[Myelopathies caused by dorsal spinal canal spondylotic stenosis. 3 cases and a review of the literature].

Thoracic spondylotic myelopathies are exceptional, only 29 observations could be found in the literature; we intend to describe three new cases here. The patients, two women and one man, 64, 69 and 72 years old, complained of weakness of the lower limbs, more marked on one side, which had been progressing slowly from several months to eight years. Examination revealed asymmetrical paraparesis with distal sensitivity deficits without thoracic sensory level. In the first case, the myelography remained virtually unchanged in front of T11, T12; in the second and third cases, there was slight extradural compression at T9 and T10 respectively. Magnetic Resonance Imaging (M.R.I.) performed in two patients was evocative of a thoracic disk herniation. A chest CT scan enabled us to establish correct diagnosis: in the three cases irregular hypertrophy of the posterior elements was evident at T11 and T12, T9 and T10, T10 and T11 respectively, with osteophytes originating in the articular process and deeply embedded in the spinal canal. Decompressive laminectomy associated with medial facetectomy resulted in the gradual improvement of walking in all three patients. Myelography and MRI are both useful in demonstrating the level compression, usually situated in the low thoracic spine, however only the CT allows differential diagnosis with other etiologies, especially anterior compression such as disk herniation.