Sarah Peterson, BS, Loris Cedeno, MD and PL Westesson MD, DDS, PhD
Clinical
Presentation:A 48-year-old female with a history of breast cancer is evaluated for brain metastases.
Radiological
Findings:
CT: shows an 8 mm, homogeneous mass, anterior to the mamillary bodies in the region of the tuber cinereum (Fig. 1A). This mass is isodense with gray matter and does not enhance on CT with contrast (Fig. 1B).
MR: reveals a nonenhancing (Fig. 2B) 8 mm mass between the mamillary bodies and the infundibulum (Fig. 3). The mass is isointense to gray matter on all sequences, including T1 (Fig. 2) and T2 (Fig. 4). This lesion causes no mass effect on adjacent structures.
Figure 1A
Figure 1B
Figure 1: Axial CT images done before (A) and after (B) contrast was given reveal a nonenhancing mass in the region of the tuber cinereum that is isodense to gray matter.
Figure 2A
Figure 2B
Figure 2: Axial T1 images demonstrate a mass in the region of the tuber cinereum that does not enhance with contrast. This mass is isointense to gray matter on both images.
Figure 3: Sagittal T1 image shows a mass in between the mamillary bodies and the pituitary stalk.
Figure 4: Coronal T2 image displays a mass that is isointense to gray matter.
Diagnosis: Hypothalamic hamartoma
Clinical Discussion: Hypothalamic hamartomas represent non-neoplastic over-growth of hypothalamic neurons, glial cells, and fiber bundles. These congenital masses are thought to be due to an anomaly in neural migration between 35 and 40 days of embryonic development, when the hypothalamus is formed. They usually appear in the first few years of life, presenting with precocious puberty or seizure, classically gelastic, activity.
These hamartomas often contain ectopic GnRH tissue, which is believed to function as a pulse generator; separate from the mechanism that inhibits the hypothalamic release of GnRH. This ectopic tissue connects with the median eminence, resulting in central precocious puberty (CPP), which in these patients, often occurs before the age of three. When CPP occurs, these hamartomas can be treated with GnRH analogs, resulting in a decrease in gonadotropin secretion, and therefore a preservation of the patient's growth potential.
Aside from CPP, hypothalamic hamartomas do not cause any other alteration in the function of the hypothalamic-pituitary axis. However, associated manifestations include seizures, visual disturbances, polydactyly, microgyria, hemispheric heterotopia, corpus callosum agenesis, mental retardation and behavioral problems. These hamartomas can be a part of Pallister-Hall syndrome, due to a frameshift mutation of chromosome 7p13, which, along with hypothalamic hamartomas, includes digital and various organ anomalies.
The clinical presentation of hypothalamic hamartomas corresponds with their radiological appearance. Patients with smaller (3-15 mm), pedunculated masses adjacent to the hypothalamus are more likely to be asymptomatic or have CPP. Those with larger (10-38 mm), sessile masses within the hypothalamus are more likely to have symptoms, particularly seizures. These tumors often remain static and thus do not impinge on surrounding tissue; however, they can grow slowly. Due to the hamartoma's generally benign nature, patients are treated with symptomatic management. Surgical resection is only indicated for patients with incapacitating seizure activity uncontrollable by medical therapy and patients whose mass is growing at a rate significant enough to cause mass effect.
Boyko OB, Curnes JT, Oakes WJ, and Burger PC. Hamartomas of the tuber cinereum: CT, MR, and pathologic findings. AJNR Am J Neuroradiol. 1991 Mar-Apr;12(2):309-14. [Medline]
Debeneix C, Bourgeois M, Trivin C, Sainte-Rose C, Brauner R. Hypothalamic hamartoma: comparison of clinical presentation and magnetic resonance images. Horm Res. 2001;56(1-2):12-8. [Medline]
