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Diastematomyelia is a rare variety of occult spinal dysraphism characterized by a complete or incomplete, congenital longitudinal splitting of the spinal cord, conus medullaris and / or filum terminale associated with splaying of vertebrae or increase in interpedicular distance [1, 2]. It is usually associated with other congenital defects especially dysraphism (meningocele, meningomyelocele), vertebral malformations (hemivertebra) and visceral abnormalities (involving genitourinary or lower intestinal tract). Isolated diastematomyelia is rarer and its antenatal recognition is crucial for deciding a future course of action [1, 2, 3].
A 25 year old primigravida came for routine antenatal sonography at five and a half months of gestation. History of any drug intake was negative. Ultrasonography (USG) revealed a 25-26 weeks old fetus with enlargement of the bony spinal canal in the lumbar region. Presence of midline, longitudinal, echogenic focal lesion was also noted within the enlarged spinal canal in its posterior part (Fig. 1, Fig. 2). Three dimensional ultrasound scans (3D US) in the examination were diagnostic (Fig. 3). The overlying skin however appeared intact. No significant abnormality was noted elsewhere in the fetus including the intracranial cavity. Hence, the diagnosis of isolated diastematomyelia was made. The parents agreed to continue the pregnancy after a thorough counseling about the condition of the fetus and lack of other risk factors. The female child was born at thirty eight weeks and four days of gestation period following an uneventful, normal vaginal delivery. Physical examination of the neonate was unremarkable. The spinal USG confirmed the presence of the longitudinal echogenic spur in the lumbar region in the absence of any external abnormality, thus confirming the diagnosis of isolated diastematomyelia. The fourteen months postnatal period was uneventful, before the patient was lost to follow up.
Typical US features of widened spinal canal with presence of echogenic spur within the spinal canal are diagnostic of diastematomyelia. The latter is seen as more than three ossification centres for vertebrae in the axial image. The 3D US images are useful in showing the presence of sagittal spur by generating images in coronal plane [1, 3]. Diagnosis can be achieved as early as early mid-trimester .
Early antenatal diagnosis can help plan future course of action. However, few case reports of favourable postnatal outcome up to 18 months have been documented in isolated diastematomyelia . Isolated diastematomyelia may remain occult for long time or may present insidiously with nonspecific complaints resulting in diagnostic delay. Thus, antenatal diagnosis of this condition may help in early institution of medical intervention in the postnatal period as well.
To summarize, isolated diastematomyelia is rare condition with a possible favourable prognosis that can be diagnosed antenatally by ultrasonography. The 3D US aids in confident diagnosis. Antenatal diagnosis can help in early institution of the surgical / medical intervention in the antenatal / postnatal period.