Radiology

A 30-year-old female presents with acute onset weakness and sensory deficits in her lower limbs. MRI of the cervical and thoracic spine is performed. Which of the following findings is most characteristic of a demyelinating lesion due to Multiple Sclerosis (MS) in the spinal cord?

A 60-year-old male presents with neurogenic claudication. On lumbar spine MRI, the sagittal diameter of the spinal canal at L4-L5 level is measured. What sagittal diameter measurement is generally considered indicative of absolute lumbar spinal stenosis?

A 40-year-old male presents with progressive weakness and sensory changes in his upper limbs. MRI of the cervical spine reveals an intramedullary mass at C4-C5 level. The mass is T1 isointense, T2 hyperintense, shows heterogeneous enhancement, and is associated with a 'cap sign' (hemosiderin rim) at its poles and an associated syrinx. These features are most characteristic of which spinal cord tumor?