Diastematomyelia (Greek: diastema = interval, myelos = marrow), also known as diplomyelia, is a rare congenital defect in which the spinal cord is split by a fibrocartilaginous or osseous septum, each half being enclosed by a dural sac. This process fixes the cord in a low position, so that its normal ascent during growth is impaired. Common skeletal anomalies associated with diastematomyelia are spina bifida (in more than 50% of the cases), kyphosis, scoliosis, and clubfoot. Vertebral defects include diminution of the anteroposterior diameter of the vertebral bodies, the presence of hemivertebrae and of block vertebrae. The aetiology of this lesion has not been determined.


The finding of bony spurs situated between the posterior ossification centres in the coronal plane should immediately arouse suspicion of diastematomyelia, although any area of widening in the spinal canal with internal echoes should alert the Ultrasonographer. The antenatal diagnosis of this rare condition can alter the natural course of the disease by early neurosurgical intervention prior to the appearance of the permanent neurological or musculoskeletal abnormalities.

Differential Diagnosis

The finding of the bony spur between the posterior ossification centres of the vertebrae is unique to this condition, and will differentiate the lesion from the commoner neural tube defects.

Sonographic Features

Bony spur between posterior ossification centres of fetal spine.

Widening of spinal canal with internal echoes.

Hemivertebrae and narrowing of anteroposterior vertebral body diameter often seen.

Spina bifida is common.

Associated Syndromes

  • None


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