Classification of sensation disturbances

1. Big picture

Sensory disturbances are one of the most useful parts of neurological localization. The examiner is not only asking “Is sensation reduced?”, but more importantly:

Which sensory modality is disturbed? Where is the sensory loss on the body? Does the pattern fit a nerve, root, spinal cord tract, brainstem, thalamus, or cortex?

For the exam, the most important idea is that sensory disturbance is classified in two ways:

1. By quality/modality — pain, temperature, touch, vibration, joint position, cortical sensory functions.

2. By anatomical distribution — peripheral nerve, polyneuropathy, radicular, spinal cord, brainstem, hemisensory cortical/subcortical pattern.

The examiner usually wants you to localize the lesion from the sensory pattern.