Hypothalamic hamartomas, also known as tuber cinereum hamartomas, are benign non-neoplastic heterotopias in the brain that typically occur in the region of the hypothalamus, arising from the tuber cinereum, a part of the hypothalamus located between the mammillary bodies and the optic chiasm.
Symptoms often begin in early infancy and are progressive, often with general cognitive and functional disability.
Lesions can cause gelastic seizures, visual problems, early onset of puberty and behavioural problems 3.
Gelastic seizures are typically of short duration (2-30 seconds) and characterised by uncontrollable laughter, without impairment of consciousness, which contrasts with frontotemporal gelastic seizures which usually are longer lasting and can result in loss of consciousness 4. Very rarely children with hypothalamic hamartomas can enter into 'status gelasticus' 4.
Although an association with Pallister-Hall syndrome has been described, in general, hypothalamic hamartomas are isolated lesions 5.
Central precocious puberty is also frequently encountered in these children, typically in patients with sessile tumours. It results from over-secretion of gonadotropin-releasing hormone (GnRH) which in turn results in over production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) 5.
A hamartoma is a focal malformation that resembles (but is not) a neoplasm (cf. other CNS neoplasms); it is not a malignant tumour, and it is composed of tissue elements normally found at that site that grow in a disorganised mass.
Histologically, hypothalamic hamartomas resemble normal hypothalamic neurones, although some dysplastic neurones and glial cells have also been described 3. They are thought to arise from anomalous neural migration between 35 and 40 days in utero (time of hypothalamic formation).
The most commonly used classification is morphologic, dividing hypothalamic hamartomas into either sessile or pedunculated morphology 3,5.:
- attached to the mammillary region and if large enough distort and displaces or incorporates the mammillary bodies
- the columns of the fornix are displaced anterolaterally 5
- degree of extension below the third ventricle is variable
- attached to the tuber cinereum
- projects into the suprasellar cistern
As they are composed of grey matter, they have imaging appearances similar to the normal cortex. They do not enhance and do not grow 3.
On conventional axial CT images, the diagnosis can be challenging, depending on slice position and thickness, although with more recent volumetric scans with coronal and sagittal reformats, the abnormality is easier to identify.
As expected it appears as a nodule of soft tissue iso-attenuating to grey matter, without calcification or contrast enhancement.
MRI, as expected, is the modality of choice for assessment of this region.
- T1: isointense to cerebral cortex
- T1 C+ (Gd): no contrast enhancement
- iso- to hyperintense to the cerebral cortex
- the higher the proportion of glial cells, the higher the T2 signal 3
- reduced NAA/Cr
- increased myoinositol 3
- increased Cho/Cr compared to the amygdala has also been reported 3
Treatment and prognosis
They are benign lesions and typically to do not grow, however, symptomatology can be progressive.
Children with central precocious puberty can be treated medically.
Intractable epilepsy can respond to surgery (resection or disconnection, depending on the morphology of the tumour) and this can be performed via an open craniotomy or more recently via an endoscope 5.
Gamma knife radiosurgery has also been used 5.
History and etymology
- tuber cinereum from the Latin meaning ash coloured mass. This stems from its colour, as it is composed of grey matter
- 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”
The differential diagnosis is broadly that of suprasellar/hypothalamic lesions, although the imaging characteristics of hypothalamic hamartomas significantly reduce the differential.
Hypothalamic-chiasmatic glioma is the main differential. Most other lesions encountered in the region either have the markedly different signal intensity or demonstrate enhancement.
- 1. Fenoglio KA, Wu J, Kim do Y et-al. Hypothalamic hamartoma: basic mechanisms of intrinsic epileptogenesis. Semin Pediatr Neurol. 2007;14 (2): 51-9. doi:10.1016/j.spen.2007.03.002 - Pubmed citation
- 2. Maixner W. Hypothalamic hamartomas--clinical, neuropathological and surgical aspects. Childs Nerv Syst. 2006;22 (8): 867-73. doi:10.1007/s00381-006-0129-0 - Pubmed citation
- 3. Amstutz DR, Coons SW, Kerrigan JF et-al. Hypothalamic hamartomas: Correlation of MR imaging and spectroscopic findings with tumor glial content. AJNR Am J Neuroradiol. 2006;27 (4): 794-8. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 4. Engel J, Pedley TA, Aicardi J. Epilepsy, A Comprehensive Textbook. Philadelphia : Wolters Kluwer Health/Lippincott Williams & Wilkins, c2008. (2007) ISBN:0781757770. Read it at Google Books - Find it at Amazon
- 5. Tonn J, Westphal M, Rutka JT. Oncology of CNS Tumors. Springer Verlag. (2009) ISBN:364202873X. Read it at Google Books - Find it at Amazon