Disassociative sensory loss is seen with :

Ans. is 'a' ie Syringomyelia Syringomyelia is a disease where cavity formation occurs in the spinal cord. As this cavity is usually a extension of the central canal, the Fibres passing from the centre of the spiral cord ie. (Spinothalamic tract) are first to be affected.Spinothalamic tract carries pain & temperature sensation. Therefore these sensation are first to be affected.The tracts which pass from the lateral parts of spinal cord are not affected in the beginning. The sensations carried by these tracts remain intact.So Syringomyelia causes selective loss of pain temperature sensations with sparing of other sensations such as fine touch and proprioception (this is carried by post column which pass in lateral parts of spinal cord) this type of sensory loss is known as dissociative sensory loss.Other important features of SvringomeveliaIn Syringomyelia there is involvement of lower cervical & high thoracic region.The classic presentation is a central cord Syndrome with disassociated sensory loss and areflexic weakness in upper limbs.