Characteristics and surgical results of the distal type of cervical spondylotic amyotrophy

Clinical article

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Object

Cervical spondylosis that causes upper-extremity muscle atrophy without gait disturbance is called cervical spondylotic amyotrophy (CSA). The distal type of CSA is characterized by weakness of the hand muscles. In this retrospective analysis, the authors describe the clinical features of the distal type of CSA and evaluate the results of surgical treatment.

Methods

The authors performed a retrospective review of 17 consecutive cases involving 16 men and 1 woman (mean age 56.3 years) who underwent surgical treatment for the distal type of CSA. The condition was diagnosed on the basis of cervical spondylosis in the presence of muscle impairment of the upper extremity (intrinsic muscle and/or finger extension muscles) without gait disturbance, and the presence of a compressive lesion involving the anterior horn of the spinal cord, the nerve root at the foramen, or both sites as seen on axial and sagittal views of MRI or CT myelography. The authors assessed spinal cord or nerve root impingement by MRI or CT myelography and evaluated surgical outcomes.

Results

The preoperative duration of symptoms averaged 11.8 months. There were 14 patients with impingement of the anterior horn of the spinal cord and 3 patients with both anterior horn and nerve root impingement. Twelve patients were treated with laminoplasty (plus foraminotomy in 1 case), 3 patients were treated with anterior cervical discectomy and fusion, and 2 patients were treated with posterior spinal fixation. The mean manual muscle testing grade was 2.4 (range 1–4) preoperatively and 3.4 (range 1–5) postoperatively. The surgical results were excellent in 7 patients, good in 2, and fair in 8.

Conclusions

Most of the patients in this series of cases of the distal type of CSA suffered from impingement of the anterior horn of the spinal cord, and surgical outcome was fair in about half of the cases.

Abbreviations used in this paper:ACDF = anterior cervical discectomy and fusion; ALS = amyotrophic lateral sclerosis; CSA = cervical spondylotic amyotrophy; MMT = manual muscle testing; MP = metacarpophalangeal.

Object

Cervical spondylosis that causes upper-extremity muscle atrophy without gait disturbance is called cervical spondylotic amyotrophy (CSA). The distal type of CSA is characterized by weakness of the hand muscles. In this retrospective analysis, the authors describe the clinical features of the distal type of CSA and evaluate the results of surgical treatment.

Methods

The authors performed a retrospective review of 17 consecutive cases involving 16 men and 1 woman (mean age 56.3 years) who underwent surgical treatment for the distal type of CSA. The condition was diagnosed on the basis of cervical spondylosis in the presence of muscle impairment of the upper extremity (intrinsic muscle and/or finger extension muscles) without gait disturbance, and the presence of a compressive lesion involving the anterior horn of the spinal cord, the nerve root at the foramen, or both sites as seen on axial and sagittal views of MRI or CT myelography. The authors assessed spinal cord or nerve root impingement by MRI or CT myelography and evaluated surgical outcomes.

Results

The preoperative duration of symptoms averaged 11.8 months. There were 14 patients with impingement of the anterior horn of the spinal cord and 3 patients with both anterior horn and nerve root impingement. Twelve patients were treated with laminoplasty (plus foraminotomy in 1 case), 3 patients were treated with anterior cervical discectomy and fusion, and 2 patients were treated with posterior spinal fixation. The mean manual muscle testing grade was 2.4 (range 1–4) preoperatively and 3.4 (range 1–5) postoperatively. The surgical results were excellent in 7 patients, good in 2, and fair in 8.

Conclusions

Most of the patients in this series of cases of the distal type of CSA suffered from impingement of the anterior horn of the spinal cord, and surgical outcome was fair in about half of the cases.

Abbreviations used in this paper:ACDF = anterior cervical discectomy and fusion; ALS = amyotrophic lateral sclerosis; CSA = cervical spondylotic amyotrophy; MMT = manual muscle testing; MP = metacarpophalangeal.

Muscle atrophy in the upper extremities without gait disturbance can occur with cervical spondylosis in middle-aged or older people. Brain et al. first reported on a case of cervical spondylosis involving muscle atrophy of the upper extremities but no sensory disturbance.2 Keegan also reported on this case at autopsy, describing it as dissociated motor loss in the upper extremities secondary to cervical spondylosis.7 From this description, this syndrome has only motor deficits such as muscle atrophy of the upper extremities without numbness or sensory disturbance and has been called Keegan type cervical spondylosis. In Japan, this type of upper limb muscle atrophy without gait disturbance in people with cervical spondylosis has been called “cervical spondylotic amyotrophy” (CSA).1,13 CSA is classified as either a proximal or distal type of muscle atrophy. Recently, CSA has been found to sometimes include sensory disturbance such as numbness and exaggerated deep tendon reflex of the lower extremities. Thus, diagnosing CSA in Japan is not dependent on the presence or absence of these symptoms. The proximal type of CSA is characterized by weakness of the deltoid, biceps, and supinator muscles, whereas the distal type is characterized by weakness of intrinsic muscles of the hand or finger extension muscles (Fig. 1). The pathophysiology and clinical features of the distal type of CSA are not well understood, and any previous reports of this syndrome involved only small numbers of patients.4–6,9 The purpose of this study was to demonstrate the clinical features of the distal type of CSA and to evaluate the results of surgical treatment.

Fig. 1.
Fig. 1.

Case 10. Preoperative photographs and T2-weighted MR images. The patient could not extend the MP joints of his left hand when the wrist was in extension (dorsiflexion) (A). The patient could not perform finger abduction and adduction with the left hand (B). Multiple stenoses were evident on sagittal MRI (C). Left C6–7 neuroforaminal stenosis can be seen in the axial image (D).

Methods

This study was performed through institutions that participate in the Nagoya Spine Group, all of which obtained institutional review board approval for this study. The medical records of patients who underwent surgical treatment for the distal type of CSA from 1991 to 2013 were reviewed. We diagnosed the patients as having the distal type of CSA if the following criteria were fulfilled: 1) the presence of cervical spondylosis, 2) the presence of muscle impairment of intrinsic hand and/or finger extension muscles), 3) absence of gait disturbance, 4) absence of bladder or bowel dysfunction, and 5) presence of a compressive lesion in the anterior horn of the spinal cord, the nerve root at the intervertebral foramen (neural foramen), or at both sites as seen on axial and sagittal views of MRI or CT myelography. We did not consider whether patients demonstrated sensory disturbance such as radicular pain, numbness or other sensory loss, or exaggerated deep tendon reflexes in the lower extremities for diagnosing the distal type of CSA. When it was difficult to distinguish between CSA and other diseases such as peripheral entrapment neuropathy and motor neuron disease in some patients, we performed preoperative electromyography and nerve conduction studies. Furthermore, when it was difficult to distinguish between CSA and amyotrophic lateral sclerosis (ALS) in some patients, a neurologist was asked to evaluate the patients to ascertain that they did not have motor neuron disease before surgery. Finally, no patient was found to have ALS or other motor neuron disease after surgery.

Radiological Studies

The radiological studies included plain radiographs, MRI, and CT myelography of the cervical spine. T1-weighted and T2-weighted sagittal and axial images were obtained. T2-weighted MR images were examined for the presence of a high-intensity area within the spinal cord. We determined the compressive lesion site of the distal type of CSA with an axial view on MRI or CT myelography. We identified lesions in the anterior horn of the spinal cord, the nerve root at the foramen, or at both sites, and considered possible corresponding lesions through radiological findings. All patients underwent postsurgical radiographic, CT, and MR imaging of the cervical spine to confirm appropriate decompression and to follow postoperative changes of spinal alignment.

Surgical Protocol

When conservative treatment was not effective or the neurological status worsened, we performed surgery (with the patient's consent). When patients had stenosis at 3 or more levels, we performed laminoplasty, whereas patients with stenosis at only 1 level were treated with anterior cervical discectomy and fusion (ACDF) and decompression. (There were no patients with stenosis at only 2 levels in this case series, but in such cases we choose between laminoplasty and ACDF.) If the patient had severe kyphosis, we performed posterior spinal fusion with laminectomy using instrumentation. We added foraminotomy with laminoplasty or posterior fusion when there was foraminal stenosis causing root impingement, as demonstrated on axial MRI or CT myelography.

Evaluation of Surgical Outcome

To evaluate the effect of surgical treatment, we used manual muscle testing (MMT), and improvements in muscle strength of the most atrophic and impaired muscles were classified into 4 grades: “excellent,” full recovery to Grade 5; “good,” 1 grade of recovery; “fair,” no improvement; “poor,” worsening effect.

Results

A total of 17 patients (16 men and 1 woman) with the distal type of CSA underwent surgical treatment. The patients' mean age was 56.3 years (range 39–69 years). The mean duration of follow-up was 35.2 months (range 9–53 months). The duration of symptoms before surgery averaged 11.8 months (range 0.8–87.2 months). A high-intensity area on T2-weighted MRI was confirmed in 5 of 17 patients. Spinal canal stenoses were found at an average of 2.7 vertebral levels (range 1 to 5 levels). Impingement at the compressive lesion site was at the anterior horn of the spinal cord in 14 patients and at both the anterior horn and nerve root in 3 patients. Twelve patients were treated with laminoplasty (plus foraminotomy in 1 case), 3 patients received ACDF and 2 patients underwent posterior spinal fusion with laminectomy and foraminotomy. Postoperative and follow-up lateral radiographs of the cervical spine did not demonstrate any severe deterioration of spinal alignment. Furthermore, postoperative MRI and CT demonstrated adequate decompression of spinal canals and neural foramina in all patients.

Evaluation of Neurological Recovery at Final Follow-up

The mean MMT grade was 2.4 (range 1–4) preoperatively and 3.4 (range 1–5) at the most recent follow-up evaluation. The surgical results were excellent in 7 cases, good in 2, fair in 8, and poor in none (Table 1). Of the 10 patients with a preoperative MMT grade lower than 3 (Table 2), 3 (30%) had an excellent recovery, whereas 4 (57%) of the 7 patients with a preoperative MMT grade of 3 or greater (Table 3) had an excellent recovery. The time required for patients who had excellent surgical outcomes to achieve full recovery averaged 4 months (range 3 days–18 months).

TABLE 1:

Characteristics and clinical findings of cases of the distal type of CSA

VariableValue
no. of patients17
age (yrs)
 mean56.3
 range47–69
male/female ratio16:1
duration of FU (mos)
 mean35.2
 range9–53
duration of Sx (mos)
 mean11.8
 range0.8–87.2
preop MMT grade2.4
levels of stenosis2.7
HIA on T2-weighted MRI5
compression site of lesion
 AH14
 NR0
 AH & NR3
surgical procedure
 LP11
 LP + FR1
 ACDF3
 PSF + LN + FR2
surgical outcome
 excellent7
 good2
 fair8
 poor0

AH = anterior horn of cord; FR = foraminotomy; FU = follow-up; HIA = high-intensity area; LN = laminectomy; LP = laminoplasty; NR = nerve root; PSF = posterior spinal fusion; Sx = symptoms.

TABLE 2:

Group 1—patients with preoperative MMT grade below 3*

Case No.Age (yrs), SexMMT GradeSurgical OutcomeSx Duration (mos)HIA on T2 MRINo. of Levels of StenosisCompressive Lesion SiteTime to Recovery (days)Surgical Procedure
PreopFinal FU
147, M23good3.0no2AH + NR545LP
255, M22fair12.2no2AHLP
363, M15excellent1.2no1AH30ACDF
469, M22fair1.7no4AHLP
563, M11fair7.7no4AHLP
658, M25excellent0.8no4AH3LP
762, M25excellent1.0no1AH14LP
847, M22fair11.0no2AHLN + PSF + FR
951, M22fair18.0no3AH + NRLN + PSF + FR
1062, M11fair4.0yes4AH + NRLP + FR

Cases are numbered according to MMT grades for purposes of data presentation and not in the order in which the patients presented.

TABLE 3:

Group 2—patients with preoperative MMT grade of 3 or greater

Case No.Age (yrs), SexMMT GradeSurgical OutcomeSx Duration (mos)HIA on T2 MRINo. of Levels of StenosisCompressive Lesion SiteTime to Recovery (days)Surgical Procedure
PreopFinal FU
1152, M33fair10.0yes3AHLP
1251, M34good18.2no1AH240ACDF
1362, F45excellent4.0yes3AH90LP
1439, M35excellent16.2no4AH150LP
1568, M33fair87.2yes2AHLP
1652, M45excellent3.0yes5AH90LP
1756, M45excellent1.9no1AH90ACDF

Discussion

The distal type of CSA is characterized by weakness of the muscles that control hand function, such as intrinsic hand muscles or finger extension muscles; the first dorsal interosseous muscle is often affected. Tanaka describes the inability to extend the metacarpophalangeal (MP) joint with the wrist in extension (dorsiflexion), referring to this sign as “drop finger,” as pathognomonic for the distal type of CSA.10 Furthermore, these patients were incapable of finger abduction and adduction due to atrophy of the interosseous muscles. Several authors reported on the pathogenetic mechanism of muscle atrophy caused by CSA as impingement against the anterior horn of the spinal cord or impingement on the nerve root due to the cervical spondylosis.4,7 Ando demonstrated that distal type CSA was caused by damage to the C-8 segment of the spinal cord or a C-8 nerve root disorder.1 On the other hand, Tanaka reported on 12 patients with “drop finger” treated by foraminotomy, and noted that the C-8 nerve root was found to be damaged in 10 of these 12 cases.10 Kaneko et al. mentioned that widespread gray matter lesions, with less involvement of the lateral posterior spinal column, contribute to the pathophysiology of distal-type CSA.6

In the current study, although most of the patients suffered from impingement against the anterior horn of the spinal cord, we performed foraminotomy in 2 patients who had foraminal stenosis, which meant there also was nerve root impingement. Thus, since we found impingement at both the anterior horn of the spinal cord and the nerve root, we considered our surgical options on a case-by-case basis as to whether there was canal stenosis or foraminal stenosis causing the distal type of CSA.

The symptoms of the distal type of CSA are similar to those of other diseases, including motor neuron diseases, posterior interosseous nerve palsy, cubital tunnel syndrome and rupture of the digital extensor tendons, and differentiation from these diseases is of considerable significance. Differentiating CSA from motor neuron diseases such as ALS is especially important. ALS is a debilitating disease with varied etiology characterized by progressive weakness, muscle atrophy, and fasciculations because of the selective damage to both upper and lower motor neurons. Generally, ALS is seen in middle-aged or older patients—as is cervical spondylosis. Thus, patients with early-stage ALS whose manifestations begin with muscle atrophy in the upper extremities can be difficult to distinguish from patients with CSA. However, atrophy of the tongue or fasciculations, dysarthria, dysphagia, diffuse muscle atrophy, and weakness of neck flexor muscles are considered pathognomonic for ALS but not for CSA. (Furthermore, in Japan it has recently been recognized that patients with CSA may indeed have sensory disturbance; apparent sensory disturbance from the segmental lesion of the spinal cord only occurs in cervical spondylosis and not in ALS.1) However, if ALS cannot be definitively ruled out, surgery should not be performed, and the case should be managed with careful observation for signs of progression. Furthermore, Ando advocated following these patients carefully and waiting to operate if there is difficulty differentiating motor neuron disease from CSA, as that the generalized muscle atrophy or weakness of motor neuron disease might be exacerbated by surgery.1

In posterior interosseous nerve palsy, sensory disturbance does not exist, and finger abduction and adduction is still possible, whereas “drop finger” (inability to extend the MP joint with the wrist in extension) is a common symptom with the distal type of CSA. In cubital tunnel syndome, intrinsic muscles of the hand weaken (as in CSA), but the MP joint can generally be extended, claw hand usually occurs, and numbness is usually limited to the ulnar side of the ring finger. In contrast, rupture of the digital extensor tendons is typically seen in rheumatoid arthritis patients who have inflammation on the ulnar side of the wrist joint, and they typically maintain finger abduction and adduction but cannot extend the MP joint. In the current study, we carefully evaluated all patients before and after surgery; no patient was subsequently diagnosed as having motor neuron disease after surgery or in follow-up.

Several authors have discussed surgical outcomes for the distal type of CSA (Table 4). Uchida et al. reported that surgical outcome in patients with the distal type of muscle atrophy was inferior to outcome in patients with the proximal type, with the distal type being associated with less muscle power improvement.12 Similarly, in our previous study, we reported that the distal type of CSA was a significant factor influencing a poor surgical outcome (in comparison with the proximal type of CSA).11 Furthermore, Fujiwara et al. reported that muscle power improved in 92% of the proximal-type cases but improved in only 38% of the distal-type cases. They explained that one possible reason for a poor surgical outcome of the distal type of CSA was that the distal type is characterized by impingement against the anterior horn, which does not have the ventral nerve root's ability to regenerate. Also, the distance to the atrophied hand muscles is much longer than the distance to the deltoid muscle (proximal type of CSA), and this may affect the recovery rate.4 On the other hand, Srinivasa and Rajshekhar reported on 7 male patients with distal-type CSA treated by central corpectomy, and they illustrated that the outcome after central corpectomy was good and long lasting except in one patient who had a coexistent motor neuron disease. Thus, they mentioned that distal-type CSA should be differentiated from motor neuron disease on the basis of subtle sensory symptoms or signs in the upper limbs.9 Nakashima et al. demonstrated that the surgical outcome in cases of CSA may be poor due to progressive axonal degeneration when the amplitude of motor evoked potentials was less than 10% preoperatively compared with the normal side.8 However, Fujiwara et al. advocated caution in ruling out the possibility of recovery, since there was no significant difference in surgical outcome between patients having greater than 10% amplitude and patients with less than 10% amplitude on preoperative Erb point-stimulated compound muscle action potentials (CMAPs), and some patients with less than 10% amplitude also recovered.3,4

TABLE 4:

Summary of literature on operative treatment and outcome in patients with the distal type of CSA*

Authors & YearNo. of PtsAge (yrs)Sex (M/F)FU (mos)MMT GradeOutcomeSurgery
PreopFU
Fujiwara et al., 2006857.4NRNR3.13.63 (38%) improvedLP in 3
LP + FR in 5
Srinivasa & Rajshekhar, 2009746.47/08.3NRNR6 (86%) improvedcentral corpectomy in 7
Uchida et al., 20091458.5NR28.82.42.75 (36%) improvedLP in 7
ant decompression in 7
present study1756.316/135.22.43.47 (41%) improvedLP in 11
LP + FR in 1
ACDF in 3
PSF + LN + FR in 2

Values for age, duration of follow-up, and MMT grade are means. ant = anterior; NR = not reported; Pts = patients.

In the present study, excellent recovery was achieved in 7 (41%) of 17 cases overall, but in the subgroup of patients with a preoperative MMT grade less than 3, excellent recovery was achieved in only 30% (3 of 10 cases). Also, most patients who had more than 3 months' preoperative symptom duration had poor surgical outcomes. Thus, the timing of surgery is important to allow the best opportunity for a good recovery after surgery. At this point, however, the optimal timing of surgery is still unclear; future studies are needed with regard to the appropriate timing of surgical treatment for the distal type of CSA.

Several limitations of our study must be acknowledged. First, this was a retrospective study, thus there was no standardized treatment protocol or surgical technique. Second, our patient sample size is also small, similar to the other studies on the distal type of CSA. However, the distal type of CSA is a rare condition, and it is quite difficult to collect large numbers of cases for a study.

Conclusions

We have reported on the patients' clinical characteristics and the surgical results obtained in 17 cases of the distal type of CSA. The distal type of CSA is a rare condition that is characterized by weakness of the hand muscles. It is important to differentiate CSA from conditions such as motor neuron disease and peripheral nerve disorders. Our results indicate that most of the patients in this case series suffered from impingement of the anterior horn of the spinal cord, and surgical outcome was fair in about half of the case series.

Acknowledgments

We are grateful to all the staff of the Nagoya Spine Group for allowing us to study their patients, and we also wish to thank I. Yamauchi for his assistance with data collection and Isaac Karikari, M.D., for assistance with the manuscript preparation.

Disclosure

The authors report no conflict of interest the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: Imagama, Tauchi. Acquisition of data: Tauchi, Inoh, Yukawa, Kanemura, Sato, Sakai, Kamiya, Yoshihara, Ito, Ando, Muramoto, Matsui, Matsumoto, Ukai, Kobayashi, Shinjo, Nakashima, Morozumi. Drafting the article: Tauchi. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Imagama. Study supervision: Ishiguro.

This article contains some figures that are displayed in color online but in black-and-white in the print edition.

References

  • 1

    Ando T: [The signs and symptoms of cervical spondylotic amyotrophy.]. Sekitsui Sekizui 22:110411092009. (Jpn)

  • 2

    Brain WRNorthfield DWilkinson M: The neurological manifestations of cervical spondylosis. Brain 75:1872251952

  • 3

    Fujiwara YSumida TFujimoto YTanaka N: [Posterior decompression for cervical spondylotic amyotrophy.]. Sekitsui Sekizui 22:112511322009. (Jpn)

    • Search Google Scholar
    • Export Citation
  • 4

    Fujiwara YTanaka NFujimoto YNakanishi KKamei NOchi M: Surgical outcome of posterior decompression for cervical spondylosis with unilateral upper extremity amyotrophy. Spine (Phila Pa 1976) 31:E728E7322006

    • Search Google Scholar
    • Export Citation
  • 5

    Inui YMiyamoto HSumi MUno K: Clinical outcomes and predictive factors relating to prognosis of conservative and surgical treatments for cervical spondylotic amyotrophy. Spine (Phila Pa 1976) 36:7947992011

    • Search Google Scholar
    • Export Citation
  • 6

    Kaneko KTaguchi TToyoda KKato YAzuma YKawai S: Distal-type cervical spondylotic amyotrophy: assessment of pathophysiology from radiological findings on magnetic resonance imaging and epidurally recorded spinal cord responses. Spine (Phila Pa 1976) 29:E185E1882004

    • Search Google Scholar
    • Export Citation
  • 7

    Keegan JJ: The cause of dissociated motor loss in the upper extremity with cervical spondylosis. J Neurosurg 23:5285361965

  • 8

    Nakashima HUchida KKobayashi SYayama TBaba H: [Pathology of proximal and distal type cervical spondylotic amyotrophy.]. Chubu Seisai 52:5015022009. (Jpn)

    • Search Google Scholar
    • Export Citation
  • 9

    Srinivasa Rao NVRajshekhar V: Distal-type cervical spondylotic amyotrophy: incidence and outcome after central corpectomy. Clinical article. J Neurosurg Spine 10:3743792009

    • Search Google Scholar
    • Export Citation
  • 10

    Tanaka Y: [Drop fingers caused by cervical radiculopathy.]. Sekitsui Sekizui 18:5785832005. (Jpn)

  • 11

    Tauchi RImagama SInoh HYukawa YKanemura TSato K: Risk factors for a poor outcome following surgical treatment of cervical spondylotic amyotrophy: a multicenter study. Eur Spine J 22:1561612013

    • Search Google Scholar
    • Export Citation
  • 12

    Uchida KNakajima HYayama TSato RKobayashi SKokubo Y: Anterior and posterior decompressive surgery for progressive amyotrophy associated with cervical spondylosis: a retrospective study of 51 patients. Clinical article. J Neurosurg Spine 11:3303372009

    • Search Google Scholar
    • Export Citation
  • 13

    Yanagi TKato HSobue I: [Clinical characteristics of cervical spondylotic amyotrophy.]. Rinsho Shinkeigaku 16:5205281976. (Jpn)

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Article Information

Contributor Notes

Address correspondence to: Shiro Imagama, M.D., Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa, Nagoya, 4668550 Japan. email: imagama@med.nagoya-u.ac.jp.Please include this information when citing this paper: published online June 13, 2014; DOI: 10.3171/2014.4.SPINE13681.
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    Case 10. Preoperative photographs and T2-weighted MR images. The patient could not extend the MP joints of his left hand when the wrist was in extension (dorsiflexion) (A). The patient could not perform finger abduction and adduction with the left hand (B). Multiple stenoses were evident on sagittal MRI (C). Left C6–7 neuroforaminal stenosis can be seen in the axial image (D).

References
  • 1

    Ando T: [The signs and symptoms of cervical spondylotic amyotrophy.]. Sekitsui Sekizui 22:110411092009. (Jpn)

  • 2

    Brain WRNorthfield DWilkinson M: The neurological manifestations of cervical spondylosis. Brain 75:1872251952

  • 3

    Fujiwara YSumida TFujimoto YTanaka N: [Posterior decompression for cervical spondylotic amyotrophy.]. Sekitsui Sekizui 22:112511322009. (Jpn)

    • Search Google Scholar
    • Export Citation
  • 4

    Fujiwara YTanaka NFujimoto YNakanishi KKamei NOchi M: Surgical outcome of posterior decompression for cervical spondylosis with unilateral upper extremity amyotrophy. Spine (Phila Pa 1976) 31:E728E7322006

    • Search Google Scholar
    • Export Citation
  • 5

    Inui YMiyamoto HSumi MUno K: Clinical outcomes and predictive factors relating to prognosis of conservative and surgical treatments for cervical spondylotic amyotrophy. Spine (Phila Pa 1976) 36:7947992011

    • Search Google Scholar
    • Export Citation
  • 6

    Kaneko KTaguchi TToyoda KKato YAzuma YKawai S: Distal-type cervical spondylotic amyotrophy: assessment of pathophysiology from radiological findings on magnetic resonance imaging and epidurally recorded spinal cord responses. Spine (Phila Pa 1976) 29:E185E1882004

    • Search Google Scholar
    • Export Citation
  • 7

    Keegan JJ: The cause of dissociated motor loss in the upper extremity with cervical spondylosis. J Neurosurg 23:5285361965

  • 8

    Nakashima HUchida KKobayashi SYayama TBaba H: [Pathology of proximal and distal type cervical spondylotic amyotrophy.]. Chubu Seisai 52:5015022009. (Jpn)

    • Search Google Scholar
    • Export Citation
  • 9

    Srinivasa Rao NVRajshekhar V: Distal-type cervical spondylotic amyotrophy: incidence and outcome after central corpectomy. Clinical article. J Neurosurg Spine 10:3743792009

    • Search Google Scholar
    • Export Citation
  • 10

    Tanaka Y: [Drop fingers caused by cervical radiculopathy.]. Sekitsui Sekizui 18:5785832005. (Jpn)

  • 11

    Tauchi RImagama SInoh HYukawa YKanemura TSato K: Risk factors for a poor outcome following surgical treatment of cervical spondylotic amyotrophy: a multicenter study. Eur Spine J 22:1561612013

    • Search Google Scholar
    • Export Citation
  • 12

    Uchida KNakajima HYayama TSato RKobayashi SKokubo Y: Anterior and posterior decompressive surgery for progressive amyotrophy associated with cervical spondylosis: a retrospective study of 51 patients. Clinical article. J Neurosurg Spine 11:3303372009

    • Search Google Scholar
    • Export Citation
  • 13

    Yanagi TKato HSobue I: [Clinical characteristics of cervical spondylotic amyotrophy.]. Rinsho Shinkeigaku 16:5205281976. (Jpn)

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