This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
Which of the following is not true regarding ossified posterior longitudinal ligament ? 
Select and explain. 
A. Most commonly involves thoracic spine, B. Gradient echo MR sequence may overestimate the canal stenosis, C. MRI is best for diagnosis, D. Low signal intensity on all MR sequences
A: Most commonly involves thoracic spine
Answer: A: Most commonly involves thoracic spine 
Explanation: Ossification of posterior longitudinal ligament (OPLL) : Variable thickness ossification along the posterior margin of veebral bodies resulting in spinal canal stenosis. More common is mid and lower cervical spine MRI is investigation of choice for spinal canal stenosis Ossification is represented as low signal on all MR sequences. In gradient echo due to blooming effect the osteophytes size may be exaggerated resulting in overestimation of spinal canal stenosis.