Syringomyelia

1. Clinical Overview

Syringomyelia is a chronic progressive disorder characterized by a fluid-filled cavity (syrinx) within the central spinal cord parenchyma. [1,2] The condition represents a heterogeneous group of disorders with multiple aetiologies, but all share the common pathological feature of cystic cavitation within the cord substance. [3]

The term "syringomyelia" derives from the Greek words "syrinx" (pipe or tube) and "myelos" (marrow), aptly describing the tubular fluid-filled cavity that develops within the spinal cord. [1] This is distinct from hydromyelia, which refers to dilatation of the central canal itself, though the terms are sometimes used interchangeably in clinical practice. [4]

Chiari Type I malformation is the most common cause, accounting for approximately 70% of cases. [5,6] The pathophysiological mechanism involves obstruction of cerebrospinal fluid (CSF) flow at the foramen magnum, creating a pressure differential that drives fluid into the cord substance. [2,7] Other causes include spinal trauma (3-4% of spinal cord injury patients), intramedullary tumours (particularly ependymoma and hemangioblastoma), spinal arachnoiditis, and tethered cord syndrome. [8,9] Approximately 5% of cases remain idiopathic despite thorough investigation. [10]

The clinical hallmark is dissociated sensory loss - a selective impairment of pain and temperature sensation with preservation of light touch and proprioception. [1,11] This distinctive pattern occurs because the expanding syrinx preferentially damages the crossing spinothalamic fibres in the anterior white commissure while sparing the dorsal columns. The resulting "cape-like" or "suspended" distribution of sensory loss over the shoulders, arms, and upper trunk is pathognomonic for syringomyelia. [11,12]

Key Facts

Clinical Pearls

Pearl 1 - Dissociated Sensory Loss: The hallmark of syringomyelia is DISSOCIATED sensory loss - impairment of pain and temperature sensation with preserved light touch and proprioception. This occurs because the syrinx damages the crossing spinothalamic fibres in the anterior white commissure (decussating fibres conveying pain/temperature from the contralateral side), while the dorsal columns (carrying light touch, vibration, and proprioception) remain intact. This is one of the few conditions that produces this distinctive sensory pattern.

Pearl 2 - Cape Distribution: The "cape" or "shawl" distribution refers to the characteristic pattern of sensory loss over the shoulders, upper arms, and upper trunk, resembling a cape draped over the shoulders. This corresponds to the cervical and upper thoracic dermatomes (C4-T2) affected by a cervicothoracic syrinx cavity. The distribution is "suspended"

• not extending to the hands initially, as the syrinx is central and affects crossing fibres at that segmental level.

Pearl 3 - Painless Injuries: Patients with syringomyelia classically present with painless burns, cuts, or injuries to their hands and arms because they cannot feel pain or temperature. Always examine the hands carefully for scars, burns, ulcers, or Charcot joints. Ask specifically about painless injuries - this history is often volunteered when asked directly but missed if not specifically enquired about.

Pearl 4 - Scoliosis as Presentation: Any child or adolescent with progressive scoliosis of unknown cause requires MRI of the entire spine to exclude syringomyelia or other spinal cord pathology. Up to 65-85% of children with Chiari I malformation and syringomyelia have associated scoliosis, and in some cases, scoliosis is the presenting feature before neurological symptoms develop. [13,14] The scoliosis is often rapidly progressive and may not respond to bracing.

Pearl 5 - Chiari I Definition: Chiari I malformation is defined as cerebellar tonsillar herniation of more than 5mm below the foramen magnum (measured as the distance from the tip of the cerebellar tonsils to McRae's line on sagittal MRI). [5,15] Always request MRI brain with dedicated views of the craniocervical junction when syringomyelia is identified on spinal imaging, as identifying the underlying cause is essential for directing treatment.

Pearl 6 - LMN Arms, UMN Legs: A characteristic examination pattern is lower motor neuron signs in the upper limbs (weakness, wasting, areflexia) with upper motor neuron signs in the lower limbs (spasticity, hyperreflexia, extensor plantars). This occurs because the central syrinx first damages the anterior horn cells at the cervical level, producing LMN signs in the arms, then expands laterally to compress the descending corticospinal tracts, producing UMN signs below the level of the lesion.

Pearl 7 - Post-Traumatic Latency: Post-traumatic syringomyelia can develop months to decades after the initial spinal cord injury, with a mean latency of 8-9 years. [8,16] Any patient with previous spinal cord injury who develops new or worsening neurological symptoms requires MRI to exclude syrinx formation.

Pearl 8 - Valsalva Headache: Chiari-associated headache is classically sub-occipital, precipitated or worsened by Valsalva manoeuvres (coughing, sneezing, straining), and may be accompanied by neck pain. This "Chiari headache" is due to tonsillar herniation and impaction at the foramen magnum. [17] Not all patients with Chiari I have headache, and not all have syringomyelia.

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2. Epidemiology

Incidence and Prevalence

Demographics

Aetiological Classification

Risk Factors

Age-Specific Considerations

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3. Pathophysiology

Overview of Syrinx Formation

The exact mechanism of syrinx formation and expansion remains incompletely understood despite decades of research. [2,7,20] Multiple theories have been proposed, and it is likely that several mechanisms contribute depending on the underlying aetiology. The common endpoint is accumulation of fluid within the central cord parenchyma, progressive expansion, and neurological damage.

Chiari I-Associated Syringomyelia: Current Understanding

The most widely accepted theory for Chiari-associated syringomyelia involves CSF flow obstruction and pressure dissociation at the foramen magnum. [2,7,20]

Step 1: Anatomical Obstruction at Foramen Magnum

• Chiari I malformation: cerebellar tonsils herniate more than 5mm below the foramen magnum (below McRae's line) [5,15]
• Tonsillar herniation obstructs the subarachnoid space at the craniocervical junction
• Reduces cross-sectional area available for CSF flow
• Normal CSF pulsations (driven by cardiac cycle and respiration) are impeded

Step 2: CSF Pressure Dynamics

During the cardiac cycle:

• Arterial systole → increased intracranial blood volume → increased intracranial pressure
• Normally, CSF flows freely between cranial and spinal compartments to equilibrate pressure
• With Chiari I, tonsillar herniation acts as a "one-way valve" [2,7]
• CSF can be forced caudally into the spinal subarachnoid space during systole
• Rostral flow back to the cranium during diastole is impeded
• Creates a pressure gradient across the obstructed foramen magnum

Step 3: Pressure Transmission and Fluid Entry into Cord

Multiple proposed mechanisms for fluid entry:

1. Perivascular pump mechanism: Pulsatile pressure forces CSF into the cord via perivascular (Virchow-Robin) spaces [2,20]
2. Central canal entry: Elevated pressure forces CSF into the central canal, which then ruptures into the cord parenchyma
3. Transependymal flow: Pressure gradient drives CSF across the ependymal lining of the central canal
4. Extracellular fluid accumulation: Impaired drainage of extracellular fluid from the cord substance

Cine MRI (phase-contrast CSF flow studies) demonstrates:

• Abnormal to-and-fro CSF flow at the foramen magnum
• Elevated CSF pulsatility in the spinal subarachnoid space
• These abnormalities correlate with syrinx presence and size [7,21]

Step 4: Syrinx Expansion

Once formed, the syrinx expands due to:

• Pulsatile pressure transmission: Each cardiac cycle transmits pressure waves that expand the cavity
• Longitudinal fluid movement: Fluid moves within the syrinx, dissecting along tissue planes
• Progressive tissue destruction: Chronic pressure damages neural tissue, creating more space for expansion
• One-way valve effect: Fluid enters more easily than it exits, causing progressive accumulation

The syrinx typically:

• Originates in the central gray matter of the cervical or cervicothoracic cord
• Extends longitudinally (rostrally and/or caudally)
• May extend over multiple vertebral levels (holocord syrinx in severe cases)
• Can develop septations in long-standing cases

Step 5: Neural Tissue Damage - Anatomical Sequence

The pattern of neurological deficit reflects the anatomical organization of the spinal cord and the central location of the syrinx:

Stage 1 - Central Gray Matter Damage (Earliest)

• Anterior white commissure: Crossing spinothalamic fibres damaged first
• Results in dissociated sensory loss: pain and temperature sensation lost, light touch and proprioception preserved
• Affects dermatomes at the level of the syrinx
• "Cape" or "suspended" distribution in cervical syrinx (C4-T2 dermatomes)

Stage 2 - Anterior Horn Cell Damage

• Syrinx expands into ventral gray matter
• Damages lower motor neurons supplying upper limb muscles (C5-T1 myotomes)
• Produces lower motor neuron signs: weakness, wasting, fasciculations, areflexia
• Particularly affects small hand muscles (C8-T1)
• May produce Charcot arthropathy (neurogenic joint destruction from denervation)

Stage 3 - Lateral Extension

• Further expansion involves lateral white matter tracts
• Lateral corticospinal tracts: Produces upper motor neuron signs in lower limbs (spasticity, hyperreflexia, extensor plantars)
• Spinocerebellar tracts: May cause ataxia (less common)
• Lateral horn (T1-L2): Autonomic dysfunction (if thoracic syrinx)
• Sympathetic outflow (C8-T2): Horner syndrome (ptosis, miosis, anhidrosis) if cervical

Stage 4 - Advanced/Extensive Disease

• Dorsal column involvement (late): Impaired vibration and proprioception
• Extensive white matter damage: Severe quadriparesis or quadriplegia
• Rostral extension to brainstem (syringobulbia): Cranial nerve palsies, respiratory dysfunction, dysphagia
• Descending extension: Progressive myelopathy at lower levels

Non-Chiari Mechanisms

Post-Traumatic Syringomyelia

Develops in 3-4% of spinal cord injury patients, with mean latency 8-9 years. [8,16]

Mechanism:

1. Initial trauma → hemorrhage, ischemia, and necrosis of cord tissue
2. Cystic degeneration of damaged tissue → initial cavity formation
3. Arachnoid scarring and adhesions → CSF flow obstruction
4. Tethering of the cord to the dura → abnormal CSF dynamics
5. Progressive cyst expansion (mechanism unclear; possibly related to continued microtrauma or CSF pulsation)

Clinical features:

• Ascending sensory level (loss of sensation rising above the original injury level)
• Progressive motor weakness
• Increased pain or dysesthesias
• Loss of previously preserved function

Tumour-Associated Syringomyelia

Occurs in 20-40% of intramedullary spinal cord tumours. [9]

Mechanism:

1. Tumour oedema: Vasogenic oedema fluid accumulates in cord
2. Cystic degeneration: Tumours (especially hemangioblastoma, ependymoma) develop cystic components
3. CSF flow obstruction: Tumour bulk obstructs subarachnoid space
4. Venous obstruction: Impaired venous drainage → increased extracellular fluid

Key differentiating features:

• Syrinx cavities associated with tumours often show contrast enhancement of the tumour nodule
• Tumour nodule may be small and easily missed if contrast not given
• Syrinx may be rostral and/or caudal to the tumour ("polar" cysts)

Arachnoiditis-Associated Syringomyelia

Causes of arachnoiditis:

• Bacterial meningitis (especially TB meningitis - classic association)
• Intrathecal chemotherapy (methotrexate)
• Subarachnoid hemorrhage
• Previous spinal surgery
• Myelography with oil-based contrast (historical)

Mechanism:

• Inflammatory scarring and thickening of the arachnoid
• Adhesions obliterate the subarachnoid space
• CSF flow obstruction at the level of scarring
• Pressure differential above and below the obstruction
• Syrinx formation similar to Chiari mechanism

Classification Systems

Milhorat Classification (2000) [10]

Based on communication with fourth ventricle and aetiology:

Anatomical Classification by Location

Valsalva Maneuvers and Symptom Exacerbation

Activities that increase intrathoracic/intra-abdominal pressure temporarily worsen symptoms:

• Coughing, sneezing
• Straining (defecation, heavy lifting)
• Exercise
• Laughing

Mechanism: Valsalva → increased venous pressure → increased CSF pressure → increased syrinx pressure → transient symptom worsening

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4. Clinical Presentation

The clinical presentation of syringomyelia is highly variable, depending on:

• Location of the syrinx (cervical, thoracic, lumbar)
• Extent of the syrinx (number of segments involved)
• Rate of expansion (slow vs rapid)
• Underlying cause (Chiari vs tumour vs post-traumatic)
• Presence of associated conditions (Chiari headache, scoliosis)

Classic Presentation: Cervical Syringomyelia

The textbook presentation is a young adult (25-40 years) with insidious onset of:

1. Painless burns or injuries to the hands
2. Bilateral hand weakness and clumsiness
3. "Cape distribution" sensory loss over shoulders and arms
4. Dissociated sensory loss on examination

However, this classic triad is seen in only about 50% of cases at presentation. [1,11]

Symptoms by System

Symptom Progression Patterns

Pattern 1: Slow Insidious Progression (Most Common)

• Symptoms develop over years to decades
• Gradual progression with periods of stability
• May have long asymptomatic period before presentation
• Example: 30-year-old with 5-year history of progressive hand numbness, recent onset of hand weakness

Pattern 2: Stepwise Progression

• Periods of stability punctuated by sudden worsening
• Worsening often precipitated by trauma, increased physical activity, or Valsalva (cough/sneeze)
• Suggests intermittent syrinx expansion
• Example: Stable symptoms for 2 years, then acute worsening after lifting heavy object

Pattern 3: Rapid Progression (Red Flag)

• Symptoms develop over weeks to months
• Suggests:
  • Underlying tumour
  • Hemorrhage into syrinx
  • Acute obstruction of CSF pathways
• Requires urgent investigation
• Example: 45-year-old with 3-month history of rapidly progressive quadriparesis

Pattern 4: Delayed Post-Traumatic

• Latent period of months to decades after spinal cord injury (mean 8-9 years) [8,16]
• New ascending sensory level above previous injury
• Progressive loss of preserved function
• Increasing pain
• Example: 40-year-old with T6 paraplegia from age 25 MVA, now developing ascending numbness to T2 level

Atypical Presentations

Red Flags Requiring Urgent Assessment

Examination Findings

See Section 5 for detailed examination findings

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5. Clinical Examination

A systematic neurological examination is essential for detecting the characteristic findings of syringomyelia and localizing the lesion.

General Inspection

Upper Limb Examination

Motor Examination - Upper Limbs

Key Myotomes to Test:

• C5: Shoulder abduction (deltoid), elbow flexion (biceps)
• C6: Elbow flexion (biceps), wrist extension (ECRL/ECRB)
• C7: Elbow extension (triceps), wrist flexion, finger extension
• C8: Finger flexion (FDP), thumb extension/abduction
• T1: Finger abduction (interossei), thumb abduction (abductor pollicis brevis)

Sensory Examination - Upper Limbs (CRITICAL)

DISSOCIATED SENSORY LOSS = Loss of pain/temperature + Preservation of light touch/vibration/proprioception

How to Test:

1. Pin prick: Use a disposable neurological pin; test systematically from hands up arms to shoulders, across upper chest (cape distribution); compare left vs right; ask patient to distinguish "sharp" vs "dull"
2. Temperature: Cold tuning fork or alcohol swab on skin; compare affected vs unaffected areas
3. Light touch: Cotton wool; test same distribution; should be INTACT
4. Vibration: 128 Hz tuning fork on bony prominences (wrist, elbow); should be INTACT
5. Proprioception: Move finger/thumb joints and ask patient to identify direction; should be INTACT

Cape Distribution:

• Over shoulders (C4-C5)
• Upper arms (C5-C6)
• Forearms (C6-C7)
• Hands may be spared initially (central syrinx affects crossing fibres, not local segments)
• Upper chest (T1-T2)
• Bilateral but often asymmetric

Reflex Examination - Upper Limbs

Lower Limb Examination

Motor Examination - Lower Limbs

Key Myotomes:

• L2: Hip flexion (iliopsoas)
• L3: Knee extension (quadriceps)
• L4: Ankle dorsiflexion (tibialis anterior)
• L5: Great toe extension (EHL), ankle eversion
• S1: Ankle plantarflexion (gastrocnemius), ankle inversion

Sensory Examination - Lower Limbs

Reflex Examination - Lower Limbs

Special Signs and Tests

Characteristic Examination Patterns

Pattern 1: Classic Cervical Syringomyelia

• Upper limbs: LMN signs (wasting, weakness, areflexia) with dissociated sensory loss (cape distribution)
• Lower limbs: UMN signs (spasticity, hyperreflexia, extensor plantars) with normal or mildly impaired sensation
• Pattern: "LMN arms, UMN legs"

Pattern 2: Syringobulbia (Cervical Syrinx + Brainstem Extension)

• All features of cervical syringomyelia PLUS:
• Cranial nerve signs: facial numbness (CN V), nystagmus, palatal weakness (CN IX, X), tongue wasting (CN XII)
• Downbeat nystagmus (classic for Chiari)
• Dysphagia, dysphonia, dysarthria

Pattern 3: Thoracic Syringomyelia

• Spares upper limbs
• Sensory level on trunk
• Lower limb UMN signs
• May have autonomic dysfunction (sweating abnormalities, bladder dysfunction)

Pattern 4: Post-Traumatic Syringomyelia

• Pre-existing neurological deficit from original injury
• New findings:
  • Ascending sensory level (rising above original injury level)
  • Progressive motor weakness
  • Increased pain (neuropathic)
  • Loss of previously preserved function

What NOT to Miss on Examination

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6. Investigations

Imaging

MRI Spine (T1 and T2 Weighted) - GOLD STANDARD

Indications:

• Suspected syringomyelia (dissociated sensory loss, LMN arms + UMN legs, progressive scoliosis)
• Chiari malformation identified on brain imaging
• Post-spinal cord injury with new symptoms
• Unexplained myelopathy

Protocol:

• Sagittal T1 and T2 weighted images (whole spine)
• Axial T2 weighted images through levels of interest
• Include craniocervical junction
• Contrast (gadolinium) if tumour suspected

Findings:

Specific MRI Features:

MRI Brain with Craniocervical Junction - ESSENTIAL

Indications:

• Every patient with confirmed syringomyelia (to identify underlying cause)
• Suspected Chiari malformation

Protocol:

• Sagittal T1 and T2 weighted images
• Include views from mid-brain to C2 vertebra
• Dedicated high-resolution views of craniocervical junction

Findings to Assess:

Chiari I Malformation Diagnostic Criteria: [5,15]

• Tonsillar herniation more than 5mm below foramen magnum (McRae's line)
• 3-5 mm: borderline; clinical correlation required
• Less than 3 mm: normal variant

CSF Flow Study (Cine MRI / Phase-Contrast MRI)

Indications:

• Surgical planning for Chiari-associated syringomyelia
• Assessing adequacy of CSF flow post-operatively
• Uncertain cases (borderline Chiari, idiopathic syrinx)

Technique:

• Phase-contrast MRI synchronized to cardiac cycle
• Measures CSF flow velocity and direction at craniocervical junction

Findings:

• Normal: To-and-fro CSF flow anterior and posterior to cord at foramen magnum
• Chiari I: Reduced or absent CSF flow; increased flow velocity; turbulent flow
• Post-decompression: Restoration of normal CSF flow pattern

Clinical utility:

• Demonstrates physiological impact of anatomical obstruction
• May predict which patients benefit from surgery
• Useful for surgical planning and post-operative assessment [7,21]

Plain Radiographs (X-ray Spine)

Limited role; largely replaced by MRI

Indications:

• Baseline assessment of scoliosis (standing AP and lateral spine X-rays)
• Follow-up of scoliosis progression
• Screening for bony abnormalities (basilar invagination, assimilation of atlas, block vertebrae)

Findings:

• Scoliosis (measure Cobb angle)
• Widened spinal canal (chronic cord expansion)
• Vertebral anomalies (Klippel-Feil, hemivertebrae)
• Cannot visualize syrinx itself

CT Myelography

Indications:

• MRI contraindicated (pacemaker, severe claustrophobia, metallic implants)
• Post-operative assessment if MRI not possible

Technique:

• Intrathecal contrast injection (lumbar puncture)
• CT imaging of spine

Findings:

• Cord expansion
• Filling defect within cord (contrast does not enter syrinx)
• Less sensitive than MRI

Disadvantages:

• Invasive (requires LP)
• Ionizing radiation
• Inferior soft tissue detail compared to MRI
• Risk of post-LP headache, infection

Contrast-Enhanced MRI (Gadolinium)

Indications:

• Suspected tumour-associated syrinx (most important indication)
• Rapid progression of symptoms
• Eccentric syrinx on non-contrast MRI
• Atypical features

Findings:

Most common tumours associated with syringomyelia: [9]

1. Ependymoma (most common intramedullary tumour)
2. Hemangioblastoma (especially in von Hippel-Lindau disease)
3. Astrocytoma

Additional Investigations

Neurophysiology

NCS/EMG Findings in Syringomyelia:

• Normal sensory nerve conduction studies (peripheral sensory nerves intact; pathology is central)
• Fibrillation potentials and positive sharp waves in affected myotomes (denervation)
• Reduced motor unit recruitment (LMN loss)
• Normal distal motor and sensory latencies (excludes peripheral neuropathy)

Sleep Study (Polysomnography)

Indication:

• Suspected syringobulbia with respiratory center involvement
• Symptoms of sleep apnea (snoring, daytime somnolence, witnessed apneas)
• Chiari malformation with brainstem compression

Findings:

• Central sleep apnea (absent respiratory effort during apneic episodes)
• Risk of sudden death during sleep

Clinical significance:

• May require CPAP or BiPAP
• May be indication for urgent surgical decompression

Urodynamic Studies

Indication:

• Bladder symptoms (urgency, frequency, incontinence)
• Assessing degree of bladder dysfunction

Findings:

• Detrusor hyperreflexia (UMN bladder dysfunction)
• Detrusor-sphincter dyssynergia

Clinical significance:

• Guides bladder management
• Provides baseline for monitoring progression

Ophthalmology Assessment

Indication:

• Headache with suspected raised intracranial pressure
• Visual symptoms

Findings:

• Papilledema (suggests raised ICP; may indicate hydrocephalus complicating Chiari)
• Normal in uncomplicated syringomyelia

Differential Diagnoses

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7. Management

Management of syringomyelia is individualized based on:

1. Underlying cause (Chiari, post-traumatic, tumour, idiopathic)
2. Symptom severity (asymptomatic vs progressive myelopathy)
3. Rate of progression (stable vs rapidly progressive)
4. Patient factors (age, comorbidities, patient preference)

Management Algorithm

SYRINGOMYELIA DIAGNOSED ON MRI
                ↓
┌──────────────────────────────────────────────────────────────┐
│  STEP 1: IDENTIFY UNDERLYING CAUSE                          │
├──────────────────────────────────────────────────────────────┤
│  • MRI brain with craniocervical junction (assess Chiari)   │
│  • MRI spine with contrast (exclude tumour)                 │
│  • Clinical history (trauma, surgery, infection)            │
└──────────────────────────────────────────────────────────────┘
                ↓
┌──────────────────────────────────────────────────────────────┐
│  STEP 2: ASSESS SYMPTOMS AND PROGRESSION                    │
├──────────────────────────────────────────────────────────────┤
│  ASYMPTOMATIC / INCIDENTAL FINDING                          │
│  → Observation                                               │
│  → Serial MRI (6-12 monthly for 2 years, then annually)     │
│  → Monitor for symptom development                           │
│                                                              │
│  MILD, STABLE SYMPTOMS                                       │
│  → Conservative management trial (3-6 months)                │
│  → Pain management                                           │
│  → Physiotherapy                                             │
│  → Serial MRI (6 monthly)                                    │
│  → Neurosurgical opinion                                     │
│                                                              │
│  PROGRESSIVE SYMPTOMS / SIGNIFICANT DEFICIT                  │
│  → Neurosurgical referral                                    │
│  → Surgical management (cause-directed)                      │
└──────────────────────────────────────────────────────────────┘
                ↓
┌──────────────────────────────────────────────────────────────┐
│  STEP 3: CAUSE-DIRECTED SURGICAL MANAGEMENT                 │
├──────────────────────────────────────────────────────────────┤
│  CHIARI I MALFORMATION (70% of cases)                       │
│  → Posterior fossa decompression (PFD)                       │
│  → ± Duraplasty (PFDD)                                       │
│  → CSF flow study may guide approach                         │
│                                                              │
│  TUMOUR-ASSOCIATED (20-40% of tumours) [9]                  │
│  → Tumour resection (± syrinx drainage)                      │
│  → Histology determines further treatment                    │
│                                                              │
│  POST-TRAUMATIC                                              │
│  → Untethering (lysis of adhesions)                          │
│  → ± Syrinx-subarachnoid shunt (if untethering insufficient)│
│                                                              │
│  TETHERED CORD                                               │
│  → Untethering (release filum terminale)                     │
│                                                              │
│  ARACHNOIDITIS                                               │
│  → Adhesiolysis (lysis of adhesions)                         │
│  → Restore CSF flow                                          │
│                                                              │
│  IDIOPATHIC / NO CAUSE IDENTIFIED                            │
│  → Syrinx-subarachnoid shunt (if progressive)                │
│  → Or observation if stable                                  │
└──────────────────────────────────────────────────────────────┘
                ↓
┌──────────────────────────────────────────────────────────────┐
│  STEP 4: POST-OPERATIVE MANAGEMENT AND MONITORING           │
├──────────────────────────────────────────────────────────────┤
│  • Clinical follow-up: 6 weeks, 3 months, 6 months, 12 months│
│  • MRI spine: 6-12 months post-op (assess syrinx size)       │
│  • Assess:                                                   │
│    - Symptom improvement/stabilization                       │
│    - Syrinx size reduction                                   │
│    - Complications                                           │
│  • Long-term: Annual review for 5 years, then PRN            │
└──────────────────────────────────────────────────────────────┘
                ↓
┌──────────────────────────────────────────────────────────────┐
│  STEP 5: MANAGEMENT OF PERSISTENT/RECURRENT SYRINX          │
├──────────────────────────────────────────────────────────────┤
│  IF SYRINX PERSISTS BUT SYMPTOMS IMPROVED:                   │
│  → Continue observation (radiological persistence common)    │
│  → Clinical improvement more important than imaging          │
│                                                              │
│  IF SYRINX PERSISTS AND SYMPTOMS WORSEN/RECUR:               │
│  → Repeat MRI brain and spine with CSF flow study            │
│  → Assess adequacy of decompression                          │
│  → Consider:                                                 │
│    - Revision decompression                                  │
│    - Syrinx shunt (syrinx-subarachnoid or syrinx-peritoneal) │
│    - Syrinx fenestration                                     │
└──────────────────────────────────────────────────────────────┘

Conservative Management

Observation (Asymptomatic or Incidental Syringomyelia)

Indications:

• Asymptomatic syrinx discovered incidentally
• Mild symptoms, stable over time
• Patient preference (informed decision)
• High surgical risk

Protocol:

• Baseline comprehensive neurological examination
• MRI spine: 6 months, 12 months, then annually for 5 years
• Patient education: warning signs to report (new weakness, sensory loss, pain)
• Low threshold for re-imaging if new symptoms develop

Evidence:

• Natural history variable; some remain stable for years
• Up to 30% may progress
• No reliable predictors of who will progress [1,11]

Pain Management (Neuropathic Pain)

Neuropathic pain occurs in 50-65% of patients and can be the most disabling symptom. [22]

Multimodal approach:

• Combine medications from different classes
• Add physiotherapy, TENS, acupuncture
• Psychological support (chronic pain management programs)
• Consider referral to pain clinic if refractory

Physiotherapy and Rehabilitation

Goals:

• Maintain muscle strength and function
• Prevent contractures
• Improve mobility and independence
• Postural training (especially if scoliosis)

Interventions:

• Range of motion exercises
• Strengthening exercises (adapted to avoid Valsalva)
• Gait training
• Assistive devices (walking aids, orthoses)

Occupational Therapy

Goals:

• Adaptive strategies for hand dysfunction
• Home modifications
• Vocational rehabilitation

Interventions:

• Adaptive equipment (thick-handled utensils, button hooks)
• Splinting for weak hands
• Burn prevention education (due to loss of pain/temperature sensation)

Surgical Management

Surgery aims to address the underlying cause of the syrinx and restore normal CSF dynamics, thereby arresting syrinx expansion and preventing further neurological deterioration.

Posterior Fossa Decompression (PFD) for Chiari I Malformation

First-line treatment for Chiari I-associated syringomyelia with symptoms. [5,6,12]

Indications:

• Chiari I malformation (tonsillar herniation more than 5mm) with symptomatic syringomyelia
• Progressive neurological symptoms
• Significant syrinx (generally more than 3-4mm diameter)

Contraindications:

• Asymptomatic (relative contraindication; controversial)
• High surgical risk outweighing potential benefit

Procedure:

1. Patient positioning: Prone or sitting (surgeon preference)

2. Incision: Midline incision from inion to C2-C3

3. Suboccipital craniectomy: Remove portion of occipital bone (approximately 3cm x 3cm) to decompress posterior fossa

4. C1 laminectomy: Remove posterior arch of C1 vertebra

5. ± C2 laminectomy: If syrinx extends below C1 or tonsillar herniation is severe

6. Dural opening (Duraplasty) - Controversial; two approaches:

   A. Posterior Fossa Decompression WITHOUT Duraplasty (PFD)

   • Bone removal only (suboccipital craniectomy + C1 laminectomy)
   • Dura left intact
   • Advantages: Lower risk of CSF leak, meningitis
   • Disadvantages: May be less effective in some cases

   B. Posterior Fossa Decompression WITH Duraplasty (PFDD)

   • Bone removal PLUS dural opening
   • Dura opened in Y-shaped incision
   • Dural graft (autologous pericranium, synthetic patch) sutured in to expand dural volume
   • Arachnoid may be opened or left intact (surgeon preference)
   • Advantages: Greater expansion of posterior fossa; may restore CSF flow more effectively
   • Disadvantages: Higher risk of CSF leak (5-15%), aseptic meningitis (up to 25%), pseudomeningocele

7. Coagulation of cerebellar tonsils (rarely performed now; not recommended)

8. Closure: Watertight dural closure (if duraplasty performed); muscle, fascia, skin closure

PFD vs PFDD: Which is better?

Controversy: No definitive evidence that one approach is superior. [12]

Current practice:

• Both techniques widely used
• Surgeon preference and experience major factor
• Consider duraplasty if:
  • Large syrinx
  • Severe tonsillar herniation
  • Failed bone-only decompression
• Consider bone-only decompression if:
  • Mild tonsillar herniation
  • Small syrinx
  • High risk of CSF complications

Surgical Outcomes (Posterior Fossa Decompression)

Prognostic factors for better outcome:

• Shorter duration of symptoms (less than 2 years)
• Milder preoperative neurological deficit
• Smaller syrinx
• Younger age
• Chiari I (vs post-traumatic or tumour-associated)

Complications of Posterior Fossa Decompression

Tumour Resection (Tumour-Associated Syringomyelia)

Indication:

• Intramedullary tumour identified on contrast MRI (enhancing nodule) [9]

Approach:

• Laminectomy at level of tumour
• Midline myelotomy (incision in dorsal midline of cord)
• Microsurgical tumour resection
• Syrinx often resolves after tumour removal

Outcomes:

• Dependent on tumour histology
• Ependymoma: Often well-demarcated; good resection; favorable prognosis
• Hemangioblastoma: Well-defined; good resection; may be associated with von Hippel-Lindau disease
• Astrocytoma: Infiltrative; incomplete resection; poorer prognosis

Note: Syrinx cavities associated with tumours are often "polar cysts" (rostral and/or caudal to tumour); these typically resolve after tumour resection and do not require separate drainage.

Syrinx Shunting Procedures (Rarely Performed Now)

Indication:

• Persistent or progressive syrinx after adequate decompression
• Post-traumatic syringomyelia unresponsive to untethering
• Idiopathic syringomyelia (no identifiable cause)

Types:

Outcomes:

• Variable success rates (50-70% improvement)
• High shunt failure rate (30-50%)
• Risk of neurological injury from cord manipulation
• Risk of shunt infection, migration
• Generally reserved for refractory cases after failure of decompression

Modern trend: Shunting procedures used much less frequently since recognition that addressing underlying cause (Chiari decompression, tumour resection, untethering) more effective and durable. [12]

Untethering Procedures

Indications:

• Post-traumatic syringomyelia with cord tethering (adhesions from injury/surgery)
• Tethered cord syndrome with syringomyelia
• Failed posterior fossa decompression with evidence of cord tethering

Procedure:

• Laminectomy at level of tethering
• Microsurgical lysis of adhesions
• Restore CSF flow around cord
• ± Duraplasty to expand subarachnoid space

Outcomes:

• Variable; dependent on extent of scarring
• May halt progression
• Syrinx may persist despite symptom improvement

Special Populations

Paediatric Patients

Special considerations:

• Scoliosis common (65-85% of Chiari-syringomyelia) [13,14]
• Rapidly progressive scoliosis may be presenting feature
• MRI spine mandatory before any scoliosis surgery
• Surgical decompression stabilizes scoliosis in 65-70% [14]
• Curve rarely improves significantly
• If curve more than 50°, may require scoliosis surgery after syrinx treatment

Management:

1. Treat syringomyelia first (posterior fossa decompression)
2. Monitor scoliosis with serial X-rays
3. If curve stabilizes (\u003c30°): observation
4. If curve progressive or more than 50°: scoliosis surgery (spinal fusion)

Pregnancy

Risks:

• Valsalva during labor may worsen symptoms
• Neurological deterioration reported during pregnancy/labor

Management:

• Multidisciplinary care (obstetrics, neurology, neurosurgery, anesthesia)
• MRI if new symptoms (without gadolinium)
• Elective cesarean section may be considered to avoid Valsalva
• Epidural anesthesia: controversial; discuss risks/benefits

Breastfeeding:

• Compatible with most neuropathic pain medications (check individually)

Elderly Patients

Considerations:

• Higher surgical risk (comorbidities)
• Slower recovery
• May have coexistent degenerative spine disease
• Less favorable outcomes

Management:

• Careful risk-benefit assessment
• May favor conservative management if symptoms mild
• If surgery undertaken, meticulous perioperative care

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8. Complications

Complications of Untreated Syringomyelia

Complications of Surgery (see Section 7)

Disease-Specific Complications

Post-Traumatic Syringomyelia

• Ascending neurological level (loss of function above original injury)
• Progressive loss of independence
• Increased neuropathic pain
• Requires re-imaging and management; untethering procedures may help

Syringobulbia (Brainstem Extension)

• Dysphagia → aspiration pneumonia
• Respiratory dysfunction → respiratory failure
• Vocal cord palsy → airway compromise
• Sleep apnea → sudden death
• Management: Urgent neurosurgical decompression; supportive care (PEG feeding, tracheostomy if needed)

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9. Prognosis and Outcomes

Natural History (Untreated Syringomyelia)

Long-Term Outcomes Post-Surgery (Posterior Fossa Decompression)

Prognostic Factors

Key Outcome Messages

1. Surgery halts progression in 85-95% but does not reverse established neurological deficits [5,6,12]
2. Radiological persistence of syrinx is common (60-80% have residual syrinx on MRI) but clinical improvement is what matters [13]
3. Early surgery (before severe deficit develops) has better outcomes [12]
4. Scoliosis stabilizes but rarely improves after surgery in children [14]
5. Neuropathic pain is difficult to treat and may persist despite successful syrinx decompression [22]
6. Long-term follow-up is essential - recurrence or late progression can occur [12]

Quality of Life

• Significant improvement in quality of life scores post-surgery in most patients
• Pain and disability major determinants of quality of life
• Psychological support important for adaptation to chronic neurological condition
• Return to work/normal activities variable; depends on preoperative deficit and occupation

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10. Evidence and Guidelines

Major Guidelines

Landmark Studies

Evidence Levels for Key Interventions

Research Gaps and Controversies

1. PFD vs PFDD: No high-quality RCT comparing bone-only decompression to duraplasty
2. Asymptomatic Chiari I with syrinx: Unclear who will progress; observation vs prophylactic surgery debated
3. Optimal timing of surgery: How early? What degree of deficit justifies surgery?
4. Predictors of progression: No reliable biomarkers or imaging features to predict who will worsen
5. Role of CSF flow studies: Useful but not universally adopted; optimal use unclear
6. Management of persistent radiological syrinx with clinical improvement: Observation vs intervention?

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11. Patient Explanation

Simple Explanation

What is syringomyelia?

Syringomyelia (pronounced "suh-ring-oh-my-EEL-ee-ah") is a condition where a fluid-filled cyst, called a syrinx, develops inside your spinal cord. Your spinal cord is a thick bundle of nerves that runs down your back inside your spine, carrying messages between your brain and the rest of your body. When a syrinx forms, it damages these nerves, causing numbness, weakness, and pain.

What causes it?

The most common cause (about 70% of cases) is a condition called Chiari malformation. This is where part of your brain (the cerebellar tonsils) pushes down through the opening at the base of your skull. This blocks the normal flow of fluid around your spinal cord, creating pressure that forces fluid into the cord itself, forming a syrinx.

Other causes include:

• Previous spinal injury - a syrinx can develop months or years after a spinal cord injury
• Spinal tumours - a tumour inside the spinal cord can cause a syrinx
• Infection or scarring - from previous meningitis or spinal surgery
• Unknown causes - in about 5% of cases, we cannot find a specific cause

What are the symptoms?

The syrinx damages nerves in your spinal cord, causing symptoms that develop slowly over months to years:

• Numbness and tingling in your hands and arms
• Loss of ability to feel pain and temperature - you may burn or cut your hands without feeling it
• Weakness in your hands, making it hard to grip things or do fine tasks like buttoning shirts
• Muscle wasting in your hands
• Stiffness in your legs
• Neck and arm pain (often burning or shooting pain)
• Headaches (especially at the back of your head if you have Chiari malformation)
• Curved spine (scoliosis) - especially in children

A unique feature of syringomyelia is that you lose the ability to feel pain and hot/cold in a "cape" pattern over your shoulders and arms, but you can still feel light touch. This is called "dissociated sensory loss" and is very characteristic of this condition.

How is it diagnosed?

The main test is an MRI scan of your spine. This shows the syrinx as a bright fluid-filled area inside your spinal cord. You will also need an MRI of your brain to check for Chiari malformation or other causes.

How is it treated?

Treatment depends on the cause and whether you have symptoms:

1. Observation - If you have no symptoms or very mild symptoms, we may simply monitor you with regular MRI scans to check if the syrinx is growing.

2. Surgery - If you have symptoms or the syrinx is getting bigger, surgery can help:

   • For Chiari malformation: The most common operation is called posterior fossa decompression. The surgeon removes a small piece of bone at the back of your skull and top of your spine to create more space and allow fluid to flow normally. This stops the syrinx from growing and often makes it shrink. About 85-95% of people improve or stop getting worse after this surgery.
   • For tumours: Removing the tumour often makes the syrinx go away.
   • For scarring: Surgery to release the scarring and restore fluid flow.

3. Medications - For pain, we can prescribe medicines like gabapentin or pregabalin that help with nerve pain.

4. Physiotherapy - To help you maintain strength and function.

What are the risks of surgery?

The main risks are:

• Fluid leak from the wound (5-15%)
• Infection (2-5%)
• Headaches
• Rarely, worsening of symptoms

What is the outlook?

• With surgery, 85-95% of people improve or stop getting worse
• The syrinx often shrinks (in 60-90% of cases), though it may not disappear completely
• Surgery cannot reverse damage that has already happened, but it can prevent further damage
• Early treatment (before severe weakness develops) gives better results
• Long-term follow-up is important to check the syrinx hasn't come back

What if I don't have treatment?

Without treatment, syringomyelia usually gets slowly worse over time, with increasing weakness, numbness, and disability. However, some people remain stable for years. The problem is we cannot predict who will worsen, so we usually recommend treatment if you have symptoms.

Important things to know:

• If you cannot feel pain in your hands, be careful with hot objects, sharp tools, and burns - you may injure yourself without realizing it
• Report any new weakness, numbness, or difficulty swallowing to your doctor urgently
• If you are a child with a curved spine (scoliosis), you should have an MRI to check for syringomyelia
• Avoid activities that involve straining or heavy lifting as these can temporarily worsen symptoms

Where can I get support?

There are patient support groups for syringomyelia and Chiari malformation that provide information and connect you with others who have the condition.

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12. References

1. Milhorat TH, Chou MW, Trinidad EM, et al. Chiari I malformation redefined: clinical and radiographic findings for 364 symptomatic patients. Neurosurgery. 1999;44(5):1005-1017. doi:10.1097/00006123-199905000-00042. PMID: 10232534

2. Oldfield EH, Muraszko K, Shawker TH, Patronas NJ. Pathophysiology of syringomyelia associated with Chiari I malformation of the cerebellar tonsils. Implications for diagnosis and treatment. J Neurosurg. 1994;80(1):3-15. doi:10.3171/jns.1994.80.1.0003. PMID: 8271018

3. Greitz D. Unraveling the riddle of syringomyelia. Neurosurg Rev. 2006;29(4):251-263. doi:10.1007/s10143-006-0029-5. PMID: 16752160

4. Levine DN. The pathogenesis of syringomyelia associated with lesions at the foramen magnum: a critical review of existing theories and proposal of a new hypothesis. J Neurol Sci. 2004;220(1-2):3-21. doi:10.1016/j.jns.2004.01.014. PMID: 15140600

5. Tubbs RS, Beckman J, Naftel RP, et al. Institutional experience with 500 cases of surgically treated pediatric Chiari malformation Type I. J Neurosurg Pediatr. 2011;7(3):248-256. doi:10.3171/2010.12.PEDS10379. PMID: 21361762

6. Klekamp J. Surgical treatment of Chiari I malformation--analysis of intraoperative findings, complications, and outcome for 371 foramen magnum decompressions. Neurosurgery. 2012;71(2):365-380. doi:10.1227/NEU.0b013e31825c3426. PMID: 22569058

7. Heiss JD, Patronas N, DeVroom HL, et al. Elucidating the pathophysiology of syringomyelia. J Neurosurg. 1999;91(4):553-562. doi:10.3171/jns.1999.91.4.0553. PMID: 10507374

8. Brodbelt AR, Stoodley MA. Post-traumatic syringomyelia: a review. J Clin Neurosci. 2003;10(4):401-408. doi:10.1016/s0967-5868(02)00326-0. PMID: 12852877

9. Lee TT, Gromelski EB, Green BA. Surgical treatment of spinal ependymoma and post-operative radiological evaluation. Acta Neurochir (Wien). 1998;140(4):309-313. doi:10.1007/s007010050101. PMID: 9689319

10. Milhorat TH, Capocelli AL Jr, Anzil AP, Kotzen RM, Milhorat RH. Pathological basis of spinal cord cavitation in syringomyelia: analysis of 105 autopsy cases. J Neurosurg. 1995;82(5):802-812. doi:10.3171/jns.1995.82.5.0802. PMID: 7714605

11. Todor DR, Mu HT, Milhorat TH. Pain and syringomyelia: a review. Neurosurg Focus. 2000;8(3):E11. doi:10.3171/foc.2000.8.3.11. PMID: 16676924

12. CNS Guidelines Committee. Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines for Patients With Chiari Malformation: Surgical Interventions. Neurosurgery. 2023;93(4):815-824. doi:10.1227/neu.0000000000002598. PMID: 37775957

13. Durham SR, Fjeld-Olenec K. Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation Type I in pediatric patients: a meta-analysis. J Neurosurg Pediatr. 2008;2(1):42-49. doi:10.3171/PED/2008/2/7/042. PMID: 18590394

14. Atchley TJ, Alford EN, Chern JJ, et al. Extradural decompression versus duraplasty in Chiari malformation type I with syrinx: outcomes on scoliosis from the Park-Reeves Syringomyelia Research Consortium. J Neurosurg Pediatr. 2021;28(2):167-175. doi:10.3171/2021.1.PEDS20917. PMID: 33507567

15. Meadows J, Kraut M, Guarnieri M, Haroun RI, Carson BS. Asymptomatic Chiari Type I malformations identified on magnetic resonance imaging. J Neurosurg. 2000;92(6):920-926. doi:10.3171/jns.2000.92.6.0920. PMID: 10839250

16. Schurch B, Wichmann W, Rossier AB. Post-traumatic syringomyelia (cystic myelopathy): a prospective study of 449 patients with spinal cord injury. J Neurol Neurosurg Psychiatry. 1996;60(1):61-67. doi:10.1136/jnnp.60.1.61. PMID: 8871935

17. Strahle J, Muraszko KM, Kapurch J, Bapuraj JR, Garton HJ, Maher CO. Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging. J Neurosurg Pediatr. 2011;8(2):205-213. doi:10.3171/2011.5.PEDS1180. PMID: 21806364

18. Vernooij MW, Ikram MA, Tanghe HL, et al. Incidental findings on brain MRI in the general population. N Engl J Med. 2007;357(18):1821-1828. doi:10.1056/NEJMoa070972. PMID: 17978290

19. Speer MC, George TM, Enterline DS, Franklin A, Wolpert CM, Milhorat TH. A genetic hypothesis for Chiari I malformation with or without syringomyelia. Neurosurg Focus. 2000;8(3):E12. doi:10.3171/foc.2000.8.3.12. PMID: 16676925

20. Stoodley MA, Jones NR, Yang L, Brown CJ. Mechanisms underlying the formation and enlargement of noncommunicating syringomyelia: experimental studies. Neurosurg Focus. 2000;8(3):E2. doi:10.3171/foc.2000.8.3.2. PMID: 16676923

21. McGirt MJ, Atiba A, Attenello FJ, et al. Correlation of hindbrain CSF flow and outcome after surgical decompression for Chiari I malformation. Childs Nerv Syst. 2008;24(7):833-840. doi:10.1007/s00381-007-0569-1. PMID: 18214499

22. Finnerup NB, Attal N, Haroutounian S, et al. Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis. Lancet Neurol. 2015;14(2):162-173. doi:10.1016/S1474-4422(14)70251-0. PMID: 25575710

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13. Examination Focus

Common Exam Questions

High-Yield Viva Points

Common Mistakes in Examinations

Viva Scenario Practice

Scenario 1: Classic Chiari-Syringomyelia

Examiner: "A 28-year-old woman presents with a 2-year history of bilateral hand weakness and numbness. On examination, she has wasting of the small hand muscles, areflexia in the upper limbs, and loss of pain sensation over the shoulders and upper arms, but light touch is intact. What is your diagnosis and management?"

Model Answer: "This is highly suggestive of syringomyelia. The key features are:

• Dissociated sensory loss (pain loss with preserved light touch) in a cape distribution
• Lower motor neuron signs in the upper limbs (wasting, areflexia)
• This pattern indicates a central cord lesion affecting the anterior commissure and anterior horn cells

I would:

1. Confirm the diagnosis with MRI spine, which would show a T2 hyperintense, T1 hypointense intramedullary cavity
2. Request MRI brain with craniocervical junction views to assess for Chiari I malformation, the most common cause
3. If Chiari I is present (tonsillar herniation more than 5mm), I would refer to neurosurgery for posterior fossa decompression
4. Explain to the patient that surgery halts progression in 85-95% and often improves symptoms, though complete recovery is uncommon [5,6,12]

Would the examiners like me to discuss surgical technique or alternative causes?"

Scenario 2: Paediatric Scoliosis

Examiner: "A 12-year-old girl is referred by her GP with a 1-year history of progressive scoliosis. Cobb angle is 35°. The orthopaedic team wants to proceed with bracing. What are your concerns?"

Model Answer: "I am concerned that this may be a neurological scoliosis secondary to underlying spinal cord pathology such as syringomyelia, tethered cord, or intramedullary tumour. This is a red flag presentation.

Before any scoliosis treatment, I would:

1. Perform a detailed neurological examination looking for:
   • Dissociated sensory loss
   • Hand weakness or wasting
   • Hyperreflexia in lower limbs
   • Bladder symptoms
   • Skin lesions (café-au-lait spots, hairy patches suggesting spinal dysraphism)
2. Request MRI of the entire spine (cervical to sacral) to exclude syringomyelia and other cord pathology

If syringomyelia is present:

• The underlying cause (usually Chiari I) must be treated first with posterior fossa decompression
• This stabilizes the scoliosis in 65-70% of cases [14]
• After syrinx treatment and observation for 12-24 months, reassess the scoliosis
• If the curve remains progressive or exceeds 50°, then scoliosis surgery (spinal fusion) may be needed

Proceeding with scoliosis treatment without investigating for cord pathology would be a serious error and potentially harmful." [13,14]

Examination Cheat Sheet

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END OF DOCUMENT

Topic: Syringomyelia
Total Lines: 1,383
Citations: 22
Status: Topic 911/1071 - Enhanced to Gold Standard