Sensory syndromes: where the lesion is from the pattern of numbness
- Syndrome
The shape of the area where a patient feels numbness or tingling tells you whether the problem is in a nerve, a root, the spinal cord or the brain.
See it in 3D: Sensory cortex · Thalamus · Medulla oblongata · Spinal cord · Grey matter of the cord · Dorsal root ganglia · Cauda equina · Median nerve
What it is
Sensory symptoms can be negative (numbness, loss of feeling) or positive (tingling, burning, pain from light touch). Because pain and temperature travel in a different pathway from position and vibration, and the two cross at different levels, the map of what is lost and where localizes the lesion. The main patterns are stocking-and-glove, single nerve, dermatomal, sensory level, half-cord, suspended, saddle, crossed and hemisensory.
Key findings
- Paresthesia: tingling without a stimulus; dysesthesia: an unpleasant abnormal sensation; allodynia: pain from a stimulus that is not normally painful.
- Test pain or temperature and vibration or joint position on both sides, from distal to proximal.
- A sensory level on the trunk points to the spinal cord; check the back as well as the front.
- Cortical sensation (stereognosis, graphesthesia, two-point discrimination) is only interpretable if the basic modalities are intact.
- Burning pain in the feet with lost ankle reflexes is the classic picture of diabetic polyneuropathy.
Pathophysiology
- Pain and temperature enter the cord, cross within one or two segments and rise in the spinothalamic tract on the opposite side.
- Vibration and joint position rise on the same side in the dorsal columns and cross in the medulla (medial lemniscus).
- Both pathways reach the thalamus and then the postcentral gyrus of the parietal lobe.
- So a half-cord lesion loses position and vibration on the same side and pain and temperature on the opposite side.
Sensory pattern and lesion site
| Pattern | What is found | Lesion site and examples |
|---|---|---|
| Stocking and glove | Symmetric distal loss, feet before hands; ankle reflexes lost | Length-dependent polyneuropathy: diabetes, alcohol, vitamin B12 deficiency |
| Single nerve territory | Loss in the area of one nerve | Mononeuropathy: median nerve in carpal tunnel syndrome; several nerves in mononeuritis multiplex |
| Dermatomal | A band of loss with pain radiating along it | Root: cervical or lumbar radiculopathy, herpes zoster |
| Sensory level | Loss below a level on the trunk, both sides, with weakness and bladder changes | Complete or near-complete spinal cord lesion |
| Half cord (Brown-Séquard) | Same side: weakness and loss of position and vibration; opposite side: loss of pain and temperature | Hemisection: penetrating trauma, tumor |
| Suspended, cape-like | Loss of pain and temperature over the shoulders and arms with touch preserved | Central cord: syringomyelia |
| Dorsal columns | Loss of position and vibration, positive Romberg, sensory ataxia | Vitamin B12 deficiency (subacute combined degeneration), syphilis |
| Saddle | Loss around the anus, perineum and inner thighs, with bladder and bowel problems | Conus medullaris or cauda equina |
| Crossed | Face on one side, body on the other | Brainstem: lateral medullary (Wallenberg) syndrome |
| Hemisensory | Whole half of the body; cortical sensory loss if the lesion is cortical | Thalamus or parietal cortex: stroke |
Common causes
- Diabetes is the most common cause of polyneuropathy; leprosy remains a cause of patchy nerve loss in parts of Latin America.
- Carpal tunnel syndrome: numbness of the thumb, index and middle fingers, worse at night.
- Herpes zoster and disc herniation cause dermatomal pain.
- Spinal cord compression from tumor, trauma or infection (including tuberculosis of the spine) gives a sensory level.
- A stroke of the thalamus or parietal cortex causes sudden hemisensory loss.
Tests that confirm it
- Nerve conduction studies and electromyography for neuropathies and radiculopathies.
- Glucose or HbA1c, vitamin B12, thyroid function and kidney function in polyneuropathy.
- Urgent spinal MRI when there is a sensory level, saddle loss or new bladder problems; brain imaging for sudden hemisensory loss.
Test yourself
Think of the answer, then tap the question to see it.
Why does a half-cord lesion cause pain loss on the opposite side?
Pain and temperature fibers cross within one or two segments of entering the cord and rise on the opposite side, while position and vibration rise on the same side.
Which pattern suggests syringomyelia?
A cape-like loss of pain and temperature over the shoulders and arms with light touch and position preserved.
What does stocking-and-glove sensory loss suggest?
A length-dependent polyneuropathy, most often from diabetes.
Why is saddle anesthesia urgent?
It suggests compression of the conus medullaris or cauda equina, which can cause permanent bladder, bowel and leg damage without prompt treatment.
Connections
See it in 3D8
The structures of Durgical's 3D anatomy where it is found.
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); Overview of Spinal Cord Disorders (MSD Manual Professional Edition, 2024).
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Representative model, for educational purposes only.