclavicular brachial plexus block. The patient did not complain of severe pain and paraesthesia while performing the block. There was no history of past injury and myoclonus occurrence. The patient had no comorbidity i.e otherwise healthy individual. The dosage of the drug used did not exceed the toxic level and was well below the upper limit. Experienced Anaesthesiologists performed the block both the times. The patient was unaware of myoclonus and there was no altered mental status or any other signs related to other forms of myoclonus except peripheral type. The patient refused to undergo electromyographic studies which could have helped in the diagnosis. Peripheral nerve blocks and botulinum toxin are used in the treatment of peripheral myoclonus. In our case myoclonus was brief, arrhythmic, involuntary twitching involving the thenar and thumb region only, which was not responding to medications. It was self-limiting and non-stimulant. Myoclonus was recurring after a periodic pause and completely disappeared after 8 hr of appearance. Traumatic peripheral nerve injury can also cause peripheral myoclonus. So, the exact mechanism which caused the peripheral myoclonus was unclear.

Conclusion

As peripheral nerve injury can cause myoclonus, care must be taken while performing peripheral nerve blocks to avoid nerve injury. Ultrasound-guided techniques should be preferred whenever feasible. The injection pressure monitor shall be used while administering the drug which reduces the risk of nerve injury

References

Caviness JN, Brown P. Myoclonus: current concepts and recent advances. Lancet Neurol 2004; 3: 598-607.
Lev A, Korn-Lubezki I, Steiner-Birmanns B, Samueloff A, Gozal Y, Iascovich A. Prolonged propriospinal myoclonus following spinal anaesthesia for a caesarean section; case report and literature review. Arch Gynecol Obstet 2012; 286: 271-2.
Assal F, Magistris MR, Vingerhoets FJ. Post-traumatic stimulus suppressible myoclonus of peripheral origin. J Neurol Neurosurg Psychiatry 1998; 64: 673-5.

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Self-limiting myoclonus following supraclavicular brachial plexus block with Ropivacaine: A rare incidence