Atretic Parietal Cephalocele with Persistent Falcine Sinus and Sinus Pericranii: A Rare Case Diagnosed on Prenatal Ultrasound

Abstract

Atretic parietal cephaloceles (APCs) are the herniation of intracranial structures like vestigial tissues (i.e., glial tissue, arachnoid tissue, or neural rests) and meninges through a cranial vault defect. These are small skin covered scalp lesions that usually occur near the lambda. The most common site is the parietal region, followed by the occipital region. Atretic cephaloceles are usually associated with intracranial venous abnormalities such as persistent falcine sinus (PFS). Association of APC and sinus pericranii (SP) is very rare. APC can be isolated or associated with intracranial abnormalities, with callosal dysgenesis, holoprosencephaly spectrum, or interhemispheric cyst being the most common. We report a case of APC with absence of straight sinus, PFS, and SP diagnosed at mid trimester on prenatal ultrasound in a diabetic mother. The diagnosis of APC was confirmed on clinical examination postnatally.

 

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Keywords

atretic cephalocele - atretic parietal cephalocele - persistent falcine sinus - scalp lesion - sinus pericranii

Introduction

Atretic cephalocele (AC) is the congenital herniation of intracranial structures through a skull vault defect, like meningeal and vestigial tissues (arachnoid, glial, or neural rests). The presence of remnants of dura, dysplastic neural tissue, and fibrotic tissue helps differentiate AC from true cephaloceles.[1] They are considered to be involuted true cephaloceles.[1] These are rare central nervous system (CNS) lesions, representing 1% of all congenital CNS anomalies and 37.5 to 50% of all parietal cephaloceles.[2] The most common site is the parietal region, followed by the occipital region.

Yokota et al[2] first described atretic parietal cephalocele (APC) as a separate entity and defined it as small midline sub scalp noncystic lesions in the vertex region. APCs are frequently associated with midline brain and venous anomalies that determine the clinical presentation, prognosis, and management.[2] Though ACs have a better prognosis than true cephaloceles, the presence of associated pathologies may complicate the clinical course.[3] A wide range of venous anomalies has been reported along with APC. This case report describes prenatal ultrasound diagnosis of APC with persistent falcine sinus (PFS) and sinus pericranii (SP) in a diabetic mother.

 

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Case Report

A 28 year old, second gravida with 5 months of pregnancy was referred for a routine mid trimester anomaly scan. There was a stillbirth in her first pregnancy for an unknown reason. She was type 2 diabetic on oral medication with good glycemic control. This was a nonconsanguineous marriage. There was no history of drug intake during first trimester or a significant family history. No first trimester screening had been done.

On ultrasound examination, fetal biometry corresponded a gestational age of 21 weeks 3 days (as per last menstrual period), with normal liquor volume. A small 11 × 9 × 4 mm sized hypoechoic sub scalp lesion was seen in the midline parietal region with a small calvarial defect measuring 4.6 mm in width ([Figs. 1] and [2]). Minimal intralesional vascularity was noted on power Doppler ([Figs. 3] and [4]). A few tiny venous channels were seen traversing through the defect into the lesion. PFS was noted reaching up to the lesion and draining the posterior one third of the superior sagittal sinus (SSS) with absence of straight sinus (SS; [Fig. 5]). Small cavum velum interpositum was also noted posteroinferior to the splenium of the corpus callosum ([Fig. 6]). The corpus callosum and posterior fossa appeared normal. No other intracranial or extracranial abnormality was found. Based on the above findings, a diagnosis of APC with PFS and SP was made. The scan findings were discussed with the couple, and they were advised fetal magnetic resonance imaging. Due to financial constraints and willingness to continue the pregnancy, they did not want further investigations and continued the pregnancy. On follow up ultrasound at 32 weeks for growth and fetal well being, there was no increase in the size of the lesion or other intracranial abnormality detected. She delivered a male baby by lower segment cesarean section at 36 weeks. The baby cried immediately after birth with a good Apgar score. The baby is now 6 months old with no neurological complaints with normal developmental milestones. Postnatal clinical examination confirmed the diagnosis of AC ([Fig. 7]).

Fig. 1 Small subscalp hypoechoic lesion in midline parietal region, measuring 11 × 9 × 4 mm in size.

Fig. 2 Small 4.6 mm calvarial defect with subcutaneous hypoechoic lesion in parietal region.

Fig. 3 HDflow showing minimal intralesional vascularity communicating with dural sinus.

Fig. 4 HDflow showing minimal intralesional vascularity communicating with dural sinus.

Fig. 5 Persistent falcine sinus communicating with internal cerebral vein and SSS and pointing toward the scalp lesion. There is also absence of SS. SS, straight sinus; SSS, superior sagittal sinus.

Fig. 6 Small cavum velum interpositum with normal corpus callosum and vermis.

Fig. 7 Clinical photograph of a baby showing atretic parietal cephalocele.

 

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Discussion

Cephaloceles are a herniation of intracranial structures through a cranial vault defect. Cephaloceles can be classified as meningoceles, encephaloceles, and meningoencephaloceles depending on the herniated contents. The most common site is the occipital region. Parietal location is an uncommon site for cephaloceles and these are usually atretic. The incidence of ACs is 4 to 17% of all cephaloceles, out of which APCs account for 37 to 50%.[1] [2]

Different theories have been described for the pathogenesis of ACs, including neural crest remnants, the result of “remnant nuchal bleb,” and near total resolution of large true cephalocele developed in early fetal life.[1] [4] APCs can be isolated in 50% of cases, and the remaining have an association with Dandy–Walker malformations, holoprosencephaly, agenesis of corpus callosum, interhemispheric cyst, Chiari II malformation, and venous anomalies.[2] [5] McLaurin first described venous anomalies like fenestrated SSS and vertical embryonic position of SS (VEPSS) with APCs.[6] Vertical course of the SS, elongated vein of Galen (VOG), and splitting of SSS have been described as some of the venous malformations. The VEPSS can be PFS.[5]

The SS appears as a continuation of the internal cerebral vein and the median prosencephalic vein at around 12 weeks of gestation. Falcine sinus is a temporary sinus in the falx cerebri connecting the anterior portion of the SS and the VOG to the posterior third of the SSS. The SS can be present or absent in cases of APCs,[5] which was absent in our case. Hsu and Chaloupka postulated that failure in the connection of VOG and SS during late embryonic or early fetal life led to the opening of the falcine sinus as etiopathology in their case.[5]

The SP is a venous channel connecting the intracranial venous system with an epicranial or subgaleal vein passing through bone.[5] Konez and Burrows reported that 93% cases of SP were associated with developmental venous or sinus anomalies.[7] No detailed embryological mechanism is currently described between SP and APC. However, Hsu and Chaloupka, in their case report, described the congenital SP as an alternative venous drainage pathway in the presence of developmental intracranial venous system anomaly.[5]

Major differential diagnoses of ACs are encephalocele, SP, hemangioma, epidermoid cyst, and dermoid cyst. The presence of the PFS is a classical finding of ACs and helps differentiate them from others. ACs with dermoid cyst or SP have also been reported rarely.[8] [9]

The prognosis of ACs is highly dependent on the presence or absence of other CNS malformations. Good prognosis is reported in isolated APCs with no other CNS abnormalities.[10] [11] Early prenatal detection of ACs helps in parental counselling and delivery planning.

 

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Conflict of Interest

None declared.

• References

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Publikationsverlauf

Artikel online veröffentlicht:
17. Juni 2025