1. Background and Importance
Bilateral C5 palsy is a rare but debilitating complication of multilevel cervical spine surgeries to correct Cervical Spondylotic Myelopathy (CSM) [1, 2, 3, 4, 5]. The incidence of this complication which negatively affects the overall quality of a patient’s life, varies from 0% [6, 7] to 1.4% [8]. David and Rao reported the first example of a bilateral C5 palsy with detailed information in 2006 [9]. Since then, six additional cases, including the current case, have been reported [10, 11, 12, 13, 14].
2. Case Presentation
The initial imaging evaluation of a 49-year-old woman with spastic quadriparesis (Modified Japanese Orthopedic Association [mJOA] score of 12) led to the diagnosis of a multilevel CSM. Her cervical MRI demonstrated a multilevel anterior spinal cord compression, predominantly at the C6-C7 level, within the background of a developmental cervical canal stenosis (Figure 1). She subsequently underwent a C6-C7 Anterior Cervical Disk Fusion (ACDF). This procedure was then followed by a 4-level laminectomy and a C2 to T1 screw rod instrumentation fusion (Figure 2). Intraoperative neuromonitoring, including SSEPs (Somatosensory Evoked Potential) and Motor Evoked Potentials (MEPs), remained stable throughout the procedure. Immediately after the patient’s arousal in the recovery room, she could rise her hands, indicating the newfound integrity of the C5 roots. However, on the second postoperative day, partial paralysis of the deltoid and biceps brachii became evident on both sides of her body. This unexpected alteration was discovered to be compatible with bilateral C5 palsy. By the third postoperative day, the disorder was found to be complete. In the following days, despite the improvement in myelopathic clinical features, her complication did not resolve, and she was ultimately discharged home (Figure 3). At home, after the initiation of routine physical therapy, muscle strength in her deltoids and biceps improved gradually on both sides (Figure 4). However, the complete recovery from this debilitating complication took roughly eight months from start to end (Figure 5). At its summation, her mJOA score became 16.
3. Discussion
Bilateral C5 motor palsy is a rare complication of all multilevel cervical spine decompression surgeries for a CSM [9, 10, 11, 12, 13, 14]. It may become evident immediately following surgery [9, 10, 13]. It can also transpire later, though usually within a few days after the operation [11, 12, 14]. Patients with this complication typically present with weakness of the deltoids and biceps on both sides of the body [9, 10, 11, 12, 13, 14]. About half the affected patients will experience numbness or intractable pain within the shoulder girdle in addition to the aforementioned muscle weakness. The information about these seven cases is presented separately in Table 1. 


Predisposing anatomical facts
The unisegmental innervations of the deltoid muscle will make C5 palsy more clinically evident [1, 2, 3, 4, 5, 6, 7, 8]. The shorter C5 root and its horizontal trajectory than the other cervical roots leave it more vulnerable to traumas and the possible backward shifting of the spinal cord [1, 2, 3, 4, 5, 6, 7, 8].
Predictive radiological factors
Considering some preoperative radiological parameters, including a kyphotic neck, a developmentally narrow canal, and a narrow C4-C5 foramen, postoperative C5 palsy can be reasonably expected [12, 15]. According to Lubelski [16 ], for every 1 mm increase in anteroposterior diameter and corresponding foramen diameter, the odds of developing C5 palsy decreases by 69% [15]. Ossification of the posterior longitudinal ligament and the presence of spinal cord myelopathy at the C4-C5 level have been mentioned as other predictors of C5 palsy [15, 17, 18, 19]. 
Intraoperative factors
The exact cause of C5 palsy is uncertain. It may be due to an intraoperative spinal cord trauma, a possible iatrogenic C5 root injury, excessive lordosis with instrumentation, or the tethering of this nerve from the backward shifting of the spinal cord. It might also result from a poor reperfusion scenario due to widened laminectomy [1, 2, 3, 4, 5, 6, 7, 8, 15, 17, 18].
Prevention
The application of intraoperative transcranial motor neuromonitoring may lower the risk of early-onset C5 palsy observed immediately upon emergence from the anesthesia [20, 21, 22]. According to Bhalodia et al., the sensitivity and specificity of transcranial MEP monitoring for identifying acute-onset deltoid weakness are 100% and 99%, respectively [23]. The sensitivity and specificity of TES-MEPs (transcranial electrical stimulation motor-evoked potentials) have been 100% and 98.4% in the Oya et al. series [24]. With the appearance of an intraoperative change in transcranial MEPs, immediate additional wide foraminotomy and the administration of steroids and, in particular, dexamethasone may help reverse any evolving injury [25, 26,  27]. 
Seldom, postoperative segmental motor paralysis after cervical laminoplasty may occur even if there are no abnormal findings during intraoperative monitoring [28]. However, there is no clear evidence that with intraoperative MEP, one can prevent or predict late-onset C5 palsy [29]. Furthermore, with the avoidance of excessive lordosis and an extensive laminectomy [15, 17, 18, 19], the surgeon may minimize the occurrence of this debilitating complication. The benefit of a C4-C5 foraminotomy in preventing C5 palsy has remained poorly understood [25, 26,  27]. 
Quality of life
Bilateral C5 root palsy negatively impacts the quality of life and can significantly reduce the capacity for self-care [9, 10, 11, 12, 13, 14, 16]. Patients with this complication are usually unable to perform the basic activities of daily living and hence require appropriate home services. Ultimately the overall cost of medical care will increase for those affected [16].
Treatment
There is an overwhelming recommendation to treat unilateral C5 palsy conservatively as “most patients make a full recovery within two years” [1, 2, 3, 4, 5, 6, 7, 8]. This same strategy can also be employed when assessing bilateral cases of C5 palsy [9, 10, 11, 12, 13, 14]. Rigorous physical therapy consisting of a muscle strengthening routine and range of motion exercises for the shoulders and elbows is paramount. This objective is best accomplished at a rehabilitation hospital during the early postoperative period and on an outpatient basis after that [9, 10, 11, 12, 13, 14].
Outcome
With respect to the rarity of this specific clinical scenario, minimal evidence regarding the natural history of this complication exists. Our review shows that less than half of the patients with this diagnosis display a complete recovery [9, 10, 11, 12, 13]. However, it appears that similar to unilateral cases, the recovery rates may largely depend on the magnitude of the postoperative C5 disorder, although this is certainly not a rule [9, 10, 11, 12, 13, 14]. 
4. Conclusion
Regarding the high financial cost, psychological implications, decreased quality of life, and the reduced capacity of self-care, surgeons should be aware of the proper management of this debilitating complication. 

Ethical Considerations
Compliance with ethical guidelines
Written consent was obtained from the patient to publish the history and corresponding radiological images.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Conceptualization and Methodology: Abolfazl Rahimizadeh, Sam Hajaliloo Sami, and Naser Asgari; Data collection: Abolfazl Rahimizadeh, Mahan Amirzadeh, Shahrzad Rahimizadeh, and Sam Hajaliloo Sami; Data analysis and interpretation: Abolfazl Rahimizadeh, Shaghayegh Rahimizadeh, and Naser Asgari; Writing – original draft: Abolfazl Rahimizadeh, Shahrzad Rahimizadeh, Naser Asgari; Data analysis: Walter L. Williamson; Reviewing submitted version of manuscript: Abolfazl Rahimizadeh, Walter L. Williamson, and Naser Asgari; Approving the final version of the manuscript: Abolfazl Rahimizadeh, Sam Hajaliloo Sami, Walter L. Williamson, and Naser Asgari.

Conflict of interest
The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper.



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