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ORIGINAL ARTICLE
Year : 2019  |  Volume : 67  |  Issue : 7  |  Page : 82--91

Injection-related iatrogenic peripheral nerve injuries: Surgical experience of 354 operated cases

Ketan Desai, Anshu C Warade, Ashish K Jha, Sanjeev Pattankar 
 Department of Neurosurgery, PD Hinduja Hospital, Mumbai, Maharashtra, India

Correspondence Address:
Dr. Ketan Desai
C/o Marylee, 1st Floor Faculty, Wing Number 4, Hinduja Clinic, Hinduja Hospital, Veer Sawarkar Marg, Mahim, Mumbai - 400 016, Maharashtra
India

Abstract

Objective: A retrospective analysis of surgically treated 354 cases of injection-related iatrogenic peripheral nerve injuries was performed. The purpose of this clinical study was to present our experience in the management of various types of injection-related peripheral nerve injuries and discuss various issues that are associated with this subset of peripheral nerve injuries. Methods: Over a 17-year period, 354 cases of injection-related iatrogenic peripheral nerve injuries were managed surgically at the Department of Neurosurgery at P.D. Hinduja Hospital and Seth G S Medical College, Mumbai. In our series, the injection-related iatrogenic nerve injuries were following intramuscular injections, brachial nerves block procedures, subclavian and jugular venous cannulation procedures for central line placements, and routine intravenous injections in the peripheral veins of the limbs. The age of the patients ranged from 5 years to 65 years. Pain, paresthesia, and sensory-motor deficits were the common presenting features in our series. The operative procedures performed in our series were external neurolysis and excision of neuroma/contused portion of the nerve and sural nerve cable grafting. The follow-up ranged from 6 months to 84 months. There were no major intraoperative complications in our series. Results: In our series, functional improvement (power grade 3 or above) was noted in 190 (53.7%) patients following surgical intervention. In 164 (46.3%) patients, there was either a non-functional status or no recovery. Neurological deterioration in the form of motor weakness was noted in 9 (2.5%) patients in our series after the surgery. The best results (90.1%) were noted with radial nerve repair following surgical intervention. Conclusion: Injection-related iatrogenic nerve injuries are not an uncommon problem. Surgery should be the preferred treatment option when the injured nerve fails to recover following the insult. The results are rewarding in a significant percentage of patients following timely intervention. The problem of litigation attached with this type of injury is also highlighted.



How to cite this article:
Desai K, Warade AC, Jha AK, Pattankar S. Injection-related iatrogenic peripheral nerve injuries: Surgical experience of 354 operated cases.Neurol India 2019;67:82-91


How to cite this URL:
Desai K, Warade AC, Jha AK, Pattankar S. Injection-related iatrogenic peripheral nerve injuries: Surgical experience of 354 operated cases. Neurol India [serial online] 2019 [cited 2019 Jul 18 ];67:82-91
Available from: http://www.neurologyindia.com/text.asp?2019/67/7/82/250703


Full Text

An injection-related iatrogenic peripheral nerve injury is a potentially serious problem. Intramuscular injection- related peripheral nerve palsies are more common among all the injection injuries in the developing countries where, besides qualified trained doctors, unqualified/untrained personnel are actively involved in the treatment of patients.[1],[2],[3],[4],[5],[6] The injection-induced iatrogenic peripheral nerve palsies are devastating, cause significant neurological disability and inflict serious mental trauma. It is estimated that more than 50% of intramuscular injections are administered in unregistered or non-formal healthcare systems.[3],[7],[8] In the last decade, various surgeries involving the limbs have been performed under nerve block technique as an alternative to as well as to avoid general or spinal anesthesia. In addition, there is a tremendous increase in the central line placement procedures in the subclavian or jugular veins, both in the intensive care unit (ICU) and during the major operative procedures.[9],[10],[11],[12],[13],[14] All these procedures have also eventually increased the frequency of injection-related peripheral nerve injuries. In our experience, patients with nerve injuries following intramuscular injections were fairly (82.5%) common. In our study, various types of injection-related injuries were retrospectively analysed and evaluated with respect to their clinical presentation, mechanism of injury, and clinical outcome related to recovery of neurological symptoms and deficits. In addition, the functional recovery was also assessed with respect to the timing of surgery from the time of insult, and various operative procedures that were performed. The literature on this subject has also been briefly reviewed.

 Materials and Methods



Patient's population

We report a retrospective analysis of 354 patients with injection-related iatrogenic peripheral nerve injuries treated at the Department of Neurosurgery, P.D Hinduja Hospital and Seth G S Medical College, Mumbai from 2001 to 2017. The clinical records, radiological images, and follow-up data inclusive of questionnaire sent to the postal addresses of the patients were studied and analysed. In our experience of 17 years, 523 patients with injection-related peripheral nerve injuries attended our clinic. The injection related injuries to the nerve occurred following intramuscular injections, brachial nerve block procedures, central lines placement in the subclavian and jugular veins in the neck, and intravenous injection in the peripheral veins.

In 354 patients, surgery was performed. In 169 patients, the surgical intervention was deferred. In this group, 48 patients were observed without any surgical intervention. In 22 patients in this subgroup, progressive improvement in the clinical symptoms and neurological deficits was noted during the follow-up visits, and these patients were, therefore, treated conservatively. In 26 patients, surgery was deferred as the clinical assessment revealed that the residual neurological deficit was unlikely to improve further following any surgical intervention. In our series, 82 patients either refused surgery or consulted us only for an opinion. Surgery was not advised in 39 patients as the patients presented very late (≥2 years) from the time of the insult and nerve repair was not possible [Table 1]. The mean age of the patients was 28 years (age range, 5–65 years). There was a male predominance with the male: female ratio being 3:1.{Table 1}

Clinical presentation and investigations

The clinical records of all 354 surgically treated patients were retrospectively reviewed with respect to the presenting complaints, as well as neurological, electrophysiological, and radiological findings. The neurogenic pain symptom was graded on the visual analog scale (VAS) of 0–10, where 0 was representative of no pain and 10 was indicative of unbearable, severe annoying pain. The paresthesia was graded from mild to severe type. The muscle power charting was graded based on the Medical Research Council (MRC) scale. The electrophysiological study (EMG-NCV) was performed preoperatively in all the 354 patients. In all patients, the preoperative documentation of delay or block in conduction across the damaged nerve on nerve conduction (NC) study, and evidence of denervation in the affected nerve on the electromyography (EMG) study was confirmed prior to surgical intervention. Magnetic resonance imaging (MRI) scan of the affected region was done in 129 (36.4%) patients in our series. In 27 (7.6%) patients, an additional MRI neurography was also performed.

Surgical approach

Surgical treatment was performed in patients with severe neurogenic pain and paresthesia following injection treatment that failed to respond to medical therapy. These patients also had a marked disturbance in their daily functioning. In addition, surgery was also offered to patients with sensorimotor neurological deficits following injection therapy that had failed to recover after 3 months of observation and conservative treatment. Surgical treatment in the form of nerve repair was deferred in patients having post-injection palsy for more than 2 years. The surgical options were external neurolysis and excision of the neuroma/contused portion of the nerve and sural nerve cable grafting. Intraoperative stimulation of the nerves and recording of the muscle activities was mandatory and was used in all patients during surgery.

Postoperative course and follow-up

The follow-up period in our series ranged from 6 months to 84 months, with a mean of 22 months. The follow-up protocol consisted of a thorough clinical examination and periodic electrophysiological assessment at 6-month intervals for a period of 2 years postoperatively. During the follow-up visits, the neurogenic pain, paresthesia, and sensorimotor neurological deficits were assessed and compared with the preoperative status and previous clinic visits. The results were evaluated based on the functional motor recovery of Medical Research Council (MRC) power grade 3 or more and improvement in the sensory complaints.

 Results



Patients population

In our series, patients with peripheral nerve injuries following intramuscular injections were much younger with a mean age of 14 years (age range, 5–46 years). In contrast, the patients with peripheral nerve palsies following brachial nerve blocks and intravenous injections in neck and limbs had a mean age of 44 years (age range, 29–65 years). Overall, in our series, 69 (19.5%) patients were below the age of 10 years and all had intramuscular injection-related nerve palsies. The duration of presenting complaints ranged from 1 month to 18 months with a mean duration of 5.6 months. The patients with brachial nerve block procedures and intravenous injection-related peripheral nerve injuries presented to us early (mean duration, 2.8 months) when compared with patients with intramuscular injection-related peripheral nerve injuries (mean duration, 8.4 months).

The incidence of iatrogenic nerve injuries following the administration of an intramuscular injection was the most common occurrence and affected 292 (82.5%) patients in our series. The nerves involved were the sciatic nerve in the gluteal region in 151 (42.7%) patients, the radial nerve in the arm in 132 (37.3%) patients, and the axillary nerve in the shoulder region in 9 (2.5%) patients. In patients sustaining brachial plexus injury following the nerve block procedure, 30 patients had a supraclavicular brachial plexus injury involving the roots and trunks. In this subgroup, injuries to the C8, T1 roots to the lower trunk were found in 25 patients. In 5 patients, the C5, C6 roots to the upper trunk were involved following supraclavicular block procedures. In this subgroup, minor degree of injury was noted in other roots and trunks without any significant neurological manifestations. There was no past history of pneumothorax in patients with brachial plexus block and intravenous cannulation procedures in the neck. Infraclavicular brachial block procedure-related brachial plexus injury was noted in 2 patients affecting the lateral and medial cords. The brachial blocks were given for orthopedic procedures such as plating for fractures of the humerus and radius-ulna. In 17 (4.8%) patients, a supraclavicular brachial plexus injury affecting the roots and trunks was noted following cannulation of either the jugular or subclavian veins in the intensive care unit (ICU) or during major operative procedures. In this subgroup, C8, T1 roots to lower trunk involvement was noted in 13 patients, whereas in 4 patients, C5, C6 roots to upper trunk were found to be affected. Intravenous injection-related peripheral nerve injury in the limbs was noted in 13 (3.7%) patients. In this subgroup, 7 patients had a median nerve injury in the elbow and forearm, following repeated attempt at intravenous punctures. In 4 patients, the femoral nerve was affected following intravenous puncture of the femoral artery or vein for an angiography and for blood sample collection procedures. In 2 patients, the superficial sensory radial nerve was injured at the wrist following an intravenous cannulation for infusion of saline and medications.

Clinical presentations and investigations

In 197 (55.6%) patients, there was neurogenic pain at the site of injection radiating to the distribution of the nerve in the affected limb. The neurogenic pain was severe and excruciating in 84 patients (VAS >6). In 113 patients, the pain was less severe (VAS 3–6). There was associated paresthesia in the affected limb in 114 (32.2%) patients. The paresthesia was severe in 78 (68.4%) patients and mild-to-moderate in 36 (31.6%) patients. In 167 (84.8%) patients, the neurogenic pain was immediate, and it was after a few hours to days in 30 (15.2%) patients following the injection procedures. The sensorimotor neurological deficit occurred immediately in 324 (91.5%) patients, and in 30 (8.5%) patients, it occurred after a few hours to days following the injection treatment. In the intramuscular injection group, severe neurogenic pain (VAS > 6) was noted in 28 (33.3%) patients. In the brachial nerve block and intravenous injection groups, severe neurogenic pain (VAS, >6) was found in 56 (66.6%) patients. It hampered daily activities and disturbed sleep in the night. In 239 (67.5%) patients, there was associated wasting of muscles supplied by the affected nerves. In patients with sciatic nerve injury following an intramuscular injection in the gluteal region, the common peroneal nerve affection with foot drop as a clinical manifestation was noted in all 151 patients. Tibial nerve involvement with plantar flexion weakness of the foot was seen in 69 (45.7%) patients in this subgroup. In patients with radial nerve palsy following intramuscular injection in the arm, wrist drop with difficulty in extension of fingers was noted in all 132 patients. All patients in this subgroup had normal triceps muscle function. All 9 patients with axillary nerve palsies following an intramuscular injection in the upper arm presented with an inability to abduct the affected shoulder beyond 15–20 degrees. There was associated deltoid muscle wasting with subluxation of the shoulder joint in all 9 patients. In the intramuscular injection group, severe neurogenic pain was predominantly seen in 25 patients (89.3%), with sciatic nerve injury in the gluteal region. The detailed clinical presentation of the patients in our series is shown in [Table 2].{Table 2}

The nerve conduction study documented either a severe delay or a block in conduction across the damaged segment of the nerve in all patients. In these patients, the EMG findings revealed an associated denervation of varying severity in the affected nerves. There was no documentation of any significant re-innervation on EMG in any of the patients. In 129 patients, the preoperative MRI scan documented hyperintense signal changes on T2-weighted sequence and on short-tau inversion recovery (STIR) at the site of the nerve damage. The MR neurography imaging revealed focal dilatation of the affected neural segment suggestive of a neuroma formation in 19 patients. There was no evidence of segmental discontinuity of the affected nerves on MRI scans in our series. In all 129 patients with a preoperative MRI scan, a hyperintense signal in the affected muscles was noted on STIR sequence, with corresponding documented denervation in the affected nerves being recorded on the EMG study.

Surgical treatment

Intraoperative findings

In patients with post-intramuscular injection palsy, perineural scarring was a common intraoperative finding in 66.4% patients. In contrast, in patients with a nerve palsy following a brachial block procedure or an intravenous cannulation in the neck and limbs, focal nerve contusion and neuroma in continuity were the more common findings noted in 74.2% patients. In patients with an intramuscular injection-related radial nerve injury, perineural scarring around the nerve was found in 90.2% patients, and was noted in 45.7% patients with sciatic nerve involvement. In contrast, focal nerve contusion and neuroma-in-continuity were the more common findings affecting the sciatic nerve following an intramuscular injection in 25.8% and 28.5% patients, respectively [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7].{Figure 1}{Figure 2}{Figure 3}{Figure 4}{Figure 5}{Figure 6}{Figure 7}

The focal contusion and neuroma-in-continuity of the affected nerve also demonstrated significant perineural scarring and tethering of the nerve to the surrounding soft tissue. In all 210 patients with only perineural scarring, the intraoperative stimulation demonstrated low amplitude conduction across the damaged segment of the nerve. In 24 patients, with focally contused nerve in the intramuscular injection group involving the radial nerve, the intraoperative stimulation yielded a low amplitude conduction across the damaged segment of the nerve, and hence, external neurolysis was performed in these patients. External neurolysis was performed in all 234 patients with demonstrable low amplitude intraoperative conduction across the damaged segment of the affected nerve. In 120 patients, with a focal nerve contusion or neuroma-in-continuity, excision of the focal damaged portion of the nerve, and a sural nerve cable grafting was performed. Intraoperative stimulation of the damaged nerve in this subgroup failed to demonstrate any electrical response [Table 3] and [Table 4].{Table 3}{Table 4}

Postoperative course and follow-up

There were no major intraoperative complications in our series. Three patients had wound infection and were treated with antibiotics. In 9 patients, there was deterioration of motor power following the surgical procedure [Table 5]. At a 1-year follow-up visit, the motor power significantly recovered in patients with the tibial nerve (1 patient) and C5–C6 roots to upper trunk (2 patients) palsies. However, in 6 patients with common peroneal nerve and C8, T1 roots to lower trunk palsies, the postoperative neurological deficit failed to recover.{Table 5}

In our series, functional recovery in the intramuscular injection group affecting the sciatic nerve occurred in 56.5% in the tibial nerve, whereas it occurred in 23.2% in the peroneal nerve. The functional recovery in the patients with intramuscular injection palsy affecting the radial and axillary nerves occurred in 90.8% and 88.8%, respectively, following surgery. In patients with brachial plexus injury following brachial block procedures, the functional recovery was better in patients with C5–C6 roots to upper trunk injury (80%). In contrast, the outcome was poor (32%) in patients with C8–T1 roots to lower trunk injury. Similar outcome with respect to functional recovery in patients with a brachial plexus injection palsy following intravenous cannulation in the neck was noted in C5–C6 roots to upper trunk (100%) and C8–T1 roots to lower trunk (15.4%) injuries [Table 6] and [Table 7]. In patients with a peripheral nerve injury following an intravenous injection, the functional recovery occurred in 75% and 57.1%, respectively, following surgeries involving femoral and median nerves.{Table 6}{Table 7}

The functional recovery was significantly better in patients operated within 6 months from the time of injury. In the intramuscular injection-related sciatic nerve palsy, the functional recovery occurred in 65.3% and 29.2% patients, respectively, in the tibial and peroneal component of the sciatic nerve. In contrast, the functional recovery significantly reduced to 35% and 12.7%, respectively, in the tibial and peroneal component of the sciatic nerve when the surgery was performed after 6 months from the time of injury. In the post intramuscular injections radial and axillary nerves palsy, the functional recovery noted was 93.8% and 100%, respectively, in patients operated within 6 months from the time of injury. The outcome, however, was encouraging with functional recovery occurring in 86.1% and 66.6%, respectively, of patients operated between 6 months and 1 year from the time of injury. In patients with brachial plexus injury following the brachial block procedure, the functional recovery was 66.6% when patients were operated within 6 months from the time of injury. In patients with C8–T1 roots to lower trunk, the functional recovery occurred in 57.1% when patients were operated within 6 months. There was no recovery noted in this subgroup of patients when the surgery was performed after 6 months from the time of insult. In the post-intravenous cannulation injection palsy affecting the brachial plexus, the functional recovery occurred in 22.2% with C8–T1 roots to lower trunk injury, and in 100% patients with C5–C6 roots to upper trunk injury in those operated within 6 months from the time of insult. The outcome was extremely poor in patients of this subgroup when the surgery was performed after 6 months from the time of injury. In the post-intravenous injection palsy in the limbs, the functional recovery occurred in 80% in patients with a median nerve palsy in the elbow and forearm following surgery within 6 months from the time of injury.

The functional outcome was superior with external neurolysis (62.3%) when compared with nerve grafting procedures (31%) in all types of injection palsies. The functional recovery was extremely poor with nerve grafting procedures involving the common peroneal nerve (13.2%) and C8–T1 roots to lower trunk palsies (16%). There was no significant difference in the functional outcome in the case of a radial nerve palsy following external neurolysis and a nerve grafting procedure.

The preoperative severe neurogenic pain (VAS > 6) found in 84 patients improved and completely disappeared in 68 (81%) patients. In 16 patients, the pain had significantly reduced in intensity (VAS 2–5). The mild-to-severe preoperative paresthesia improved in 102 (89.5%) patients.

 Discussion



Injection-related peripheral nerve injury is an iatrogenic problem. The previous literature reports an overall incidence that ranges from 1.5% to as high as 15%.[7],[15],[16],[17] A high incidence of indiscriminate use of intramuscular injections is reported in the developing world. The incidence of post-injection palsy has drastically reduced in the developed world due to an excellent healthcare system that only permits trained individuals to be involved in the treatment of patients.[2],[4],[5],[6],[8],[15],[17],[18],[19],[20],[21]

Injection-related iatrogenic nerve palsy is an unforeseen problem both for the patient and the treating physician. It manifests as a new problem in the background of an already existing disease. The incidence of litigation is very high in developed countries. In developing countries like India, the incidence of litigation following an iatrogenic nerve palsy is significantly less. However, with changing times, it is on an upswing trend. Another major issue related with iatrogenic nerve injuries is the delayed reference to specialized centres for timely and aggressive treatment. A significant amount of time is wasted in performing physiotherapy, and as a result, the denervation process in the nerves is significant and the ultimate outcome is poor. There is also a reluctance from patients in undergoing surgery for treatment of iatrogenic nerve injuries. All these factors combine to make this problem more difficult to treat than other types of nerve injuries.[15],[22]

Patient population

Patients with an intramuscular injection-related nerve palsy were much younger with a mean age of 14 years. In this group, 69 (23.6%) patients were below the age of 10 years. This may be attributed to the thin muscle mass and the general tendency of favouring an intramuscular injection in children. In contrast, patients with nerve injuries following a brachial block, jugular-subclavian vein cannulation in the neck, and intravenous cannulation in limbs were much older with a mean age of 44 years. The likely cause of their being older was that a high percentage of these procedures have been performed in adult patients. The early presentation of the patients (mean duration, 2.8 months) in our clinic with post brachial blocks and intravenous injection-related nerve palsies was probably attributed to a more severe neurogenic pain and neurological deficits that compelled them to seek an early consultation. In contrast, in the intramuscular injection injury group of patients, motor weakness was more common than severe sensory symptoms, which propelled them towards physical therapy.[1],[3],[6],[15],[17],[21]

Pathophysiology

Intramuscular injections in children should be avoided at all costs as the morbidity of the procedure is relatively high. The misconception that avoidance of intravenous injections in children will lead to disastrous consequences, should be rejected. This will help in reducing the incidence of intramuscular injection injuries to a significant extent. In our series, 91.5% of the patients had a neurological deficit immediately following the injection therapy. In 8.5% of the patients, it was after a few hours to days following the injection treatment. The occurrence of immediate neurological compromise is suggestive of direct neural injury by the needle of the injection and the medication that is released within the nerve. There is intraneural hemorrhage and damage to the myelin sheath and axons, which eventually leads to nerve denervation and perineural scarring. In contrast, a delayed neurological insult is probably more due to perineural damage caused by the caustic effect of the medications. There is associated muscle necrosis with secondary neural damage and tethering of the nerve to the surrounding muscle and soft tissue.[1],[6],[19],[20],[23]

In the brachial block procedures and intravenous cannulation-related nerve injuries, penetrating injury of the nerve by the needle is often more severe as repeated attempts are made, which eventually inflicts severe neural damage along with intraneural or perineural hematoma formation. During the intravenous cannulation or block procedure, development of neurogenic pain or paresthesia radiating along the nerve is strongly suggestive of neural injury and the needle should be withdrawn and the procedure should be terminated. The complications are relatively higher with interscalene supraclavicular brachial plexus block than with infraclavicular axillary block procedures.[9],[10],[24],[25],[26] The incidence of neural complications following the block procedures and intravenous cannulation in the neck has significantly decreased with more experience, knowledge of the local anatomy of brachial plexus, and use of ultrasonography and nerve stimulator.[12],[27],[28],[29],[30] It is absolutely mandatory to use ultrasonography during the block procedure and intravenous cannulation in the neck, as complications with the use of free hand techniques are high in the compact space between scalenus anterior and medius that harbours the brachial plexus.[9],[10],[11],[13],[26],[31],[32],[33],[34],[35] A study conducted by Zhou et al., concluded that the outcome and complication rate are not significantly different with the combined use of ultrasonography and nerve stimulator, and ultrasonography alone during the block procedures.[27]

The common medications that are given by intramuscular route are antibiotics, such as penicillin, ampicillin; analgesics, such as diclofenac sodium; antiemetics, such as promethazine, dimenhydrinate; antimalarial quinine; and oil-based multivitamins. All medications when injected directly into the nerves are potentially more damaging to the myelin sheath and axons. In contrast, these medications cause less neurological damage when they are injected in the perineural tissue or adjacent muscle mass.[6],[17],[18],[20],[36],[37]

Clinical features

In our series, the neurogenic pain and motor weakness were of immediate onset in a majority of patients following the intramuscular injection, post brachial block, and intravenous cannulation procedure in the neck and limbs. These findings highlighted the fact that neural injury was immediate following the injection therapy, and that secondary involvement of the nerve that manifests late, was not a common phenomenon. In our series, involvement of the C8–T1 roots to the lower trunk was a common presentation in patients with brachial plexus injury following a block procedure and intravenous cannulation in the neck. The probable cause of these roots being involved was the close proximity of the subclavian and jugular veins to the lower roots and the medial direction of the needle during the block procedure and the intravenous cannulation. Severe neurogenic pain (VAS >6) was more common in patients following a brachial plexus block and an intravenous cannulation procedure. In contrast, severe neurogenic pain was not a common manifestation following an intramuscular injection-related peripheral nerve injury. The probable cause of this difference was more severe axonal damage due to repeated attempts at puncturing the tissues during the brachial block and intravenous cannulation procedure.[13],[14],[32]

In the case of post-intramuscular injection sciatic nerve injuries in the gluteal region, the peroneal nerve was affected in all the patients (100%). In contrast, the tibial nerve was affected in only 45.7% patients. The probable reason for a higher incidence of the peroneal rather than the tibial nerve involvement was the posterolateral location of the peroneal nerve in the sciatic nerve and the lesser degree of connective tissue, axons, and vascularity in the peroneal nerve.[3],[17],[18],[19],[36] This was reflected in the functional recovery of the sciatic nerve also. In the tibial division of sciatic nerve, the functional recovery was 56.5% while it was only 23.2% in the peroneal nerve component of the sciatic nerve.

Investigations and surgery

Magnetic resonance imaging (MRI) scan in the patients suffering from iatrogenic injection-related peripheral nerve injuries is useful in localizing the site of injury by revealing a hyperintense signal on T2-weighted and STIR sequences. MRI neurography can demonstrate a neuroma at the site of the damaged segment. However, its use is often limited as the management decision cannot be based on MRI findings.[6],[19]

Electrophysiological study (EMG-NC) is an absolutely mandatory investigation and should be performed in all patients with iatrogenic nerves injuries. It helps to diagnose and localize the site of injury. It also provides information regarding the re-innervation or denervation process in the injured nerve. The EMG findings help in taking a decision regarding surgical intervention.[1],[37],[38],[39],[40] Clinically, it is essential to diagnose the problem and avoid delay. Surgical intervention is strongly recommended if the clinical findings and electrophysiological tests are suggestive of severe nerve injury with denervation. Timely and aggressive intervention have a favourable outcome with respect to sensorimotor recovery. In patients with intramuscular injection-related peripheral nerve injuries, an early exploration and saline irrigation with external neurolysis is also recommended. However, its usefulness is limited as it has only a small role to play in patients with injuries due to intraneural injections.[41],[42],[43]

Intraoperative nerve stimulation is very important during surgery. Documentation of nerve action potential (NAP) across the damaged segment indicates conduction in the injured portion of the nerve, and external neurolysis can be an ideal surgical option. In situ ation where NAP is not demonstrated across the injured nerve, excision of the damaged segment and a nerve cable grafting should be ideally performed.[1],[19],[37],[38],[43],[44]

In the post intramuscular injection group, perineural scarring was a common finding in 66.4% patients. In contrast, focal nerve contusion and neuroma formation were more commonly noted (in 74.2%) in patients following the brachial block procedure and the intravenous cannulation-related nerve injury. This important observation highlighted the fact that injury in the intramuscular group is more indirect in the perineural tissue, whereas in the iatrogenic post brachial block and the intravenous cannulation procedure group, it is a direct neural injury that causes nerve contusion and neuroma formation. In the intramuscular injection group, perineural scarring involving the radial nerve was a common intraoperative finding, whereas in the sciatic nerve, contusion and neuroma formation were found in 54.3% of the patients. This finding demonstrates the nature of injury in these nerves.

 Functional Recovery



In the intramuscular group, the functional recovery after surgical intervention was excellent in the radial and axillary nerves.[19],[20],[21],[36] The functional recovery was relatively poor in the peroneal component (23.2%) of the sciatic nerve. A similar poor functional recovery was noted in patients with C8–T1 roots to lower trunk injuries following the post brachial block and intravenous cannulation procedures. The probable cause of a poor functional recovery in the latter group was a more severe neural injury and a longer distance for reinnervation.[9],[13],[14],[32],[33] The functional recovery in all groups of patients was significantly better when the patients were operated within 6 months from the time of injury. The results deteriorated considerably in patients with post injection sciatic nerve, brachial plexus, and other peripheral nerve injuries following surgery performed after 6 months of injury. The results further worsened in patients with the peroneal nerve and C8-T1 roots to the lower trunk post injection injuries. The delayed intervention caused extensive denervation in the affected nerve following the injection injury. The functional outcome following external neurolysis was superior than the nerve grafting procedures. These findings were consistent with the literature review.[6],[7],[15],[19],[44] The axonal continuity and presence of NAP across the injured nerve were the factors responsible for a good clinical outcome following an external neurolysis. In contrast, re-innervation across the cable grafts in a denervated nerve was often not possible, affecting the functional recovery. The marked improvement in the sensory symptoms such as neurogenic pain and paresthesia in our series was following the detethering of the injured nerve, excision of the perineural scar around the nerve, and excision of the damaged segment of the nerve. The functional recovery was superior in patients treated with surgery than in those managed conservatively. A large series has documented that patients with conservative management have either no recovery or partial recovery in 65%–82% of the cases.[4],[6],[7],[8]

Following iatrogenic injection-related peripheral nerve injuries, litigation and medicolegal issues are a common occurrence. The iatrogenic injuries cause both distress and disability to the patients. The treating physician should be aware of the potential medicolegal ramifications while performing any procedure. It is, therefore, mandatory that proper explanation be given prior to the procedure and all possible complications be brought to the notice of the patient. Lawsuits related to peripheral nerve injuries have cited surgical error, inadequate or absent informed consent, and failure to immediately diagnose the injury, as factors that prompted the litigation. The exact incidence of iatrogenic injection-related peripheral nerve injuries is not known. In this type of injury, a significant portion of cases remain unreported with the fear of highlighting the problem and litigation problems. The majority of iatrogenic injection-related nerve injuries are avoidable and can be prevented. The knowledge of surgical anatomy of the peripheral nerves and the use of adjuncts such as ultrasonography can help to prevent this injury. In the event of occurrence of this problem, it should be diagnosed early and aggressively treated to achieve a good outcome. It is the failure to diagnose this injury and in not taking the patient into confidence that invites lawsuits in a majority of cases.[4],[8],[10],[22],[31],[44],[45]

 Conclusion



An iatrogenic injection-related peripheral nerve injury is not an uncommon problem. An early diagnosis, timely reference to a specialized peripheral nerve center, and an early intervention are few important factors that can provide an encouraging outcome, and thereby decreases the incidence of medicolegal litigations. In majority of the cases, the problem can be avoided by having a thorough anatomical knowledge and a proper counselling of the patients prior to the procedure.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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