Sensory examination: modalities and dermatomes !

Exam technique

A check of touch, pain, temperature, vibration and position sense to find where sensation fails.

Updated 2026-11-01

See it in 3D: Spinal cord · Neck nerve roots · Mid-back nerve roots · Dorsal root ganglia · Sensory cortex · Thalamus

What it is

Sensation travels in two main pathways: the spinothalamic tract (pain and temperature), which crosses in the cord soon after entering, and the dorsal columns (vibration, position and fine touch), which ascend on the same side and cross in the medulla. Testing both and drawing the map of loss (one dermatome, one nerve, stocking and glove, a level or one side of the body) shows the site of the lesion.

Landmark anatomy

Dorsal root ganglion: cell body of the first sensory neuron.
Spinothalamic tract: crosses in the anterior commissure of the cord and ascends in the opposite lateral column.
Dorsal columns: ascend on the same side to the medullary nuclei, cross, and reach the thalamus and the postcentral gyrus.
Dermatome: the skin area supplied by a single root; neighbouring roots overlap.

Technique, step by step

Explain the test with the eyes open, then ask the patient to close them.
Pain: touch with a disposable sharp object and a blunt one in random order and ask 'sharp or blunt?'.
Temperature: apply the cold tuning fork and compare with the other side.
Vibration: place a 128 Hz tuning fork on the big toe joint and ask when it stops; if absent, move up to the ankle and knee.
Position: move the big toe up or down, holding it by the sides, and ask which way it moved.
Work from distal to proximal and from the abnormal to the normal area to mark the border.
Cortical sensation: recognise a coin in the hand (stereognosis) or a number drawn on the palm (graphaesthesia).
Draw the findings on a dermatome chart.

Abnormal findings

Loss of vibration and position with a positive Romberg: dorsal columns (B12 deficiency, tertiary syphilis) or large-fibre neuropathy.
Cape-like loss of pain and temperature over the shoulders and arms with touch preserved: a central cord lesion such as syringomyelia.
Loss in a single dermatome with radiating pain: radiculopathy.
Reduced sensation over one side of the body including the face: a lesion of the opposite thalamus or cortex.

Common errors

Leading the answer ('does it feel less here?') instead of asking neutrally.
Reusing pins: the sharp object is discarded after each patient.
Mapping the whole body in detail when the patient has no symptoms: a distal screen is enough.

Test yourself

Think of the answer, then tap the question to see it.

Which pathway carries pain and temperature, and where does it cross?

The spinothalamic tract, which crosses in the spinal cord shortly after entry and ascends on the opposite side.

Which dermatome covers the umbilicus?

T10.

Which sensory pattern suggests polyneuropathy?

Symmetric distal stocking-and-glove loss that starts in the feet; vibration is often lost first.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of the clinical exam

Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: How To Assess Sensation (MSD Manual Professional Edition, 2024); 16.4 The Sensory and Motor Exams (OpenStax, Anatomy and Physiology 2e, 2022).

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Representative model, for educational purposes only.