The reported overall incidence of myelomeningocele in the British Isles was 2.0–3.5 cases per 1000 births. Since then, the rate has fallen dramatically with 0.15 per 1000 live births reported in 1998, though this decline is partially accounted for because some fetuses are aborted when tests show signs of spina bifida (see Pregnancy screening above). Research
1980 – Fetal surgical techniques using animal models were first developed at the University of California, San Francisco by Michael R. Harrison, N. Scott Adzick and research colleagues. 1994 – A surgical model that simulates the human disease is the fetal lamb model of myelomeningocele (MMC) introduced by Meuli and Adzick in 1994. The MMC-like defect was surgically created at 75 days of gestation (term 145 to 150 days) by a lumbo-sacral laminectomy. Approximately 3 weeks after creation of the defect a reversed latissimus dorsi flap was used to cover the exposed neural placode and the animals were delivered by cesarean section just prior term. Human MMC-like lesions with similar neurological deficit were found in the control newborn lambs. In contrast, animals that underwent closure had near-normal neurological function and well-preserved cytoarchitecture of the covered spinal cord on histopathological examination. Despite mild paraparesis, they were able to stand, walk, perform demanding motor test and demonstrated no signs of incontinence. Furthermore, sensory function of the hind limbs was present clinically and confirmed electrophysiologically.
A large chylothorax may lead to breathlessness or a feeling of pressure in the chest, caused by fluid restricting the expansion of the lungs, although large chylothoraces may remain asymptomatic if the chylothorax has accumulated slowly, as the lungs may have had time to become used to the pressure. Fever or chest pain are not usually associated with chylothorax, as chyle does not generate inflammation by itself.On examination, chylothorax may lead to reduced breath sounds on the affected side, associated with a dull sound when the chest is tapped or percussed. In cases of postoperative chylothorax, the first sign may be persistent drainage from intercostal drains. Large chylothoraces may cause signs related to the loss of nutrients, including features of malnutrition or decreased ability to fight infections. Rapidly accumulating chylothoraces can cause a sudden drop in blood volume, leading to low blood pressure. Causes
There are three main types of chylothorax: traumatic, non-traumatic, and idiopathic. Historically the most common form of chylothorax was non-traumatic, but traumatic chylothoraces now represent the majority of cases, with most arising as postoperative complications of surgery. The most common cause of non-traumatic chylothoraces is cancer. Chylothoraces can also be classified as low- or high-output based on the rate of chyle accumulation: low-output chylothoraces accumulate <500 mL of chyle per 24 hours, while high-output chylothoraces accumulate >1000 mL per 24 hours. Non-traumatic
Malignancies are the most frequent cause of non-traumatic chylothorax. Cancers like chronic lymphocytic leukemia, lung cancer, lymphoma, Kaposi sarcoma, metastatic carcinoma or esophageal cancer are potential causes of chylothorax.