# Syringomyelia and Chiari Malformation

> Syringomyelia and Chiari malformation for NEET-PG Medicine covering cape-like dissociated sensory loss, Chiari I anatomy, MRI findings and decompression.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/syringomyelia-and-chiari-malformation
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-08
- Last updated: 2026-10-08
- Reference basis: Adams and Victor's Principles of Neurology; Greenberg's Handbook of Neurosurgery; Bradley's Neurology in Clinical Practice
- How to cite: "Syringomyelia and Chiari Malformation", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/syringomyelia-and-chiari-malformation

## Direct answer

Syringomyelia is a fluid-filled cavity within the spinal cord, classically causing cape-like loss of pain and temperature with preserved light touch and position sense. Chiari malformation type I is downward displacement of the cerebellar tonsils through the foramen magnum, and it is the commonest association of syringomyelia in adults. MRI of the whole spine and craniocervical junction confirms the syrinx, and symptomatic cases are usually treated with foramen magnum decompression.

## What you must remember

- **Dissociated sensory loss:** pain and temperature lost while touch and proprioception are preserved, because the syrinx interrupts the crossing spinothalamic fibres.
- **Cape-like distribution:** loss over the shoulders, upper back and arms, the classic sign of central cord disease.
- **Chiari I:** cerebellar tonsils more than 5 mm below the foramen magnum on MRI, with suboccipital pain and headache worsened by cough or straining.
- **Chiari II:** associated with myelomeningocele and hydrocephalus, with brainstem and medullary kinking, usually presenting in infancy.
- **Other causes:** trauma, arachnoiditis, intramedullary tumours such as ependymoma, and cord infarction must be excluded on MRI.
- **Late features:** wasting of intrinsic hand muscles, Horner syndrome, scoliosis and Charcot joints as the syrinx expands.
- **Surgery:** foramen magnum decompression with duraplasty for symptomatic Chiari I, with syrinx shunting when the cavity persists.

## A route from burns she did not feel to a decompression decision

A 36-year-old woman has two years of reduced pain sensation in both upper arms and hands, and she has accidentally burnt her fingers without noticing. Examination shows loss of pain and temperature in a cape-like pattern, with preserved light touch and joint position sense, and wasting of the intrinsic hand muscles.

1. **Recognise central cord disease:** The cape-like pattern points to central cord disease rather than peripheral neuropathy.
2. **Image the whole spine:** A sagittal T2 MRI of the whole spine and craniocervical junction is performed, and it shows a syrinx that extends over several segments.
3. **Confirm Chiari I:** The tonsils are seen to descend below the foramen magnum, which establishes a Chiari I malformation.
4. **Exclude a tumour:** The MRI is also checked for an intramedullary tumour, which needs a different plan, and for signs of spinal dysraphism.
5. **Decide on surgery:** The decision to operate depends on symptoms. A progressive deficit or disabling pain with the syrinx justifies foramen magnum decompression with duraplasty, while an asymptomatic finding is observed.
6. **Follow the syrinx:** Follow-up MRI tracks whether the syrinx is shrinking or enlarging after surgery.

## Where the sensory picture misleads the candidate

The cape-like dissociated sensory loss is a classic clue, and it is also the main trap.

- **Trap:** Diagnosing syringomyelia from the sensory pattern alone. — **Correct:** Intramedullary tumours, multiple sclerosis and cord infarction can produce a similar pattern, so a full spine MRI is needed first.
- **Trap:** Operating on an incidental Chiari I finding in an asymptomatic adult. — **Correct:** A small tonsillar descent is common and does not by itself justify surgery.
- **Trap:** Confusing Chiari I with Chiari II. — **Correct:** Chiari II is tied to myelomeningocele and hydrocephalus, while Chiari I is a disorder of the adult craniocervical junction.

Students who operate on every syrinx without checking symptoms miss the point of the management question.

## Frequently asked questions

### What is the classic sensory pattern of syringomyelia?

Syringomyelia classically causes dissociated sensory loss, where pain and temperature are lost in a cape-like distribution over the shoulders and arms while light touch and joint position sense are preserved. The syrinx expands in the central cord, where the spinothalamic fibres cross.

### What MRI finding defines Chiari I malformation?

Chiari type I malformation is defined on MRI by cerebellar tonsils that extend more than 5 mm below the foramen magnum. Sagittal imaging also shows crowding at the craniocervical junction, and a syrinx can be assessed on the same study.

### When is surgery indicated in Chiari malformation with syringomyelia?

Surgery is indicated in Chiari malformation with syringomyelia when there is progressive neurological deficit or disabling headache or syrinx-related pain, with foramen magnum decompression as the usual first procedure. Asymptomatic tonsillar descent is generally observed rather than operated.

### How does Chiari II differ from Chiari I?

Chiari II malformation is associated with myelomeningocele and hydrocephalus and usually presents in infancy, whereas Chiari I is an isolated descent of the cerebellar tonsils seen in adults. Chiari II involves more of the brainstem and cerebellum, and surgical planning depends on hydrocephalus and bulbar symptoms.