What is the recommended management for a 3-month-old with dilation of the spinal central canal (syringomyelia)?

Management of Spinal Central Canal Dilation in a 3-Month-Old Infant

Immediate Diagnostic Workup

The first priority is to determine whether this represents true syringomyelia requiring intervention or benign hydromyelia (dilated central canal) that can be observed, and to identify any underlying cause such as Chiari malformation, tethered cord, or achondroplasia. 1

Essential Imaging and Testing

• Complete spine MRI with T1, T2, FLAIR, and CISS sequences is mandatory to characterize the cavity and identify underlying pathology 1, 2
• Brain MRI must be obtained to evaluate for Chiari I malformation, which is the most common cause of syringomyelia in children 1, 3
• Measure the maximum cavity diameter: cavities >6 mm are more likely to represent true syringomyelia requiring intervention, while those ≤6 mm may represent benign hydromyelia 2
• If achondroplasia is suspected based on phenotype (macrocephaly, frontal bossing, rhizomelic shortening), obtain genetic testing for FGFR3 mutations and evaluate for foramen magnum stenosis 1

Clinical Assessment

• Neurological examination focusing on: motor strength in all extremities, deep tendon reflexes, muscle tone abnormalities, and bulbar function (swallowing, respiratory effort) 1
• Assess for signs of cervicomedullary compression in achondroplasia patients: apnea/cyanosis (most common presenting symptom in 48-85% of cases), respiratory difficulties, or delayed motor milestones 1
• Examine the lower back for sacral dimple, cutaneous stigmata, or signs of tethered cord 1, 4
• Bladder and bowel function assessment - any dysfunction suggests significant cord pathology 1

Treatment Algorithm Based on Etiology

If Associated with Chiari I Malformation

Surgical intervention with posterior fossa decompression (with or without duraplasty) is indicated if the infant is symptomatic OR if there is T2 signal change in the cord, regardless of symptoms. 1, 3

• Symptomatic presentation at 3 months warrants urgent surgical decompression to prevent catastrophic neurological deterioration 1
• Either posterior fossa decompression alone or with duraplasty are acceptable first-line options (Grade C recommendation) 1
• Wait 6-12 months after decompression before considering additional surgery if syrinx persists, as delayed resolution is common (Grade B recommendation) 1
• Untreated symptomatic cervicomedullary compression carries a 16% mortality rate 1

If Associated with Achondroplasia

Foramen magnum decompression with cervical laminectomy is indicated for symptomatic cervicomedullary compression or cord signal change on MRI, even in the absence of overt symptoms. 1

• Timing is critical: mean age at surgery is 31 months, but symptomatic infants require earlier intervention 1
• Surgical approach: foramen magnum decompression (99% of cases) plus cervical laminectomy (65% of cases) 1
• Instrumented fusion should be considered depending on age and extent of decompression to prevent kyphotic progression 1
• Expected outcomes: 91% symptom resolution, but 2% perioperative mortality, 9% reoperation rate, and 21% complication rate 1
• Asymptomatic patients with only radiographic compression remain controversial, but the recently proposed achondroplasia foramen magnum scores may help guide decision-making 1

If Associated with Tethered Cord

Early surgical untethering is recommended even in asymptomatic patients to prevent future neurological deterioration. 1, 4

• Obtain lumbar spine MRI if sacral dimple present, lower limb upper motor neuron signs, or bladder/bowel dysfunction 1
• Surgical technique: subtotal lipoma excision, suturing of spinal pia mater, and section of filum terminale 4
• Early operation prevents development of neurological deficits - 20/20 asymptomatic patients remained symptom-free postoperatively in one series 4

If Benign Hydromyelia (Dilated Central Canal)

Conservative management with serial MRI surveillance is appropriate if the cavity is ≤6 mm, there are no neurological deficits on examination, and electrophysiological studies (if obtained) are normal. 2

• This represents a dilated central canal without underlying pathology 2
• No clinical or radiological progression occurs over time (mean follow-up 36.9 months in one study) 2
• Serial imaging every 6-12 months initially to confirm stability 1, 2

Critical Pitfalls to Avoid

• Do not delay imaging: MRI must be performed urgently (within 12-24 hours) if any signs of myelopathy or cervicomedullary compression are present 1
• Do not assume all central canal dilation requires surgery: benign hydromyelia ≤6 mm without neurological findings can be observed 2
• Do not miss Chiari malformation: brain imaging is mandatory as this is the most common cause of pediatric syringomyelia 1, 3
• Do not wait for gross neurological deficits to develop before intervening in achondroplasia patients with cord signal change - early surgery prevents irreversible damage 1, 3
• Do not perform isolated syrinx shunting as first-line treatment: address the underlying cause (Chiari decompression, cord untethering) rather than shunting the cavity itself 3
• In achondroplasia, do not perform laminectomy alone without considering fusion in older children, as this leads to kyphotic progression requiring reoperation 1

Monitoring and Follow-Up

• Postoperative MRI at 6-12 months to assess syrinx resolution after decompressive surgery 1
• Clinical neurological examination at regular intervals to detect any deterioration 1, 2
• In achondroplasia patients, polysomnography may be indicated to assess for sleep apnea related to cervicomedullary compression 1
• If syrinx persists or enlarges despite appropriate initial surgery, consider repeat decompression or alternative interventions after 6-12 months 1