What is a cape-like distribution of sensory loss?

It is loss of pain and temperature sensation over the area a cape would cover: the neck, both shoulders, the arms and hands, and the upper trunk. It is bilateral and segmental, so sensation is normal above and below the band, and touch, vibration and position sense are preserved. It points to a lesion in the center of the cervical cord, classically syringomyelia, that damages spinothalamic fibers as they cross in the anterior white commissure. Intramedullary tumors and acute central cord syndrome can produce a similar pattern.

Why are pain and temperature lost but touch preserved in syringomyelia?

Pain and temperature fibers cross to the opposite side in the anterior white commissure, just in front of the central canal, so a cavity expanding from the center of the cord damages them first. Fine touch, vibration and position sense ascend on the same side in the dorsal columns, at the back of the cord, and do not cross until the medulla, so they are spared until late. This split between the two sensory systems is called dissociated sensory loss.

What is the most common cause of syringomyelia?

Chiari I malformation, in which the cerebellar tonsils sit at least 5 mm below the foramen magnum and obstruct CSF flow; the 2022 international pediatric consensus also accepts 3 to 5 mm when a syrinx or peg-like tonsils are present. Other causes include spinal cord injury, often many years earlier, arachnoiditis after meningitis or surgery, intramedullary tumors, tethered cord, and idiopathic cases. A syrinx with no Chiari malformation or injury needs contrast MRI to look for a tumor.

Why does syringomyelia cause weak, wasted hands but spastic legs?

As the cavity widens it destroys anterior horn cells at its own level, typically the cervical segments that supply the hands, causing lower motor neuron signs in the hands and arms: weakness, wasting, fasciculations, claw hand and reduced arm reflexes. It also compresses the lateral corticospinal tracts, which carry fibers to segments below the syrinx, causing upper motor neuron signs in the legs: spasticity, hyperreflexia and Babinski signs. Lower motor neuron signs at the level and upper motor neuron signs below it fit any expanding central cord lesion.

How is syringomyelia diagnosed and treated?

MRI of the brain and entire spinal cord shows the cavity, its extent and any Chiari malformation; gadolinium helps find a tumor and is essential when Chiari I does not explain the syrinx. A stable syrinx without symptoms is usually monitored. A symptomatic or growing syrinx is treated by fixing the cause: posterior fossa decompression, often with duraplasty, for Chiari I; freeing scar tissue after injury or infection; or removing a tumor. Shunting the syrinx is a fallback when these fail.

What is the difference between syringomyelia and central cord syndrome?

Syringomyelia develops slowly, usually with a Chiari I malformation, and causes bilateral cape-like pain and temperature loss, hand wasting and, later, leg spasticity. Acute traumatic central cord syndrome follows a hyperextension injury, classically a fall in an older adult with cervical spondylosis: weakness starts immediately, the arms are much weaker than the legs, the hands are worst, and urinary retention is common. A syrinx is itself one cause of a central cord pattern, and MRI shows the cavity.

Syringomyelia: Cape-Like Sensory Loss, Chiari I & MRI

Syringomyelia is a fluid-filled cavity (syrinx) inside the spinal cord, usually beginning in the cervical cord, and a Chiari I malformation is its most common cause. Because the cavity expands from the center of the cord, it first cuts the pain and temperature fibers crossing in the anterior white commissure, producing bilateral, cape-like loss of pain and temperature over the neck, shoulders, arms and upper trunk while light touch, vibration and position sense are spared (dissociated sensory loss). As it enlarges it adds lower motor neuron (LMN) signs in the hands at the level of the syrinx and upper motor neuron (UMN) signs in the legs below it. MRI of the brain and whole spine makes the diagnosis.

Syringomyelia at a glance

Feature	High-yield facts
What it is	Fluid-filled cavity in the spinal cord, usually starting in the cervical cord; can extend down the cord or up into the medulla (syringobulbia)
First structure damaged	Anterior white commissure: second-order spinothalamic fibers crossing in front of the central canal
Classic sensory sign	Bilateral, segmental, cape-like loss of pain and temperature; light touch, vibration and position spared
Motor signs	LMN at the level (weak, wasted hands, fasciculations, reduced arm reflexes); UMN below (spastic legs, hyperreflexia, Babinski sign)
Other clues	Painless burns or cuts, neuropathic pain, Horner syndrome, scoliosis, Charcot shoulder or elbow, bladder dysfunction
Causes	Chiari I (most common), old spinal cord injury, arachnoiditis after meningitis or surgery, intramedullary tumor, tethered cord, idiopathic
Onset	Insidious, usually between adolescence and about 45; congenital (mostly Chiari-related) cases typically start at 25–40
Diagnosis	MRI of the brain and entire spinal cord, with gadolinium to look for a tumor (essential when Chiari I does not explain the syrinx)
Treatment	Observe most asymptomatic, stable cases; otherwise treat the cause (posterior fossa decompression for Chiari I); shunt the syrinx only as a fallback
Exam twin	Acute traumatic central cord syndrome: hyperextension injury in an older adult, arms weaker than legs

What "cape-like distribution" means

A cape-like distribution is sensory loss over the area a cape or shawl would cover: the neck, both shoulders, the arms and hands, and the upper trunk. Three features define it:

Both sides. Fibers from the left and right cross through the same small midline region, so one central lesion takes out both.
A band, not a level. Sensation is normal above and below the affected segments. Cord compression, transverse myelitis and anterior cord infarcts instead cause loss below a sensory level.
Pain and temperature only. Early on, touch, vibration and joint position are normal: the patient feels the pan handle but not that it is hot.

Other patterns to tell apart: glove-and-stocking loss is a length-dependent polyneuropathy, loss in a single dermatome is a radiculopathy, and loss of all modalities over one side of the body points to the brain.

Lesion that can give a cape	How it presents
Syringomyelia	Insidious over months to years; Chiari I with Valsalva headache
Post-traumatic syrinx	Years after a cord injury; new pain and a rising sensory level
Intramedullary tumor	Progressive; about a third of people with a spinal cord tumor develop a syrinx; the tumor usually enhances with gadolinium
Acute central cord syndrome	Sudden, after a hyperextension injury; weakness dominates, arms more than legs

Why the loss is cape-like and dissociated

Pain and temperature fibers enter through the dorsal root and synapse in the dorsal horn. The second-order neurons cross in the anterior white commissure, just in front of the central canal, and ascend in the opposite lateral spinothalamic tract. A cavity centered on the canal hits these crossing fibers before anything else.

Bilateral: crossing fibers from both sides pass through the damaged midline.
Segmental: fibers from lower segments crossed further down and already run in the lateral spinothalamic tracts near the cord surface, so the legs keep pain and temperature sensation until the cavity is large.
Cape-shaped: a cervical syrinx spans the segments supplying the neck, shoulders, arms and upper trunk.
Dissociated: fine touch, vibration and position sense ascend on the same side in the dorsal columns and do not cross until the medulla, so they are spared until late.
Often asymmetric: the cavity is usually paramedian and irregular, so one side can be worse.

A painless burn or cut may be the first abnormality recognized. Poorly localized, non-radicular neuropathic pain is another typical symptom. For where each tract runs and crosses, see this spinal cord tracts visual hack.

"Dissociated" alone is not specific: anterior cord syndrome and Brown-Séquard syndrome also split pain and temperature from dorsal column sensation. What is specific to a syrinx is that the loss is bilateral and segmental.

What a growing syrinx damages next

Structure	Finding	Where
Anterior white commissure	Bilateral pain and temperature loss (the "cape")	At the syrinx level
Anterior horn cells	LMN: weakness, wasting and fasciculations of the hands and arms, claw hand, reduced biceps and triceps reflexes	At the syrinx level
Lateral corticospinal tracts	UMN: spastic leg weakness, hyperreflexia, Babinski sign	Below the syrinx
Descending sympathetic pathway (cervical or upper thoracic syrinx)	Horner syndrome: ptosis, miosis, anhidrosis	Same side as the damage
Motor neurons to the paraspinal muscles	Progressive scoliosis, which may be the only sign in a child	Spine
Joints that have lost pain protection	Neuropathic (Charcot) joints, especially shoulder and elbow	Upper limb and spine
Bladder pathways	Bladder dysfunction can occur; bowel problems are uncommon until late	Pelvic organs
Dorsal columns	Loss of vibration and position sense	Late, if at all
Medulla (syringobulbia)	Vertigo, nystagmus, facial sensory loss, tongue atrophy and weakness, dysarthria, dysphagia, hoarseness	Lower brainstem

Syringobulbia is rare and is usually a slit-like cavity in the lower brainstem. Map each sign to its nucleus: the spinal trigeminal nucleus (facial pain and temperature loss), the hypoglossal nucleus (tongue wasting), the nucleus ambiguus (dysphagia, hoarseness, dysarthria) and the vestibular nuclei (vertigo, nystagmus). This brainstem rule-of-4 mnemonic places each nucleus.

Causes: Chiari I first

Most syrinxes form where something partly blocks CSF flow, at the foramen magnum or in the spinal subarachnoid space. How fluid enters the cord is debated (water-hammer, pressure-dissociation and piston theories); none is proven. At least half of syrinxes occur with congenital anomalies such as Chiari malformation.

Cause	Key points	Vignette clue
Chiari I malformation (most common)	Cerebellar tonsils ≥5 mm below the foramen magnum (McRae line), or 3–5 mm with a syrinx or peg-like tonsils (2022 international pediatric consensus); a syrinx is reported in 23–80% of Chiari I series	Brief suboccipital headache brought on by coughing or straining
Post-traumatic	Affects about 3–9% of people after spinal cord injury, while MRI follow-up finds a syrinx in up to 30% over 30 years, most without symptoms; diagnosed a median 9–15 years after injury (range 1 month to 45 years); highest risk after complete injuries	New neuropathic pain worse with coughing or straining, a rising sensory level, lost reflexes, new weakness, excessive sweating
Arachnoiditis	Scarring after meningitis or spinal surgery obstructs subarachnoid CSF flow	Past meningitis or spine surgery
Intramedullary tumor	About a third of people with a spinal cord tumor eventually develop a syrinx; ependymoma, glioma, hemangioblastoma (von Hippel-Lindau)	Enhancing nodule on gadolinium MRI
Other	Tethered cord, basilar invagination, myelomeningocele; some cases are idiopathic	No cause found despite contrast MRI

Chiari I can cause no symptoms at all, and when it does they often first appear in the teens or adulthood. Do not confuse it with Chiari II: herniation of the cerebellar vermis and brainstem with a lumbosacral myelomeningocele and, usually, hydrocephalus, recognized at or before birth. Intramedullary tumors are the reason a syrinx without an obvious cause gets contrast; for one of the classic ones, see this ependymoma breakdown.

Diagnosis: MRI, and when contrast is needed

MRI of the brain and entire spinal cord is the test. It shows the cavity (CSF signal), its length and width, tonsillar descent, hydrocephalus and anything blocking CSF flow. The 2022 international pediatric consensus says MRI in Chiari I should include the brain and the whole spinal cord, because a syrinx must always be ruled out.
Gadolinium: Merck and StatPearls include contrast to detect an associated tumor, and the consensus specifically calls for contrast-enhanced MRI when a syrinx is not explained by Chiari I. A syrinx itself does not enhance; an enhancing nodule or mass suggests a tumor.
Cine (phase-contrast) MRI shows CSF flow at the foramen magnum. It is optional: the pediatric consensus calls it helpful but not necessary in every case when checking the result of surgery.
CT myelography is the fallback when MRI is contraindicated.
EMG and nerve conduction studies do not diagnose a syrinx but help exclude a peripheral neuropathy.

Report terms that confuse students:

Term	Meaning
Syrinx	The fluid-filled cavity itself
Syringomyelia	A syrinx in the spinal cord
Syringobulbia	A syrinx in the lower brainstem, usually slit-like
Hydromyelia	A thin, central dilatation of the central canal, usually asymptomatic
Syringohydromyelia	Used because MRI cannot reliably tell a syrinx from hydromyelia
Acquired tonsillar ectopia	Tonsils displaced by hydrocephalus, a mass or low CSF pressure: not Chiari I

Management: observe, decompress or shunt?

The aim is to restore normal CSF flow by treating the cause, not simply to drain the cavity.

No symptoms, stable syrinx: usually monitored rather than treated, with advice to avoid straining activities such as heavy lifting. The natural history of a Chiari-related syrinx is usually benign; spontaneous resolution is common in children and occurs in some adults. One exception in the pediatric consensus: surgery is indicated for an asymptomatic child with Chiari I and a syrinx wider than 5–8 mm.
Symptoms or progression: surgery is usually recommended, because delay risks permanent cord damage.
Chiari I: posterior fossa (foramen magnum) decompression, a suboccipital craniectomy usually including removal of the back of C1 (C1 laminectomy), with or without a dural patch (duraplasty). The syrinx improves or resolves in nearly 80% of patients, but it persists, recurs or worsens in 10–50%.
Post-traumatic or arachnoiditis: free the scarred subarachnoid space (arachnolysis, untethering) and enlarge the dura; this has been reported to work better than shunting, since shunts often clog. Fewer than half of operated patients improve long term.
Tumor: removing a causative tumor almost always eliminates the syrinx.
Shunting the syrinx (syringosubarachnoid, syringoperitoneal or syringopleural) is a fallback for a growing idiopathic syrinx or after the causal operation fails, because block and failure rates are high. Coexisting hydrocephalus is treated first, with a ventricular shunt or endoscopic third ventriculostomy; the Chiari is decompressed afterwards only if symptoms persist.

What current guidance says about Chiari-related disease:

Question	2022 international consensus (children)	2023 CNS guideline (US neurosurgeons)
Chiari I, no symptoms, no syrinx	Surgery not indicated	No prophylactic surgery and no activity restrictions (Grade C)
Chiari I, no symptoms, with syrinx	Surgery indicated if the syrinx is wider than 5–8 mm, or smaller but growing	Not addressed (its no-surgery advice excludes patients with a syrinx)
Chiari I with symptoms	Symptoms are the main indication, whatever the syrinx size	Bony decompression with or without duraplasty may be used first line (Grade C)
Technique when a syrinx is present	Bony decompression plus duraplasty preferred; tonsillar coagulation or resection for very low tonsils or a recurrent or residual syrinx	Tonsillar reduction may be done to improve the syrinx or symptoms (Grade C)
Syrinx shunting	Not among its Chiari options; for a non-Chiari syrinx, only after the causal treatment fails	No formal recommendation
Syrinx not improving	Reoperate children with persistent symptoms and syrinx at 6–12 months	Further surgery may be considered if the syrinx has not improved 6–12 months after the first (Grade B)

The CNS recommendations rest on low-level evidence, mostly Class III. A companion adult consensus from the same 2019 Milan conference (63 statements on definitions, planning, surgery and isolated syringomyelia) was published in 2022.

Outlook: surgery usually halts progression but rarely reverses severe, established deficits, and the syrinx can recur. Motor recovery tracks syrinx shrinkage better than pain or sensory recovery does, and symptoms can improve even when the syrinx shrinks only slightly.

How USMLE tests it: look-alikes

Condition	Setting	Pain and temperature	Vibration and position	Motor and clinchers
Syringomyelia	Insidious; Chiari I or old cord injury	Bilateral, segmental, cape-like loss	Spared early	LMN hands at the level, UMN legs below
Acute central cord syndrome	Hyperextension injury, often a fall, in an older adult with cervical spondylosis	Variable, sometimes cape-like; sacral sensation usually spared	Variable	Arms weaker than legs, worst in the hands; urinary retention
Anterior cord syndrome	Anterior spinal artery infarct (aortic atherosclerosis, dissection, surgical clamping); sudden back pain	Lost below the lesion, both sides	Preserved	Bilateral paralysis below the lesion
Brown-Séquard syndrome	Hemisection: penetrating trauma, multiple sclerosis	Lost on the opposite side	Lost on the same side	Weakness on the same side
Subacute combined degeneration	B12 deficiency, including repeated nitrous oxide exposure	Relatively spared	Lost early; ataxia follows	Later spasticity and extensor plantars; reflexes may be reduced
Tabes dorsalis	Tertiary syphilis, 20–30 years after infection	Lightning pains; deep pain reduced	Lost; Romberg sign	No UMN signs; leg reflexes lost; Argyll Robertson pupils; Charcot knee or hip
ALS	Degeneration of upper and lower motor neurons	Normal	Normal	Mixed UMN and LMN signs with fasciculations
Hydromyelia or prominent central canal	Often an incidental MRI finding	Normal	Normal	Normal; thin central dilatation

Classic traps:

Cape-like loss right after a fall in an older adult with arms weaker than legs is acute central cord syndrome, not syringomyelia.
Hand wasting plus leg spasticity with normal sensation is ALS. Add bilateral pain and temperature loss and it becomes a syrinx (or an intramedullary tumor).
A sensory level with paraplegia and intact vibration after aortic surgery is anterior cord syndrome; the syrinx pattern is a band.
Other splits: pain and temperature lost on one side with vibration and strength lost on the other is Brown-Séquard syndrome; vibration and position loss with spastic legs is subacute combined degeneration; lightning pains with Argyll Robertson pupils mean tabes dorsalis.
Charcot joint location: shoulder or elbow means syringomyelia; knee or hip, tabes dorsalis; foot or ankle, diabetes.
One-sided Horner syndrome, hand wasting and shoulder pain in a smoker is a Pancoast tumor, not a syrinx; there is no bilateral cape.
Tonsils pushed down by a mass or hydrocephalus, or sagging from low CSF pressure, are acquired tonsillar ectopia, not Chiari I.

Worked vignettes

Vignette 1. A 34-year-old woman notices painless burns on both hands from cooking. She has had brief occipital headaches that worsen when she coughs. Pain and temperature sensation are absent over both shoulders and arms, while vibration and joint position sense are normal. The intrinsic hand muscles are wasted, the biceps and triceps reflexes are reduced, and the knee reflexes are brisk with bilateral extensor plantar responses. Which structure was damaged first, and what will MRI most likely show?

Answer: The anterior white commissure; MRI shows a cervical syrinx with cerebellar tonsils ≥5 mm below the foramen magnum (Chiari I malformation).

Reasoning: Bilateral, cape-like pain and temperature loss with intact dorsal column function localizes to the crossing spinothalamic fibers. Hand wasting with reduced arm reflexes means anterior horn damage at the syrinx level; brisk knee reflexes and extensor plantars mean lateral corticospinal involvement below it. Cough headache points to Chiari I. Because she has symptoms and a syrinx, the usual treatment is posterior fossa decompression, often with duraplasty.

Vignette 2. A 46-year-old man with a complete T6 spinal cord injury from a car crash 11 years ago develops burning pain in his upper chest and inner arms that worsens when he coughs. His loss of pain and temperature now extends up to the upper chest, his triceps reflexes have disappeared and his grip is weaker. What is the most likely diagnosis?

Answer: Post-traumatic syringomyelia extending upward from the injury site; confirm it with spine MRI.

Reasoning: Post-traumatic syringomyelia affects about 3–9% of people after spinal cord injury, usually years later, and complete injuries carry the highest risk. Neuropathic pain made worse by coughing or straining is often the first symptom, followed by a rising sensory level, lost reflexes and new weakness. Surgery aims to restore CSF flow by freeing the scarred arachnoid, with duraplasty; shunts frequently fail.

Vignette 3. A 74-year-old man trips and strikes his chin on a table. Within minutes he cannot use his hands. His arms are much weaker than his legs, the weakness is worst in the fingers, he has urinary retention, and sensation is patchy over the shoulders and arms. Radiographs show cervical spondylosis without a fracture. What is the most likely diagnosis?

Answer: Acute traumatic central cord syndrome.

Reasoning: Hyperextension pinches the cord in a narrowed, spondylotic canal, causing the most common incomplete spinal cord injury. Sudden onset after trauma and a dominant motor deficit, worst in the hands, separate it from the slow course of syringomyelia, even when sensory loss is cape-like. Walking and bladder function often recover before hand dexterity.

Key takeaways

A syrinx is a fluid-filled cavity in the cord, usually beginning in the cervical cord; Chiari I is the most common cause.
First lesion: the anterior white commissure, giving bilateral, segmental, cape-like pain and temperature loss with touch, vibration and position spared.
Expansion adds LMN signs in the hands at the level, UMN signs in the legs below, Horner syndrome, scoliosis, Charcot shoulder or elbow, and syringobulbia.
Other causes: old cord injury (years later), arachnoiditis, intramedullary tumor, tethered cord.
MRI of the brain and whole spine, with gadolinium whenever Chiari I does not explain the syrinx.
Asymptomatic and stable: observe. Symptomatic Chiari-related syrinx: posterior fossa decompression, often with duraplasty. Shunt only when the cause cannot be fixed or decompression fails.
Look-alike after a fall in an older adult: acute central cord syndrome.