Clinically symptomatic thoracic disc herniations that require surgical intervention are relatively rare.7,14 Patients typically present with symptoms of thoracic myelopathy or radiculopathy.15 An association between sleep apnea and thoracic stenosis as a result of a disc herniation has not been documented in the literature. In this case, delayed diagnosis was caused by both the atypical presentation of sleep apnea as well as the the upper and lower extremity allodynia.5 Allodynia has been associated with thoracic disc herniation – though it is less common.16 When present, allodynia typically occurs at the level of the herniation itself.9 In this patient, both upper and lower extremity involvement in allodynia were atypical. Furthermore, the sleep apnea itself was also atypical.
We acknowledge that it is difficult to associate direct causality of the resolution of the patient’s sleep apnea with his discectomy. It is possible that the resolution of the sleep disturbance was due to the resolution of pain following decompression of the thoracic spinal cord. However, such is unlikely because the patient’s obstructive sleep apnea was documented in sleep studies – and less-likely due to symptoms of pain. It is more likely that the sleep apnea and its resolution is related to the disc herniation and treatment.
Sleep apnea is caused by anatomic or partial obstruction of the airway during sleep.17,18 The estimated prevalence of sleep apnea is around 3% to 7%.19 While studies have associated spinal cord injury with sleep apnea – particularly within the cervical region – there has been little research about the association of sleep apnea and thoracic disc herniation.20 One documented case reported transient onset of central sleep apnea, following cervical laminectomy.21 However, to date, no studies have explored an association between thoracic herniations and such sleep pathology. Because sleep apnea is caused by airway pathology and the thoracic and cervical spinal cord is closely related, it is possible that the relationship between thoracic nerves and chest wall muscles may be involved. T1 through T11 are associated with chest wall movement and there have been studies associating thoracic spinal cord injury with sleep apnea.22–24 It is thought that weakness in chest muscles, caused by spinal cord injury, produces symptoms of sleep apnea. Specific to the cervical region, cervical spine-related sleep apnea is caused by injury to neck muscles that affect airway patency – a pathophysiologic relationship which is reversible upon treatment of the cervical pathology.17 This phenomenon could be applicable to the thoracic region, too. Possibly, thoracic herniation mimicked pathology similar to that induced by spinal cord injury and chest wall muscle strength – as it relates to sleep apnea; the symptoms of sleep apnea were therefore resolved, following resolution of the pressure from spinal cord injury. Without further case reports and studies, however, we are unsure of whether or not this is the underlying pathophysiologic mechanism behind the resolution of apnea in this case report.
Here we presented the case of a patient with thoracic disc herniation treated surgically. The patient presented with sleep apnea as part of his symptomatology – a complaint that was completely resolved, following treatment of the thoracic HNP alone. We hypothesize that the herniation produced symptoms of sleep apnea, in line with the way thoracic spinal cord injury has produced symptoms of sleep apnea. In the case of the thoracic HNP, because it was treatable surgically, the apnea resolved. Additional work needs to be done, in order to explore this relationship further.