Transligamentous extension of herniated disc materials through the ruptured PLL is more important to its reduction in size than is the initial size of the herniated disc. Decrease in herniation ratio of more than 20% seems to correspond to successful clinical outcome.

A prospective and longitudinal investigation concerning clinical outcomes and morphologic changes of large lumbar disc herniations by MR imaging. To compare the clinical outcomes and the natural morphologic changes of between sequestered and large central extruded disc herniations. The spontaneous disappearance or diminution of large herniated lumbar discs in the spinal canal is known. Poor clinical outcome and small changes of herniated discs have been shown for large central extruded disc herniations with conservative treatment. The study population consisted of 22 patients with sequestration and a large central as extrusion established by an MR imaging study. Seventeen (11 patients with sequestration, and 6 patients with a large central extrusion) patients underwent a follow-up MR imaging study. The size of the herniated disc was measured on serial MR imaging studies, and the changes in size were classified into four categories. Clinical evaluations were also performed using a visual analogue scale (VAS), the Oswestry low back pain disability questionnaire, the straight leg raising test (SLRT) and so forth. Both the sequestered and large central extruded disc herniations showed a successful clinical outcome after conservative treatment in 17 of 22 patients (77%) in total: 11 of 13 patients (85%) with sequestered disc herniations, and 6 of 9 patients (67%) with large central extruded disc herniations. VAS and Oswestry disability scoring showed a greater change in the group with sequestration than in the group with large central extrusions. In the group with sequestration, seven patients reported the disappearance of herniated disc materials, and four patients showed a marked decrease in the size of their herniated discs in follow-up MR images. However, in the group with large central extrusions, only two patients showed a decrease in the size of their herniated discs. Large central extruded disc herniations can be treated successfully by conservative treatment. Outcomes seemed to be as good as or slightly inferior to those of sequestered disc herniations. However, a greater morphologic decrease in the herniated discs occurred more frequently for sequestered disc herniations than for large central extruded disc herniations.

Demyelination is characterized by the loss of myelin with the preservation of axons. Demyelinating diseases can be classified into several categories: demyelination due to inflammation, viral infection, osmotic derangements and hypoxic ischemia. In particular, osmotic myelinolysis is representative, and is associated with hyperosmolality, hypokalemia or rapid correction of hyponatremia. Osmotic myelinolysis was reported to be associated with underlying conditions, such as alcoholism, diuretics and malnutrition. A 67-year-old woman with hypertension was scheduled to undergo both total knee replacements (TKR). She was observed to be lethargic with dysphagia and quadriplegia after the second TKR. She had been taking diuretics for a long time, and did not have an adequate amount of food intake due to patient controlled analgesia and a gastric ulcer after the first TKR. A laboratory examination revealed hypokalemia but normonatremia. T2 weighted-MRI revealed abnormal high signal intensity in the basal ganglia and periventricular area. This case was diagnosed with osmotic myelinolysis associated with hypokalemia without an apparent sodium imbalance.

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