Peripheral nerve injuries: A retrospective survey of 1124 cases
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/neuroindia.NI_987_16
Source of Support: None, Conflict of Interest: None
Background: Peripheral nerve injuries (PNIs) remain an important health problem often leading to severe motor disabilities predominantly in the younger population.
Keywords: Brachial plexus, electromyography, nerve injury, peripheral neuropathy, trauma
Peripheral nerve injuries (PNIs) remain a major medical problem worldwide. These lesions are caused mainly by motor vehicular accidents, penetrating trauma after stabbing incidents, gunshot injuries, and stretching or crushing injuries after falls. Fractures of the adjacent bones are commonly associated with PNIs, such as humeral fractures associated with radial neuropathy., Depending on the mechanism of the injury, the PNIs can be sharp or blunt, transected or lacerated; the nerves may be displaced, contused, stretched, or even partially divided, leading to neuromas or lesions in continuity. The incidence of PNIs is frequently underestimated and a relative scarcity of large clinical series in the published literature remains a major limitation to our knowledge regarding PNIs.
It is estimated that roughly 2–3% of the patients admitted to trauma centers have PNIs,, and this percentage is higher if the plexus and root injuries are included. As PNIs may be accompanied by central nervous system (CNS) trauma, their initial identification also remains problematic. This is exemplified by the fact that 10–34% of the patients with traumatic brain injury admitted to rehabilitation units are found to have associated PNIs.,,
In our previous report, we analyzed 456 patients with PNIs (557 nerve lesions) from 1989 to 2004. In this study, we have added our further experience gathered between 2004 and 2014 and analyzed a total of 1124 patients (1418 nerve lesions) from 1989 to 2014.
From January 1989 to December 2014, 1124 consecutive patients were referred for electrodiagnostic consultation after having sustained a PNI. Only the first electromyography (EMG) requested after the trauma was considered. All the patients were symptomatic, either reporting motor (weakness) or sensory (positive or negative) symptoms. Patients with trauma to the spine with consequent acute, subacute, or chronic radiculopathy, myelopathy, or cauda equina syndrome were not considered in this study. Iatrogenic nerve injuries and obstetrical brachial plexus injuries were also not considered in this study. In certain cases of radial nerve lesions associated with humerus fractures where surgical intervention was required, occasionally, doubt existed regarding whether the peripheral nerve lesion was due to the trauma itself or caused by the orthopedic procedure to fix the bone. When surgery was done on the very first day, clinical examination could have been incomplete or could have missed a PNI, and it was difficult to state if a radial nerve palsy was present immediately following the injury or developed later on due to iatrogenic damage during fixing of the fracture. Patients were referred to us after a variable time from injury. Late referrals and long term EMGs (>1 year) were useless. We believe that most of time doctors that request the exam do not know about that or the patient itself pressure the doctor to request (inconformity to the sequel). Among a total of 1124 cases included here, 1418 nerve lesions were identified in the facial nerve on the face or peripheral nerves in the limbs. Data on age, gender, referring specialty, and the time interval between the injury and the first EMG conducted, were collected.
Majority of the EMGs were performed by the principal author. In other cases, a board electromyographer from the neuromuscular staff performed the tests. The results were retrospectively analyzed. According to the Seddon classification, nerve injuries may be a combination of any of the following: neurotmesis, axonotmesis, or neurapraxia. The classification implies ongoing morphological damage to fascicles, and hence is not suitable for grading based on only one EMG evaluation. Neurotmesis was suspected when sensory nerve action potential (SNAP) or compound muscular action potential (CMAP) after distal stimulation of the affected nerve was absent and EMG revealed profuse fibrillation potentials (FIB), and positive sharp wave potentials (PSW), as well as an absence of any volitionally recruited motor unit action potentials (MUAP). We preferred to refer to these cases as complete denervation. Axonotmesis was suspected when mild-to-profuse FIBs and PSWs were present and MUAP recruitment was reduced. We labeled these lesions as partial denervation. Neurapraxia comprised absent or rare FIBs and PSWs, normal MUAP morphology with reduced recruitment, and normal or reduced/absent SNAP or CMAP amplitude depending on whether the stimulation was distal or proximal to the conduction block. Neuropraxias, however, was very uncommon among our recruited patients with PNIs. MUAP morphology from reinnervation was also evaluated at the same time. Root avulsion was considered when SNAP was found in the same myotome with complete denervation.
The electrophysiological examination of the brachial plexus (BP) injuries was conducted based on the supposition that one particular nerve of the BP was involved regardless of any associated root avulsion. All injuries involving the ulnar nerve injuries, like the main trunk in the forearm, cutaneous dorsal branch, deep motor terminal branch, and deep and superficial terminal branch were considered together. Similarly, median nerve injuries at various locations were considered together irrespective of the site of injury, so that all forearm, palmar cutaneous nerve, and all terminal digital branches were considered together. Sensory nerve injuries were considered as complete denervation when there was no SNAP response. Patients were classified as having single or multiple PNIs; the maximum number of PNIs observed in our study was in a patient with injury to five different nerves.
Descriptive statistics were used, including means and frequencies. The protocol for the retrospective study was approved by the institutional ethics committee.
The 1124 patients with PNIs constituted 4.0% of all cases referred for electrodiagnostic consultations at our center. There were 862 (76.7%) males and 262 (23.3%) female patients with a mean age of 34.2 years (range: 2 to 92 years). The female patients were slightly older than males (38.9 versus 32.7 years). EMG was performed within the first 180 days (approximately 6 months) after PNI in 57.1%, between 6 and 24 months in 26.7%, and more than 2 years after the injury in 16.2% of the cases. Injuries to the nerves in the upper limbs represented 72.6% of PNIs where as injuries to the lower limb and the face accounted for 21.4% and 6% of the injuries, respectively. Considering the patients with bilateral nerve injuries, 6 patients had lower limb involvement, 4 had upper-limb injuries and 2 patients had facial involvement. Concomitant upper and lower limb nerve lesions were reported in only one case. Medical referral for the EMG study most commonly came from the departments of Orthopedics (46.7%) followed by Neurosurgery (21.5%), Plastic Surgery (10.5%), and Neurology (10%).
The etiology of PNI could be identified in 866 of the 1124 (77%) patients or in 1082 nerves; the most common cause of PNI was vehicular accident that represented almost half of all cases [Table 1]. There were 909 (80.9%) patients with a single and 215 (19.1%) patients with multiple PNIs. Multiple nerve lesions involved 2 nerves in 157 cases, 3 nerves in 42 cases, 4 nerves in 11 cases, and 5 nerves in 5 cases. The most frequently isolated nerve injuries, were the ulnar, BP, median, radial, fibular, and sciatic nerve injuries [Table 2]. The most common combinations of two-nerve injuries were the ulnar plus median nerve injuries (34.4%), fibular plus tibial nerve injuries (20.4%), sciatic plus femoral nerve injuries (4.5%), and radial plus axillary nerve injuires (4.5%). The most common combination of 3-nerve injury was the ulnar, median, and radial nerve injury (38.1%).
The percentage of the 14 most frequent nerve trunk injuries and their relationship to the etiological categories of trauma are shown in [Table 3]. Vehicular accident was the most frequent category for all nerve trunk injuries [except the median, ulnar, and superficial radial nerve injury (in which penetrating trauma was the more frequent etiology), superficial fibular nerve (in which penetrating trauma and fall were the more frequent etiologies), and lumbar, lumbosacral, or sacral plexus (in which vehicular accidents and gunshot wounds were the more frequent etiologies)]. Only one case of anterior interosseous nerve injury (due to penetrating trauma) was recorded in our database.
Complete denervation injury was found in 35.2% of the cases. The majority of the PNIs were partial denervation injuries (52.4% moderate-to-severe and 12.4% mild). Complete denervation occurred more often with the BP and fibular nerves (51.2% each), followed by the sciatic (47.7%) and posterior interosseous (40%) nerves. The most common isolated nerves that were injured were the radial (96.5%) and facial nerves (94.2%) followed by the BP (93%) and posterior interosseous (86.7%) nerves. On the other hand, the musculocutaneous, superior gluteal, inferior gluteal, lateral cutaneous of the forearm, saphenous, and obturator nerve injuries were associated with other nerve injuries.
Sciatic nerve injuries (88 cases) were classified into fibular and tibial nerve injuries. 29.5% of the patients had equally serious injury of both the nerves. The less common sciatic nerve injuries included only fibular nerve injury (10.2%), only tibial nerve injury (5.7%), with the severity of tibial nerve injury being more than that of the fibular nerve injury (2.3%).
BP injuries (213 cases) with electrophysiological evidence of root avulsion were found in 61 (28.6%) cases. Of these cases, 47.5% corresponded to C5/6, 14.8% corresponded to C5/6/7/8/T1 and 11.5% corresponded to C8/T1 nerve roots. BP injuries were the most common PNIs in the vehicular accident group, accounting for one-fourth (25.5%) of all lesions. Compared to car accidents, motorcycle accidents affecting the BP were much more common (46.1% versus 17.1%). Most patients who sustained a PNI due to motor cycle accident (when compared with car accidents) were males (94.7% versus 82.8%) with a lower mean age (27.9 versus 32 years); root avulsions were more frequent in them (41.5% versus 31%); complete denervation occurred almost twice as often (67% versus 37.9%); and, the right side was more affected than the left (56.4% versus 31%).
Facial nerve injury occurred mostly in the vehicular accident group (80%). There was a striking decline in the incidence of facial nerve lesions related to motorcycle accidents from 1989–2001 versus the period between 2002–2014 (50% versus 16%) in spite of the increase in the number of accidents of this kind.
In our previous study, we studied 456 cases from 1989 to 2004, and in the current study, we obtained data of 1124 cases from 1989 to 2014 based on EMG consultation at various time intervals after the trauma.
EMG is the most appropriate diagnostic method used in the evaluation of the topography and severity of PNIs. The degree or amount of axonal loss has a large impact on the prognosis of PNIs. Magnetic resonance imaging also provides additional information regarding root avulsion after traction injury to the BP. Patients should be referred for electro-diagnostic consultations within a 6-month period after PNI; this timing is neither too early to miss severe axonal degeneration nor too late to minimize possible surgical benefits. Clinical and electrophysiological changes should be carefully followed on a monthly schedule to evaluate the possibility of early reinnervation. Patients frequently have multiple injuries and various medical specialties may be involved in their care. Thus, the clinical-electrophysiological correlation may be missed or misinterpreted unless a repeated surveillance program is adopted.
The proportion of single versus multiple nerve injuries was the same as described elsewhere in the literature (20% to 80%). Young and male patients were more likely to experience PNIs. In fact, 91.7% of motorcycle accidents involved males, and 76.4% of BP injuries resulting from vehicular accidents came from motorcycle accidents, which is a striking increase in the recent years. Motorcycle accidents numbered 61 between 1989 and 2001 and 144 between 2002 and 2014. Trauma related to sports only affected males, particularly soccer players (66.7%), with fibular nerve lesions being the most common type of injury (71.4%). Most PNIs related to vehicular accidents were similar to those reported previously. The striking decline of facial nerve injuries related to motorcycle accidents in 2002–2014 compared to the same duration from 1989–2001 was probably related to the rigorous implementation of laws concerning helmet use in Brazil. Motorcycle accidents are frequently associated with temporal bone fractures. Ulnar nerve injury was the most frequent nerve lesion, occurring either in isolation or in association with median nerve involvement. Ulnar nerve injury was the most common type of injury following penetrating trauma. Ulnar and median nerve lesions were the most frequently associated injuries because of their close anatomical relationship, specifically in the distal forearm and wrist, where penetrating trauma was very common, presumably because of the greater exposure to knife and glass wounds during performance of manual tasks. Penetrating trauma leads to transections or lacerations; the instrument involved may be a sharp object where little force is necessary to divide the nerve; or it may be a blunt instrument in which a greater force is required for causing transection of the nerve.
Most BPIs resulted from vehicular crashes. We found the incidence of root avulsion in 28.6% of the cases, which is slightly more than that described by Midha et al. (20%). Almost half of these injuries were found in the C5/C6, 14.8% in C5 to T1, and 11.5% in C8-T1 nerve roots. Complete BP injury was found in 15.9% patients and these had a very poor prognosis. In sciatic nerve injuries, the lateral fibular portion was predominantly affected in most cases, as described previously. Further, 10.2% developed electrophysiological abnormalities only in the fibular portion of the sciatic nerve.
Despite differences in the population characteristics in the various reported studies, a higher incidence of PNIs in the upper limbs is consistently reported in the literature,, and the most frequently affected nerves in the earlier reports were the ulnar, radial,, or the digital nerves. For the lower limbs, the most frequently affected nerves reportedly were the fibular , or the sciatic nerves. All previously reported studies have shown a clear predilection towards these injuries (74.2-96%).,,, The mechanism of injury varied widely in the previously published literature.,, The age of the patients in these series ranged from 16 to 38 years.,, Three studies specifically referred to PNIs and sports accidents where upper limbs were reported to be most frequently affected.,, These results differ from ours where the lower limbs (predominantly fibular nerve injuries) were most often affected in sports injuries. Our findings corroborated with the literature which states that PNIs are proportionally similar in either right or left side., EMG was performed within an appropriate period of less than 180 days after PNIs in 57.1% of cases, which is less than the previous reported figure of 67%. This result is important because surgical options may be less effective when EMG is performed later than this optimum time.
Some limitations of this study include underestimation of the frequency of injuries in patients who have sustained multiple traumatic injuries, and also the possible underestimation of the severity of PNIs in patients who stayed in the hospital for weeks to months. The series also includes many patients without other central nervous system (CNS) injuries at the time of the EMG consultation. As, many of these patients with severe CNS involvement due to trauma present initially to the rehabilitation centers, their PNIs could have been missed or misdiagnosed as being a manifestation of the primary CNS pathology.,,
In conclusion, PNIs most frequently occurred from vehicular accidents and mostly affected young men. Injuries to the ulnar nerve, BP, and median nerve were the most prevalent ones in our series.
Financial support and sponsorship
This work was supported by a BAP research grant from the Faculdade de Medicina de São José do Rio Preto (JAK) and a PIBIC/CNPq research grant for medical students (VFMF).
Conflicts of interest
There are no conflicts of interest.
[Table 1], [Table 2], [Table 3]