What are the next steps for a patient with a myelocystocele (a type of spinal dysraphism) identified on Magnetic Resonance Imaging (MRI)?

Management of Myelocystocele Identified on MRI

Once a myelocystocele is confirmed on MRI, the patient should be referred urgently to a pediatric neurosurgeon for surgical evaluation and planning, as early surgical intervention is recommended in all cases to prevent neurological deterioration from spinal cord tethering. 1, 2

Immediate Clinical Assessment

Upon MRI confirmation, perform a focused neurological examination specifically evaluating:

• Lower extremity motor function (strength testing in all muscle groups, as 7 of 8 symptomatic patients in one series had lower-limb weakness) 2
• Bladder and bowel function (assess for urinary incontinence and constipation) 2
• Presence of complete paraplegia (occurred in 2 of 17 patients in one series) 2
• Associated cutaneous markers including dermal sinus tracts, skin dimples, or congenital talipes equinovarus deformity 2

Notably, approximately 50% of patients with terminal myelocystocele may have no neurological deficits at presentation (9 of 17 cases in one series), but this does not preclude the need for surgery. 2

Complete Imaging Evaluation

Obtain comprehensive MRI screening of the entire spine and brain, not just the lesion site, as myelocystoceles frequently occur with multiple associated malformations: 3

• Brain MRI to evaluate for hydrocephalus (present in 70% of meningomyelocele cases) and Chiari type II malformation (present in 98% of cases) 4
• Whole spine MRI to identify associated split cord malformations, syringomyelia (affects 40-80% of patients), or other levels of dysraphism 4, 3
• Three-dimensional constructive interference in steady-state (CISS) sequences when available for optimal visualization 5

The characteristic MRI findings you should confirm include the "sac within a sac" appearance: (1) a dilated terminal spinal cord contained within (2) an even more largely dilated distal dural sac, and (3) an adjacent spinal cord lipoma. 1, 4

Distinguish Terminal from Nonterminal Lesions

Determine whether the myelocystocele is terminal (lumbosacral) or nonterminal (cervical, thoracic, or upper lumbar), as this affects surgical approach and prognosis: 5

• Terminal myelocystoceles present as lumbosacral masses with the classic three-component MRI appearance 1, 5
• Nonterminal myelocystoceles can occur at cervical (1 case), thoracic (6 cases), or lumbar (2 cases) levels and are classified as Rossi Type I or Type II 5, 3

Neurosurgical Referral and Surgical Planning

Refer immediately to a pediatric neurosurgeon experienced in spinal dysraphism, as the surgical approach differs from other skin-covered spinal masses and requires specific expertise. 5, 2

The surgical procedure typically involves:

• Excision of the meningocele sac 5, 2
• Drainage of the syringocele/myelocystocele 5, 2
• Untethering of the spinal cord by incising bands tethering the myelocystocele to the meningocele sac 5, 2
• For nonterminal Type I lesions: excision of the fibroneurovascular stalk 5
• Preservation of nerve roots with as little damage as possible during untethering 2

Management of Associated Conditions

If hydrocephalus is present, coordinate with neurosurgery for potential ventriculoperitoneal shunt placement, which may be performed in the same surgical session as the myelocystocele repair. 3

Early surgery is recommended in all cases, even in asymptomatic patients, because: 2

• Surgery prevents future neurological deterioration from progressive cord tethering 6, 2
• The procedure is not merely cosmetic but prophylactic 6
• Posterior tethering by adhesions can cause delayed deterioration 6

Critical Pitfalls to Avoid

• Do not delay referral based on absence of neurological deficits, as approximately half of patients are asymptomatic initially but still require surgery 2
• Do not assume the lesion is a simple meningocele or lipomyelomeningocele without proper MRI characterization, as myelocystoceles require different surgical treatment and have different prognosis 5, 2
• Do not limit imaging to the visible lesion site; always screen the entire neuraxis for associated malformations 3
• Do not confuse prenatal ultrasound findings with definitive diagnosis; prenatal MRI should be performed if the diagnosis is uncertain 6

Expected Outcomes

Postoperative neurological status typically remains stable with no deterioration if surgery is performed appropriately, though improvement in pre-existing deficits is uncommon. 5, 2 Potential complications include postoperative CSF leakage (occurred in 2 of 17 patients in one series) and subcutaneous CSF collection (2 of 17 patients), with rare need for reexploration. 2