Bony Occipital Prominence in a Neonate.

Abstract

A term male infant is born at 39 weeks of gestation via spontaneous vaginal delivery to a 35-year-old gravida 2, para 2 woman; she had been diagnosed with hypothyroidism and adequately treated with levothyroxine. At delivery, the infant is vigorous and does not require resuscitation. His birthweight is 3,595 g (69th percentile), length is 48 cm (20th percentile), and head circumference is 35 cm (75th percentile). On the first day after birth, the infant undergoes an initial examination. The parents note a bony “bump” on the back of his head, which does not appear to be painful. He has been able to breastfeed since birth and has been active. The parents have no other concerns. The infant’s vital signs are within normal limits. On examination, the head appears normocephalic. The anterior fontanel is open, flat, and soft. He has normal coronal, sagittal, and lambdoid sutures. A bony 1- to 2-cm midline occipital prominence (Fig 1) is noted. There is no caput succedaneum, cephalohematoma, or other soft tissue swelling. The remainder of his physical examination findings are normal.A left lateral skull plain radiograph (Fig 2) is obtained on the second day after birth. The radiograph shows a prominent occipital shelf inferior to the lambdoid sutures and patent mendosal suture. No fractures or skull abnormalities are observed. The infant continues to feed well and behave normally. There is no change in the appearance of the bony prominence, and he is discharged from the nursery on the second day after birth.At follow-up, the infant’s mother reports gradual resolution of the bony prominence beginning at 5 months of age. By 14 months of age, only a residual occipital prominence is noted on palpation. She does not report any parental concerns or concerns from the child’s primary pediatrician regarding his growth or development. No further imaging is performed in the outpatient setting.The midline bony occipital prominence in an otherwise normal skull and head, along with characteristic radiographic findings, was most consistent with a diagnosis of bathrocephaly and patent mendosal suture. As this finding is most commonly a benign variant, the infant was discharged from the hospital with instructions to follow up with his primary pediatrician with no additional imaging required.Bathrocephaly is a cranial deformity characterized by bulging of the interparietal portion of the occipital bone. (1) This deformity has been described as “shelf-like.” The mendosal suture is located between the interparietal and supraoccipital portions on the squamous segment of the occipital bone (Fig 3). It typically fuses after other primary sutures in the occipital bone. In children, patent mendosal sutures have been identified up to age 5 years, but most commonly within the first year. (2) Mendosal sutures have also been identified in adult skulls. (3)Gallagher and colleagues described 17 infants who had a bony occipital prominence consistent with bathrocephaly, with most cases associated with patent mendosal sutures. (4) One of the infants was found to have an ossified occipital cephalohematoma. The authors suggested that the clinical history and examination can narrow the differential diagnosis, without requiring imaging studies to confirm the diagnosis.Other case reports of infants with bathrocephaly and associated patent mendosal suture have shown gradual resolution in the occipital prominence over time, as with our patient. (5)(6) These case series demonstrate the generally benign nature and course of bathrocephaly and associated patent mendosal suture. Infants with this finding can be followed clinically.The differential diagnosis of a palpable prominence on the skull of a newborn can include caput succedaneum, cephalohematoma, and subgaleal hematoma. The consistency of these lesions is typically much softer than the bony lesion of bathrocephaly.Craniosynostoses and dolichocephaly usually present with global changes in head shape, rather than a small isolated bony prominence. Importantly, the mendosal suture can be confused with skull fracture on imaging, so an awareness of its persistence into early childhood and even adulthood should inform clinical decision-making if there is no history of head trauma. (5)(7) Intracranial malformations such as encephaloceles can also be considered on the differential diagnosis, although encephaloceles tend to be pulsatile. (4)In our patient, otherwise normal findings on physical examination with radiographic findings of a patent mendosal suture and bulging intraparietal occipital bone led to a diagnosis of bathrocephaly. Gradual resolution of the bony occipital prominence from 5 to 6 months to 14 months was observed, consistent with the benign course of previously reported cases. Bathrocephaly in an otherwise well newborn is a benign finding. Close observation without imaging is recommended as the lesion is expected to resolve spontaneously.Bathrocephaly with patent mendosal suture is a benign skull variant that can be identified in the newborn period and gradually resolves over time.This skull finding can be followed clinically without the need for additional imaging.