Could anterior cervical xation be an alternative method in the management of Hirayama disease?

The study aimed to evaluate the clinical ecacy and feasibility of surgical treatment for Hirayama disease(HD) by anterior cervical xation(ACF). From August 2008 to November 2015, 13 patients(12 males and 1 female, average age, 16.3 ± 1.1 years) with HD underwent ACF. Surgery-related indexes, clinical ecacy, and radiographic parameters were used to evaluate the clinical outcomes of surgery. The surgery duration time range from 67 to 128 min(average 89.2 ± 19.9 min)and the blood loss range from 40 to 120 ml(average 68.1 ± 26.3 ml). Four patients got resolved tremor, and the other patients stopped progressing. Grip strength signicantly improved from preoperative 15.6 ± 1.7 kilogram to postoperative 18.6 ± 1.9 kilogram(P < 0.001). The cross-sectional areas of the spinal cord at C6 and C7 levels increased from 0.7 ± 0.1 cm 2 to 0.8 ± 0.1 cm 2 (P = 0.018) and from 0.6 ± 0.2 cm 2 to 0.7 ± 0.1 cm 2 (P = 0.049) respectively. The cervical lordosis increased from 2.4 ± 3.4° to 7.0 ± 3.5°(P = 0.001). The range of cervical exion was signicantly decreased from preoperative 31.3 ± 11.5° to postoperative 14.3 ± 7.5°(P < 0.001). No surgical related complications such as hoarseness, cerebral uid leakage, and surgical site infection were observed after surgery. Two patients, felt abnormal sensation of throat occasionally, showed screw loosening and internal xators were removed nally. Athough screw loosening was observed, ACF could serve as an effective treatment in the management of the HD.


Introduction
Hirayama disease (HD), rst reported in 1959 [7], is also known as juvenile muscular atrophy of the distal upper extremities, which usually affects young males in their second decade. The disorder is featured with progressing muscular atrophy in forearms and hands, followed by a plateau of symptom within 5 years after onset [7]. Symptoms, like cold paralysis, fasciculation, and tremor, are also noted in HD patients [4,18]. The other feature of HD is an anterior shifting of the posterior dural sac during neck exion, which leads to spinal cord compression against the vertebral body. Repetitive microtraumas to the anterior horn motor neurons during neck exion are now considered as the possible pathogenesis of the disorder [10,16]. In view of this, cervical collars, which could restrain the neck exion, have been widely used in the treatment of HD and brought out favorable outcomes [4]. Although cervical collars are regarded as the mainstay of the treatment, surgical interventions are well established as an alternative for HD patients who are in advanced conditions, irresponsive to conservative treatment, or intolerant to cervical collars [5,8,12,15]. Therefore, this study aims to evaluate the clinical e cacy and feasibility of ACF for HD.  [6,20]. Surgery was performed on patients who cannot tolerate the use of cervical collars or with progressing symptoms. Detailed patient information is shown in Table 1.

Operative technique
Surgery was performed under general endotracheal anesthesia. All patients were placed in the supine position with the neck mildly extended. A transverse incision was made in the anterior right side of the neck. Then, tissues were separated layer by layer, until targeted spinal segments were reached. Targeted spinal segments were con rmed by a intraoperative uoroscopy and xed with titanium plate and screws. (Fig. 1) Postoperative management After surgery, we monitored the vital signs of patients and directed them to expel sputum. The drainage tube was removed when the volume of drainage was less than 30 ml/24 h. The patients were allowed to turn in bed on the rst postoperative day, sit with a cervical collar on the second postoperative day, and then encouraged to stand or walk. All patients took X-rays of the cervical spine at one week, three months, six months and twelve months after surgery, and then once a year thereafter. Neuron nutrition drugs (mecobalamin, 1.5 mg/day) were prescribed to accelerate neurological recovery and rehabilitation exercise was carried out for all patients during the early stage of recovery.

Statistical Analysis
All continuous data were presented as mean ± SD. All data were statistically analyzed using SPSS 21.0 software (IBM Corp., Armonk, NY, USA). To compare the preoperative, postoperative clinical and radiological data, the Paired Sample t-test was used, and a p value < 0.05 was considered statistically signi cant.

Discussion
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 exion and eliminate compression of spinal cord. Chiba et al. [3] 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. [1] performed laminectomy and duraplasty without spinal fusion to increase the room for the spinal cord. Brandicourt et al. [2]  Lin et al. [13] suggested that anterior decompressive approach can achieve good outcomes and no signi cant 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. [17] 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 signi cantly reduce intraoperative blood loss and operation time.
In this study, we quantitatively assessed and compared the grip strength of upper extremities, range of cervical exion, cross-sectional areas of spinal cord, and cervical lordosis before and after surgery.
Wang et al. [19] reported improvement of grip strength after anterior cervical approach, which was also observed in the present study. Koutsis et al. [11] described that spinal cord compression caused by anterior shift of dural sac during neck ection induced the nger tremor in HD patients. Due to the restriction to cervical exion, 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. [22] demonstrated an increased exed 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 exed motion was signi cantly decreased in the present study.
Misra et al. [14] 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 signi cantly 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 [9]. 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 e cacy 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 [21]. In our study, no patient occurred severe complications such as postoperative dysphagia, hoarseness, cerebral uid 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 xator could be removed when the disease stabilized in order to reduce the risk of other complications such as dysphagia or esophageal stula.
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.

Conclusion
ACF was able to provide favorable clinical e cacy as well as radiographic improvements for HD patients.
Athough screw loosening was observed, ACF could serve as an effective treatment in the management of the HD.

Declarations Funding
No funding was received for this research.
Availability of data and material (data transparency) All data used by or generated in this study is available from the corresponding author upon reasonable request.
Code availability Not applicable.

Con ict of interest
The authors declare that they have no competing interests.

Ethical approval
This study was approved by the Ethics Committee of First A liated Hospital of Fujian Medical University.

Consent to participate
Signed written informed consents were obtained from all participants before the study.

Consent for publication
All participants gave written informed consent for their personal or clinical details along with any identifying images to be published in this study.

Authors' Contribution
The authors' contributions to this study were as follows: WCW, ZCL and HJZ contributed equally to the study design. WCW, ZCL, RQL and JHL contributed to the data collection and statistical analysis. All authors wrote and approved the manuscript.