Hypothalamic lesions

From the case: Hypothalamus diagrams

The tuber cinereum is a part of the hypothalamus located between the mamillary bodies and the optic chiasma.

A hamartoma is a focal malformation that resembles a neoplasm; it is not a malignant tumor and it is composed of tissue elements normally found at that site that grow in a disorganized mass.

Hypothalamic hamartoma in the brain typically occurs in the hypothalamus and presents as a discrete mass isointense to cortex on both T1 and T2, without contrast enhancement (notice that this picture is a post-contrast T1). This lesion may cause gelastic seizures, visual problems or early onset of puberty. The symptoms often begin in early infancy and are progressive, often with general cognitive and/or functional disability.

Curiously: tuber cinereum is named after its colour…in fact, being gray matter it is called “cinereum” - the colour of the ash.

The word “hamartoma” derives from the greek “hamartia”: in Greek tragedy, the concept of “hamartia” is an error in judgment or unwitting mistake, normally applied to the actions of the hero…in the same view, in medicine, hamartoma is considered an error of development.

“Gelastic” is a term often used in medical terminology to indicate an association of a symptom or syndrome with laughter. The word originates from the Greek “gelaein” that means “to laugh”.

There is also an incidental Chiari malformation type I.

References

1. Fenoglio KA, Wu J, Kim do Y et al. Hypothalamic hamartoma: basic mechanisms of intrinsic epileptogenesis. Semin Pediatr Neurol. 2007 Jun;14(2):51-9.
2. Maixner W. Hypothalamic hamartomas–clinical, neuropathological and surgical aspects. Childs Nerv Syst. 2006 Aug;22(8):867-73.

Credit

Dr Eytan Raz

There is diffuse enlargement and increased T2 signal change of the optic chiasm and optic nerves. There is diffuse abnormal T2-hyperintense signal change also involving the hypothalamus, basal ganglia, thalami, pons and midbrain. The appearances are suggestive of hypothalamic-optochiasmatic glioma.

This entity is a subset of astrocytic tumors which occur in patients with neurofibromatosis type 1. These may involve the optic nerves, the optic chiasm, and the optic tracts. Most are juvenile pilocytic astrocytomas, but their imaging characteristics are not specific with regard to their histologic features. Varying degrees of cystic change and enhancement are demonstrated. These tumors may appear smooth, fusiform, eccentric, or lobulated.

Gliomas of the optic chiasm and hypothalamus account for 10%–15% of supratentorial tumors in children. Males and females are approximately equally affected. Between 20% and 50% of patients with hypothalamic gliomas have a positive family history of von Recklinghausen disease (NF-1). Gliomas of the optic chiasm and hypothalamus in children with NF-1 usually have a more indolent course. Tumors may grow more slowly and occasionally regress spontaneously. MR imaging is optimal for showing the relationship of the mass to the hypothalamus, optic chiasm, and infundibulum as well as the intraorbital and intracanalicular components of the mass. Gliomas of the optic chiasm and hypothalamus are almost always hypointense with T1-weighted sequences and hyperintense with T2-weighted and FLAIR sequences. Large tumors are typically heterogeneous with cystic and solid components, with the latter often enhancing after contrast administration.

Reference

Kollias SS, Barkovich AJ, Edwards MS. Magnetic resonance analysis of suprasellar tumors of childhood. Pediatr Neurosurg 1991–1992; 17: 284–303.

Credit

Dr Abhijit Datir

From the case: Germinoma of the third ventricle