Revision 27 for 'Diastematomyelia'

A diastematomyelia refers to a type of spinal dysraphism when there is a  longitudinal split in the spinal cord. 

Location

It can occur involving multiple levels :

• 50% occur between L1 and L3
• 25% occur between T7 and T12

Types

• type I  (external) : has two dural sacs ; midline spur is more common; these patients are usually symptomatic.
• type II (internal) : has a single dural sac with two hemicords ; there is no spur in this type. these patients are generally asymptomatic

Associations

There may be an associated meningocele, neuroenteric cyst or dermoid.

Associated bony, cartilagenous or fibrous spurs project through the dura mater forwards from the neural arch is visible in 33% of cases ¹. 

Laminar fusion associated with a neural arch defect is a good predictor of diastematomyelia and occurs the level of the defect, or at an adjacent level. 

Other associations include

• club foot
• spinal cord lipoma
• haemangioma overlying spine
• unilateral muscle wasting
• scoliosis

Radiographic features

Antenatal ultrasound

There presence of an extra echogenic focus in the midline between the foetal spinal posterior elements has been described as a reliable sign ². 

Plain film

may show

• multi level spina bifida
• widening of interpedicular distance : but this may be remote from the site of the spur
• as associated scoliosis 
• anteroposterior narrowing of vertebral bodies

CT

In addition to the plain film features may show 

• AP bony septum on axial images (case 2)

It is the modality of choice owing to superior anatomical detail. (More content to come)

Differential diagnoses

diplomyelia : which is a true splitting of the spinal cord. 

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