We report the case of a giant hypothalamic hamartoma with a large intracranial cyst in a neonate. On ultrasonography, the lesion presented as a lobulated, mass-like lesion with similar echogenicity to the adjacent brain parenchyma, located anterior to the underdeveloped and compressed left temporal lobe, and presenting as an intracranial cyst in the left cerebral convexity without definite internal echogenicity or septa. The presence of a hypothalamic hamartoma and intracranial neurenteric cyst were confirmed by surgical biopsy. The association of a giant hypothalamic hamartoma and a neurenteric cyst is rare. Due to the rarity of this association, the large size of the intracranial cyst, and the resulting distortion in the regional anatomy, the diagnosis of the solid mass was not made correctly on prenatal high-resolution ultrasonography.
Hypothalamic hamartomas are rare, non-neoplastic, congenital malformations of the posterior hypothalamus that consist of ectopic neural tissue and rarely exceed 2 cm in diameter. When they exceed 30-40 mm in diameter, they are defined as giant hypothalamic hamartomas, and it is unclear whether the extent of a hypothalamic hamartoma affects its manifestation. To the best of our knowledge, their radiologic appearance with respect to changes in adjacent structures has not been well studied. A search of the MEDLINE and PubMed databases identified only nine articles describing 11 patients, but those studies mostly focused on the clinical features and histopathological findings of giant hypothalamic hamartomas [
A 38-year-old gravida 1, para 1 female was referred to our tertiary referral center for the evaluation of an intracranial cyst demonstrated by high-resolution fetal ultrasonography at the gestational age of 25 weeks. Prenatal high-resolution ultrasonography at the gestational age of 28 weeks revealed an intracranial extra-axial cystic lesion at the left cerebral convexity with no internal echogenicity (
MR imaging at 3.0 T using high-resolution and gadolinium-enhanced T1-weighted sequences with standard T2-weighted sequences was performed on postnatal day 4. MR imaging demonstrated a large (60×30×43 mm), lobulated left frontal solid lesion with isointense signals relative to the cortex on all pulse sequences (
The histologic evaluation of the cyst wall revealed single or stratified cuboidal or columnar epithelial lining instead of delicate fibrous connective tissue lined by meningothelial cells, and it was diagnosed as an intracranial neurenteric cyst. A pathologic specimen of the solid mass revealed aggregated small cells, which were not reactive to antibodies for glial fibrillary acidic protein or neuronal nuclear antigen. The background tissue expressed synaptophysin, but only few myelinated axons were observed on a Luxol fast blue-stained slide. Only a few cell processes were reactive to phosphorylated neurofilament. No cellular atypia was noted. All these features are consistent with a hypothalamic hamartoma (
With a benign and congenital nature, hypothalamic hamartomas are non-neoplastic, rare (1:200,000) lesions formed by ectopic neural tissue, and are commonly associated with gelastic seizures and precocious puberty. Patients with giant hypothalamic hamartomas frequently have seizures (63.6%), with the majority of the seizures belonging to the gelastic type and a prevalence similar to that observed in patients with non-giant hypothalamic hamartomas [
Hypothalamic hamartomas are also commonly associated with precocious puberty (63%), and are the most common identifiable neurological cause of this phenomenon, followed by hypothalamic and chiasmatic gliomas, germ cell tumors, arachnoid cysts, and isolated hydrocephalus. The theory for the pathogenesis of precocious puberty is that the hamartoma may be directly involved in neurosecretion or result in a physical perturbation of inhibitory pathways. In contrast to the non-giant hypothalamic hamartomas, giant hypothalamic hamartomas were associated with precocious puberty only in 36.3% of the patients. This report describes the first case of a giant hypothalamic hamartoma associated with a non-arachnoid, neurenteric intracranial cyst. As hypothalamic hamartomas have been attributed to abnormal splitting of the notochord, which could result in other known associated congenital anomalies of the craniofacial and central nerve system, hypothalamic hamartomas may be part of the wide spectrum of associated craniofacial developmental abnormalities, including hypertelorism, cleft lip and palate, basal encephaloceles, septo-optic dysplasia, callosal agenesis, and holoprosencephaly [
Previously, the coexistence of an arachnoid cyst and a hypothalamic hamartoma has been reported in a few cases, and has been explained through two theories [
The presence of large intracranial cysts associated with a hamartoma can lead to significant alterations in the regional anatomy and an incorrect preoperative diagnosis. Although the association with intracranial cysts is rare, the presumptive diagnosis of hamartoma should be made when the MR imaging features of the solid component are typical for a hypothalamic hamartoma and exhibit continuity with the remaining hypothalamus. These features should be evaluated in any patient presenting with a huge brain parenchymal mass, which is too large for its origin to be clearly demonstrated due to distortions in the regional anatomy. We suggest that isointense lamellate gyriform masses in fetal and postnatal MR imaging should be carefully evaluated for continuity with the adjacent structures, especially with the hypothalamus, as well as for their signal intensity relative to the adjacent cortex.
No potential conflict of interest relevant to this article was reported.
Sonogram demonstrates a 42×17-mm intracranial cyst (dotted lines) in the left cerebral convexity without definite internal echogenicity or septa.
A. Sonogram reveals a 51×35-mm lobulated, mass-like lesion (arrowheads) with similar echogenicity to the adjacent brain parenchyma, located anterior to the left underdeveloped and compressed temporal lobe. B. A 56×22-mm intracranial cyst (asterisk) in the left cerebral convexity is also depicted near the mass (arrowheads) on different sections of the sonograms. M, mass.
A-C. MR images demonstrate a left frontal solid mass of mixed signal intensity (A, T2-weighted images; B, T1-weighted images) with great similarity to the adjacent brain parenchyma and its contiguity with the contralateral hypothalamus, which is well visualized on the coronal T2-weighted image (C). D. Post-contrast MR image obtained 1 week later reveals a lack of enhancement in the mass on contrast enhanced, fat-saturated T1-weighted images. A huge (73×41×65 mm), extra-axial fluid collection (asterisk) along the left frontoparietal convexity corresponds to the lesion depicted on prenatal ultrasonography. Cystic lesion showed a similar signal intensity to the cerebrospinal fluid in all imaging sequences.
A, B. Giant hypothalamic hamartoma (A) and the white matter of the dysplastic brain (B) showed a similar chemical composition to each other on MR spectroscopic analysis.
A. Solid mass demonstrated an aggregation of small cells that were not reactive to antibodies for glial fibrillary acidic protein and neuronal nuclear antigen. No cellular atypia was noted. All these features are consistent with a hypothalamic hamartoma (H&E, ×400). B. Cyst wall exhibited single or stratified cuboidal or columnar epithelial lining instead of the delicate fibrous connective tissue lined by meningothelial cells associated with intracranial neurenteric cysts (H&E, ×100).