# Sensory Pathways and Sensory Loss Patterns

> Sensory pathways for NEET-PG Medicine covering dorsal column and spinothalamic tracts, dissociated loss, Brown-Sequard syndrome and neuraxis localisation.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/sensory-pathways-and-sensory-loss-patterns
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Adams and Victor's Principles of Neurology; Guyton and Hall Textbook of Medical Physiology
- How to cite: "Sensory Pathways and Sensory Loss Patterns", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/sensory-pathways-and-sensory-loss-patterns

## Direct answer

Sensory pathways carry touch, vibration and joint position through the dorsal columns, and pain and temperature through the spinothalamic tract. The two systems cross at different levels, so a lesion's position along the neuraxis produces a predictable pattern of loss. Dorsal column second-order fibres decussate in the medulla, whereas spinothalamic second-order fibres cross within one or two segments of entry.

## What you must remember

- **Dorsal column pathway:** carries fine touch, vibration and joint position; first-order fibres ascend ipsilaterally and the second-order fibres cross in the medulla.
- **Spinothalamic tract:** carries pain and temperature; second-order fibres cross in the anterior white commissure within one or two segments of entry and ascend on the opposite side.
- **Brown-Sequard syndrome:** hemisection gives ipsilateral loss of posterior column modalities and motor weakness, with contralateral pain and temperature loss a few segments below.
- **Dissociated sensory loss:** loss of pain and temperature with preserved touch and vibration, classic for central cord lesions such as syringomyelia.
- **Syringomyelia:** crossing spinothalamic fibres are damaged first, producing bilateral, cape-like loss over the shoulders and arms, often with hand wasting.
- **Tabes dorsalis:** neurosyphilis damages the dorsal roots and columns, causing sensory ataxia, a positive Romberg test and lightning pains.
- **Thalamic and cortical lesions:** thalamic lesions cause contralateral hemianaesthesia, while parietal cortical lesions abolish stereognosis, graphaesthesia and two-point discrimination.

## A pathway for localising sensory loss along the neuraxis

Sensory examination reveals the level and tract involved, and the pattern of loss tells the examiner whether the lesion is peripheral, spinal, brainstem or cortical. The steps below move from the broadest test to the most specific.

1. **Map the modalities:** Test pinprick, temperature, light touch, vibration and joint position separately, because the answer shows which tract is affected.
2. **Check for a sensory level:** A sharply defined level on the trunk suggests a transverse cord lesion, whereas a stocking-and-glove pattern suggests a length-dependent peripheral neuropathy.
3. **Look for dissociation:** Pain and temperature loss with intact touch and vibration implicates the central grey matter and anterior commissure, as in syringomyelia.
4. **Assess the hemisection pattern:** Ipsilateral loss of position sense and weakness, with contralateral pain loss a few segments below, points to a hemicord lesion.
5. **Test cortical discrimination:** Preserved basic sensation with lost stereognosis, graphaesthesia or two-point discrimination indicates a parietal cortical lesion.
6. **Check the Romberg test:** Swaying with the eyes closed reflects posterior column failure, as in tabes dorsalis or vitamin B12 deficiency.

## Where the questions mislead

Each trap below turns on which tract carries which modality, and on which side the loss appears.

- **Trap:** Expecting Romberg to be positive in a pure spinothalamic lesion — **Correct:** Romberg depends on position sense from the dorsal columns, so a spinothalamic lesion leaves the test negative.
- **Trap:** Locating a cape-like loss to the dorsal columns — **Correct:** cape-like dissociated loss with preserved touch points to syringomyelia, which affects the central grey matter, not the dorsal columns.
- **Trap:** Expecting ipsilateral pain loss in Brown-Sequard syndrome — **Correct:** pain and temperature are lost on the opposite side, a few segments below, because second-order fibres have already crossed.
- **Trap:** Assuming distal vibration loss is always central — **Correct:** a length-dependent peripheral neuropathy also causes distal vibration loss, so reflexes and the overall pattern are checked first.

## Frequently asked questions

### Which sensory modalities travel in the dorsal column pathway?
The dorsal column pathway carries fine touch, vibration sense and joint position sense, also called proprioception. First-order fibres enter through the dorsal roots and ascend on the same side before the second-order fibres cross in the medulla. Loss of these modalities produces sensory ataxia.

### Where does the spinothalamic tract cross to the opposite side?
The spinothalamic tract crosses in the anterior white commissure of the spinal cord, usually within one or two segments of its entry level. Its second-order fibres then ascend in the contralateral lateral spinothalamic tract to the thalamus. This is why pain and temperature loss appears on the opposite side of the body.

### What is dissociated sensory loss and which lesion causes it?
Dissociated sensory loss means pain and temperature are lost while touch, vibration and position sense are preserved. Syringomyelia, a central cord lesion, classically produces it because it destroys the crossing spinothalamic fibres first. The loss typically follows a bilateral cape-like distribution.

### What is Brown-Sequard syndrome?
Brown-Sequard syndrome results from hemisection of the spinal cord, causing ipsilateral loss of touch, vibration and position sense with ipsilateral weakness below the lesion. Pain and temperature are lost on the opposite side a few segments below. It is a classic example of localising a cord lesion from the pattern of loss.

### Why does tabes dorsalis cause a positive Romberg test?
Tabes dorsalis, the late stage of neurosyphilis, damages the dorsal roots and dorsal columns, impairing position sense. Patients then rely on vision to maintain balance, so their sway increases when the eyes close. This sensory ataxia is the basis of the positive Romberg test.