This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
A dissociated sensory loss is seen in 
Select and explain. 
A. Syringomyelia, B. Vitamin B12 deficiency, C. Transverse myelitis, D. Pellagra
A: Syringomyelia
Answer: A: Syringomyelia 
Explanation: Impairment of pinprick and temperature appreciation but relative preservation of light touch, position sense and vibration senseA dissociated sensory loss can reflect spinothalamic tract involvement in the spinal cord, especially if the deficit is unilateral and has an upper level on the torsoBilateral spinothalamic tract involvement occurs with lesions affecting the center of the spinal cord, such as in syringomyeliaRef: Davidson's 21/e p1157