What is the most likely head imaging finding in a 3-hour-old boy with a large myelomeningocele and flaccid bilateral lower extremities, born at 38 weeks gestation via spontaneous vaginal delivery (SVD) to a 25-year-old woman, gravida 2, para 2, with no prenatal care?

From the Guidelines

The head imaging of this 3-hour-old boy is most likely to reveal inferior displacement of the medulla and cerebellum. This finding, known as Arnold-Chiari malformation type II, is commonly associated with myelomeningocele, as discussed in the context of congenital brain and spinal cord malformations 1. The clinical presentation strongly supports this diagnosis, with the presence of a large myelomeningocele on the back, flaccid lower extremities indicating neurological deficit, and a full fontanelle suggesting increased intracranial pressure. The macrocephaly (head circumference at 90th percentile) with normal weight (25th percentile) further supports this diagnosis. In Arnold-Chiari malformation type II, the hindbrain structures are pulled downward through the foramen magnum due to tethering associated with the spinal defect. This displacement often leads to hydrocephalus, which explains the full fontanelle and increased head circumference observed in this newborn. The combination of myelomeningocele and these cranial findings represents a neural tube defect that typically occurs during early embryonic development, around the fourth week of gestation.

Key points to consider in this diagnosis include:

• The association between myelomeningocele and Arnold-Chiari malformation type II, as well as other congenital central nervous system malformations and cutaneous markers 1.
• The importance of meticulous neurologic and ophthalmologic examination in patients with suspected intracranial tumors or increased intracranial pressure, as highlighted in the evaluation of headache in children 1.
• The role of MRI in diagnosing conditions such as Arnold-Chiari malformation type II, given its superior sensitivity for detecting abnormalities in the cranio-cervical junction and its non-invasive nature 1.

Given the clinical presentation and the association between myelomeningocele and Arnold-Chiari malformation type II, inferior displacement of the medulla and cerebellum is the most likely finding on head imaging, as it is a common complication of myelomeningocele and can lead to significant morbidity if not promptly diagnosed and managed. The recent study on the update on urological management of spina bifida from prenatal diagnosis to adulthood 1 also emphasizes the importance of early diagnosis and management of associated conditions, including hydrocephalus and Arnold-Chiari malformation type II, to improve outcomes in patients with myelomeningocele.

From the Research

Head Imaging Findings

The patient's head imaging is most likely to reveal findings associated with Chiari II malformation, given the presence of a large myelomeningocele. Key findings may include:

• Inferior displacement of the cerebellum and medulla, which is a characteristic feature of Chiari II malformation 2, 3, 4
• Hydrocephalus, which is often associated with Chiari II malformation 2, 4, 5
• Syringomyelia, which can occur in patients with Chiari II malformation 2, 4, 6

Specific Imaging Features

The specific imaging feature that is most likely to be revealed is:

• Inferior displacement of the medulla and cerebellum, which is a direct consequence of the Chiari II malformation 3, 4, 5

Clinical Correlation

The clinical correlation of these imaging findings is crucial, as patients with Chiari II malformation can present with a range of symptoms, including:

• Neurological deficits, such as weakness or paralysis of the lower extremities 2, 4
• Hydrocephalus, which can cause increased intracranial pressure and other symptoms 2, 4, 5
• Syringomyelia, which can cause pain, weakness, and other symptoms 2, 4, 6