A case of thoracic disc herniation characterized by marked posture-related dynamic changes in neurological symptoms

Thoracic disc herniation is less common than lumbar and cervical disc herniations. It is usually accompanied by severe myelopathy, which often leads to surgery. Because the thoracic spine is less mobile, thoracic disc herniation is considered to be minimally affected by dynamic spine factors in cases with myelopathy. We experienced a case of thoracic disc herniation (T4/5 and T6/7) characterized by posture-related dynamic changes in neurological symptoms; that is, numbness extending from the trunk to the entire lower limbs was deteriorated in the standing and sitting positions, was relieved in the supine position, and disappeared in the prone position. In addition, the patient reported dysuria with a delay when attempting to urinate in the standing position. Computed tomographic myelography revealed diffuse idiopathic skeletal hyperostosis extending from T3 to T11, and the kyphosis angles at T1 to T11 levels were 68 degrees in the half-sitting position and 58 degrees in the prone position, showing posture-related changes. The patient underwent the posterior fusion in the prone position, by which symptoms disappeared, without undergoing disc herniotomy or laminectomy, and favorable outcomes were achieved. Thoracic disc herniation with marked posture-related neurological symptoms is extremely rare. Here we report a case presentation and literature review of pathophysiology observed in our patient.