General physical examination
The neonate with a cervical encephalocele must undergo a thorough physical examination including measurement of head circumference and assessment of general vigor (especially cry and suck), upper and lower extremity motor and sensory function, site and size of encephalocele sac, signs and symptoms of hydrocephalus, and associated deformities or congenital anomalies.
- Skin covered: Most of these lesions are covered with skin and can be repaired electively.
- Small encephalocele and normal examination: Infants with small encephaloceles with little or no herniating brain tissue may present with adequate breathing and a normal neurological examination.
- Large encephalocele and extensive deficits: Larger encephaloceles typically contain herniating brain tissue and are often associated with microcrania and extensive neurological deficits. These deficits include lower cranial nerve deficits (causing problems such as weak or absent cry, inadequate sucking and feeding, or difficulty breathing with inspiratory stridor), weakness/spasticity in upper and lower extremities, opisthotonic posturing, blindness, and profound developmental delay (1). Neonates with extensive deficits may require mechanical ventilatory support and feeding tube placement for nutritional supplementation prior to encephalocele repair.
- Hydrocephalus: Infants with large encephaloceles frequently develop hydrocephalus that can cause macrocrania and accelerated head growth.
- Alpha-fetoprotein level usually normal: The alpha-fetoprotein level, which is particularly helpful in the diagnosis of most open NTDs, is not typically elevated in encephaloceles because these defects are covered by skin.
- Fetal ultrasound limited: Most encephaloceles can be detected prenatally on routine ultrasound (22). However, prenatal sonography can be limited by the mother’s body habitus, the surrounding amniotic fluid, and the position of the fetus during the study.
- CT scan for bony anatomy: Postnatal high-resolution CT imaging with 3D reformations may be obtained to reveal abnormal bony anatomy, but the intracranial connection and the extent of cerebral tissue in the encephalocele are best defined with MRI.
- Fetal MRI for classification: Fetal MRI is a useful noninvasive adjunct to prenatal sonography in the early evaluation of occipital and cervical encephaloceles (22). It can help to distinguish between cervical encephaloceles and cystic dysraphic lesions occurring in the cervical region (i.e., cervical myelomeningoceles) (23), both of which can present as skin-covered sacs protruding from the back of the neck on prenatal ultrasound.
- Fetal MRI for sac contents: MRI produces better images of soft tissue, and bone or dense tissue does not interfere with the image as it can with ultrasound. Thus, fetal MRI can provide a more detailed picture of the contents of the protruding sac as well as any associated CNS anomalies and abnormal bony morphology (22). An example is a case described by Smith et al in which the use of fetal MRI permitted diagnosis of a Chiari III malformation in a 23-week-old fetus (22). This information can be extremely helpful in counseling the parents.
- Fetal MRI for obstetrical planning: Fetal MRI can also aid in obstetrical decisions about where, when, and how to deliver the infant (22).
- Fetal MRI for complete fetus examination: Once an encephalocele is diagnosed on prenatal MRI, a thorough examination of the remainder of the fetus can be performed to look for other congenital anomalies such as hydrocephalus that can be present prenatally or may develop after birth.
- Post-delivery images for surgical planning: Postnatal MRI is an important part of preoperative planning. It is the best imaging modality for identifying the contents of an encephalocele and the presence of hydrocephalus prior to surgery (20) and, therefore, aids in prognosis and surgical planning.
- Venography for surgical planning: Postnatal MRI with MR venography can also be used to demonstrate the degree of venous involvement, including anomalous venous drainage, as well as any associated intracranial anomalies. Such information plays an essential role in the preoperative planning of the neurosurgical repair of the defect (9).
Nuclear Medicine Tests
Correlation of Tests
- Postnatal MRI essential for diagnosis and preoperative planning: The extent of cerebral tissue in the encephalocele sac and the degree of venous involvement, including anomalous venous drainage, as well as any associated intracranial anomalies, are determined from the postnatal MRI. Such information guides the neurosurgical repair of the defect.