<prompt> In coarctation of aorta, site of rib notching is?Superior to ribInferior to ribAt sternumAt Vertebra  <response>: Ans. b Inferior to ribCauses of inferior rib notchingCauses of superior rib notching Arterial: aortic coarctation, aortic thrombosis, pulmonary- oligemiaAV malformation, Blalock Taussig shunt, Tetralogy of fallot, absent pulmonary artery and pulmonary stenosis. Venous: AV Malfomations of chest wall, superior vena cava or other central venous obstruction. Neurogenic: Intercostal neuroma, Neurofibromatosis type 1, poliomyelitis. Osseous: Hyperparathyroidism, Thalassemia Poliomyelitis Osteogenesis Imperfecta Neurofibromatosis Marfans Syndrome Collagen vascular disease Hyperparathyroidism. 