Anterior and posterior decompressive surgery for progressive amyotrophy associated with cervical spondylosis: a retrospective study of 51 patients

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The aims of this study were to review the clinicoradiological findings in patients who underwent decompressive surgery for proximal and distal types of muscle atrophy caused by cervical spondylosis and to discuss the outcome and techniques of surgical intervention.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Fifty-one patients (43 men and 8 women) with proximal (37, with arm drop) and distal muscle atrophy (14, with wrist drop) underwent cervical decompression (39 anterior decompressions and 12 open-door C3–7 laminoplasties with microsurgical foraminotomy) for muscle weakness in the upper extremities. The clinical course, type of spinal cord compression, abnormal signal intensity on high-resolution MR imaging, and postdecompression improvement in muscle power were reviewed at a mean follow-up of 2.6 years (range 0.8–9.4 years).</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The most commonly affected vertebrae were C4–5 and C5–6, and C5–6 and C6–7 in patients with proximal or distal muscle atrophy, respectively; the respective numbers of affected vertebrae were 1.5 and 2.2. Transaxial MR imaging showed medial compression of the spinal cord in 20 patients (in 12 with proximal and 8 with distal muscle atrophy), paramedial compression in 22 (17 and 5 patients, respectively), and foraminal compression in 9 (8 and 1 patient, respectively). Increased signal intensity on MR imaging was observed in 85.0, 22.7, and 11.1% of cases of medial, paramedial, and foraminal compression, respectively. Increased signal intensity at the affected muscle segment level was observed in 52.9, 40.0, and 0% of cases, respectively. Sixty-two percent of patients with proximal muscle atrophy gained 1 or more grades of muscle power on manual muscle testing (MMT), whereas 64.3% with distal muscle atrophy failed to gain even 1 grade of improvement. The recovery of muscle power correlated with disease duration and the percent voltage of Erb point or wrist-stimulated muscle evoked potentials but not with preoperative MMT, longitudinal range of spinal cord compression, signal change on T2-weighted MR imaging, or surgical procedure.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Surgical outcome in patients with distal muscle atrophy was inferior to that in patients with proximal atrophy. The distal type was characterized by a long preoperative period, a greater number of cervical spine misalignments, a narrow spinal canal, and increased signal intensity on T2-weighted MR imaging. It is essential to perform a careful neurological evaluation, including sensory examination of the lower limbs, as well as neuroradiological and neurophysiological assessments to avoid confusion with motor neuron disease and to detect the coexistence of amyotrophic lateral sclerosis, especially when surgical treatment of cervical spondylosis is planned. The results of careful physical examination, MR imaging studies, and electromyography studies should be comprehensively evaluated to ascertain the pathophysiology of the muscle atrophy. It is very important to distinguish the pathophysiology caused by nerve root impingements from anterior horn dysfunction when making decisions about treatment strategy. Surgical treatment—with or without foraminotomy—for amyotrophy in cervical spondylosis requires urgent action with regard to human neuroanatomy and neural innervation of the paralyzed muscles.</jats:p></jats:sec>

Prognostic factors for cervical spondylotic amyotrophy: are signs of spinal cord involvement associated with the neurological prognosis?

“…On the other hand, a high signal intensity change on T2-weighted MRI was not associated with the neurological prognosis in patients who required conversion to surgery, similar to some previous studies. 16,17 There were several limitations to the present study that should be kept in mind when interpreting the results. First, the treatment protocol, including the observational follow-up period, indications for surgical treatment and the type of surgery were not unified in the patients, because this was a retrospective study.…”

Cervical spondylotic amyotrophy

“…Difficulty in shoulder abduction, positive arm-drop sign, or positive wrist-drop sign is always found in patients with cervical spondylotic amyotrophy [30,46]. Recently, Ahdab et al [2] reported that a 65-year-old man with cervical spondylotic amyotrophy was referred for a dropped head syndrome because posterior neck and shoulder girdle muscles were atrophic.…”

“…Electromyographic changes in patients with anterior radix or nerve root injury are characterized by fibrillation and positive sharp waves, whereas fasciculation and synchronization are often significant electromyographic findings in motor neuron injury of the anterior horn. However, fasciculation and synchronization are evident in patients with cervical spondylotic amyotrophy [46]. Thus, the anterior horn and motor axons could be damaged in cervical spondylotic amyotrophy.In addition, evoked spinal cord potentials (ESCPs) and cervical motion evoked potentials (MEPs) are useful for diagnosing cervical spondylotic amyotrophy.…”

“…With regard to human neuroanatomy and neural innervation of the paralyzed muscles, decompression of the spinal cord and/or the nerve roots should be undertaken. Uchida et al [46] suggest that surgical treatment of cervical spondylotic amyotrophy requires urgent action. However, Ebara et al [12] suggested that patients with distal cervical spondylotic amyotrophy undergo cervical traction at first and that they should only undergo surgery if there was a certain measure of improvement in grip power, finger pinch, or finger function.…”

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

“…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).…”