Syringomyelia

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Normal cerebrospinal fluid movement around the foramen magnum and cord can be disturbed by crowding, scar, tethering or a mass. Pulsatile pressure then drives fluid into or through cord tissue, forming and enlarging a syrinx. In Chiari I, the cerebellar tonsils descend through the foramen magnum and obstruct flow. Post-traumatic syringomyelia can emerge years after apparently stable spinal injury, while tumour-associated cavities require histological and oncological treatment.

The neurological pattern reflects radial expansion. Crossing pain-temperature fibres lie centrally and are affected early, while posterior columns are initially spared, producing dissociated sensation. Further enlargement reaches anterior horns and segmental roots, then lateral corticospinal and sympathetic pathways. This explains the apparently contradictory combination of wasted areflexic hands, impaired pain sensation and stiff hyperreflexic legs. Cough- or Valsalva-triggered occipital headache suggests associated Chiari but is not specific.

MRI findings and symptoms must be correlated. A narrow central canal prominence can be incidental, while a smaller strategically placed cavity can be symptomatic. The neurosurgical question is whether there is progression and a correctable cause. Decompression, tumour removal, untethering or arachnolysis may restore CSF dynamics; direct shunting is selected when other approaches fail or no correctable obstruction exists and carries blockage, infection and recurrence risks.

Key points

Syringomyelia is a fluid-filled cavity within spinal-cord tissue or the central canal, most often cervical and commonly associated with Chiari I malformation or another obstruction to CSF flow.
Other causes include intramedullary tumour, previous trauma, arachnoiditis, meningitis, tethering and postoperative scarring; the cause must be sought rather than treating the word syrinx as complete.
Expansion across the anterior white commissure disrupts crossing spinothalamic fibres, causing bilateral segmental loss of pain and temperature with preserved vibration and position.
A cervical cavity can create a cape-like sensory loss across shoulders and arms, painless burns or injuries and neuropathic pain, although real patterns are often patchy or asymmetric.
Anterior-horn involvement produces hand weakness, wasting, fasciculation and reduced arm reflexes at the level, while corticospinal expansion causes spastic, brisk legs below.
Horner syndrome, scoliosis and autonomic or trophic hand changes are additional clues; extension into the medulla can impair swallowing, voice, tongue and breathing.
MRI brain and the craniocervical junction plus the whole relevant spinal cord defines the cavity, Chiari anatomy, tumour and CSF obstruction; contrast helps identify an underlying mass.
Cavity size alone does not predict symptoms or mandate surgery. Incidental stable syrinxes may be observed with clinical and MRI surveillance through a specialist plan.
Progressive symptomatic Chiari-associated disease is usually treated by restoring CSF flow with posterior fossa decompression rather than directly shunting the cavity first.
Established cord loss may not reverse after successful surgery, so prevention of progression, injury education, pain care and rehabilitation are realistic goals.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Chiari-related CSF obstruction

Chiari malformation commonly disrupts flow at the foramen magnum and promotes cervical spinal-cord cavity formation over time.

Post-traumatic disease

Spinal injury and scarring alter subarachnoid flow, with a syrinx sometimes enlarging years after the original trauma.

Tumour and arachnoiditis

Intramedullary tumour, meningitis, inflammation and postoperative arachnoid scarring obstruct cerebrospinal-fluid movement and may generate a cavity.

Tethering and developmental disease

Cord tethering and other craniovertebral or spinal abnormalities create abnormal pressure gradients and require cause-directed assessment.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Cerebrospinal-fluid flow obstruction
A block around the cord creates abnormal pulsatile pressure differences between subarachnoid spaces and spinal tissue.
2
Fluid cavity expansion
Fluid enters or accumulates within central cord tissue, progressively enlarging the syrinx along spinal segments over time.
3
Central tract disruption
Expansion first injures crossing spinothalamic fibres, initially causing segmental pain-and-temperature loss with preserved vibration and position.
4
Motor and long-tract extension
Further enlargement damages anterior horns and corticospinal tracts, producing hand wasting at the level and spastic legs below.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Dissociated cape sensation

Pain and temperature are reduced over shoulders, arms or hands while light touch, vibration and joint position are relatively preserved, leading to unnoticed burns or cuts.

Segmental hand motor lossRed flag

Intrinsic hand muscles weaken and waste, reflexes at affected cervical segments fall and fasciculation may appear, despite brisk legs from long-tract involvement below.

Chiari-associated symptoms

Occipital or upper-neck headache worsens with coughing or straining and coexists with imbalance, nystagmus, sensory symptoms or sleep-disordered breathing.

Post-traumatic progressionRed flag

Years after spinal injury, a patient develops new ascending sensory loss, pain, weakness, spasticity or autonomic change above or below the original neurological level.

SyringobulbiaRed flag

Nystagmus, facial sensory change, palatal or tongue weakness, dysphonia, dysphagia and respiratory symptoms suggest extension into the brainstem and require expedited review.

Tumour-associated cavityRed flag

Rapid progression, marked focal pain, cord expansion or an enhancing nodule raises ependymoma, haemangioblastoma or another intramedullary tumour rather than isolated flow disturbance.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
MRI brain and craniocervical junctionFirst step
Why
Identify Chiari I, foramen-magnum crowding, hydrocephalus and brainstem extension that determine cause and operation.
Interpretation and limitations
Measure anatomy in context rather than diagnosing from tonsillar descent alone. Cine CSF-flow imaging may be requested by specialists but does not replace clinical correlation.
02
MRI whole spine with contrast
Why
Map cavity length and diameter and detect tumour, tethering, arachnoiditis, trauma or additional levels.
Interpretation and limitations
An enhancing nodule or disproportionate cord expansion suggests tumour. Compare with prior images and symptoms; radiological enlargement without clinical change still needs specialist interpretation.
03
Modality-specific neurological examination
Why
Demonstrate central dissociation and establish segmental motor and long-tract involvement.
Interpretation and limitations
Map pinprick and temperature separately from vibration and proprioception, then examine hand bulk, reflexes, plantars, gait, Horner signs and trophic injuries.
04
Bulbar and respiratory assessment
Why
Detect high cervical or medullary complications that may threaten airway, sleep and nutrition.
Interpretation and limitations
Use speech-and-language assessment, forced vital capacity, sleep study, ENT or brainstem review according to dysphagia, dysphonia, stridor or apnoea.
05
Neurophysiology when diagnosis is mixed
Why
Distinguish segmental anterior-horn loss from entrapment neuropathy, root disease or motor neurone disease.
Interpretation and limitations
EMG can define denervation but cannot show the cavity or establish its cause; normal studies do not exclude sensory-predominant syringomyelia.
06
Functional and injury assessment
Why
Quantify hand use, gait, pain, scoliosis and burns or joint injury caused by lost protective sensation.
Interpretation and limitations
Inspect skin and joints, record occupational heat and tool exposure and assess autonomic, bladder and bowel change, especially after prior cord injury.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Cervical spondylotic myelopathy

Degenerative compression with hand clumsiness and brisk gait may mimic syrinx, but MRI shows external canal narrowing rather than a central cavity.

Motor neurone disease

Hand wasting and fasciculation without sensory loss can resemble anterior-horn involvement; dissociated sensation and cord imaging support syringomyelia.

Peripheral neuropathy

Length-dependent sensory loss and distal areflexia follow peripheral nerves rather than a cape-like segmental cord pattern.

Intramedullary tumour

Progressive cord enlargement, enhancement and disproportionate pain may reveal a tumour causing or mimicking a syrinx.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01New suspected syrinxMap the cavity and obstructionFirst stepDissociated sensation, segmental hand wasting or mixed arm and leg signs suggest central cord disease.

1Document pain-temperature versus dorsal-column sensation, segmental power and reflexes, long-tract signs, bulbar function, trauma, meningitis, surgery and Valsalva headache history.
2Arrange MRI of brain, craniocervical junction and whole spine with contrast as appropriate, seeking Chiari, tumour, tethering, scar and cavity extent.
3Refer to a specialist neurosurgical service and provide protection advice for burns, pressure and insensate joints while progression and cause are assessed.

02Progressive Chiari syrinxRestore CSF flowSymptoms or objective deficits progress and imaging shows a Chiari-related cavity with foramen-magnum obstruction.

1Confirm that symptoms, neurological change and imaging correlate, assess hydrocephalus and sleep or bulbar risk and discuss realistic recovery goals.
2The neurosurgeon considers posterior fossa or foramen-magnum decompression and dural strategy to restore flow rather than selecting direct cavity drainage by default.
3Repeat examination and MRI after surgery, monitoring wound, CSF leak, infection, headache, swallowing and whether the syrinx shrinks or progression stops.

03Other or stable causeTreat cause or observe deliberatelyA tumour, post-traumatic scar, tethering or an incidental stable cavity is identified.

1For tumour or tethering, coordinate resection, biopsy, oncology or untethering according to pathology and neurological risk; for trauma, assess CSF obstruction and spinal stability.
2AlternativeUse direct syrinx shunting only after specialist assessment of recurrence, blockage and alternative correction, not because a cavity is visually large.
3For incidental stable disease, agree symptom triggers, examination and interval MRI rather than offering no follow-up or unnecessary emergency surgery.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Clarifies why progressive structural disease requires neurosurgical assessment rather than repeated empirical drugs.

No cavity-shrinking medicine

There is no oral or intravenous regimen that reliably removes a syrinx or restores CSF flow.

Symptom relief can coexist with continued cord injury, so improvement in pain must not replace neurological and MRI follow-up.

May reduce burning, shooting or central pain and improve sleep or rehabilitation participation.

Neuropathic-pain treatment

Choose and titrate one formulary agent according to renal function, comorbidity and functional response.

Sedation, falls, anticholinergic burden, dependence and cognitive effects differ; protective sensory loss and weakness will not be restored by analgesia.

Restores flow at the foramen magnum and can stop progression or reduce a Chiari-associated syrinx.

Posterior fossa decompression

A specialist neurosurgical procedure is tailored to Chiari anatomy and CSF-flow obstruction.

Consent covers CSF leak, infection, haemorrhage, neurological injury, persistent symptoms and need for further treatment; established deficits may remain.

Drains selected persistent or progressive cavities when correction of the primary obstruction is impossible or unsuccessful.

Syrinx shunt

Catheter type and destination are selected only by an experienced neurosurgical service.

Blockage, migration, infection, cord injury and recurrence are important, making shunting a cause- and case-specific option rather than first-line routine.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Painless burns and injury

Loss of pain and temperature permits unnoticed skin damage, ulcers and neuropathic joint destruction over time.

Weakness and spastic disability

Anterior-horn and corticospinal injury causes hand atrophy, gait stiffness, falls and loss of independence over time.

Scoliosis and chronic pain

Muscle imbalance and cord distortion contribute to spinal deformity, neuropathic pain and seating difficulties during progression.

Bulbar and respiratory dysfunction

Extension into the medulla can impair swallowing, voice, tongue movement and breathing, creating aspiration and ventilatory risk.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Repeat modality-specific sensory maps, hand bulk and power, arm and leg reflexes, gait and sphincter findings to detect radial or longitudinal progression.
Inspect insensate skin and joints and reinforce heat, sharp-tool, footwear and pressure protection; painless injury can be the main morbidity.
Ask about swallowing, voice, sleep-disordered breathing, cough headache and respiratory change at every high-cervical or brainstem review.
Compare serial MRI cavity dimensions, cord expansion, Chiari anatomy and any enhancing lesion with clinical function rather than treating image size alone.
After surgery, monitor CSF leak, wound, meningism, new deficit and longer-term syrinx response through the neurosurgical schedule.
Escalate rapid weakness, new walking or bladder loss, progressive bulbar symptoms or post-traumatic neurological change urgently.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Sensation dissociates centrally

Crossing spinothalamic fibres lie near the central canal, while dorsal columns are posterior and often preserved until later expansion.

Hands lower, legs upper

A cervical cavity can injure anterior horns at its level and corticospinal tracts below, producing wasted hands with spastic legs.

Trauma has a long memory

Post-traumatic syringomyelia may arise years later, so new neurological ascent after a stable spinal injury deserves fresh whole-spine imaging.

Chiari measurement is contextual

Tonsillar descent alone does not prove symptom causation; crowding, CSF flow, cavity and clinical pattern guide specialist decisions.

Fix flow before drainage

When a correctable obstruction drives the cavity, restoring CSF dynamics is generally more durable than treating the syrinx as an isolated cyst.

Stopping decline is success

Chronic anterior-horn and tract injury may be irreversible even when postoperative imaging improves, so goals must be realistic.

11Common pitfallsFrequent interpretation and management errors.

01
Testing light touch alone and missing segmental loss of pain and temperature.
02
Calling wasted hands peripheral neuropathy without examining legs, plantars and the sensory modality pattern.
03
Attributing every cavity to Chiari and overlooking tumour, trauma, tethering or arachnoid scarring.
04
Recommending surgery solely from syrinx diameter without clinical progression or cause correlation.
05
Shunting a Chiari-associated cavity before considering restoration of foramen-magnum CSF flow.
06
Failing to teach burn and joint protection to someone with lost protective sensation.