Anterior interosseous nerve palsy. A review of 16 cases

Isolated Palsy of the Anterior Interosseous Nerve to Flexor Pollicis Longus, Magnetic Resonance Imaging and Clinical Correlation: A Case Report

CASE

Anterior interosseous nerve (AIN) palsy is an uncommon, though well-described, clinical entity. When isolated to the thumb, it can be confused with atraumatic rupture of the flexor pollicis longus (FPL) tendon. A 57-year-old man experienced atraumatic onset of difficulty flexing the distal interphalangeal thumb joint. Magnetic resonance imaging (MRI) demonstrated denervation edema of the FPL, suggesting atypical AIN palsy. Resolution of symptoms and MRI findings occurred concomitantly with nonoperative treatment.

CONCLUSION

Atypical AIN palsy limited to the FPL is a rare clinical entity whose diagnosis can be supported with MRI. Here, we report a successful case of nonoperative management.

Peripheral neuropathies after shoulder arthroscopy: a systematic review

Purpose

Peripheral neuropathies after shoulder arthroscopy are rare, though likely under-reported. Many resolve spontaneously, but some patients are left with permanent neurological deficits. The purpose of this study was to review the literature to better characterize this patient population, diagnostic tests performed, the timing and type of surgical intervention, and report clinical outcomes.

Methods

A systematic literature review was performed. Articles in English were identified from PubMed, EMBASE, and CINAHL in August 2021. Article titles and abstracts were screened for relevance by two authors and discordant abstracts were resolved by the senior author. Data were subsequently extracted from the included articles.

Results

Seventeen articles were identified yielding a total of 91 patients. The average age was 53 ± 12 years, and most patients were male (72%). Rotator cuff repair (62%) was the most common procedure performed. A peripheral neuropathy was identified an average of 80 ± 81 days from the index procedure (range, 0-240 days). Most commonly, peripheral nerve injury presented as a mononeuropathy, with the median nerve (39%) and ulnar nerve (17%) affected predominantly. Seventeen percent of patients underwent a secondary surgery at an average of 232 ± 157 days after the index procedure. At the final follow-up, 55% of neuropathies had resolved, 14% partially improved, and 22% showed no clinical improvement. The most proposed etiologies were postoperative immobilization (29%) and intraoperative positioning (20%), but several possible etiologies have been suggested.

Conclusions

Peripheral neuropathies after arthroscopic shoulder procedures are rare. While most spontaneously resolve, up to 1 in 5 patients may have persistent neuropathic symptoms. A high index of suspicion should be maintained throughout the postoperative period. When neurologic deficits are identified, patients should undergo a thorough diagnostic workup and be referred to a subspecialist in a timely manner.

Persistent Hourglass Constriction in Recovered Anterior Interosseous Nerve Palsy Due to Neuralgic Amyotrophy: A Case Report

The current articles recommended the interfascicular neurolysis for anterior interosseous nerve (AIN) palsy with hourglass-like fascicular constrictions (FCs) detected by ultrasonography or surgical exploration to realign to the fascicular torsion for those who failed to recover spontaneously. We present the case report of spontaneous AIN palsy recovered after conservative treatment; however, ultrasonographic findings showed persistent FCs of AIN in the arm at the beginning, at 6 weeks, and subsequent 3-year follow-ups, even after complete clinical recovery of palsy. This finding calls into question the current notion that AIN paralysis is due to FCs and that neurolysis is the best surgical treatment when spontaneous recovery does not occur for a considerable observation period. Level of Evidence: Level V (Therapeutic).

Anterior interosseous nerve syndrome following infection with COVID-19: a case report

BACKGROUND

Various neurological manifestations associated with coronavirus disease 2019 have been increasingly reported. Herein, we report a rare case of anterior interosseous nerve syndrome, which occurred 5 days after the onset of coronavirus disease 2019.

CASE PRESENTATION

A 62-year-old Asian woman with a history of coronavirus disease 2019 who developed a complete motor deficit in the left flexor pollicis longus and pronator quadratus without sensory deficits. The symptoms appeared as a sudden onset fatigue and severe pain of the left arm, 5 days after the onset of coronavirus disease 2019. She noticed paralysis of the left thumb at 2 weeks after the onset of coronavirus disease 2019. Electromyography assessment of the anterior interosseous nerve-dominated muscles revealed neurogenic changes such as positive sharp wave and fibrillation in flexor pollicis longus and pronator quadratus, confirming the diagnosis of anterior interosseous nerve syndrome. There were no other diseases that could have resulted in peripheral nerve palsy. We performed a functional reconstruction surgery of the thumb by tendon transfer from the extensor carpi radialis longus to the flexor pollicis longus. The patient reported a good patient-reported outcome (2.27 points in QuickDASH Disability/Symptom scoring and 5 points in Hand20 scoring) at final follow-up (1 year after the surgery).

CONCLUSION

This case highlights the need for vigilance regarding the possible development of anterior interosseous nerve syndrome in patients with coronavirus disease 2019. Tendon transfer from extensor carpi radialis longus to flexor pollicis longus can provide good functional recovery for unrecovered motor paralysis after anterior interosseous nerve syndrome.

Anterior Interosseous Nerve Syndrome

Anterior interosseous nerve syndrome (AINS) is a rare form of peripheral neuropathy which involves disruption of the anterior interosseous nerve. The pathophysiology of AINS remains unclear. AINS typically initially presents with forearm pain and may gradually progress to palsy of the deep muscles of the anterior forearm. Diagnosis of AINS requires thorough patient history and physical exam. EMG is the preferred diagnostic study and classically reveals abnormal activity and prolonged latency periods within the evoked action potentials of the FPL and PQ. Due to the self-limiting nature of AINS, there is general agreement that conservative and symptomatic management should be explored for up to 6 months as first line therapy, which usually includes analgesics and nonsteroidal anti-inflammatory drugs, contracture prevention, hand therapy, and hand splinting. Surgical options such as internal neurolysis and minimally invasive endoscopic decompression may be explored if functional recovery from conservative management is limited.

Surgical Treatment of Parsonage Turner Syndrome With Primary Nerve Transfers: A Case Series and Cadaver Dissection

ABSTRACT

Parsonage Turner syndrome (PTS) is the development of severe, spontaneous pain with subsequent nerve palsy. Unfortunately, many patients never achieve full functional recovery, and many have chronic pain. The use of nerve transfers in PTS has not been reported in the literature. We present 4 cases of PTS treated surgically with primary nerve transfer and neurolysis of the affected nerve following the absence of clinical and electrodiagnostic recovery at 5 months from onset. In addition, we present a cadaver dissection demonstrating an interfascicular dissection of the anterior interosseous nerve (AIN) into its components to enable a fascicular transfer in partial AIN neuropathy. Two patients with complete axillary neuropathy underwent a neurorrhaphy between the nerve branch to the lateral head of the triceps and the anterior/middle deltoid nerve branch of the axillary nerve. Two patients with partial AIN neuropathy involving the FDP to the index finger (FDP2) underwent a neurorrhaphy between an extensor carpi radialis brevis nerve branch and the FDP2 nerve branch. All patients had neurolysis of the affected nerves. All subjects recovered at least M4 motor strength. The cadaver dissection demonstrates 3 separate nerve fascicles of the AIN into FPL, FDP2, and pronator quadratus that can be individually selected for reinnervation with a fascicular nerve transfer. Functional recovery for patients with PTS with neurolysis alone is variable. Surgical treatment with neurolysis and a nerve transfer to improve functional recovery when no recovery is seen by 5 months is an option.

Anterior Interosseous Nerve Syndrome Reconsidered: A Critical Analysis Review

Anterior interosseous nerve syndrome (AINS) represents a form of neuralgic amyotrophy (Parsonage-Turner syndrome). AINS does not originate from external compression of the AIN in the forearm. Fascicular constrictions (FCs) of the median nerve are identified within the anterior interosseous fascicular group at or above the medial epicondyle. Spontaneous recovery is not ensured, leaving up to 30% of patients with permanent weakness or palsy. Fascicular microneurolysis of the median nerve, performed at or above the elbow, is a treatment option for patients who do not recover spontaneously.

Pseudo-Anterior Interosseus Nerve Syndrome: A Case Report and a Review of Clinical Signs, Pathology and Functional Anatomy of the Precision Grip

Precision grip, a prehensile function of humans, is exacted through the action of the median nerve and its main tributary, the anterior interosseus nerve (AIN). In the forearm, the AIN can be subject to nerve entrapment by tendinous and fibrous arches or accessory and variant muscles. It is also vulnerable to trauma of the upper arm and forearm. To the neurologist, an isolated neuritis or an immune-mediated medial cord or lower trunk brachial plexopathy (Parsonage-Turner syndrome) is the usual mode of presentation. When the spread of muscle weakness is beyond the territory of the AIN, the syndrome is referred to as a pseudo-AIN. The AIN is grouped into fascicles that are compartmentalized separately from the median nerve proper, and trauma in the upper arm may selectively involve the AIN. We present a case of pseudo-AIN following elbow arthroscopic surgery and outline the pathology, clinical signs, and functional anatomy of the AIN and the precision grip.

"Anterior interosseous nerve syndrome (Kiloh Nevin Syndrome) revealing Gantzer muscle and simultaneous myasthenia gravis"

There hasn't been a previous case report of the anterior interosseous nerve injury secondary to the presence of the muscle of Gantzer in a patient with myasthenia gravis in literature before. The anterior interosseous nerve compressive syndrome, also known as Kiloh-Nevin syndrome, is a rare disorder comprising less than 1% of all upper limb neuropathies. Establishing the etiology of anterior interosseous nerve compressive syndrome is challenging because of the lack of specific clinical findings or testing. Herein is the case of a 46 years-old male presented with left eye ptosis, ophthalmoparesis, diplopia, and right-hand weakness. On physical examination, the Pinch Grip test was positive. Electromyography studies showed neurogenic atrophy in the muscles innervated by the anterior interosseous nerve, as well as a pathological decrement of the muscle action potential of more than 10% on repetitive nerve stimulation. Concluding that the presence of the Gantzer muscle caused anterior interosseous nerve compressive syndrome was mainly a diagnosis of exclusion, after careful consideration of other possible etiologies including carpal tunnel syndrome, cervical radiculopathy, and Parsonage-Turner Syndrome. Even though anterior interosseous nerve compressive syndrome is very rare, clinical suspicion ought to arise in the presence of weak radial flexor digitorum profundus and flexor pollicis longus muscles. This case highlights the importance of a thorough medical history, a meticulous physical examination, and particularly the significance of electromyography studies in diagnosing different neuropathological entities. When appropriate, these steps offer information crucial to the differential diagnosis and eventual surgical management, assisting physicians in making informed and accurate treatment decisions.

Anterior Interosseous Nerve Palsy After Shoulder Arthroscopy Treated With Surgical Decompression: A Case Series and Systematic Review of the Literature

Background: Anterior interosseous nerve (AIN) palsy is a very uncommon cause of upper extremity pain and weakness that comprises less than 1% of all upper extremity nerve palsies. Rarely reported but also mentioned in the literature is AIN palsy after shoulder arthroscopy. Methods: A systematic review of the literature to date using PubMed was conducted to identify patients who suffered AIN palsy after shoulder arthroscopy procedures. Articles included met the following criteria: (1) published in English; (2) primary presentation of the data; (3) patients had undergone shoulder arthroscopy before developing symptoms of AIN palsy; and (4) diagnosis was confirmed with clinical symptoms of AIN palsy. Measured outcomes included patient demographics, specific shoulder procedure, anesthesia procedure, intra-operative patient positioning, intra-operative compressive dressing, intra-operative traction, surgical versus conservative treatment, abnormal findings during decompression procedure, proposed mechanism of injury, and follow-up. Results: The search yielded 6 articles, of which 4 (13 cases) met inclusion criteria. An additional 2 cases were included in this report totaling 15 cases. The average patient age was 49 years (range: 31-64) with 73% males. At average follow-up of 24 months, 67% of patients experienced complete resolution of symptoms-more than half of which underwent surgical decompression. Patients who failed to progress experienced weakness of the flexor digitorum profundus and flexor pollicis longus muscles. Conclusions: Proposed injury mechanisms for AIN palsy after shoulder arthroscopy range from mechanical trauma, compressive hematoma, and direct anesthetic neurotoxicity. Management should be directed by clinical symptoms, imaging, and patient factors with majority of patients expected to have excellent clinical outcomes.

Anterior Interosseous Nerve Syndrome: Is it a Compressive Neuropathy?

BACKGROUND

Anterior interosseous nerve (AIN) syndrome is a rare disease whose pathophysiology is controversial. Despite efforts to elucidate the pathophysiology of AIN syndrome, it has not yet been resolved. We reinterpret electrodiagnostic studies, magnetic resonance imaging (MRI), and surgical findings to clarify the pathophysiology of AIN syndrome.

MATERIALS AND METHODS

In this retrospective case series, we included surgically treated 20 cases of nontraumatic AIN syndrome. Surgery was performed after a minimum of 12 weeks of conservative treatment. The clinical data and operation records were extracted from the medical records for analysis. All electrodiagnostic tests were reinterpreted by physicians with an American Board Certification in electrodiagnostic medicine. Moreover, every contrast-enhanced MRI performed during the assessment was reviewed by a musculoskeletal radiologist.

RESULTS

Of the twenty re-analyzed cases, nine AIN syndromes (45%) showed abnormal electromyography in non-AIN innervated muscles. Sensory nerve conduction studies were normal in all cases. Five magnetic resonance images (46%) showed signal changes in non-AIN-innervated muscles. Only four cases (20%) revealed definitive compression of the AIN during surgery.

CONCLUSIONS

Electrodiagnostic study and MRI indicated that many patients with AIN syndrome exhibited a diffuse pathologic involvement of the motor component of the median nerve. We conclude that the main pathophysiology of AIN syndrome would be diffuse motor fascicle neuritis of the median nerve in the upper arm.

Treatment of spontaneous anterior interosseous nerve palsy

OBJECTIVE

The purpose of this study was to clarify the clinical outcomes of spontaneous anterior interosseous nerve palsy (AINP) treated nonsurgically or surgically.

METHODS

The authors retrospectively evaluated the clinical course of 27 patients affected with AINP, treated nonsurgically or surgically. Thirteen patients underwent surgical treatment (interfascicular neurolysis), and 14 patients underwent conservative nonsurgical treatment. The mean patient age at the onset of symptoms was 49 years (range 17–77 years). The mean follow-up duration from onset to the latest follow-up examination was 23 months (range 12–38 months).

RESULTS

In 12 of 14 patients receiving conservative treatment, signs of recovery from the palsy were obtained within 6 months. These patients showed a recovery of manual muscle test (MMT) grade ≥ 3. In contrast, 2 patients who took more than 12 months from symptom onset to initial recovery showed poor recovery (MMT grade ≤ 2). Surgical treatment was performed in 13 patients because of no sign of recovery from palsy. The mean period from symptom onset to the operation was 8.4 months (range 6–14 months). Ten of 13 patients who underwent surgical treatment within 8 months after symptom onset showed good recovery, with MMT grade ≥ 4. However, 3 patients who underwent surgical treatment more than 12 months after onset showed recovery with MMT grade ≤ 3.

CONCLUSIONS

Conservative treatment for AINP may be continued when patients show signs of recovery within 6 months after symptom onset. In contrast, surgical treatment may be performed within 8 months from the onset of symptoms when the patients show no recovery signs for 6 months.

Bilateral anterior interosseous nerve syndrome with 6-year interval

Flexor pollicis longus paralysis related to idiopathic anterior interosseous nerve syndrome is well known, but few reports exist on bilateral disease. A 24-year-old man with no personal or family history of neurological disease developed isolated total loss of active flexion of the right thumb's interphalangeal joint after undergoing a wrist arthroscopy. Surgical exploration 5 weeks after onset showed flexor pollicis longus tendon to be intact; anterior interosseous nerve decompression was done with no abnormalities found. Because of persistent paralysis, electromyography was performed showing findings consistent with anterior interosseous nerve syndrome. After 7 months without recovery, the patient underwent tendon transfer. After 6 years, the patient presented with left-sided isolated flexor pollicis longus paralysis and electromyography indicated anterior interosseous nerve syndrome. Examination 9 months after onset showed persistent complete flexor pollicis longus paralysis but by 15 months spontaneous complete recovery had occurred. Anterior interosseous nerve syndrome can occur bilaterally and is likely to resolve completely without intervention but recovery may take longer than a year.

Mixed neuropathy presenting clinically as an anterior interosseous nerve palsy following shoulder arthroscopy: a report of four cases

BACKGROUND

Anterior interosseous nerve (AIN) palsies can arise spontaneously or be attributed to one of many causes. We present 4 cases, the largest series to date, in which a mixed peripheral neuropathy presented primarily as an AIN palsy following ipsilateral shoulder arthroscopy. In this report, we detail the patient's presenting symptoms, describe our management of the complication, and provide hypotheses for the mechanism behind the complication.

METHODS

Four different surgeons performed the initial arthroscopic surgeries, but the senior author in all cases managed follow-up and treatment of the neuropathy. All patients were informed and agreed to have their cases published.

RESULTS

All four patients experienced significant recovery, although 2 of 4 required AIN decompression and exploration because of failure to improve with conservative management.

CONCLUSION

Whereas variables such as position, index surgical procedure, and use of regional anesthesia varied among our patients, the one constant was the fluid extravasation from the arthroscopy itself, and for this reason we believe that if there is one singular cause to explain all of these neuropathies, it would be increased pressure in the upper arm and forearm from fluid extravasation in patients with at-risk anatomy. Outside of prevention, recognizing this complication and providing appropriate intervention or referral to a surgeon capable of appropriate intervention are important for any surgeon performing shoulder arthroscopies.

High-resolution ultrasonographic evaluation of "hourglass-like fascicular constriction" in peripheral nerves: a preliminary report

An hourglass-like constriction is a focal fascicular lesion observed in one or a few places in one or a few fascicles of a peripheral nerve trunk, and usually affects the anterior interosseous (AIN) or posterior interosseous (PIN) nerve. Constrictions have previously been discovered only by surgical exploration, and have been unable to be recognized on pre-operative imaging. We encountered some cases in which the lesion was able to be diagnosed pre-operatively by high-resolution ultrasonography; these findings were then confirmed intra-operatively. Five consecutive cases were included in this study. In three cases with constrictions revealed on pre-operative ultrasound, the findings were confirmed intra-operatively. In the remaining two cases in which no constrictions were detected pre-operatively, no constriction was revealed intra-operatively. High-resolution ultrasonography may play a significant role in the diagnosis of hourglass-like constrictions, and may thus lead to significant changes in treatment strategies for AIN and PIN palsy.

Minimally invasive endoscopic decompression for anterior interosseous nerve syndrome: technical notes

Anterior interosseous nerve syndrome (Nevin-Kiloh syndrome) is a rare entity caused by compression of the purely motor anterior interosseous nerve in the forearm. Historically, conventional surgical treatment has consisted of open decompression of the nerve. Unfortunately, open decompression is often complicated by scarring and significant morbidity. Endoscopic decompression is an alternative means of surgical intervention in the hands of well-trained surgeons comfortable with soft tissue endoscopy. In this report, we review relevant anatomy, offer technical hints, and present our personal experience with 4 illustrative cases, all with greater than 1.5 years of follow-up. Our patients showed considerable improvement of their symptoms with minimal scarring. No significant complications occurred.

The anatomical basis for anterior interosseous nerve palsy secondary to supracondylar humerus fractures in children

INTRODUCTION

Various studies have found that 6.6 to 31% of supracondylar elbow fractures in children have nerve-related complications. One-third of these are cases of anterior interosseous nerve (AIN) palsy that usually result in a deficit of active thumb and index flexion. The goal of this cadaver study was to describe the course of the AIN to achieve a better understanding of how it may get injured.

MATERIALS AND METHODS

On 35 cadaver specimens, the median nerve and its collateral branches destined to muscles were dissected at the elbow and forearm levels. The distance at which the various branches arose was measured relative to the humeral intercondylar line. Interfascicular dissection of the AIN was used to map its distribution within the median nerve.

RESULTS

The AIN arises at an average of 45 mm from the humeral intercondylar line. Before emerging from the median nerve, the AIN fascicles were always found in the dorsal part of the median nerve. After emerging, the AIN was divided into two zones. Zone 1 was the transitional portion from its exit point until its entrance into the interosseous space, where it changes direction. Zone 2 was the interosseous portion between the radius and ulna that comes into contact with the anterior interosseous membrane to which it is attached over its entire length until it ends in the pronator quadratus (PQ) muscle. The muscle branches of the AIN destined for the flexor pollicis longus (FPL) and flexor digitorum profundus (FDP) muscles mostly originated in Zone 1, which is the transitional portion between the median nerve and the fixed Zone 2. The branches destined to the pronator teres (PT) and flexor carpi radialis (FCR) originating from the median nerve are more proximal and superficial.

DISCUSSION

The injury mechanisms leading to selective AIN palsy secondary to supracondylar elbow fracture in children are probably the result of two factors: direct contusion of the posterior aspect of the median nerve, and thereby the AIN fascicles, by the proximal fragment; stretching of AIN in Zone 1, which has less ability to withstand stretching than the median nerve and its other branches because the AIN is fixed in Zone 2.

CONCLUSION

Details about the origin and course of the AIN can explain the high percentage of AIN palsy in supracondylar elbow fractures in children.

LEVEL OF EVIDENCE

Level IV. Anatomic study.

Spontaneous anterior interosseous nerve syndrome: clinical analysis of eleven surgical cases

The aetiology of anterior interosseous nerve (AIN) syndrome and an optimal treatment strategy remain controversial. Eleven patients with spontaneous AIN syndrome, who were treated by surgical exploration, were reviewed at a mean of 32.5 months after the operation. Eight men and three women were included in the study. None of the patients had a history of trauma and there was no evidence of a neuropathy other than AIN syndrome. Six patients showed complete paralysis of the flexor pollicis longus (FPL) and the flexor digitorum profundus of the index finger (FDS1). Five patients had incomplete paralysis, with isolated lesions of the FPL in two and the FDP1 in three. Surgery was performed 7.8 months after the onset of paralysis. The most common structure of nerve compression was a fibrous band of the flexor digitorum sublimis muscle. However, no definitive compression site or anatomic abnormality could be found in four patients. Ten of the 11 patients had recovered muscle strength above grade 4 within 12 months of the operation. Good results were obtained in 10 patients and fair in only one at final assessment. Four patients (one man and three women) raised cosmetic concerns due to excessive scar formation on the upper forearm. Surgical exploration is recommended only in cases where AIN syndrome is apparent, no other neuronal lesions are apparent, and where there was no recovery after 6 months of conservative treatment. Careful preoperative examination is essential to avoid misdiagnosis and inappropriate operation, particularly in cases of incomplete AIN syndrome.

Compression and entrapment neuropathies

Peripheral nerve entrapments are frequent. They usually appear in anatomical tunnels such as the carpal tunnel. Nerve compressions may be due to external pressure such as the fibular nerve at the fibular head. Malignant or benign tumors may also damage the nerve. For each nerve from the upper and lower limbs, detailed clinical, electrophysiological, imaging, and therapeutic aspects are described. In the upper limbs, carpal tunnel syndrome and ulnar neuropathy at the elbow are the most frequent manifestations; the radial nerve is less frequently involved. Other nerves may occasionally be damaged and these are described also. In the lower limbs, the fibular nerve is most frequently involved, usually at the fibular head by external compression. Other nerves may also be involved and are therefore described. The clinical and electrophysiological examination are very important for the diagnosis, but imaging is also of great use. Treatments available for each nerve disease are discussed.

Anterior interosseous nerve compression syndrome: is there a role for endoscopy?

BACKGROUND

Anterior interosseous nerve syndrome is characterized by paralysis of the flexor digitorum profundus, the flexor pollicis longus and the pronator quadratus muscles without sensory loss. Extended exploration of the anterior interosseous nerve is the surgical treatment of choice. The present study evaluates the feasibility of an endoscopic approach for nerve decompression.

METHODS

Preparation of the anterior interosseous nerve was performed in ten human cadaver arms. Subsequently, one female patient suffering from anterior interosseous nerve syndrome was endoscopically operated on.

FINDINGS

A skin incision of 3-4 cm in the proximal direction was made at the forearm, and the median nerve was visualized between the pronator teres muscle and the flexor digitorum superficialis. Subsequently, the anterior interosseus nerve branch was identified, followed distally and decompressed under endoscopic view. The procedure could be accomplished in all cases under endoscopic view. Due to the very steep surgical angle, a branch of the anterior interosseus nerve was injured in one cadaver case. In all other cases, no adverse effects were observed. In the clinical case, the anterior interosseus nerve was endoscopically identified and decompressed, but a skin incision of 5 cm was required.

CONCLUSIONS

The results demonstrate that an endoscopic decompression of the anterior interosseus nerve is possible. Several difficulties occurred: Due to the depth of the surgical approach, especially in case of bulky muscles and very small skin incisions, the view is limited, harboring a higher risk of nerve injury. With more experience and specially designed endoscopes, application of this technique in anterior interosseus nerve compression syndrome might become more feasible.

Anterior interosseous nerve syndrome: retrospective analysis of 14 patients

INTRODUCTION

The anterior interosseous nerve (AIN) is a only motor nerve innervating the deep muscles of the forearm. Its compression is rare. We present a retrospective analysis of 14 patients with an AIN syndrome with a variety of clinical manifestations who underwent operative and conservative treatment.

PATIENTS AND METHODS

Fourteen patients (six female, eight male, mean age 48 ± 9 years) were included. In six patients, the right limb was affected, and in eight patients the left limb. Conservative treatment was started for every patient. If no signs of recovery appeared within 3 months, operative exploration was performed. Final assessment was performed between 2 and 9 years after the onset of paralysis (mean duration of follow-up 46 ± 11 months). Patients were examined clinically for return of power, range of motion, pinch and grip strengths. Also the disability of the arm, shoulder, and hand (DASH) score was calculated.

RESULTS

Seven of our 14 patients had incomplete AIN palsy with isolated total loss of function of flexor pollicis longus (FPL), five of FPL and flexor digitorum profundus (FDP)1 simultaneously, and two of FDP1. Weakness of FDP2 could be seen in four patients. Pronator teres was paralysed in two patients. Pain in the forearm was present in nine patients. Four patients had predisposing factors. Eight patients treated conservatively exhibited spontaneous recovery from their paralysis during 3-12 months after the onset. In six patients, the AIN was explored 12 weeks after the initial symptoms and released from compressing structures. Thirteen patients showed good limb function. In one patient with poor result a tendon transfer was necessary. The DASH score of patients treated conservatively and operatively presented no significant difference.

CONCLUSION

AIN syndrome can have different clinical manifestations. If no signs of spontaneous recovery appear within 12 weeks, operative treatment should be performed.

Unusual compression neuropathies of the forearm, part II: median nerve

We have previously discussed compression neuropathies of the radial nerve in the forearm. In the second half of this 2-part review, we will now turn our attention to 2 compression neuropathies affecting the proximal median nerve, before its entry through the carpal tunnel: (1) pronator syndrome and (2) anterior interosseous nerve syndrome.

Anterior interosseous nerve palsy after open capsular release for elbow stiffness: report of 2 cases

Surgical release of elbow contracture has been associated with injury to structures traversing the elbow. Injury to ulnar and radial nerves has been reported, but this review describes 2 cases of anterior interosseous nerve palsy after open release of an established elbow contracture.

Neurolysis is not required for young patients with a spontaneous palsy of the anterior interosseous nerve

We studied 21 patients with a spontaneous palsy of the anterior interosseous nerve. There were 11 men and 10 women with a mean age at onset of 39 years (17 to 65).

Pain around the elbow or another region (forearm, shoulder, upper arm, systemic arthralgia) was present in 17 patients and typically lasted for two to three weeks. It had settled within six weeks in every case. In ten cases the palsy developed as the pain settled. A complete palsy of flexor pollicis longus and flexor digitorum profundus to the index finger was seen in 13 cases and an isolated palsy of flexor pollicis longus in five. All patients were treated without operation. The mean time to initial muscle contraction was nine months (2 to 18) in palsy of the flexor digitorum profundus to the index finger, and ten months (1 to 24) for a complete palsy of flexor pollicis longus. An improvement in muscle strength to British Medical Research Council grade 4 or better was seen in all 15 patients with a complete palsy of the flexor digitorum profundus and in 16 of 18 with a complete palsy of flexor pollicis longus.

There was no significant correlation between the duration of pain and either the time to initial muscle contraction or final muscle strength. Prolonged pain was not always associated with a poor outcome but the age of the patient when the palsy developed was strongly correlated. Recovery occurred within 12 months in patients under the age of 40 years who achieved a final British Medical Research Council grade of 4 or better. Surgical decompression does not appear to be indicated for young patients with this condition.

Occupational and Sport Related Traumatic Neuropathy

BACKGROUND

Sport and occupation related traumatic nerve injury is a common problem in the United States. While the physical requirements of each pursuit place participants at risk for injury to certain peripheral nervous system structures, the vast numbers of professional and recreational pursuits limits the ability to become familiar with nerve injuries specific to each. A more pragmatic approach is to apply knowledge of mechanisms of injury, physiology of nerve injury, regional anatomy, and at-risk peripheral nervous system structures to the routine neurologic history and physical assessment to arrive at a localizing and etiologic diagnosis.

REVIEW SUMMARY

The authors discuss potential mechanisms of nerve injury, the role of electrodiagnostic testing, regional peripheral nervous system anatomic considerations and lesion localization.

CONCLUSIONS

Despite the wide variety of professionally and recreationally induced peripheral nerve injuries, application of anatomic, physiologic and mechanistic considerations allow the neurologist to make an etiologic and localizing diagnosis.

Flexor digitorum superficialis nerve transfer to restore pronation: two case reports and anatomic study

Loss of pronation affects most activities of daily living. We report 2 cases of traumatic loss of pronator teres function and successful reconstruction by transfer of a redundant motor branch to the flexor digitorum superficialis to the pronator teres branch(es). Follow-up period was 2 years and pronation strength was restored to +4/5 and 5/5 in the 2 patients. The anatomy of the median nerve in the proximal forearm was examined by dissecting 31 cadaver specimens. A branching scheme was formulated. The histomorphometric properties of the individual muscular branches were studied in 15 fresh specimens to evaluate their suitability and size match for nerve transfer.

Recurrent anterior interosseous nerve palsies related to pregnancy

A rare association of anterior interosseous nerve palsy with pregnancy has been reported previously (Sood and Burke, 1997). We report further on this patient who has now experienced three separate anterior interosseous nerve palsies associated with pregnancies.