Hirayama disease, mainly found in Asia, is a rare cervical myelopathy that predominantly affects young men (male-to-female ratio of 20:1). Due to fact that the disease tends to stabilize naturally within 5 years, conservative treatment remains the mainstay for the treatment. For patients who are intolerant of wearing cervical collars or patients with progressing symptoms, surgical treatment is still required. The aim of surgery for HD patients is to restrict cervical flexion and eliminate compression of spinal cord. Chiba et al. reported that advanced HD patient had successful improvement of daily activities after operative reconstruction. However, as different surgical techniques have been effectively practiced in HD patients, which one is the ideal is still debatable. Arrese et al. performed laminectomy and duraplasty without spinal fusion to increase the room for the spinal cord. Brandicourt et al. reported 3 patients treated by posterior cervical decompression with coagulation of the epidural venous plexus. Although aforementioned posterior approaches brought out satisfying outcomes, posterior decompression destroyed the integrity of spine and compromised the spinal stability. But, to our knowledge, no literature in surgical treatment for HD by ACF had been reported. The purpose of this study was to evaluate the clinical efficacy and feasibility of ACF for HD by means of surgery-related indexes, clinical efficacy, and radiographic parameters.
Lin et al. suggested that anterior decompressive approach can achieve good outcomes and no significant complications for HD patients with disc protrusion, cervical instability, or severe cervical kyphosis. Limitations of anterior cervical fusion are also apparent. Song J et al. suggested that the bone graft fusion may lead to permanent activity limitation and induce degenerative process at adjacent levels due to the biomechanical changes. What is more, to our knowledge, anterior decompressive approach will cause a high rate of pseudarthrosis due to the issue of incomplete decompression, limited visual exposure, and injury to the cord. Due to the absence of discectomy or corpectomy and bone fusion, ACF could significantly reduce intraoperative blood loss and operation time.
In this study, we quantitatively assessed and compared the grip strength of upper extremities, range of cervical flexion, cross-sectional areas of spinal cord, and cervical lordosis before and after surgery.
Wang et al. reported improvement of grip strength after anterior cervical approach, which was also observed in the present study. Koutsis et al. described that spinal cord compression caused by anterior shift of dural sac during neck flection induced the finger tremor in HD patients. Due to the restriction to cervical flexion, spinal cord compression was eliminated after surgery. As a result, 4 patients got resolved tremor, and the other patients stopped progressing in the present study. The symptoms, including oblique atrophy, cold paralysis, fasciculation, were not observed in all HD patients in our study. Xu X et al. demonstrated an increased flexed motion range of cervical spine, which would aggravate the forward displacement of posterior dura mater, and lead to trauma to the anterior portion of the spinal cord for HD patients. Postoperative range of cervical flexed motion was significantly decreased in the present study.
Misra et al. reported that more than two-thirds of HD patients have segmental cord atrophy that was most pronounced at the level of C6 and C7 vertebral body. The cross-sectional areas of spinal cord of C6 and C7 were significantly increased after surgery. The concept of sagittal balance has been proposed for cervical spine treatment. Cervical lordosis is used to determine the sagittal balance of the cervical spine. Improvements of radiographic parameters were observed in terms of the cross-sectional area of spinal and cervical lordosis, indicating ACF can achieve satisfactory outcomes. Therefore, ACF was able to provide favorable clinical efficacy as well as radiographic improvements for HD patients.
The most commonly reported complications associated with the anterior cervical surgical approach are postoperative dysphagia, hematoma and recurrent laryngeal nerve palsy. In our study, no patient occurred severe complications such as postoperative dysphagia, hoarseness, cerebral fluid leakage and infection after surgery. Nevertheless, two patients, felt abnormal sensation of throat occasionally, showed screw loosening. Since HD is a self-limiting disease, ACF can prevent the progression of HD, and then internal fixator could be removed when the disease stabilized in order to reduce the risk of other complications such as dysphagia or esophageal fistula.
There are several limitations to our study. Firstly, this study was a single-center and retrospective study rather than a prospective study which existed selection bias. Secondly, HD is so rare that a small number of patients were enrolled. Thirdly, although our cases showed a satisfactory outcome, it should be prudent when making a decision of surgical interference. Further comparative studies are required to compare surgery with conventional cervical collar therapy.