Neurological Exam - Sensory Examination

What are the two sets of sensory modalities?

Primary sensory modalities → processed by the primary sensory cortex

Secondary sensory modalities → depend on the unimodal association area of the parietal cortex

What are the primary sensory modalities?

Pain and temperature

Vibration and proprioception

Light touch

What pathway carries pain and temperature?

Lightly myelinated peripheral nerves → spinothalamic tracts → thalamus → primary sensory cortex

What pathway carries vibration and proprioception?

Thickly myelinated peripheral nerves → dorsal columns → thalamus → primary sensory cortex

What are the secondary sensory modalities?

2-point discrimination

Graphesthesia

Stereognosis

Double simultaneous stimulation

What pathways carry light touch?

Both the spinothalamic tracts and dorsal columns

Why is light touch clinically tested as discriminative touch?

Because discriminative touch is primarily carried through the dorsal columns

Light touch testing direction?

Proximal → distal

Where can abnormal sensation occur?

Unilaterally

In a single dermatome

In the distribution of a peripheral nerve

Along a particular spinal pathway

What does sensory loss in a single dermatome suggest?

Involvement of a single spinal nerve root

What pathway primarily carries discriminative touch?

The dorsal column

What should the patient report during light-touch testing?

When they feel the stimulus

Whether the sensation changes from one side to the other

What pathway carries pain and temperature?

Spinothalamic tracts and small unmyelinated peripheral nerve fibers

What does proprioception measure?

Position sense

In what order should proprioception be tested?

Distal → proximal

How does passive motion testing differ from position sense testing?

Passive motion is a more dynamic test and requires integration of CNS commands to both the right and left extremities

What pathways carry vibration?

Dorsal columns and large, myelinated peripheral nerve fibers

Pain/temp peripheral fibers?

Lightly myelinated/small unmyelinated fibers

Vibration/proprioception peripheral fibers?

Large, thickly myelinated fibers