Microcephaly, Agenesis of the Corpus Callosum, and Suspected Blake Pouch Cyst Presenting With Failure to Thrive in an Infant.

Infants presenting with microcephaly may present with misshapen head abnormalities that warrant surgical intervention or further investigation. Cranial growth restriction may occur secondary to impaired cerebral development with patent sutures, a diagnostic distinction with critical implications for management. Craniosynostosis, characterized by premature fusion of cranial sutures, is a common consideration in infants presenting with abnormal skull morphology and microcephaly. Agenesis of the corpus callosum (ACC) is a congenital brain malformation that may present with microcephaly, failure to thrive, and early developmental delay, potentially mimicking craniosynostosis on physical examination. A two-month-old male infant born at term via uncomplicated vaginal delivery presented with microcephaly, failure to thrive, and unmet developmental milestones. Based on the infant's abnormal head shape, he was suspected of having craniosynostosis. Growth parameters demonstrated severe restriction: length 2nd percentile, weight less than the 1st percentile, and head circumference less than the 1st percentile, with minimal interval growth from birth to 2 months. Physical examination revealed palpable ridging along the coronal sutures and a small, flat anterior fontanelle. Neurologic assessment demonstrated absent social smile and poor eye contact despite intact pupillary responses, full conjugate eye movements, and normal extremity movement. Feeding difficulties requiring post-prandial suctioning raised concern for laryngomalacia or another upper airway obstruction with a possible need for nasogastric tube placement. Computed tomography demonstrated no evidence of craniosynostosis. Subsequent magnetic resonance imaging revealed complex ACC with colpocephaly, parallel lateral ventricles, and a Blake pouch cyst (BPC). Pediatric neurosurgical evaluation concluded that cranial growth restriction was secondary to impaired cerebral development rather than primary suture pathology. Genetic evaluation and neurodevelopmental follow-up were initiated. This case illustrates a critical diagnostic pitfall: cranial suture ridging and microcephaly do not always indicate craniosynostosis. In infants with failure to thrive, abnormal head growth and underlying brain malformations, such as ACC, may produce secondary cranial restriction with patent sutures. The presence of congenital microcephaly and early developmental concerns, such as absent social interaction, should heighten suspicion for underlying structural brain abnormalities. Early recognition of this distinction is essential to initiate appropriate genetic evaluation and neurodevelopmental monitoring. Complex ACC with associated anomalies warrants a comprehensive workup with multidisciplinary evaluations, as outcomes depend significantly on the presence of additional malformations and underlying genetic etiology.