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Surgical Reconstruction for Upper-Extremity Paralysis Following Acute Flaccid Myelitis

Doi, Kazuteru MD, PhD1; Sem, Sei Haw MBBS, MS(Ortho)1,2; Hattori, Yasunori MD, PhD1; Sakamoto, Sotetsu MD1; Hayashi, Kota MD1; De la Red-Gallego, Maria Angeles MD, PhD1,3

JBJS Open Access: October-December 2019 - Volume 4 - Issue 4 - p e0030
doi: 10.2106/JBJS.OA.19.00030
Scientific Articles
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Disclosures

Background: Acute flaccid myelitis (AFM) is a debilitating illness that is defined by the sudden onset of flaccid paralysis in the extremities with spinal magnetic resonance imaging (MRI) demonstrating a longitudinal lesion confined to the gray matter. The purpose of this study was to report the types of upper-extremity palsy and outcomes of surgical reconstruction in patients with AFM.

Methods: Eight patients with a median age at onset of 3.8 years (range, 2.3 to 9.9 years) were identified. There was loss of shoulder abduction and external rotation in all patients, loss of elbow flexion in 5 patients, complete or partial loss of hand function in 3 patients, and spinal accessory nerve palsy in 2 patients. All patients underwent surgical reconstruction, which was categorized into 3 main groups: nerve transfer, secondary muscle transfer, and free muscle transfer.

Results: The median follow-up period was 39 months (range, 30 to 94 months). Four patients obtained ≥90° of shoulder abduction whereas the other 4 patients had shoulder abduction of ≤70°. The 5 patients who received free muscle transfer or nerve transfer to restore elbow function obtained ≥140° of elbow flexion. Two patients treated with free muscle transfer to restore finger function obtained satisfactory total active motion of the fingers (180°).

Conclusions: The patterns of paralysis and the strategy and outcomes of surgical reconstruction for patients with AFM differed from those for traumatic and obstetric brachial plexus palsy. All patients had loss of shoulder abduction, and 2 had spinal accessory nerve palsy. Restoration of shoulder function was unpredictable and depended on the quality of the donor nerves and recovery of synergistic muscles. Restoration of elbow and hand function was more consistent and satisfactory.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete list of levels of evidence.

1Department of Orthopedic Surgery, Ogori Daiichi General Hospital, Yamaguchi, Japan

2Department of Orthopaedics, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia

3Hospital Universitario Marques de Valdecilla, Santander, Spain

Email address for K. Doi: doimicro@saikyo.or.jp

Investigation performed at the Department of Orthopedic Surgery, Ogori Daiichi General Hospital, Yamaguchi, Japan

Disclosure: The authors indicated that no external funding was received for any aspect of this work. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSOA/A116).

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

Acute flaccid myelitis (AFM) is a poliomyelitis-like illness that is characterized by an acute onset of flaccid paralysis in the extremities with spinal magnetic resonance imaging (MRI) demonstrating a longitudinal lesion confined to the gray matter. AFM was first reported in the United States in 2012, and clusters of cases were observed every 2 to 3 years since then in many countries1-7. It is a disease with a seasonal pattern, with most patients having the onset of AFM between August and November.

There was a high epidemic association between AFM and enterovirus D68 (EV-D68), but the definite causative agent is yet to be determined. Most of the patients experienced a few days of prodromal illness with respiratory symptoms before the onset of neurological deficits, which progressed rapidly from muscle weakness to complete paralysis of the affected limb without sensory involvement.

A nationwide survey in Japan revealed the paralysis in the acute stage to involve 1 limb in 37% of patients, 2 limbs in 39%, 3 limbs in 5%, and 4 limbs in 19%7. Involvement of family members of patients with AFM has not been reported to our knowledge.

While many authors reported that patients with AFM regained some strength as time passed8-12, the majority of patients did not recover fully. About 90% of patients still have motor deficits during follow-up regardless of the mode of treatment of the disease6,7. Therefore, reconstructive surgery is needed to improve the function of the affected limb. The basic principle of surgical reconstruction for patients with AFM is based on the treatment for traumatic or obstetric brachial plexus palsy. Nerve transfer is preferable for patients who present early after the onset of paralysis whereas free or pedicled muscle transfer is better for patients with late presentation8-13.

The objective of this study was to report the types of upper-limb palsy and the outcomes of surgical reconstruction in patients with AFM—hence to update orthopaedic and microsurgeons about AFM and the current surgical treatment strategy for this disease.

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Materials and Methods

This was a retrospective study of patients with upper-limb paralysis due to AFM who were referred to our hospital for surgical reconstruction. This study was approved by the local hospital institutional ethics committee, and written informed consent was obtained from all patients.

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Diagnostic Definition of AFM

Standardized definitions of “confirmed” and “probable” cases of AFM provided by the U.S. Centers for Disease Control and Prevention (CDC)1,2 on the basis of clinical and laboratory criteria are shown in Table I.

TABLE I - Case Definitions of AFM by the U.S. CDC*
Case Designation Criteria
Confirmed (1) Acute onset of flaccid limb weakness AND (2) MRI showing a spinal cord lesion largely restricted to gray matter and spanning ≥1 spinal segment
Probable (1) Acute onset of flaccid limb weakness AND (2) cerebrospinal fluid with pleocytosis (white blood-cell count >5 cells/mm3, adjusted for presence of red blood cells by subtracting 1 white blood cell for every 500 red blood cells present)
*

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Patients Demographic (Table II)

Eight patients with confirmed AFM fulfilled the inclusion criteria. There were 3 girls and 5 boys with a median age at onset of 3.8 years (range, 2.3 to 9.9 years). Three patients had bronchial asthma whereas 5 patients were healthy before the onset of the AFM. Seven patients experienced prodromal illness with fever and respiratory symptoms. All patients had a sudden onset of neurological symptoms (upper-limb flaccid paralysis without sensory impairment) after 1 to 8 days (median, 3 days) of prodromal symptoms. All patients had pleocytosis in the cerebrospinal fluid, and their spinal MRIs demonstrated longitudinal abnormal signals confined to the gray matter and/or anterior horn cells and spanning ≥1 vertebral levels (Figs. 1 and 2). After the onset of paralysis, 7 patients received immunomodulation therapy consisting of high-dose intravenous immunoglobulin, pulse methylprednisolone, or a combination of the 2, but there was no substantial clinical improvement of the neurological deficits.

TABLE II - Demographic Data*
Case Age at Onset (yr) Onset Date (yr/mo/day) Sex Final Involved Side Asthma Flu-Like Symptoms with High Fever AFP After Symptom Onset (days) Initial Paralysis EV-D68 Test T2-Wt. MRI High-Intensity Signal Indicating Lesion CSF Cell Count (cells /mm 3 ) AFM Designation Initial Treatment
1 4.3 2010/9/16 F L Yes No 7 Monoplegia NR Yes 12 Confirmed mPSL
2 2.9 2010/9/24 M R No Yes 1 Monoplegia NR Yes 192 Confirmed No treatment
3 4.3 2015/9/9 M R No Yes 3 Monoplegia Yes 10 Confirmed PSL, IVIG
4 9.9 2015/9/11 M L No Yes 3 Monoplegia Yes 131 Confirmed mPSL, IVIG, acyclovir
5 3.8 2015/9/19 F R Yes Yes 8 Diplegia Yes 54 Confirmed mPSL
6 3.6 2015/8/28 M L No Yes 3 Monoplegia + Yes 33 Confirmed mPSL, IVIG
7 3.7 2015/9/7 F L Yes Yes 3 Monoplegia Yes 153 Confirmed mPSL
8 2.3 2010/9/11 M L No Yes 7 Monoplegia + Yes 67 Confirmed mPSL
Median 3.8 3
Range 2.3-9.9 1-8
*
NR = not reported by primary pediatric neurologist, and CSF = cerebrospinal fluid.
mPSL = high-dose methylprednisolone, PSL = prednisolone, IVIG = intravenous immunoglobulin, and acyclovir = anti-viral (herpes) drug.

Fig. 1

Fig. 1

Fig. 2

Fig. 2

Seven patients underwent neurophysiological tests within 2 weeks after onset (Table III). The median nerve demonstrated no electrical responses in the 3 patients with hand palsy whereas it showed normal motor conduction velocity in the 4 patients without involvement of the hand. The median nerve showed decreased F-wave persistence (0% to 56%) in all 7 cases, which suggested that the anterior horn cells were affected from C8 to T1.

TABLE III - Results of Preoperative Electrophysiological Tests*
Case Exam. Time After Onset (days) Nerve Conduction Velocity of Median Nerve on Involved Side
M-Wave (MCV) (m/s) Amplitude (CMAP) (mV) F-Wave(%) SCV (m/s)
1 7 0 0 0 54.1
2 1 0 0 0 NR
3 3 52.1 7.3 37 46.3
4 3 62.1 10.99 56 NR
5 8 57.7 2.2 0 57.7
6 4 0 0 0 NR
7 3 60.5 1.57 35 60.0
8 NR NR NR NR NR
Median 3
Range 1-8
*
MCV = motor conduction velocity, SCV = sensory nerve conduction velocity, and NR = not reported by a primary pediatric neurologist.
F-wave persistence of the median nerve.

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Preoperative Evaluations

Preoperatively, all patients except Case 8 (who presented late after the onset of paralysis) were followed at 2 to 3-month intervals until the plateau of recovery was achieved.

Preoperative neurological evaluations were performed at a median of 3 months (range, 1 to 8 months) after the AFM onset. It was difficult to classify the types of paralysis according to the spinal segments that were involved—as is done in traumatic brachial plexus palsy—because there was a great variety of paralysis combinations, with certain types appearing more frequently than others1,7. Furthermore, the involvement of neck muscles is not uncommon in patients with AFM; this differs from brachial plexus palsy, in which the injuries are classified according to the nerve roots involved (such as C5-C6 or C5-C6-C7 palsy).

In view of the small number of AFM cases in our study, we categorized them according to the region with completely paralyzed muscles (no motor action potential on surface electromyography [EMG]) (Table IV). There were 3 patients with shoulder paralysis (loss of shoulder abduction and external rotation) without elbow paralysis, 3 patients with shoulder and elbow paralysis (loss of elbow flexion in addition to shoulder involvement) without hand paralysis, and 2 patients with shoulder, elbow, and hand paralysis (loss of all upper-limb muscle function). Each of the patients with shoulder or shoulder-elbow palsy had additional paralysis of neck muscles, with involvement of the sternocleidomastoid, trapezius, and diaphragm as well. One patient with shoulder palsy had paralysis of the hand (wrist extensors and flexors and intrinsic muscles) due to incomplete recovery. In general, there was loss of shoulder abduction and external rotation in all patients, loss of elbow flexion in 5 patients, and complete or partial loss of hand function in 3 patients (Table V).

TABLE IV - Preliminary Classification of AFM*
AFM: Neck AFM: Shoulder AFM: Elbow AFM: Hand
Sternocleidomastoid Trapezius Diaphragm Deltoid Supraspinatus/ Infraspinatus Pect. Maj.: Clavicular Pect. Maj.: Sternal Biceps Triceps Wrist Ext.: ECRB Wrist Flex.: FCR Finger Ext: EDC Finger Flex.: FDP Intrinsic Muscles
Spinal root segment C2-C3, XI C3-C4, XI C4 C5-C6 C5-C6 C5-C6 C6-T1 C5-C6 C6-C8 C7-C8 C6-C7 C7-C8 C8-T1 C8-T1
Brachial plexus palsy type
 C2-C4 + + +
 C5-T1 + + + + + + + + + + +
 C5-C6 + + + +
 C5-C7 + + + + + + +
 C5-C8 + + + + + + + + +
 T1 +
*
ECRB = extensor carpi radialis brevis, FCR = flexor carpi radialis, EDC = extensor digitorum communis, FDP = flexor digitorum profundus, C = cervical nerve root, XI = 11th cranial nerve, T1 = 1st thoracic nerve root, + = paralyzed, and − = not paralyzed.

TABLE V - MRC Grades of Preoperative Muscle Power
Case MRC Grade Type of Palsy*
Sternocleidomastoid Trapezius Phrenic N. Palsy Shoulder Abduction Shoulder Ext. Rotation Pectoralis Major Elbow Flexion Elbow Extension Wrist Extension Wrist Flexion Finger Extension Finger Flexion Intrinsic muscles
Clavicular Sternal
1 5 5 No 0 0 0 0 0 0 0 0 0 0 0 S-E-H
2 5 5 No 0 0 0 0 2 0 2 0 0 0 0 S-E-H
3 4 4 No 0 0 0 4 0 3 4 4 4 4 4 S-E
4 2 0 Yes 0 0 0 0 2 2 5 5 5 5 5 N-S-E
5 3 0 Yes 0 0 0 0 2 3 4 4 4 4 4 N-S
6 5 5 No 0 0 0 0 3 2 0 0 4 2, 0§ 2, 0§ S-H
7 4 3 No 0 0 0 0 0 2 4 4 4 4 4 S-E
8# 4 4 No 0 1 0 3 3 4 5 5 5 5 5 S
*
S = shoulder, E = elbow, H = hand, and N = neck.
Confirmed by needle electromyography or intraoperative nerve stimulation.
Biceps was completely paralyzed, but elbow could be flexed by forearm muscles.
§
Only the ulnar nerve-innervated intrinsic muscles.
#
Case 8, who presented late after the onset of paralysis, was the only patient not followed at 2 to 3-month intervals until the plateau of recovery was achieved.

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Surgical Reconstruction (Table VI)

Reconstruction to restore shoulder joint function: Nerve transfer surgery was preferred in cases with early presentation (<12 months after the onset of paralysis). The spinal accessory nerve was preferred as the donor nerve to address suprascapular nerve palsy. However, the contralateral C7 nerve root was used if the spinal accessory nerve was not available (due to paralysis or reserving it for free muscle transfer), and the contralateral C7 nerve root was routed to the suprascapular nerve and spinal accessory nerve. For patients with neck muscle paralysis, the function of the deltoid was reconstructed in addition to the suprascapular muscle, with the intercostal nerves or thoracodorsal nerve transferred to the axillary nerve. For the patient with late presentation (>12 months after the onset of paralysis), multiple muscle transfer was inevitable. This patient (Case 8) underwent transfer of the trapezius, pectoralis major, latissimus dorsi, and short head of the biceps for the left shoulder.

TABLE VI - Types of Surgical Reconstruction
Case Type of Palsy* Time Between Palsy and Op. (mo) Age at Op. (yr) Primary Surgical Reconstruction Secondary Reconstruction
Shoulder Elbow Wrist & Fingers
1 S-E-H 6 5 Contralat. C7 n. root to long thoracic n. + suprascapular n. Double free muscle transfer Double free muscle transfer Zancolli metacarpophalangeal joint capsulodesis
2 S-E-H 13 4 Spinal accessory n. to suprascapular n. Single muscle transfer§ Single muscle transfer Biceps rerouting, extensor digitorum communis tenodesis, Zancolli metacarpophalangeal joint capsulodesis
3 S-E 5 5 Spinal accessory n. to suprascapular n. Partial ulnar n. to musculocutan. n.
4 N-S-E 8 10 Contralat. C7 n. root to spinal accessory n. + suprascapular n.; intercostal n. to axillary n. Partial ulnar n. to musculocutan. nerve
5 N-S 6 4 Contralat. C7 n. root to spinal accessory n. + suprascapular n.; thoracodorsal n. to axillary n.
6 S-H 10 5 Spinal accessory n. to suprascapular n. Ant. interosseous n. to ulnar n. Tendon transfer
7 S-E 10 4 Spinal accessory n. to suprascapular n. Partial ulnar n. to musculocutan. n. Long head of triceps to acromion#
8 S 83 10 Multiple muscle transfer
Median 9 5
Range 5∼83 4∼10
*
S = shoulder, E = elbow, H = hand, and N = neck.
Double free muscle transfer was innervated from the spinal accessory and intercostal nerves.
The Zancolli metacarpophalangeal joint capsulodesis was useful to control claw-finger deformity.
§
Single muscle transfer was innervated from the intercostal nerves.
#
The transfer of the long head of the triceps to the acromion did not increase the active range of shoulder abduction.

Reconstruction to restore elbow, wrist, and finger function: Five patients required reconstruction to restore elbow function, with 3 of them receiving partial ulnar nerve-to-musculocutaneous nerve transfer and 2 patients receiving free muscle transfer (single in one and double in the other) to restore wrist and finger movement at the same time.

Secondary procedures: Four patients underwent secondary reconstruction to correct remaining disabilities. Procedures performed included Zancolli capsulodesis of the metacarpophalangeal joints for claw-finger correction, tenodesis to restore wrist extension, rerouting of the biceps tendon to restore forearm pronation, and transfer of the long head of the triceps to the acromion in an attempt to restore shoulder abduction.

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Postoperative Management and Assessment

The shoulder and elbow were immobilized with an air cushion splint following shoulder and elbow joint reconstruction, and an additional long-arm cast was applied after hand reconstruction, for 4 weeks postoperatively. EMG was used to monitor the recovery process following nerve transfer surgery, starting at approximately 3 months postoperatively and continuing until full recovery of the motor unit potentials; EMG was needed to distinguish nerve recovery from recovery of synergic muscle function. Following electromyographic documentation of reinnervation, muscle reeducation training was started using an EMG feedback technique with a myotrainer and surface electrodes.

Upper-limb function was assessed by measuring the active range of shoulder abduction and external rotation and elbow flexion and extension as well as the total active motion of the fingers. The Mallet functional scoring system was used to assess shoulder abduction and external rotation deficits. The strength of elbow flexion was measured qualitatively with the British Medical Research Council (MRC) grading scale and quantitatively with a handheld dynamometer (microFET2; Hoggan Scientific).

Early and long-term outcome measures were analyzed, with the early results based on the timing of muscle reinnervation as determined with needle EMG and the long-term results based on the functional improvement of the affected limb. The Child Health Questionnaire-Parent Form 28 (CHQ-PF28) was used as a patient (parent)-reported outcome measure to assess overall improvement in quality of life.

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Statistical Analysis

All data are presented as medians with ranges. Statistical analysis was not performed because of the small sample size.

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Results

The reinnervation periods differed according to the muscles and the procedures performed (Table VII). The time for muscle reinnervation following contralateral C7 nerve root transfer was 6 months for the trapezius, 4 and 7 months for the deltoid, and 5 to 8 months for the infraspinatus. The infraspinatus muscles were reinnervated as early as 3 to 4 months following transfer of the spinal accessory nerve to the suprascapular nerve. Two patients had documented reinnervation at 6 and 13 months but mature motor unit potentials were evidenced at the time of these examinations; thus, the actual time of reinnervation was long before the documented period. As for the biceps muscle, the reinnervation periods were 2.5 to 4 months after partial ulnar nerve-to-musculocutaneous nerve transfer. The 3 transferred gracilis muscles in 2 patients survived well with no vascular complications and were reinnervated by 3 to 4 months after surgery.

TABLE VII - Early Results: Time of Muscle Reinnervation Demonstrated by EMG
Case Reinnervation* After Surgery (After Palsy Onset) (mo)
Trapezius Deltoid Infraspinatus Biceps Grafted Muscle Abductor Digiti Minimi
1 5 (11.5) 3, 4
2 <13 (<24) 3
3 3 (8.5) 3 (8.5)
4 6.5 (14.5) 4 (12) 6.5 (14.5) 2.5 (10.5)
5 6 (12) 7 (13) 8 (14)
6 <6 (<16) <6 (<16)
7 4 (13.5) 4 (13.5)
8
*
The reinnervation of all muscles except 2 in Case 1 was confirmed by needle EMG.
< = far less than the estimated periods because the motor unit potentials were already mature at the time of examination.
Reinnervation was defined by visible contraction of the muscle.

The median duration of follow-up after the final surgical procedures was 39 months (range, 30 to 94 months) (Table VIII). The median ranges of shoulder abduction and external rotation were both 80° (range, 30° to 180° and 10° to 90°, respectively). Four patients obtained at least 90° of shoulder abduction whereas the other 4 patients had shoulder abduction of ≤70°. The median Mallet score increased from 7 (range, 5 to 15) preoperatively to 19 (range, 12 to 25) postoperatively, with a median difference of 12 (range, 2 to 20) (Table IX). Elbow flexion in the 5 patients who received reconstruction (free muscle transfer or partial ulnar nerve-musculocutaneous nerve transfer) to restore elbow function was ≥140°, with the quantitative measurement of elbow flexion strength showing a median value of 30% (range, 14% to 59%) of the uninvolved side. Total active motion of the fingers for the 2 patients who underwent free muscle transfer to restore finger function was satisfactory (180°) (Table VIII, Figs. 3-A through 4-D, and Video 1).

TABLE VIII - Long-Term Functional Outcomes
Case Type of Palsy* Follow-up (mo) MRC Grade of Muscle Power Range of Active Joint Motion*(°) Power of Elbow Flexion
Sternocleidomastoid Trapezius Pectoralis Maj. S Abd. S Ext. Rot. E Flex. F Total Active Motion MRC Grade Hand-Held Dynamometer (% of uninvolved side)
1 S-E-H 94 5 5 0 90 60 140 180 3 26
2 S-E-H 75 5 5 2 40 80 140 180 3 Not tested
3 S-E 44 4 4 3 180 90 150 Full 4 47
4 N-S-E 39 3 2 0 50 80 140 Full 4 34
5 N-S 39 3 3 4 160 90 140 Full 4 59
6 S-H 38 5 5 4 130 70 150 150 3 22
7 S-E 38 4 4 0 30 90 140 Full 3 14
8 S 30 4 4 3 70 10 140 Full 3 Not tested
Median 39 80 80 140 180 3 30
Range 30-94 30-180 10-90 140-150 150-180 3-4 14-59
*
S = shoulder, E = elbow, H = hand, and N = neck.
Supplementary action using shoulder flexion after 90° of shoulder abduction.
Spontaneous recovery of biceps.

TABLE IX - Preoperative and Postoperative Quality-of-Life Scores*
Case Mallet Score CHQ-PF28
Preop. Postop. Diff. Physical Psychosocial
Preop. Postop. Diff. Preop. Postop. Diff.
1 5 20 15 19 54 35 62 53 −9
2 5 17 12 25 31 6 60 61 1
3 5 25 20 8 33 25 34 47 13
4 10 12 2 19 36 17 29 46 17
5 11 24 13 15 34 19 25 46 21
6 15 21 6 38 40 2 60 64 4
7 6 12 6 24 29 5 32 45 13
8 8 16 8 21 26 5 43 50 7
Median 7 19 12 20 34 12 39 49 10
Range 5-15 12-25 2-20 8-38 26-54 2-35 25-62 45-64 −9-21
*
Diff. = difference (change from preoperative to postoperative score).

Figs. 3-A, 3-B, and 3-C Case 1. A 5-year-old girl sustained complete paralysis of the left upper limb (C5∼T1). She underwent transfer of the contralateral C7 nerve root to the left suprascapular nerve and the long thoracic nerve for restoration of function of the left shoulder at the first operation. Double free muscle transfers for restoration of finger and elbow function were performed at the second and third operations. The final surgery was performed to correct secondary claw-finger deformities with Zancolli metacarpophalangeal joint capsulodesis. Fig. 3-A Preoperative appearance showing complete paralysis of the left upper extremity. Figs. 3-B and 3-C Five years after the final operation. Fig. 3-B Photograph showing the patient’s ability to abduct the left shoulder 90°. Fig. 3-C Photograph showing that full flexion of the left elbow was possible. Her finger motion is shown in Video 1.

Fig. 3-A

Fig. 3-A

Fig. 3-B

Fig. 3-B

Fig. 3-C

Fig. 3-C

Figs. 4-A through 4-D Case 5. A 4-year-old girl sustained right C2∼C6 palsy with complete paralysis of the right trapezius, deltoid, supraspinatus, and biceps muscles, but flexion of the right elbow was possible with supplementary action of the forearm muscles. She underwent transfer of the contralateral C7 nerve root to the right spinal accessory nerve and suprascapular nerve at the first operation and transfer of the thoracodorsal nerve to the axillary nerve at the second operation.

Fig. 4-A

Fig. 4-A

Fig. 4-B

Fig. 4-B

Fig. 4-C

Fig. 4-C

Fig. 4-D

Fig. 4-D

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In terms of quality-of-life improvement, the median physical and psychosocial summary scores of the CHQ-PF28 increased from 20 (range, 8 to 38) preoperatively to 34 (range, 26 to 54) postoperatively and from 39 (range, 25 to 62) to 49 (range, 45 to 64), respectively (Table IX).

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Discussion

The patterns of motor paralysis in AFM are different from those in traumatic and obstetric brachial plexus palsy because of the involvement of the spinal cord anterior horn cells with widespread muscle dysfunction in AFM. Thus, AFM does not always follow the typical myotome distribution of a spinal segment8-12.

All of the patients initially presented with monoplegia except for Case 5, who had diplegia; that patient’s left upper limb recovered fully without surgical treatment. Our preoperative assessments (Table V) showed involvement of the shoulder and elbow muscles in the majority of patients. There was complete paralysis of the deltoid, supraspinatus, and pectoralis major (clavicular head) in all patients and of the biceps in 5 patients. This pattern is similar to the spinal type of paralytic poliomyelitis, in which the proximal part of the limb is more commonly affected than the distal part13. However, the reason for the predominant involvement of the shoulder and elbow muscles in AFM is still unclear.

Although, to our knowledge, complete paralysis of the trapezius has not been reported previously in patients with poliomyelitis-like paralysis8-12, 2 of our patients had complete paralysis of the trapezius and ipsilateral diaphragm and a third patient had partial recovery of the involved trapezius. Furthermore, Ruggieri et al. reported on 4 patients with diaphragmatic paralysis and respiratory failure requiring mechanical ventilation in a cluster of 11 patients with AFM14. Therefore, high cervical cord involvement is relatively common in AFM.

The prognosis of a paralytic muscle may depend on the status of associated muscles that are innervated by the same spinal segments, as is the case in poliomyelitis15. However, there is no evidence that this association with spinal segments occurs in the same way in AFM, the pathomechanism of which is still not well understood.

The outcomes of shoulder joint reconstruction in AFM have been inconsistent, just as they have been in brachial plexus palsy and poliomyelitis8-12. Transfer of the spinal accessory nerve to the suprascapular nerve was the most reliable surgical method for restoration of shoulder abduction in patients with brachial plexus palsy16. For our patients, the integrity of the donor nerve (spinal accessory nerve) was confirmed intraoperatively by a strong contraction of the trapezius seen on electrical stimulation. Nevertheless, half of the patients did not regain the expected shoulder abduction. The trapezius and/or spinal accessory nerve could be affected by the disease process as well, which might have prevented full recovery or allowed relapse even after a technically successful reinnervation.

Intraoperative electrical stimulation of the spinal accessory nerve is probably not reliable enough to prove a healthy donor nerve, as it is not a quantitative measurement. Also, restoration of the supraspinatus muscle alone might not be as effective as it is in patients with brachial plexus palsy, in whom concurrent partial palsy of the spinal accessory nerve is rare. Thus, we propose that, before performing shoulder reconstruction in AFM, the trapezius muscle strength be assessed with manual muscle testing17 together with testing of compound muscle action potentials (CMAPs); neurotization of the axillary nerve would be necessary to restore deltoid function with a donor nerve not involved by the lesion, such as the triceps branch of the radial nerve.

Two of our patients had spinal accessory nerve palsy, and they were treated with transfer of the contralateral C7 nerve root to the affected spinal accessory nerve and suprascapular nerve. This technique has been proven to be useful in children with brachial plexus palsy18,19. Nerve transfer to the axillary nerve was also performed in the same patients to restore deltoid function. However, only 1 patient achieved a full range of shoulder abduction (Case 5) while the other patient’s outcome (Case 4) was unsatisfactory because of relative weakness of synergistic muscles.

In our series, the outcomes in terms of elbow flexion were consistent for patients with either partial ulnar nerve transfer or free muscle transfer. They obtained elbow flexion of 140°, a median MRC grade of 3, and a median of 30% of the strength of the unaffected side (Table VIII). This was compatible with the reported surgical outcomes in several studies of nerve transfer for poliomyelitis-like paralysis, although half of the cases in those studies had spontaneous recovery8-12. Spontaneous recovery of biceps function in AFM was not unusual although the presence of elbow flexion could have been due to the action of the brachialis or forearm muscles. Two patients (Cases 5 and 6) with complete biceps paralysis initially had spontaneous reinnervation of the biceps with good elbow flexion power. Therefore, it might not be necessary to perform a reconstruction to restore elbow flexion in the early stage for patients with shoulder and elbow paralysis as long as the elbow flexion can be elicited clinically via supplementary action. Furthermore, it is always possible to restore elbow flexion at a late stage by free muscle transfer if the recovery is unsatisfactory8.

To date, there are no standardized selection criteria for the donor nerves. Nationwide surveillance of a cluster of patients with AFM in Japan had identified normal F-wave persistence as the only significant independent factor for a good prognosis7. Preserved F-waves indicate an unaffected area of anterior horn cells for specific spinal segments. Thus, persistence of F-waves for median and/or ulnar nerves, although reduced or abnormal, could be a good indicator of the suitability of a donor nerve such as for a partial ulnar nerve transfer.

There is no method other than free muscle transfer that can provide satisfactory finger movement for patients with brachial plexus palsy. A similar technique can be employed effectively to restore grasping motion to patients with AFM10,18. Satisfactory total active motion was achieved for the 2 patients who underwent free muscle transfer (Cases 1 and 2).

The median Mallet score for the patients with AFM increased by 12 (range, 2 to 20), which was comparable with findings for patients with obstetric brachial plexus palsy18. Both the physical and psychological scores on the health-related quality-of-life assessment measured with the CHQ-PF28 improved postoperatively. However, the scores (Table IX) were still lower than those in children without any chronic condition, who demonstrated mean physical and psychosocial scores of 58.53 ± 4.28 and 53.86 ± 5.87, respectively, in a large population-based study by Bai et al.20,21. Thus, the postoperative improvements of the patients with AFM were still inadequate to meet parental expectations.

Although the small sample size of our study limits us from establishing any solid conclusions, there are a few important points that we would like to emphasize. We found a great variety of paralytic patterns in AFM, with involvement of high cervical segments and the spinal accessory nerve not being uncommon. All patients had loss of shoulder abduction, and restoration of shoulder function was less predictable and depended on the quality of the donor nerves and recovery of the synergistic muscles. In contrast, the outcomes of the reconstructions to restore elbow and hand function were more consistent and satisfactory.

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