Incidence of PNI secondary to PNB is hard to define. Literature estimates from 0.014% to 0.04%.¹ The mechanism of injury can be multifactorial. Diagnosing neural injury will assist in ascertaining the exact site of the damage and the likely aetiology. Early diagnosis in these patients will help guide management and in doing so hopefully reduce long term sequalae of such a rare complication.

Protocols to help manage nerve injury associated with regional anaesthesia are available from RAUK,² ASRA¹ and NYSORA.³ The limited literature on this topic may be testament to the plethora of information relating to avoiding PNI from regional anaesthesia.

NYSORA recommend a three step approach to evaluating the patient with suspected PNI³. Firstly the presence of an active process (perineural haematoma) amenable to intervention must be considered. Careful history will guide the investigations such as CT or ultrasound when this is suspected. Secondly, Is the PNI related to surgery? When this is the case urgent surgical exploration may be warranted. Finally, try to localise the deficit. Careful clinical examination should differentiate between sensory and motor deficit whilst determining if a single peripheral nerve, plexus or nerve root is involved.⁴ This will indicate the severity and therefore prognosis as set out in the Seddon classification of nerve injuries.⁵ In deciphering the severity of injury the clinician will be guided to the need for nerve conduction studies and electromyelography (EMG). Electroneuromyography is the standard to assess PNI.⁶ It is important to remember that serial EMG studies are required as Wallerian degeneration may take time.⁷

Diagnosing PNI will require a multidisciplinary approach however the existence of a ‘best protocol’ is something that warrants discussion.

References

1. Watson JC, Huntoon MA. Neurologic evaluation and management of perioperative nerve injury. Reg Anesth Pain Med 2015;40:491–501.

2. https://www.ra-uk.org/images/NERVE_INJURY_management_algorithm_RAUK_April2015.pdf. Accessed 1/6/19.

3. https://www.nysora.com/foundations-of-regional-anesthesia/complications/assessment-neurologic-complications-regional-anesthesia/. Accessed 1/6/19.

4. Paul David Weyker, Christopher Allen-John Webb, Thoha M Pham. Workup and management of persistent neuralgia following nerve block. Case Reports in Anesthesiology2016; 2016:6. Article ID9863492.

5. Sawyer, et al. Peripheral nerve injuries associated with anaesthesia. Anaesthesia 2000;55:980–991.

6. Alain Borgeat, Jose Aguirre. Assessment and treatment of postblock neurological injury. Anesthesiology Clinics 2011;29(2):243–256.

7. O’Flaherty D. BJA Education 2018;18(12):384e390. Nerve injury after peripheral nerve block. Current understanding and guidelines.