Central Nervous System
Stereoanesthesia is due to lesion of-
I. Stereognosis→The ability to identify objects by HANDLING them without looking at them is called stereognosis
II. This information is earned by Posterior column (dorsal column) to the cerebral cortex.
III. Posterior column has two components:
a. Gracilefaciculus→carries information from sacral and lumbar regions.
b. Cuneatefasiculus→carries information from cervical and thoracic regions.
Hence, as definition, stereognosis is the ability to identify objects by handling, and the information from hand goes through cervical and thoracic parts i.e. cuneatefasiculus, therefore lesion of cuneatefasiculus, causes stereoanesthesia. Note that stereognosis has large cortical component, therefore impaired stereognosis is an early sign of damage to cerebral cortex.
a. Dorsal column (Posterior column) → carries sensations for Touch (Fine), pressure, vibration, joint position (proprioception), and two point discrimination.
b. Spinothalamic tract carries sensation for Pain and temperature (by lateral spino thalamic tract); and crude touch and pressure (by ventral spino thalamic tract)