This short chapter turns sensory physiology around and uses it backwards: given a pattern of sensory loss, where is the lesion? It walks up the sensory neuraxis from a single peripheral nerve through the roots, ganglia, spinal cord, brainstem and thalamus to the cortex, and ends with the three ways sensation is tested. Long questions are not usually set from it; the one that recurs is a short note on Brown-Séquard syndrome, and viva questions on the cord syndromes, thalamic syndrome, cortical lesions and the names of the sensory function tests.
Topics, in the book’s order
- Sensory lesions and sensory function tests · pp. 1037–1039 · asked 3 times
When you’ve read them: Quiz 124 · Sensory Abnormalities, 15 questions.
After this chapter you should be able to
- use what you know of sensory physiology to explain how sensory disorders arise
- name the deficit produced at each level of the sensory pathways
- work out the sensory loss expected from a lesion at any level of the sensory system
- explain the physiological reasoning behind each sensory function test
Viva checklist
- Why localizing the level matters as much as naming the deficit
- Which fibres a compressing lesion picks off first, and which it spares
- Glove and stocking anesthesia: which lesion, and why it is distal
- Why a single root lesion never leaves skin completely numb
- How a dorsal root ganglion lesion differs from a root lesion
- The six cord syndromes, and the part of the cord each destroys
- What Brown-Séquard syndrome is, how it is produced, and its features
- Why the sensory loss in hemisection splits between the two sides
- Dissociated sensory loss: what it means and which lesions cause it
- Which cord syndrome spares proprioception, and why
- Crossed sensory loss, and where in the brainstem it comes from
- Thalamic syndrome: the nuclei involved and its features
- The cortical sensations, and what a cortical lesion does to them
- Topagnosia, astereognosis and sensory neglect
- Name the sensory function tests, and what each one detects