Neurology India, Vol. 58, No. 2, March-April, 2010, pp. 230-234
Analysis of proximal radial nerve injury in the arm
Bülent Düz, Ïlker Solmaz, Erdinç Civelek, M Bülent Önal, Serhat Pusat, Mehmet Daneyemez
Department of Neurosurgery, Gülhane Military Medical Academy, Etlik Ankara, Turkey
Correspondence Address: Erdinç Civelek, Department of Neurosurgery, Gülhane Military Medical Academy, Etlik Ankara, Turkey, email@example.com
Date of Acceptance: 23-Oct-2009
Code Number: ni10061
Background: Radial nerve is the most frequently injured major nerve in the upper extremity. Proximal part of the radial nerve involvement can result from a humerus fracture, direct nerve trauma, compression and rarely from tumors.
Keywords: Arm, outcome, radial nerve injury, surgery
Radial nerve arises from the posterior cord of the brachial plexus with contribution from C5, C6, C7, C8, and T1 and then travels dorsal to the axillary artery and vein and closely abutting the shaft of the humerus near the spiral groove.  It emerges from the intermuscular septum on the lateral arm and descends distally along the border of the brachialis muscle. Within 3 cm above or below the elbow, the radial nerve divides into a superficial and a deep branch. The radial nerve is the most frequently injured major nerve in the upper extremity.  The most commonly observed radial nerve injuries are proximal to the elbow. These include ′′Saturday night′′ palsy and proximal radial palsy resulting from the humeral shaft fracture. Radial nerve compression may result in a wide range of clinical symptoms, from weakness of wrist extension to complete paralysis. The current study is a retrospective review of a clinical series of patients with proximal radial nerve compression neuropathy.
Materials and Methods
Between June 2000 and June 2008, 46 patients with proximal radial nerve injuries were treated medically and surgically at our hospital. Data collection was performed by review of the medical records. Radial nerve lesions in the forearm were excluded. All the patients had X-rays of the arm. None of the patients had either magnetic resonance imaging (MRI) nor computed tomography (CT).
All the patients were treated medically with antibiotics, nonsteroidal anti-inflammatory drugs and analgesics for 45 days before considering surgical treatment. Patients also received physical therapy during this period. Patients were followed-up clinically and also by electrodiagnostic tests. If there was an improvement in motor function or in electrophysiological parameters patients were continued on physical therapy. Surgical decompression was generally performed after three months of initial presentation and indications included lack of clinical and electrophysiological improvement at the end of the first three months. Operations were performed under general anesthesia without using a tourniquet and microsurgically when nerve repair was needed. The patient was placed in lateral position and the skin incision was made from the posterior margin of the deltoid muscle to just above the medial epicondyle at the elbow. The incision between the long and lateral heads of the triceps extended distally and medially to the lateral epicondyle [Figure - 1]. After the brachial fascia was opened through the entire length of the incision, the plane between the long and the lateral heads of the triceps muscle was palpated. These heads were separated by blunt dissection to reach the radial nerve and the radial collateral artery. The long head of the triceps muscle was retracted gently because the ulnar nerve is located just beneath the long head of the muscle [Figure - 2]. As the nerve reaches the distal third of the humerus and pierces the lateral intermuscular septum, the nerve was approached in this area from the medial side to preserve the motor branches to the supracondylar muscles. External neurolysis was the initial procedure and was performed from the areas of healthy tissue to injured areas. Neurolysis was most readily accomplished both proximally and distally to the involved segment. Potential areas of entrapment were released. Prednisolone was not administered before or after the operation.
The outcome was evaluated in terms of the overall improvement in power of the target muscle as well as the functional usefulness of such recovery. The outcome was categorized as improved or unchanged. In the improved group, results were further categorized as follows: poor, power less than grade 2 (M2; active joint motion present with gravity eliminated); fair, power grade 3 (M3; muscle can move joint through full range of motion against gravity); or good, power grade 4 or greater (M4; full range of motion against gravity and some resistance).
The mean age of the patients was 32.14 (+ 13.35 years) and 44 (95.6%) patients were males [Table - 1]. The mean duration between injury and presentation was 6 days, (1 day-18 days); the median was 11.5 days. Eleven of the patients were treated medically and the remaining 35 patients underwent surgery. Patients were followed-up for 12 to 18 months after the surgical procedure (15 months on average). The most common complaint was weakness in the arm. A deep aching pain in the proximal forearm and radiation into the shoulder and neck was the major complaint especially in the patients with radial nerve compression. The other presenting symptoms included weakness of wrist extension (wrist drop), weakness of finger extensors and paresthesias in radial nerve distribution. Twenty-one of the patients (45%) had weakness in both wrist and finger extensors. Tinel sign at radial nerve in forearm was present in all patients with radial nerve compression in spiral groove.The most consistent preoperative physical finding in the patients with radial nerve compression in spiral groove was tenderness over the radial nerve at the level of the proximal part of the supinator muscle [Table - 2]. .The type of injury included: humeral fracture in 11, radial nerve compression in spiral groove in 12, missile injuries in 15 and radial nerve cut by sharp devices in eight [Table - 3]. X-rays of the arm showed humerus fracture and callus formation in 11 patients and metallic fragments in eight patients.
Electrodiagnostic studies were performed before medical treatment or surgical decompression in all the patients [Table - 4]. Electrodiagnostic studies showed prolonged distal latency, reduced compound motor action potential amplitude and decreased motor conduction velocity of radial nerve in 20 of the patients who underwent surgery. Among the patients with radial nerve compression in the spiral groove, only five showed electrophysiologic abnormality. Only five of the non-operated patients had abnormal electrophysiologic finding such as slower motor conduction velocity and increased polyphasic electromyoneurography (EMNG) patterns in wrist and finger extensors. In five of the patients with radial nerve compression in the spiral groove and in patients with humerus fracture, there was a minimal electrophysiological improvement postoperatively at six months. The patients from these groups showed better outcome. In non-operated patients there was very significant electrophysiological improvement at six months.
During the operation, a prominent gross pathology was found in 28 of the 35 patients. These changes were increased vascularity and dense scar in 25 patients, defect in radial nerve in five, loss of anatomical integrity in two and thin radial nerve in five, and thick radial nerve in 13. Five patients with fracture humerus were operated. Significant nerve contusion and granulation tissue were observed at surgery in these patients. Twelve patients with radial nerve compression also underwent surgery. There was no prominent pathology in these patients but the radial nerve was slightly thin and compressed. Thirteen patients with missile and sharp device injuries were operated and a significant nerve injury was observed at operation. There was no nerve continuity in five of them [Table - 3]. Harvested nerve grafting was done in two patients with missile injuries. Primary nerve suturing was done in three patients. Patient with radial entrapment neuropathy had neurologically improvement following surgery.. We observed good recovery (M4) from decompression of callus of old humeral fracture. Poor and fair results (M2 and M3) were observed in the direct missile injuries of the radial nerve.
For radial nerve palsy caused by fracture of humerus, generally the consensus is observation for an appropriate period. However, there is no consensus for radial nerve palsy secondary to compression, missile and sharp device injuries. Surgical exploration is indicated for nerve palsy following fracture manipulation. [2,3] Observations in our study suggests that the outcomes may be good for radial nerve palsy secondary to compression at the spiral groove and also due to penetrating injuries.
Nerve injuries are classified into six degrees ,,, : (1) first degree injury - neuropraxia, segmental demyelination without loss of nerve continuity or Wallerian degeneration; (2) second-degree injury - axonotemesis with injury to the axon, but intact endoneural tissue and Schwann cell tubes; (3) third-degree injury - an additional endoneural injury with intact perineurium; (4) fourth-degree injury - neuroma with complete scar and block of nerve function; (5) fifth-degree injury - transected nerve; and (6) sixth-degree injury - a combination of any of the above injuries. , In our series, fifth-degree injuries were observed in only five patients.
The causes of radial nerve palsy in the forearm include: elbow trauma,  and mass lesions in the forarm, ,, The common cause of radial nerve palsy is due to compression in the spiral grove, ,,. In addition to the causes seen in this series other cause of proximal radial nerve palsy include tourniquet application and intramuscular injection.  Intramuscular injuction-related nerve injury is commonly seen with radial and sciatic nerves. . Peri-operative radial nerve palsy may be related to positioning of the upper extremity and also compression from blood pressure cuffs.
Clinical presentation of radial nerve paraly depends on the underlying cause and the level of nerve involvement. It will be prudent to distinguish radial nerve palsy from lesions affecting the nerve roots or the brachial plexus. Tenderness of the radial nerve in the proximal forearm at the level of supinator muscle as seen in this study is an important finding in patients with radial nerve compression in the spiral grove.  Patients often complain of deep pain in the forearm. Most often detailed history and physical examination helps in localizing the level of lesion. Plain x-rays of the involved area are necessary if a fracture, dislocation, or a foreign body is suspected. MRI may be obtained if a mass lesion is suspected along the course of the radial nerve. In our series, plain x-rays revealed fracture humerus in 11 patients and metallic fragments in eight patients.
Electrodiagnostic studies are rarely helpful in the first few weeks following nerve injury to prognosticate the outcomes. However, studies done after 12 weeks my help to assess which patients are likely to improve and which patients may require surgery. We agree with the previous authors that electrodiagnostic testing offers limited help in the diagnosis of radial nerve compression in spiral groove. Abnormal electrophysiologic findings are usually observed in severely affected patients. Electrodiagnostic testing may not be mandatory before surgical decompression, if the history and physical findings are strongly suggestive of the diagnosis. However, electrophysiological tests are important for the objective evaluation of surgical treatment. In our series, we used electrodiagnostic parameters: amplitude of the compound motor action potential, motor latency and motor conduction velocity of radial nerve while evaluating the outcomes following surgery. In our series electrophysiological improvement was significant in patients with fracture humerus and radial nerve compression, but poor in patients with missile and sharp device injuries following surgery.
The first step while manageing these patients is to classify wheather the lesion open or closed. Radial nerve lesions with open wound should be explored surgically. If the nerve is intact at exploration it is treated as a closed injury. Primay nerve repair is indicated if the radial nerve is sharply transected, but there is adequate nerve length. The procedure can be performed without tension by gently mobilizing the nerve. The reported results following primary repait are excellent ranging between 78% and 90%  In children, the results are much better, probably related to better neuronal regeneration. ,, Peripheral nerve injuries are not fatal, but may be associated with wide spectrum of morbidity. Hence an appropriate nerve repair procedures are of importantance to achieve good quality of life. ,, The surgeon should make the choice of best technical approach to achieve the best possible recovery. It will be prudent to perform nerve repair procedures under magnification. , In closed radial nerve injuries, the patient should be followed-up closely for a period of three months. , Closed radial nerve palsies are either neuropraxia or second- or third-degree injury and usually good recovery is possible with time. Surgical intervention is indicated if there is no clinical or electrophysiological evidence of reinnervation is seen within three months.
No prominent pathology of the nerve was observed in the majority of patients (58%) with radial nerve compression in spiral groove and all the patients in this group showed improvement. In the missile and sharp device injury groups, however, the results were poor. Two patients were treated by nerve graft and three patients by primary nerve repair. Motor power recovery was less than M2) in three patients treated with sural nerve grafts and one patient rreated by primary nerve repair and was fair, motor power M3, in one treated with primary repair. Neurological improvement following surgery in patients with radial nerve compression in the spiral grove. Similar excellent to good, 92% to 95%, were reported in the earlier studies. , We observed good recovery from decompression of callus of old humeral fracture. The worst results are observed in patients with direct missile injuries of the radial nerve. ,, When the radial nerve is sharply divided, the clinical results after primary repair have been good to fair in most instances, if the nerve is explored early and repaired without tension. 
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