Arnold Chiari type III malformation

Clinical History

A 3-month-old male baby was presented with a high cervical encephalocele mass in combination with multiple cerebellar and brain stem anomalies.

Imaging Findings

A 3-month-old boy with a high cervical mass was admitted to our hospital. The results of his neurological examination were found to be normal except for the presence of a 14 x 12 x 9 cm diameter cervical encephalocele. The craniovertebral junction's sagittal SE T1- and T2-weighted MRI showed a high cervical encephalocele within the cerebellar tonsils. There was herniation of the cerebellar tonsils and medulla oblongata from the foramen magnum to the cervical canal. The posterior fossa was small. The posterior parts of C1 and C2 were defective. The cervical spinal canal was larger than normal. There was a medullar kink, large massa intermedia, tectal beaking, and partial corpus callosum agenesis. The cranial MRI image showed the presence of hydrocephalus; however, the diameter of the head was normal. His cognitive function was not tested. In the concord position, the encephalocele was excised while protecting the neural tissue, and the defect was repaired. In a second operation, VP shunting was applied. After two months, his neurological status was the same except for minimal cognitive dysfunction. On doing the follow-up MRI, it was found that the mass was absent, and VP shunting was functional. The baby is still being followed up.

Discussion

ACM type III is the most severe variant of ACM. Patients with ACM III cannot lead a healthy life, even when given appropriate treatment. Infants with ACM III have a poorer prognosis than patients with ACM I and ACM II. It can be diagnosed by an MRI easily. Documentation available on ACM III is extremely rare, and so far there are only five reports on ACM III cases and their MRI findings. MRI readily establishes the presence and the contents of encephaloceles, the position of the brain stem, the medulla, and potential anomalies of venous drainage associated with the encephalocele. In ACM III cases, there are also noticeable features of ACM II and herniation of the fourth and lateral ventricles. A spinal MRI can show neural tube defects, syringomyelia, tethered cord syndrome and other associated anomalies, which have to be operated on. A prenatal diagnosis based on a foetal MRI or USG is pertinent, in order to inform and prepare the patient's family. ACM III usually requires surgery. The purpose of the surgery is to remove the encephalocele while trying to keep the neurological function intact and to repair the dura and bone in order to continue CSF circulation.The microcephalic infants who have severe neurological deficits may be left unoperated. If the amount of neural tissue within the sac exceeds the remaining brain tissue within the cranium, it is recommended that the lesion not be repaired. An encephalocele is generally covered with normal skin, so it rarely needs urgent surgery. For better results, the anatomy of the malformation could be evaluated by using MRI. As hydrocephalus plays a significant role in the poor outcome of these children, it is important that an early diagnosis be made and an appropriate treatment be initiated. In our case, early VP shunting might have improved the neurological condition of this patient. Although surgery was performed, there was minimal cognitive dysfunction. The severity of cognitive dysfunction correlated to the amount of brain tissue within the mass, the degree of herniation, and the presence of other brain anomalies as in the literature.

Differential Diagnosis List

Final Diagnosis

Arnold Chiari type III malformation.

URL:	https://eurorad.org/case/2639
DOI:	10.1594/EURORAD/CASE.2639
ISSN:	1563-4086