Concurrent Hypothalamic Hamartoma and Suprasellar Arachnoid Cyst

A 4-year-old boy presented to the outpatient department with symptoms of precocious puberty. Neurological examination is within normal limits. Magnetic resonance imaging (MRI) examination revealed a well-defined non-enhancing hypothalamic lesion measuring 9 mm × 26 mm, which was T1 isointense and T2, fluid attenuation inversion recovery (FLAIR) mildly hyperintense to gray matter. Another well-defined non-enhancing lesion measuring 27 mm × 29 mm × 30 mm, which was isointense to cerebrospinal fluid (CSF) on all sequences, was noted in the suprasellar region, contiguous to the hypothalamic lesion on its superior aspect [Figure 1a-h]. The lesion was abutting and splaying bilateral cerebral peduncles with the widening of the interpeduncular cistern. No enhancement was seen on post contrast study [Figure 1i and j].Figure 1: Magnetic resonance imaging (MRI) of the brain of the patient with hypothalamic hamartoma and arachnoid cyst in the suprasellar region. Axial T2 (a), Fluid attenuation inversion recovery sequence (FLAIR) (b) showed lesion in the hypothalamus with solid component in its anteroinferior aspect (white arrow) and T2 hyperintense cystic component in the posterosuperior aspect showing suppression on FLAIR (black arrow). The solid component of the lesion was T1 isointense (white arrow in c) and cystic component was T1 hypointense (black arrow in c). Coronal T2 (d) and T1 (e) images showed the lesion in the hypothalamic and suprasellar region with solid component in its inferior aspect (white arrows in d and e) and cystic component in superior aspect (black arrows in d and e). No restricted diffusion on diffusion weighted imaging (DWI) (f), apparent diffusion coefficient (ADC) (g) and no blooming on susceptibility weighted imaging (SWI) (h). No enhancement on post contrast study (i and j)Hypothalamic hamartomas are benign heterotopic collections composed of ectopic neural tissue that is most likely congenital in origin. It usually presents with developmental delay and gelastic seizures.[1] It is a solid, non-enhancing mass with signal intensity like gray matter. It can be sessile or pedunculated. Large sessile lesions are more frequently associated with seizures, while pedunculated and smaller lesions typically manifest as precocious puberty.[2] Because of the mass effect of arachnoid cysts in the suprasellar region on the hypothalamus and infundibulum, it may cause short stature, obesity, amenorrhea, and precocious puberty.[1] This coexistence of arachnoid cysts and hypothalamic hamartomas may be caused by the hamartoma disrupting the formation of the prenatal subarachnoid space or by the presence of meningeal or arachnoid tissue within the hamartoma, which later develops into an arachnoid cyst.[1,2] The location of arachnoid cysts correlates with age, which is reported in the middle cranial fossa in older patients and suprasellar region in patients under five years.[3] Possible differentials of cystic lesions in suprasellar region include Craniopharyngioma (Mixed solid cystic, calcifications present, enhances after contrast), Epidermoid cyst (restricted diffusion, incomplete FLAIR suppression), Neuroglial cyst (CSF intensity lesion, intra-axial location), Rathke’s cleft cyst (thin rim of enhancement post contrast), Cystic degeneration of Pituitary macroadenoma (solid component enhances with contrast). In asymptomatic cases, routine clinical and imaging monitoring is recommended; in symptomatic cases, microsurgical excision can be carried out. Gamma knife radiosurgery, stereotactic thermoablation (radiofrequency thermoablation or laser mediated) are the procedure for patients who are at a high risk of surgery.[4] Hormone replacement therapy can be used when pituitary function is compromised. In the event of obstructive hydrocephalus, ventriculo-peritoneal shunting or cyst fenestration can be performed. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.