Hamartoma of the tuber cinereum (ECR 2015 Case of the Day)

Clinical History

A 21-month-old infant boy was referred to the radiology department for evaluation of precocious puberty. Clinical examination demonstrated a child, above the 95th percentile in height and weight. There was pubic hair development and abnormal testicular enlargement at ultrasound. Plasma prolactine level was elevated. Plasma FSH and LH levels were normal.

Imaging Findings

Conventional radiography was obtained to assess skeletal maturation. Plain film of the left hand (Fig. 1) showed an increased growth velocity, with a bone age of 6 years, according to the Greulich and Pyle atlas.
Subsequent MRI of the brain (Fig. 2 and 3) demonstrated a large, well-defined solid mass in the suprasellar region, posterior of the optic chiasm. The mass was located between the mammillary bodies and infundibulum and was contiguous with the tuber cinereum. It was isointense to the grey matter on T1WI and iso-to hyperintense on T2WI. There was no enhancement after administration of gadolinium.

Discussion

A hypothalamic or tuber cinereum hamartoma is a congenital, non-neoplastic, tumour-like lesion, located in the region of the hypothalamus and contiguous with the tuber cinereum. It is considered a benign heterotopic nodular mass, resembling normal hypothalamic grey matter. Prevalence is 1/50000 to 1/100000 births [1]. Size is variable, ranging from a few millimetres to 5 cm.

Hypothalamic hamartomas most often present with the triad of precocious puberty, gelastic epilepsy (automatic bursts of laughter) and developmental delay [2]. Precocious puberty is defined as the appearance of secondary sex characteristics before the age of 8 years in girls and 9 years in boys. There are two types of precocious puberty: central precocious puberty (CPP) and peripheral precocious puberty (PPP). Hypothalamic hamartoma is the lesion most commonly associated with CPP. It affects the normal hypothalamic functions, causing early activation of the hypothalamic-pituitary axis, with gonadotropin-releasing hormone (GnRH)-stimulated gonadotropin secretion and subsequently gonadal maturation [3, 4].

Patients usually present between 1 and 3 years of age with early development of secondary sex characteristics and an accelerated growth. Assessment of growth velocity is important because bone age is typically advanced in precocious puberty and it can limit potential adult height. Imaging of the central nervous system is indicated to detect intracranial lesions, which can cause precocious puberty [4].

MRI of the brain reveals a mass lesion, located in the suprasellar region. The mass is iso-to hypointense on T1WI and iso-to slightly hyperintense on T2WI. Cyst formation or calcifications are very uncommon. There is no enhancement after administration of gadolinium, which is a very important finding to distinguish a hamartoma from other, more common suprasellar masses like a craniopharyngioma, germ cell tumour, hypothalamic astrocytoma or an optic glioma [5].

Hamartomas usually do not grow. The aim of treatment is to preserve final height and reverse physical changes to pre-pubertal stage congruous to chronological age. Precocious puberty can be controlled by long-acting GnRH agonists, which inhibit gonadotropin secretion and the associated pubertal changes. Surgery is only indicated if there is no response to medical treatment or in case of refractory seizures [2].

In conclusion, in case of a suprasellar mass and an early onset of puberty one should always consider the possibility of a hypothalamic hamartoma. Diagnosis of this rare lesion is based on clinical examination, plasma hormonal levels and radiological findings. A hamartoma does not show any enhancement, which is important for differentiation with other suprasellar masses.

Differential Diagnosis List

Final Diagnosis

Hamartoma of the tuber cinereum

URL:	https://www.eurorad.org/case/12750
DOI:	10.1594/EURORAD/CASE.12750
ISSN:	1563-4086